math entities list activities refactored + categories added

AndroidManifest.xml

@@ -61,7 +61,11 @@
 				  a:label="@string/c_help"
 				  a:configChanges="orientation|keyboardHidden"/>
 
-		<activity a:name=".CalculatorFunctionsActivity"
+        <activity a:name=".CalculatorFunctionsActivity"
+                  a:label="@string/c_functions"
+                  a:configChanges="orientation|keyboardHidden"/>
+
+		<activity a:name=".CalculatorFunctionsTabActivity"
 				  a:label="@string/c_functions"
 				  a:configChanges="orientation|keyboardHidden"/>
 
@@ -69,7 +73,11 @@
 				  a:label="@string/c_operators"
 				  a:configChanges="orientation|keyboardHidden"/>
 
-		<activity a:name=".CalculatorVarsActivity"
+        <activity a:name=".CalculatorVarsActivity"
+                  a:label="@string/c_vars_and_constants"
+                  a:configChanges="orientation|keyboardHidden"/>
+
+		<activity a:name=".CalculatorVarsTabActivity"
 				  a:label="@string/c_vars_and_constants"
 				  a:configChanges="orientation|keyboardHidden"/>
 

res/layout/history_tabs.xml

@@ -1,30 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-
-<!--
-  ~ Copyright (c) 2009-2011. Created by serso aka se.solovyev.
-  ~ For more information, please, contact se.solovyev@gmail.com
-  ~ or visit http://se.solovyev.org
-  -->
-
-<TabHost xmlns:a="http://schemas.android.com/apk/res/android"
-		 a:id="@android:id/tabhost"
-		 a:layout_width="fill_parent"
-		 a:layout_height="fill_parent">
-
-	<LinearLayout
-			a:orientation="vertical"
-			a:layout_width="fill_parent"
-			a:layout_height="fill_parent">
-
-		<TabWidget
-				a:id="@android:id/tabs"
-				a:layout_width="fill_parent"
-				a:layout_height="wrap_content"/>
-
-		<FrameLayout
-				a:id="@android:id/tabcontent"
-				a:layout_width="fill_parent"
-				a:layout_height="fill_parent"/>
-
-	</LinearLayout>
-</TabHost>

res/layout/math_entity.xml

@@ -16,18 +16,18 @@
 			a:layout_width="fill_parent"
 			a:layout_height="fill_parent">
 
-		<TextView a:id="@+id/var_text"
+		<TextView a:id="@+id/math_entity_text"
 				  a:layout_width="fill_parent"
 				  a:layout_height="fill_parent"
-				  style="@style/var_text">
+				  style="@style/math_entity_text">
 		</TextView>
 
 	</LinearLayout>
 
-	<TextView a:id="@+id/var_description"
+	<TextView a:id="@+id/math_entity_description"
 			  a:layout_width="fill_parent"
 			  a:layout_height="fill_parent"
-			  style="@style/var_description">
+			  style="@style/math_entity_description">
 	</TextView>
 
 </LinearLayout>

res/layout/operators.xml

@@ -1,20 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-
-<!--
-  ~ Copyright (c) 2009-2011. Created by serso aka se.solovyev.
-  ~ For more information, please, contact se.solovyev@gmail.com
-  ~ or visit http://se.solovyev.org
-  -->
-
-<LinearLayout xmlns:a="http://schemas.android.com/apk/res/android"
-    a:orientation="vertical"
-    a:layout_width="fill_parent"
-    a:layout_height="fill_parent">
-
-    <ListView
-        a:layout_width="fill_parent"
-        a:layout_height="fill_parent"
-        a:layout_weight="1"
-        a:id="@android:id/list"/>
-
-</LinearLayout>

res/layout/tabs.xml

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<!--
+  ~ Copyright (c) 2009-2011. Created by serso aka se.solovyev.
+  ~ For more information, please, contact se.solovyev@gmail.com
+  ~ or visit http://se.solovyev.org
+  -->
+
+<TabHost xmlns:a="http://schemas.android.com/apk/res/android"
+         a:id="@android:id/tabhost"
+         a:layout_width="fill_parent"
+         a:layout_height="fill_parent">
+
+    <LinearLayout
+            a:orientation="vertical"
+            a:layout_width="fill_parent"
+            a:layout_height="fill_parent">
+
+        <TabWidget
+                a:id="@android:id/tabs"
+                a:layout_width="fill_parent"
+                a:layout_height="wrap_content"/>
+
+        <FrameLayout
+                a:id="@android:id/tabcontent"
+                a:layout_width="fill_parent"
+                a:layout_height="fill_parent"/>
+
+    </LinearLayout>
+</TabHost>

res/values-hdpi/styles.xml

@@ -30,11 +30,11 @@
 		<item name="android:padding">5dp</item>
 	</style>
 
-	<style name="var_text_parent">
+	<style name="math_entity_text_parent">
 		<item name="android:textSize">20dp</item>
 	</style>
 
-	<style name="var_description_parent">
+	<style name="math_entity_description_parent">
 		<item name="android:textSize">15dp</item>
 	</style>
 

res/values-ldpi/styles.xml

@@ -30,11 +30,11 @@
 		<item name="android:padding">5dp</item>
 	</style>
 
-	<style name="var_text_parent">
+	<style name="math_entity_text_parent">
 		<item name="android:textSize">20dp</item>
 	</style>
 
-	<style name="var_description_parent">
+	<style name="math_entity_description_parent">
 		<item name="android:textSize">15dp</item>
 	</style>
 

res/values-mdpi/styles.xml

@@ -30,11 +30,11 @@
 		<item name="android:padding">5dp</item>
 	</style>
 
-	<style name="var_text_parent">
+	<style name="math_entity_text_parent">
 		<item name="android:textSize">20dp</item>
 	</style>
 
-	<style name="var_description_parent">
+	<style name="math_entity_description_parent">
 		<item name="android:textSize">15dp</item>
 	</style>
 

res/values/strings.xml

@@ -321,4 +321,13 @@ Check the \'Round result\' preference in application settings - it should be tur
 	<string name="c_history_was_removed">History was successfully removed!</string>
 	<string name="c_history_saved">History was successfully saved!</string>
 
+
+	<string name="c_fun_category_trig">Trigonometric</string>
+	<string name="c_fun_category_hyper_trig">Hyperbolic trigonometric</string>
+	<string name="c_fun_category_comparison">Comparison</string>
+	<string name="c_fun_category_common">Common</string>
+
+	<string name="c_var_system">System</string>
+	<string name="c_var_my">My</string>
+
 </resources>

res/values/styles-common-history.xml

@@ -6,10 +6,10 @@
 
 <resources>
 
-	<style name="history_time" parent="var_text"/>
+	<style name="history_time" parent="math_entity_text"/>
 
-	<style name="history_item" parent="var_description"/>
+	<style name="history_item" parent="math_entity_description"/>
-	<style name="history_item_label" parent="var_description">
+	<style name="history_item_label" parent="math_entity_description">
 		<item name="android:textStyle">bold</item>
 		<item name="android:textColor">@android:color/white</item>
 	</style>

res/values/styles-common-var.xml

@@ -7,7 +7,7 @@
 
 <resources>
 
-	<style name="var_text" parent="var_text_parent">
+	<style name="math_entity_text" parent="math_entity_text_parent">
 		<item name="android:paddingTop">6dp</item>
 		<item name="android:paddingLeft">6dp</item>
 		<item name="android:paddingRight">6dp</item>
@@ -16,7 +16,7 @@
 		<item name="android:textColor">@android:color/white</item>
 	</style>
 
-	<style name="var_description" parent="var_description_parent">
+	<style name="math_entity_description" parent="math_entity_description_parent">
 		<item name="android:paddingTop">0dp</item>
 		<item name="android:paddingLeft">6dp</item>
 		<item name="android:paddingRight">6dp</item>

res/values/styles.xml

@@ -44,11 +44,11 @@
 		<item name="android:padding">5dp</item>
 	</style>
 
-	<style name="var_text_parent">
+	<style name="math_entity_text_parent">
 		<item name="android:textSize">20dp</item>
 	</style>
 
-	<style name="var_description_parent">
+	<style name="math_entity_description_parent">
 		<item name="android:textSize">15dp</item>
 	</style>
 

src/main/java/org/solovyev/android/calculator/AbstractMathEntityListActivity.java

@@ -0,0 +1,213 @@
+/*
+ * Copyright (c) 2009-2011. Created by serso aka se.solovyev.
+ * For more information, please, contact se.solovyev@gmail.com
+ * or visit http://se.solovyev.org
+ */
+
+package org.solovyev.android.calculator;
+
+import android.app.Activity;
+import android.app.ListActivity;
+import android.content.Context;
+import android.content.Intent;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.*;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.solovyev.android.calculator.model.AndroidMathRegistry;
+import org.solovyev.common.math.MathEntity;
+import org.solovyev.common.utils.EqualsTool;
+import org.solovyev.common.utils.Filter;
+import org.solovyev.common.utils.FilterRule;
+import org.solovyev.common.utils.StringUtils;
+
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ * User: serso
+ * Date: 12/21/11
+ * Time: 9:24 PM
+ */
+public abstract class AbstractMathEntityListActivity<T extends MathEntity> extends ListActivity {
+
+    public static final String MATH_ENTITY_CATEGORY_EXTRA_STRING = "org.solovyev.android.calculator.CalculatorVarsActivity_math_entity_category";
+
+    @NotNull
+    private MathEntityArrayAdapter<T> adapter;
+    
+    @Nullable
+    private String category;
+
+    static void createTab(@NotNull Context context,
+                          @NotNull TabHost tabHost,
+                          @NotNull String tabId,
+                          @NotNull String categoryId,
+                          int tabCaptionId,
+                          @NotNull Class<? extends Activity> activityClass,
+                          @Nullable Intent parentIntent) {
+
+        TabHost.TabSpec spec;
+
+        final Intent intent;
+        if (parentIntent != null) {
+            intent = new Intent(parentIntent);
+        } else {
+            intent = new Intent();
+        }
+        intent.setClass(context, activityClass);
+        intent.putExtra(MATH_ENTITY_CATEGORY_EXTRA_STRING, categoryId);
+
+        // Initialize a TabSpec for each tab and add it to the TabHost
+        spec = tabHost.newTabSpec(tabId).setIndicator(context.getString(tabCaptionId)).setContent(intent);
+
+        tabHost.addTab(spec);
+    }
+
+    protected int getLayoutId() {
+        return R.layout.math_entities;
+    }
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        setContentView(getLayoutId());
+
+        final Intent intent = getIntent();
+        if ( intent != null ) {
+            category = intent.getStringExtra(MATH_ENTITY_CATEGORY_EXTRA_STRING);
+        }
+
+        final ListView lv = getListView();
+        lv.setTextFilterEnabled(true);
+
+        lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
+            public void onItemClick(final AdapterView<?> parent,
+                                    final View view,
+                                    final int position,
+                                    final long id) {
+
+                CalculatorModel.instance.processDigitButtonAction(((MathEntity) parent.getItemAtPosition(position)).getName(), false);
+
+                AbstractMathEntityListActivity.this.finish();
+            }
+        });
+    }
+
+    @Override
+    protected void onResume() {
+        super.onResume();
+
+        adapter = new MathEntityArrayAdapter<T>(getDescriptionGetter(), this, R.layout.math_entity, R.id.math_entity_text, getMathEntitiesByCategory());
+        setListAdapter(adapter);
+
+        sort();
+    }
+
+    @NotNull
+    private List<T> getMathEntitiesByCategory() {
+        final List<T> result = getMathEntities();
+
+        new Filter<T>(new FilterRule<T>() {
+            @Override
+            public boolean isFiltered(T t) {
+                return !isInCategory(t);
+            }
+        }).filter(result.iterator());
+        
+        return result; 
+    }
+
+    protected boolean isInCategory(@Nullable T t) {
+        return t != null && EqualsTool.areEqual(getMathEntityCategory(t), category);
+    }
+
+    @NotNull
+    protected MathEntityArrayAdapter<T> getAdapter() {
+        return adapter;
+    }
+
+    @NotNull
+    protected abstract MathEntityDescriptionGetter getDescriptionGetter();
+
+    @NotNull
+    protected abstract List<T> getMathEntities();
+    
+    @Nullable
+    protected abstract String getMathEntityCategory(@NotNull T t);
+
+    protected void sort() {
+        AbstractMathEntityListActivity.this.adapter.sort(new Comparator<T>() {
+            @Override
+            public int compare(T function1, T function2) {
+                return function1.getName().compareTo(function2.getName());
+            }
+        });
+
+        AbstractMathEntityListActivity.this.adapter.notifyDataSetChanged();
+    }
+
+    protected static class MathEntityArrayAdapter<T extends MathEntity> extends ArrayAdapter<T> {
+
+        @NotNull
+        private final MathEntityDescriptionGetter descriptionGetter;
+
+        private MathEntityArrayAdapter(@NotNull MathEntityDescriptionGetter descriptionGetter,  @NotNull Context context, int resource, int textViewResourceId, @NotNull List<T> objects) {
+            super(context, resource, textViewResourceId, objects);
+            this.descriptionGetter = descriptionGetter;
+        }
+
+        @Override
+        public View getView(int position, View convertView, ViewGroup parent) {
+            final ViewGroup result = (ViewGroup) super.getView(position, convertView, parent);
+
+            final T mathEntity = getItem(position);
+
+            final String mathEntityDescription = descriptionGetter.getDescription(getContext(), mathEntity.getName());
+            if (!StringUtils.isEmpty(mathEntityDescription)) {
+                TextView description = (TextView) result.findViewById(R.id.math_entity_description);
+                if (description == null) {
+                    final LayoutInflater layoutInflater = (LayoutInflater) getContext().getSystemService(LAYOUT_INFLATER_SERVICE);
+                    final ViewGroup itemView = (ViewGroup) layoutInflater.inflate(R.layout.math_entity, null);
+                    description = (TextView) itemView.findViewById(R.id.math_entity_description);
+                    itemView.removeView(description);
+                    result.addView(description);
+                }
+                description.setText(mathEntityDescription);
+            } else {
+                TextView description = (TextView) result.findViewById(R.id.math_entity_description);
+                if (description != null) {
+                    result.removeView(description);
+                }
+            }
+
+
+            return result;
+        }
+    }
+
+    protected static class MathEntityDescriptionGetterImpl implements MathEntityDescriptionGetter {
+
+        @NotNull
+        private final AndroidMathRegistry<?> mathRegistry;
+
+        public MathEntityDescriptionGetterImpl(@NotNull AndroidMathRegistry<?> mathRegistry) {
+            this.mathRegistry = mathRegistry;
+        }
+
+        @Override
+        public String getDescription(@NotNull Context context, @NotNull String mathEntityName) {
+            return this.mathRegistry.getDescription(context, mathEntityName);
+        }
+    }
+
+    protected static interface MathEntityDescriptionGetter {
+
+        @Nullable
+        String getDescription(@NotNull Context context, @NotNull String mathEntityName);
+    }
+}

src/main/java/org/solovyev/android/calculator/CalculatorActivityLauncher.java

@@ -58,9 +58,9 @@ public class CalculatorActivityLauncher {
 		if (calculatorModel.getDisplay().isValid() ) {
 			final String varValue = calculatorModel.getDisplay().getText().toString();
 			if (!StringUtils.isEmpty(varValue)) {
-				if (CalculatorVarsActivity.isValidValue(varValue)) {
+				if (CalculatorVarsTabActivity.isValidValue(varValue)) {
 					final Intent intent = new Intent(context, CalculatorVarsActivity.class);
-					intent.putExtra(CalculatorVarsActivity.CREATE_VAR_EXTRA_STRING, varValue);
+					intent.putExtra(CalculatorVarsTabActivity.CREATE_VAR_EXTRA_STRING, varValue);
 					context.startActivity(intent);
 				} else {
 					Toast.makeText(context, R.string.c_not_valid_result, Toast.LENGTH_SHORT).show();

src/main/java/org/solovyev/android/calculator/CalculatorFunctionsActivity.java

@@ -6,106 +6,33 @@
 
 package org.solovyev.android.calculator;
 
-import android.app.ListActivity;
+import android.app.TabActivity;
-import android.content.Context;
 import android.os.Bundle;
-import android.view.LayoutInflater;
+import android.widget.TabHost;
-import android.view.View;
+import org.jetbrains.annotations.Nullable;
-import android.view.ViewGroup;
+import org.solovyev.android.calculator.model.AndroidFunctionsMathRegistry;
-import android.widget.*;
+import org.solovyev.android.view.prefs.AndroidUtils;
-import jscl.math.function.Function;
-import org.jetbrains.annotations.NotNull;
-import org.solovyev.android.calculator.model.CalculatorEngine;
-import org.solovyev.android.calculator.model.Var;
-import org.solovyev.common.utils.StringUtils;
-
-import java.util.ArrayList;
-import java.util.Comparator;
-import java.util.List;
 
 /**
  * User: serso
- * Date: 10/29/11
+ * Date: 12/21/11
- * Time: 4:55 PM
+ * Time: 10:33 PM
  */
-public class CalculatorFunctionsActivity extends ListActivity {
+public class CalculatorFunctionsActivity extends TabActivity {
 
-	@NotNull
+    @Override
-	private FunctionsArrayAdapter adapter;
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
 
-	@Override
+        setContentView(R.layout.tabs);
-	protected void onCreate(Bundle savedInstanceState) {
-		super.onCreate(savedInstanceState);
 
-		setContentView(R.layout.functions);
+        final TabHost tabHost = getTabHost();
 
-		adapter = new FunctionsArrayAdapter(this, R.layout.var, R.id.var_text, new ArrayList<Function>(CalculatorEngine.instance.getFunctionsRegistry().getEntities()));
+        for (AndroidFunctionsMathRegistry.Category category : AndroidFunctionsMathRegistry.Category.getCategoriesByTabOrder()) {
-		setListAdapter(adapter);
+            AbstractMathEntityListActivity.createTab(this, tabHost, category.name(), category.name(), category.getCaptionId(), CalculatorFunctionsTabActivity.class, null);
-
+        }
-		final ListView lv = getListView();
-		lv.setTextFilterEnabled(true);
-
-		lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
-			public void onItemClick(final AdapterView<?> parent,
-									final View view,
-									final int position,
-									final long id) {
-
-				CalculatorModel.instance.processDigitButtonAction(((Function) parent.getItemAtPosition(position)).getName(), false);
-
-				CalculatorFunctionsActivity.this.finish();
-			}
-		});
-
-		sort();
-
-	}
-
-	private void sort() {
-		CalculatorFunctionsActivity.this.adapter.sort(new Comparator<Function>() {
-			@Override
-			public int compare(Function function1, Function function2) {
-				return function1.getName().compareTo(function2.getName());
-			}
-		});
-
-		CalculatorFunctionsActivity.this.adapter.notifyDataSetChanged();
-	}
-
-	private class FunctionsArrayAdapter extends ArrayAdapter<Function> {
-
-		private FunctionsArrayAdapter(Context context, int resource, int textViewResourceId, List<Function> objects) {
-			super(context, resource, textViewResourceId, objects);
-		}
-
-		@Override
-		public View getView(int position, View convertView, ViewGroup parent) {
-			final ViewGroup result = (ViewGroup) super.getView(position, convertView, parent);
-
-			final Function function = getItem(position);
-
-			final String functionDescription = CalculatorEngine.instance.getFunctionsRegistry().getDescription(getContext(), function.getName());
-			if (!StringUtils.isEmpty(functionDescription)) {
-				TextView description = (TextView) result.findViewById(R.id.var_description);
-				if (description == null) {
-					final LayoutInflater layoutInflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
-					final ViewGroup itemView = (ViewGroup) layoutInflater.inflate(R.layout.var, null);
-					description = (TextView) itemView.findViewById(R.id.var_description);
-					itemView.removeView(description);
-					result.addView(description);
-				}
-				description.setText(functionDescription);
-			} else {
-				TextView description = (TextView) result.findViewById(R.id.var_description);
-				if (description != null) {
-					result.removeView(description);
-				}
-			}
-
-
-			return result;
-		}
-	}
 
+        AndroidUtils.centerAndWrapTabsFor(tabHost);
+    }
 
 }

src/main/java/org/solovyev/android/calculator/CalculatorFunctionsTabActivity.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2009-2011. Created by serso aka se.solovyev.
+ * For more information, please, contact se.solovyev@gmail.com
+ * or visit http://se.solovyev.org
+ */
+
+package org.solovyev.android.calculator;
+
+import jscl.math.function.Function;
+import org.jetbrains.annotations.NotNull;
+import org.solovyev.android.calculator.model.CalculatorEngine;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * User: serso
+ * Date: 10/29/11
+ * Time: 4:55 PM
+ */
+public class CalculatorFunctionsTabActivity extends AbstractMathEntityListActivity<Function> {
+
+    @NotNull
+    @Override
+    protected MathEntityDescriptionGetter getDescriptionGetter() {
+        return new MathEntityDescriptionGetterImpl(CalculatorEngine.instance.getFunctionsRegistry());
+    }
+
+    @NotNull
+    @Override
+    protected List<Function> getMathEntities() {
+        return new ArrayList<Function>(CalculatorEngine.instance.getFunctionsRegistry().getEntities());
+    }
+
+    @Override
+    protected String getMathEntityCategory(@NotNull Function function) {
+        return CalculatorEngine.instance.getFunctionsRegistry().getCategory(function);
+    }
+}

src/main/java/org/solovyev/android/calculator/CalculatorOperatorsActivity.java

@@ -1,22 +1,12 @@
 package org.solovyev.android.calculator;
 
-import android.app.ListActivity;
 import android.content.Context;
-import android.os.Bundle;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-import android.widget.AdapterView;
-import android.widget.ArrayAdapter;
-import android.widget.ListView;
-import android.widget.TextView;
 import jscl.math.operator.Operator;
 import org.jetbrains.annotations.NotNull;
 import org.solovyev.android.calculator.model.CalculatorEngine;
 import org.solovyev.common.utils.StringUtils;
 
 import java.util.ArrayList;
-import java.util.Comparator;
 import java.util.List;
 
 /**
@@ -25,92 +15,48 @@ import java.util.List;
  * Time: 1:53 PM
  */
 
-public class CalculatorOperatorsActivity extends ListActivity {
+public class CalculatorOperatorsActivity extends AbstractMathEntityListActivity<Operator> {
 
-	@NotNull
+    @NotNull
-	private OperatorsArrayAdapter adapter;
+    @Override
-
+    protected MathEntityDescriptionGetter getDescriptionGetter() {
-	@Override
+        return new OperatorDescriptionGetter();
-	protected void onCreate(Bundle savedInstanceState) {
+    }
-		super.onCreate(savedInstanceState);
-
-		setContentView(R.layout.operators);
-
-		List<Operator> elements = new ArrayList<Operator>();
-		elements.addAll(CalculatorEngine.instance.getOperatorsRegistry().getEntities());
-		elements.addAll(CalculatorEngine.instance.getPostfixFunctionsRegistry().getEntities());
-		adapter = new OperatorsArrayAdapter(this, R.layout.var, R.id.var_text, elements);
-		setListAdapter(adapter);
-
-		final ListView lv = getListView();
-		lv.setTextFilterEnabled(true);
-
-		lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
-			public void onItemClick(final AdapterView<?> parent,
-									final View view,
-									final int position,
-									final long id) {
-
-				CalculatorModel.instance.processDigitButtonAction(((Operator) parent.getItemAtPosition(position)).getName(), false);
-
-				CalculatorOperatorsActivity.this.finish();
-			}
-		});
-
-		sort();
-
-	}
-
-	private void sort() {
-		CalculatorOperatorsActivity.this.adapter.sort(new Comparator<Operator>() {
-			@Override
-			public int compare(Operator operator1, Operator operator2) {
-				return operator1.getName().compareTo(operator2.getName());
-			}
-		});
-
-		CalculatorOperatorsActivity.this.adapter.notifyDataSetChanged();
-	}
-
-	private class OperatorsArrayAdapter extends ArrayAdapter<Operator> {
-
-		private OperatorsArrayAdapter(Context context, int resource, int textViewResourceId, List<Operator> objects) {
-			super(context, resource, textViewResourceId, objects);
-		}
-
-		@Override
-		public View getView(int position, View convertView, ViewGroup parent) {
-			final ViewGroup result = (ViewGroup) super.getView(position, convertView, parent);
-
-			final Operator operator = getItem(position);
-
-			String operatorDescription = CalculatorEngine.instance.getOperatorsRegistry().getDescription(getContext(), operator.getName());
-			if (StringUtils.isEmpty(operatorDescription)) {
-				operatorDescription = CalculatorEngine.instance.getPostfixFunctionsRegistry().getDescription(getContext(), operator.getName());
-			}
-
-			if (!StringUtils.isEmpty(operatorDescription)) {
-				TextView description = (TextView) result.findViewById(R.id.var_description);
-				if (description == null) {
-					final LayoutInflater layoutInflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
-					final ViewGroup itemView = (ViewGroup) layoutInflater.inflate(R.layout.var, null);
-					description = (TextView) itemView.findViewById(R.id.var_description);
-					itemView.removeView(description);
-					result.addView(description);
-				}
-				description.setText(operatorDescription);
-			} else {
-				TextView description = (TextView) result.findViewById(R.id.var_description);
-				if (description != null) {
-					result.removeView(description);
-				}
-			}
 
 
-			return result;
+    @NotNull
-		}
+    @Override
-	}
+    protected List<Operator> getMathEntities() {
+        final List<Operator> result = new ArrayList<Operator>();
 
+        result.addAll(CalculatorEngine.instance.getOperatorsRegistry().getEntities());
+        result.addAll(CalculatorEngine.instance.getPostfixFunctionsRegistry().getEntities());
+
+        return result;
+    }
+
+    @Override
+    protected String getMathEntityCategory(@NotNull Operator operator) {
+        String result = CalculatorEngine.instance.getOperatorsRegistry().getCategory(operator);
+        if (result == null) {
+            result = CalculatorEngine.instance.getPostfixFunctionsRegistry().getCategory(operator);
+        }
+
+        return result;
+    }
+
+    private static class OperatorDescriptionGetter implements MathEntityDescriptionGetter {
+
+        @Override
+        public String getDescription(@NotNull Context context, @NotNull String mathEntityName) {
+            String result = CalculatorEngine.instance.getOperatorsRegistry().getDescription(context, mathEntityName);
+            if (StringUtils.isEmpty(result)) {
+                result = CalculatorEngine.instance.getPostfixFunctionsRegistry().getDescription(context, mathEntityName);
+            }
+
+            return result;
+        }
+    }
 
 }
 

src/main/java/org/solovyev/android/calculator/CalculatorVarsActivity.java

@@ -6,415 +6,38 @@
 
 package org.solovyev.android.calculator;
 
-import android.app.AlertDialog;
+import android.app.TabActivity;
-import android.app.ListActivity;
-import android.content.Context;
-import android.content.DialogInterface;
-import android.content.Intent;
 import android.os.Bundle;
-import android.text.Editable;
+import android.widget.TabHost;
-import android.text.TextWatcher;
-import android.view.*;
-import android.widget.*;
-import jscl.text.Identifier;
-import jscl.text.MutableInt;
-import jscl.text.ParseException;
-import jscl.text.Parser;
-import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
-import org.solovyev.android.calculator.math.MathType;
 import org.solovyev.android.calculator.model.AndroidVarsRegistry;
-import org.solovyev.android.calculator.model.CalculatorEngine;
+import org.solovyev.android.view.prefs.AndroidUtils;
-import org.solovyev.android.calculator.model.Var;
-import org.solovyev.common.utils.CollectionsUtils;
-import org.solovyev.common.utils.Finder;
-import org.solovyev.common.utils.StringUtils;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Comparator;
-import java.util.List;
 
 /**
  * User: serso
- * Date: 9/28/11
+ * Date: 12/21/11
- * Time: 10:55 PM
+ * Time: 11:05 PM
  */
-public class CalculatorVarsActivity extends ListActivity {
+public class CalculatorVarsActivity extends TabActivity {
 
-	public static final String CREATE_VAR_EXTRA_STRING = "org.solovyev.android.calculator.CalculatorVarsActivity_create_var";
+    @Override
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
 
-	private final static List<Character> acceptableChars = Arrays.asList(StringUtils.toObject("1234567890abcdefghijklmnopqrstuvwxyzйцукенгшщзхъфывапролджэячсмитьбюё_".toCharArray()));
+        setContentView(R.layout.tabs);
 
-	@NotNull
+        final TabHost tabHost = getTabHost();
-	private VarsArrayAdapter adapter;
 
-	@Override
+        for (AndroidVarsRegistry.Category category : AndroidVarsRegistry.Category.getCategoriesByTabOrder()) {
-	protected void onCreate(Bundle savedInstanceState) {
+            if (category == AndroidVarsRegistry.Category.my) {
-		super.onCreate(savedInstanceState);
+                AbstractMathEntityListActivity.createTab(this, tabHost, category.name(), category.name(), category.getCaptionId(), CalculatorVarsTabActivity.class, getIntent());
+            } else {
+                AbstractMathEntityListActivity.createTab(this, tabHost, category.name(), category.name(), category.getCaptionId(), CalculatorVarsTabActivity.class, null);
+            }
+        }
 
-		setContentView(R.layout.vars);
+        tabHost.setCurrentTab(0);
+        AndroidUtils.centerAndWrapTabsFor(tabHost);
+    }
 
-		final List<Var> vars = new ArrayList<Var>(CalculatorEngine.instance.getVarsRegister().getEntities());
-		CollectionsUtils.removeAll(vars, new Finder<Var>() {
-			@Override
-			public boolean isFound(@Nullable Var var) {
-				return var != null && CollectionsUtils.contains(var.getName(), MathType.INFINITY_JSCL, MathType.NAN);
-			}
-		});
-		adapter = new VarsArrayAdapter(this, R.layout.var, R.id.var_text, vars);
-		setListAdapter(adapter);
-
-		final ListView lv = getListView();
-		lv.setTextFilterEnabled(true);
-
-
-		lv.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
-			@Override
-			public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
-				final Var var = (Var) parent.getItemAtPosition(position);
-				createEditVariableDialog(var, var.getName(), StringUtils.getNotEmpty(var.getValue(), ""), var.getDescription());
-				return true;
-			}
-		});
-
-		lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
-			public void onItemClick(final AdapterView<?> parent,
-									final View view,
-									final int position,
-									final long id) {
-
-				CalculatorModel.instance.doTextOperation(new CalculatorModel.TextOperation() {
-					@Override
-					public void doOperation(@NotNull EditText editor) {
-						editor.getText().insert(editor.getSelectionStart(), ((Var) parent.getItemAtPosition(position)).getName());
-					}
-				}, false);
-
-				CalculatorVarsActivity.this.finish();
-			}
-		});
-
-		sort();
-
-		final Intent intent = getIntent();
-		if ( intent != null ) {
-			final String varValue = intent.getStringExtra(CREATE_VAR_EXTRA_STRING);
-			if (!StringUtils.isEmpty(varValue)) {
-				createEditVariableDialog(null, null, varValue, null);
-			}
-		}
-
-	}
-
-	@SuppressWarnings({"UnusedDeclaration"})
-	public void addVarButtonClickHandler(@NotNull View v) {
-		createEditVariableDialog(null, null, null, null);
-	}
-
-
-	private void createEditVariableDialog(@Nullable final Var var, @Nullable final String name, @Nullable final String value, @Nullable final String description) {
-		if (var == null || !var.isSystem()) {
-
-			final LayoutInflater layoutInflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
-			final View editView = layoutInflater.inflate(R.layout.var_edit, null);
-
-			final String errorMsg = CalculatorVarsActivity.this.getString(R.string.c_char_is_not_accepted);
-
-			final EditText editName = (EditText) editView.findViewById(R.id.var_edit_name);
-			editName.setText(name);
-			editName.addTextChangedListener(new TextWatcher() {
-
-				@Override
-				public void beforeTextChanged(CharSequence s, int start, int count, int after) {
-				}
-
-				@Override
-				public void onTextChanged(CharSequence s, int start, int before, int count) {
-				}
-
-				@Override
-				public void afterTextChanged(Editable s) {
-					for ( int i = 0; i < s.length(); i++ ) {
-						char c = s.charAt(i);
-						if (!acceptableChars.contains(c)) {
-							s.delete(i, i+1);
-							Toast.makeText(CalculatorVarsActivity.this, String.format(errorMsg, c), Toast.LENGTH_SHORT).show();
-						}
-					}
-				}
-			});
-
-			final EditText editValue = (EditText) editView.findViewById(R.id.var_edit_value);
-			if (!StringUtils.isEmpty(value)) {
-				editValue.setText(value);
-			}
-
-			final EditText editDescription = (EditText) editView.findViewById(R.id.var_edit_description);
-			editDescription.setText(description);
-
-			final Var.Builder varBuilder;
-			if (var != null) {
-				varBuilder = new Var.Builder(var);
-			} else {
-				varBuilder = new Var.Builder();
-			}
-
-			final AlertDialog.Builder builder = new AlertDialog.Builder(this)
-					.setCancelable(true)
-					.setNegativeButton(R.string.c_cancel, null)
-					.setPositiveButton(R.string.c_save, new VarEditorSaver(varBuilder, var, editView))
-					.setView(editView);
-
-			if ( var != null ) {
-				// EDIT mode
-
-				builder.setTitle(R.string.c_var_edit_var);
-				builder.setNeutralButton(R.string.c_remove, new VarEditorRemover(var, new DialogInterface.OnClickListener() {
-					@Override
-					public void onClick(DialogInterface dialog, int which) {
-						createEditVariableDialog(var, name, value, description);
-					}
-				}));
-			} else {
-				// CREATE mode
-
-				builder.setTitle(R.string.c_var_create_var);
-			}
-
-			builder.create().show();
-		} else {
-			Toast.makeText(this, getString(R.string.c_sys_var_cannot_be_changed), Toast.LENGTH_LONG).show();
-		}
-	}
-
-	private class VarEditorSaver implements DialogInterface.OnClickListener {
-
-		@NotNull
-		private Var.Builder varBuilder;
-
-		@Nullable
-		private final Var editedInstance;
-
-		@NotNull
-		private View editView;
-
-		public VarEditorSaver(@NotNull Var.Builder varBuilder, @Nullable Var editedInstance, @NotNull View editView) {
-			this.varBuilder = varBuilder;
-			this.editedInstance = editedInstance;
-			this.editView = editView;
-		}
-
-		@Override
-		public void onClick(DialogInterface dialog, int which) {
-			if (which == DialogInterface.BUTTON_POSITIVE) {
-				final Integer error;
-
-				final EditText editName = (EditText) editView.findViewById(R.id.var_edit_name);
-				String name = editName.getText().toString();
-
-				final EditText editValue = (EditText) editView.findViewById(R.id.var_edit_value);
-				String value = editValue.getText().toString();
-
-				final EditText editDescription = (EditText) editView.findViewById(R.id.var_edit_description);
-				String description = editDescription.getText().toString();
-
-
-				final AndroidVarsRegistry varsRegistry = CalculatorEngine.instance.getVarsRegister();
-				if (isValidName(name)) {
-
-					boolean canBeSaved = false;
-
-					final Var varFromRegister = varsRegistry.get(name);
-					if ( varFromRegister == null ) {
-						canBeSaved = true;
-					} else if ( editedInstance != null && varFromRegister.getId().equals(editedInstance.getId()) ) {
-						canBeSaved = true;
-					}
-
-					if (canBeSaved) {
-						final MathType.Result mathType = MathType.getType(name, 0, false);
-
-						if (mathType.getMathType() == MathType.text || mathType.getMathType() == MathType.constant) {
-
-							if (StringUtils.isEmpty(value)) {
-								// value is empty => undefined variable
-								varBuilder.setName(name);
-								varBuilder.setDescription(description);
-								varBuilder.setValue(null);
-								error = null;
-							} else {
-								// value is not empty => must be a number
-								boolean valid = isValidValue(value);
-
-								if (valid) {
-									varBuilder.setName(name);
-									varBuilder.setDescription(description);
-									varBuilder.setValue(value);
-									error = null;
-								} else {
-									error = R.string.c_value_is_not_a_number;
-								}
-							}
-						} else {
-							error = R.string.c_var_name_clashes;
-						}
-					} else {
-						error = R.string.c_var_already_exists;
-					}
-				} else {
-					error = R.string.c_name_is_not_valid;
-				}
-
-				if (error != null) {
-					Toast.makeText(CalculatorVarsActivity.this, getString(error), Toast.LENGTH_LONG).show();
-					createEditVariableDialog(editedInstance, name, value, description);
-				} else {
-					if ( editedInstance == null ) {
-						CalculatorVarsActivity.this.adapter.add(varsRegistry.add(varBuilder));
-					} else {
-						final Var newInstance = varsRegistry.add(varBuilder);
-						CalculatorVarsActivity.this.adapter.remove(editedInstance);
-						CalculatorVarsActivity.this.adapter.add(newInstance);
-					}
-
-					varsRegistry.save(CalculatorVarsActivity.this);
-
-					sort();
-				}
-			}
-		}
-	}
-
-	private void sort() {
-		CalculatorVarsActivity.this.adapter.sort(new Comparator<Var>() {
-			@Override
-			public int compare(Var var, Var var1) {
-				return var.getName().compareTo(var1.getName());
-			}
-		});
-
-		CalculatorVarsActivity.this.adapter.notifyDataSetChanged();
-	}
-
-	private static boolean isValidName(@Nullable String name) {
-		boolean result = false;
-
-		if (!StringUtils.isEmpty(name)) {
-			try {
-				Identifier.parser.parse(Parser.Parameters.newInstance(name, new MutableInt(0), CalculatorEngine.instance.getEngine()), null);
-				result = true;
-			} catch (ParseException e) {
-				// not valid name;
-			}
-		}
-
-		return result;
-	}
-
-	public static boolean isValidValue(@NotNull String value) {
-		// now every string might be constant
-		return true;
-	}
-
-	private class VarsArrayAdapter extends ArrayAdapter<Var> {
-
-		private VarsArrayAdapter(Context context, int resource, int textViewResourceId, List<Var> objects) {
-			super(context, resource, textViewResourceId, objects);
-		}
-
-		@Override
-		public View getView(int position, View convertView, ViewGroup parent) {
-			final ViewGroup result = (ViewGroup) super.getView(position, convertView, parent);
-
-			final Var var = getItem(position);
-
-			if (!StringUtils.isEmpty(var.getDescription())) {
-				TextView description = (TextView) result.findViewById(R.id.var_description);
-				if (description == null) {
-					final LayoutInflater layoutInflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
-					final ViewGroup itemView = (ViewGroup) layoutInflater.inflate(R.layout.var, null);
-					description = (TextView) itemView.findViewById(R.id.var_description);
-					itemView.removeView(description);
-					result.addView(description);
-				}
-				description.setText(var.getDescription());
-			} else {
-				TextView description = (TextView) result.findViewById(R.id.var_description);
-				if (description != null) {
-					result.removeView(description);
-				}
-			}
-
-
-			return result;
-		}
-	}
-
-	@Override
-	public boolean onCreateOptionsMenu(Menu menu) {
-		final MenuInflater menuInflater = getMenuInflater();
-		menuInflater.inflate(R.menu.var_menu, menu);
-		return true;
-	}
-
-	@Override
-	public boolean onOptionsItemSelected(MenuItem item) {
-		boolean result;
-
-		switch (item.getItemId()) {
-			case R.id.var_menu_add_var:
-				createEditVariableDialog(null, null, null, null);
-				result = true;
-				break;
-			default:
-				result = super.onOptionsItemSelected(item);
-		}
-
-		return result;
-	}
-
-	private class VarEditorRemover implements DialogInterface.OnClickListener {
-
-		@NotNull
-		private final Var var;
-
-		@Nullable
-		private final DialogInterface.OnClickListener callbackOnCancel;
-
-		private final boolean confirmed;
-
-		public VarEditorRemover(@NotNull Var var, @Nullable DialogInterface.OnClickListener callbackOnCancel) {
-			this(var, callbackOnCancel, false);
-		}
-
-		public VarEditorRemover(@NotNull Var var, @Nullable DialogInterface.OnClickListener callbackOnCancel, boolean confirmed) {
-			this.var = var;
-			this.callbackOnCancel = callbackOnCancel;
-			this.confirmed = confirmed;
-		}
-
-		@Override
-		public void onClick(DialogInterface dialog, int which) {
-			if (!confirmed) {
-				final TextView question = new TextView(CalculatorVarsActivity.this);
-				question.setText(String.format(getString(R.string.c_var_removal_confirmation_question), var.getName()));
-				question.setPadding(6, 6, 6, 6);
-				final AlertDialog.Builder builder = new AlertDialog.Builder(CalculatorVarsActivity.this)
-						.setCancelable(true)
-						.setView(question)
-						.setTitle(R.string.c_var_removal_confirmation)
-						.setNegativeButton(R.string.c_no, callbackOnCancel)
-						.setPositiveButton(R.string.c_yes, new VarEditorRemover(var, callbackOnCancel, true));
-
-				builder.create().show();
-			} else {
-				adapter.remove(var);
-				final AndroidVarsRegistry varsRegistry = CalculatorEngine.instance.getVarsRegister();
-				varsRegistry.remove(var);
-				varsRegistry.save(CalculatorVarsActivity.this);
-				CalculatorVarsActivity.this.adapter.notifyDataSetChanged();
-			}
-		}
-	}
 }

src/main/java/org/solovyev/android/calculator/CalculatorVarsTabActivity.java

@@ -0,0 +1,375 @@
+/*
+ * Copyright (c) 2009-2011. Created by serso aka se.solovyev.
+ * For more information, please, contact se.solovyev@gmail.com
+ * or visit http://se.solovyev.org
+ */
+
+package org.solovyev.android.calculator;
+
+import android.app.AlertDialog;
+import android.content.DialogInterface;
+import android.content.Intent;
+import android.os.Bundle;
+import android.text.Editable;
+import android.text.TextWatcher;
+import android.view.*;
+import android.widget.AdapterView;
+import android.widget.EditText;
+import android.widget.TextView;
+import android.widget.Toast;
+import jscl.text.Identifier;
+import jscl.text.MutableInt;
+import jscl.text.ParseException;
+import jscl.text.Parser;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.solovyev.android.calculator.math.MathType;
+import org.solovyev.android.calculator.model.AndroidVarsRegistry;
+import org.solovyev.android.calculator.model.CalculatorEngine;
+import org.solovyev.android.calculator.model.Var;
+import org.solovyev.common.utils.CollectionsUtils;
+import org.solovyev.common.utils.Finder;
+import org.solovyev.common.utils.StringUtils;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * User: serso
+ * Date: 9/28/11
+ * Time: 10:55 PM
+ */
+public class CalculatorVarsTabActivity extends AbstractMathEntityListActivity<Var> {
+
+	public static final String CREATE_VAR_EXTRA_STRING = "org.solovyev.android.calculator.CalculatorVarsActivity_create_var";
+
+	private final static List<Character> acceptableChars = Arrays.asList(StringUtils.toObject("1234567890abcdefghijklmnopqrstuvwxyzйцукенгшщзхъфывапролджэячсмитьбюё_".toCharArray()));
+
+    @Override
+    protected int getLayoutId() {
+        return R.layout.vars;
+    }
+
+    @Override
+	protected void onCreate(Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+
+		getListView().setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
+            @Override
+            public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
+                final Var var = (Var) parent.getItemAtPosition(position);
+                createEditVariableDialog(var, var.getName(), StringUtils.getNotEmpty(var.getValue(), ""), var.getDescription());
+                return true;
+            }
+        });
+
+		final Intent intent = getIntent();
+		if ( intent != null ) {
+			final String varValue = intent.getStringExtra(CREATE_VAR_EXTRA_STRING);
+			if (!StringUtils.isEmpty(varValue)) {
+				createEditVariableDialog(null, null, varValue, null);
+
+                // in order to stop intent for other tabs
+                intent.removeExtra(CREATE_VAR_EXTRA_STRING);
+			}
+		}
+	}
+
+    @NotNull
+    @Override
+    protected MathEntityDescriptionGetter getDescriptionGetter() {
+        return new MathEntityDescriptionGetterImpl(CalculatorEngine.instance.getVarsRegister());
+    }
+
+    @SuppressWarnings({"UnusedDeclaration"})
+	public void addVarButtonClickHandler(@NotNull View v) {
+		createEditVariableDialog(null, null, null, null);
+	}
+
+    @NotNull
+    @Override
+    protected List<Var> getMathEntities() {
+        final List<Var> result = new ArrayList<Var>(CalculatorEngine.instance.getVarsRegister().getEntities());
+
+        CollectionsUtils.removeAll(result, new Finder<Var>() {
+            @Override
+            public boolean isFound(@Nullable Var var) {
+                return var != null && CollectionsUtils.contains(var.getName(), MathType.INFINITY_JSCL, MathType.NAN);
+            }
+        });
+
+        return result;
+    }
+
+    @Override
+    protected String getMathEntityCategory(@NotNull Var var) {
+        return CalculatorEngine.instance.getVarsRegister().getCategory(var);
+    }
+
+    private void createEditVariableDialog(@Nullable final Var var, @Nullable final String name, @Nullable final String value, @Nullable final String description) {
+		if (var == null || !var.isSystem()) {
+
+			final LayoutInflater layoutInflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
+			final View editView = layoutInflater.inflate(R.layout.var_edit, null);
+
+			final String errorMsg = CalculatorVarsTabActivity.this.getString(R.string.c_char_is_not_accepted);
+
+			final EditText editName = (EditText) editView.findViewById(R.id.var_edit_name);
+			editName.setText(name);
+			editName.addTextChangedListener(new TextWatcher() {
+
+				@Override
+				public void beforeTextChanged(CharSequence s, int start, int count, int after) {
+				}
+
+				@Override
+				public void onTextChanged(CharSequence s, int start, int before, int count) {
+				}
+
+				@Override
+				public void afterTextChanged(Editable s) {
+					for ( int i = 0; i < s.length(); i++ ) {
+						char c = s.charAt(i);
+						if (!acceptableChars.contains(c)) {
+							s.delete(i, i+1);
+							Toast.makeText(CalculatorVarsTabActivity.this, String.format(errorMsg, c), Toast.LENGTH_SHORT).show();
+						}
+					}
+				}
+			});
+
+			final EditText editValue = (EditText) editView.findViewById(R.id.var_edit_value);
+			if (!StringUtils.isEmpty(value)) {
+				editValue.setText(value);
+			}
+
+			final EditText editDescription = (EditText) editView.findViewById(R.id.var_edit_description);
+			editDescription.setText(description);
+
+			final Var.Builder varBuilder;
+			if (var != null) {
+				varBuilder = new Var.Builder(var);
+			} else {
+				varBuilder = new Var.Builder();
+			}
+
+			final AlertDialog.Builder builder = new AlertDialog.Builder(this)
+					.setCancelable(true)
+					.setNegativeButton(R.string.c_cancel, null)
+					.setPositiveButton(R.string.c_save, new VarEditorSaver(varBuilder, var, editView))
+					.setView(editView);
+
+			if ( var != null ) {
+				// EDIT mode
+
+				builder.setTitle(R.string.c_var_edit_var);
+				builder.setNeutralButton(R.string.c_remove, new VarEditorRemover(var, new DialogInterface.OnClickListener() {
+					@Override
+					public void onClick(DialogInterface dialog, int which) {
+						createEditVariableDialog(var, name, value, description);
+					}
+				}));
+			} else {
+				// CREATE mode
+
+				builder.setTitle(R.string.c_var_create_var);
+			}
+
+			builder.create().show();
+		} else {
+			Toast.makeText(this, getString(R.string.c_sys_var_cannot_be_changed), Toast.LENGTH_LONG).show();
+		}
+	}
+
+	private class VarEditorSaver implements DialogInterface.OnClickListener {
+
+		@NotNull
+		private Var.Builder varBuilder;
+
+		@Nullable
+		private final Var editedInstance;
+
+		@NotNull
+		private View editView;
+
+		public VarEditorSaver(@NotNull Var.Builder varBuilder, @Nullable Var editedInstance, @NotNull View editView) {
+			this.varBuilder = varBuilder;
+			this.editedInstance = editedInstance;
+			this.editView = editView;
+		}
+
+		@Override
+		public void onClick(DialogInterface dialog, int which) {
+			if (which == DialogInterface.BUTTON_POSITIVE) {
+				final Integer error;
+
+				final EditText editName = (EditText) editView.findViewById(R.id.var_edit_name);
+				String name = editName.getText().toString();
+
+				final EditText editValue = (EditText) editView.findViewById(R.id.var_edit_value);
+				String value = editValue.getText().toString();
+
+				final EditText editDescription = (EditText) editView.findViewById(R.id.var_edit_description);
+				String description = editDescription.getText().toString();
+
+
+				final AndroidVarsRegistry varsRegistry = CalculatorEngine.instance.getVarsRegister();
+				if (isValidName(name)) {
+
+					boolean canBeSaved = false;
+
+					final Var varFromRegister = varsRegistry.get(name);
+					if ( varFromRegister == null ) {
+						canBeSaved = true;
+					} else if ( editedInstance != null && varFromRegister.getId().equals(editedInstance.getId()) ) {
+						canBeSaved = true;
+					}
+
+					if (canBeSaved) {
+						final MathType.Result mathType = MathType.getType(name, 0, false);
+
+						if (mathType.getMathType() == MathType.text || mathType.getMathType() == MathType.constant) {
+
+							if (StringUtils.isEmpty(value)) {
+								// value is empty => undefined variable
+								varBuilder.setName(name);
+								varBuilder.setDescription(description);
+								varBuilder.setValue(null);
+								error = null;
+							} else {
+								// value is not empty => must be a number
+								boolean valid = isValidValue(value);
+
+								if (valid) {
+									varBuilder.setName(name);
+									varBuilder.setDescription(description);
+									varBuilder.setValue(value);
+									error = null;
+								} else {
+									error = R.string.c_value_is_not_a_number;
+								}
+							}
+						} else {
+							error = R.string.c_var_name_clashes;
+						}
+					} else {
+						error = R.string.c_var_already_exists;
+					}
+				} else {
+					error = R.string.c_name_is_not_valid;
+				}
+
+				if (error != null) {
+					Toast.makeText(CalculatorVarsTabActivity.this, getString(error), Toast.LENGTH_LONG).show();
+					createEditVariableDialog(editedInstance, name, value, description);
+				} else {
+                    final Var addedVar = varsRegistry.add(varBuilder);
+	                if (isInCategory(addedVar)) {
+                        if ( editedInstance != null ) {
+                            CalculatorVarsTabActivity.this.getAdapter().remove(editedInstance);
+                        }
+                        CalculatorVarsTabActivity.this.getAdapter().add(addedVar);
+                    }
+
+					varsRegistry.save(CalculatorVarsTabActivity.this);
+
+                    if (isInCategory(addedVar)) {
+                        sort();
+                    }
+                }
+			}
+		}
+	}
+
+	private static boolean isValidName(@Nullable String name) {
+		boolean result = false;
+
+		if (!StringUtils.isEmpty(name)) {
+			try {
+				Identifier.parser.parse(Parser.Parameters.newInstance(name, new MutableInt(0), CalculatorEngine.instance.getEngine()), null);
+				result = true;
+			} catch (ParseException e) {
+				// not valid name;
+			}
+		}
+
+		return result;
+	}
+
+	public static boolean isValidValue(@NotNull String value) {
+		// now every string might be constant
+		return true;
+	}
+
+	@Override
+	public boolean onCreateOptionsMenu(Menu menu) {
+		final MenuInflater menuInflater = getMenuInflater();
+		menuInflater.inflate(R.menu.var_menu, menu);
+		return true;
+	}
+
+	@Override
+	public boolean onOptionsItemSelected(MenuItem item) {
+		boolean result;
+
+		switch (item.getItemId()) {
+			case R.id.var_menu_add_var:
+				createEditVariableDialog(null, null, null, null);
+				result = true;
+				break;
+			default:
+				result = super.onOptionsItemSelected(item);
+		}
+
+		return result;
+	}
+
+	private class VarEditorRemover implements DialogInterface.OnClickListener {
+
+		@NotNull
+		private final Var var;
+
+		@Nullable
+		private final DialogInterface.OnClickListener callbackOnCancel;
+
+		private final boolean confirmed;
+
+		public VarEditorRemover(@NotNull Var var, @Nullable DialogInterface.OnClickListener callbackOnCancel) {
+			this(var, callbackOnCancel, false);
+		}
+
+		public VarEditorRemover(@NotNull Var var, @Nullable DialogInterface.OnClickListener callbackOnCancel, boolean confirmed) {
+			this.var = var;
+			this.callbackOnCancel = callbackOnCancel;
+			this.confirmed = confirmed;
+		}
+
+		@Override
+		public void onClick(DialogInterface dialog, int which) {
+			if (!confirmed) {
+				final TextView question = new TextView(CalculatorVarsTabActivity.this);
+				question.setText(String.format(getString(R.string.c_var_removal_confirmation_question), var.getName()));
+				question.setPadding(6, 6, 6, 6);
+				final AlertDialog.Builder builder = new AlertDialog.Builder(CalculatorVarsTabActivity.this)
+						.setCancelable(true)
+						.setView(question)
+						.setTitle(R.string.c_var_removal_confirmation)
+						.setNegativeButton(R.string.c_no, callbackOnCancel)
+						.setPositiveButton(R.string.c_yes, new VarEditorRemover(var, callbackOnCancel, true));
+
+				builder.create().show();
+			} else {
+                if (isInCategory(var)) {
+                    getAdapter().remove(var);
+                }
+                final AndroidVarsRegistry varsRegistry = CalculatorEngine.instance.getVarsRegister();
+				varsRegistry.remove(var);
+				varsRegistry.save(CalculatorVarsTabActivity.this);
+                if (isInCategory(var)) {
+                    CalculatorVarsTabActivity.this.getAdapter().notifyDataSetChanged();
+                }
+            }
+		}
+	}
+}

src/main/java/org/solovyev/android/calculator/history/CalculatorHistoryActivity.java

@@ -14,6 +14,7 @@ import android.widget.TabHost;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.solovyev.android.calculator.R;
+import org.solovyev.android.view.prefs.AndroidUtils;
 
 /**
  * User: serso
@@ -26,7 +27,7 @@ public class CalculatorHistoryActivity extends TabActivity {
 	public void onCreate(@Nullable Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
-		setContentView(R.layout.history_tabs);
+		setContentView(R.layout.tabs);
 
 		final TabHost tabHost = getTabHost();
 
@@ -34,6 +35,8 @@ public class CalculatorHistoryActivity extends TabActivity {
 		createTab(tabHost, "history", R.string.c_history, HistoryActivityTab.class);
 
 		tabHost.setCurrentTab(0);
+
+        AndroidUtils.centerAndWrapTabsFor(tabHost);
 	}
 
 	private void createTab(@NotNull TabHost tabHost,
@@ -46,7 +49,7 @@ public class CalculatorHistoryActivity extends TabActivity {
 		final Intent intent = new Intent().setClass(this, activityClass);
 
 		// Initialize a TabSpec for each tab and add it to the TabHost
-		spec = tabHost.newTabSpec(tabId).setIndicator(getString(tabCaptionId)).setContent(intent);
+		spec = tabHost.newTabSpec(tabId).setIndicator(this.getString(tabCaptionId)).setContent(intent);
 
 		tabHost.addTab(spec);
 	}

src/main/java/org/solovyev/android/calculator/model/AndroidFunctionsMathRegistry.java

@@ -6,11 +6,16 @@
 
 package org.solovyev.android.calculator.model;
 
+import jscl.math.function.ArcTrigonometric;
+import jscl.math.function.Comparison;
+import jscl.math.function.Function;
+import jscl.math.function.Trigonometric;
 import org.jetbrains.annotations.NotNull;
+import org.solovyev.android.calculator.R;
 import org.solovyev.common.math.MathRegistry;
+import org.solovyev.common.utils.CollectionsUtils;
 
-import java.util.HashMap;
+import java.util.*;
-import java.util.Map;
 
 /**
  * User: serso
@@ -19,6 +24,77 @@ import java.util.Map;
  */
 public class AndroidFunctionsMathRegistry extends AndroidMathRegistryImpl<jscl.math.function.Function> {
 
+    public static enum Category {
+
+        trigonometric(R.string.c_fun_category_trig, 100){
+            @Override
+            boolean isInCategory(@NotNull Function function) {
+                return (function instanceof Trigonometric || function instanceof ArcTrigonometric) && !hyperbolic_trigonometric.isInCategory(function);
+            }
+        },
+        
+        hyperbolic_trigonometric(R.string.c_fun_category_hyper_trig, 300) {
+
+            private final List<String> names = Arrays.asList("sinh", "cosh", "tanh", "coth", "asinh", "acosh", "atanh", "acoth");
+            
+            @Override
+            boolean isInCategory(@NotNull Function function) {
+                return names.contains(function.getName());
+            }
+        },
+        
+        comparison(R.string.c_fun_category_comparison, 200) {
+            @Override
+            boolean isInCategory(@NotNull Function function) {
+                return function instanceof Comparison;
+            }
+        },
+        
+        common(R.string.c_fun_category_common, 0) {
+            @Override
+            boolean isInCategory(@NotNull Function function) {
+                for (Category category : values()) {
+                    if ( category != this ) {
+                        if ( category.isInCategory(function) ) {
+                            return false;
+                        }
+                    }
+                }
+                
+                return true;
+            }
+        };
+
+        private final int captionId;
+        
+        private final int tabOrder;
+
+        Category(int captionId, int tabOrder) {
+            this.captionId = captionId;
+            this.tabOrder = tabOrder;
+        }
+
+        public int getCaptionId() {
+            return captionId;
+        }
+        
+        abstract boolean isInCategory(@NotNull Function function);
+        
+        @NotNull
+        public static List<Category> getCategoriesByTabOrder() {
+            final List<Category> result = CollectionsUtils.asList(Category.values());
+
+            Collections.sort(result, new Comparator<Category>() {
+                @Override
+                public int compare(Category category, Category category1) {
+                    return category.tabOrder - category1.tabOrder;
+                }
+            });
+
+            return result;
+        }
+    }
+
 	@NotNull
 	private static final Map<String, String> substitutes = new HashMap<String, String>();
 	static {
@@ -37,4 +113,15 @@ public class AndroidFunctionsMathRegistry extends AndroidMathRegistryImpl<jscl.m
 	protected Map<String, String> getSubstitutes() {
 		return substitutes;
 	}
+
+    @Override
+    public String getCategory(@NotNull Function function) {
+        for (Category category : Category.values()) {
+            if ( category.isInCategory(function) ) {
+                return category.name();
+            }
+        }
+        
+        return null;
+    }
 }

src/main/java/org/solovyev/android/calculator/model/AndroidMathRegistry.java

@@ -7,7 +7,6 @@
 package org.solovyev.android.calculator.model;
 
 import android.content.Context;
-import jscl.math.function.Function;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.solovyev.common.math.MathEntity;
@@ -21,5 +20,8 @@ import org.solovyev.common.math.MathRegistry;
 public interface AndroidMathRegistry<T extends MathEntity> extends MathRegistry<T> {
 
 	@Nullable
-	String getDescription(@NotNull Context context, @NotNull String functionName);
+	String getDescription(@NotNull Context context, @NotNull String mathEntityName);
+
+    @Nullable
+    String getCategory(@NotNull T mathEntity);
 }

src/main/java/org/solovyev/android/calculator/model/AndroidMathRegistryImpl.java

@@ -40,13 +40,13 @@ public abstract class AndroidMathRegistryImpl<T extends MathEntity> implements A
 
 	@Nullable
 	@Override
-	public String getDescription(@NotNull Context context, @NotNull String name) {
+	public String getDescription(@NotNull Context context, @NotNull String mathEntityName) {
 		final String stringName;
 
 		final Map<String, String> substitutes = getSubstitutes();
-		final String substitute = substitutes.get(name);
+		final String substitute = substitutes.get(mathEntityName);
 		if (substitute == null) {
-			stringName = prefix + name;
+			stringName = prefix + mathEntityName;
 		} else {
 			stringName = prefix + substitute;
 		}

src/main/java/org/solovyev/android/calculator/model/AndroidOperatorsMathRegistry.java

@@ -43,4 +43,9 @@ public class AndroidOperatorsMathRegistry extends AndroidMathRegistryImpl<Operat
 	protected Map<String, String> getSubstitutes() {
 		return substitutes;
 	}
+
+    @Override
+    public String getCategory(@NotNull Operator mathEntity) {
+        return null;
+    }
 }

src/main/java/org/solovyev/android/calculator/model/AndroidPostfixFunctionsRegistry.java

@@ -42,4 +42,9 @@ public class AndroidPostfixFunctionsRegistry extends AndroidMathRegistryImpl<Ope
 	protected Map<String, String> getSubstitutes() {
 		return substitutes;
 	}
+
+    @Override
+    public String getCategory(@NotNull Operator mathEntity) {
+        return null;
+    }
 }

src/main/java/org/solovyev/android/calculator/model/AndroidVarsRegistry.java

@@ -10,14 +10,65 @@ import android.content.Context;
 import android.content.SharedPreferences;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
-import org.solovyev.common.math.MathRegistry;
+import org.solovyev.android.calculator.R;
+import org.solovyev.common.utils.CollectionsUtils;
+
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
 
 /**
  * User: serso
  * Date: 10/6/11
  * Time: 9:31 PM
  */
-public interface AndroidVarsRegistry extends MathRegistry<Var>{
+public interface AndroidVarsRegistry extends AndroidMathRegistry<Var>{
+
+    public static enum Category {
+
+        system(R.string.c_var_system, 100){
+            @Override
+            boolean isInCategory(@NotNull Var var) {
+                return var.isSystem();
+            }
+        },
+
+        my(R.string.c_var_my, 0) {
+            @Override
+            boolean isInCategory(@NotNull Var var) {
+                return !var.isSystem();
+            }
+        };
+
+        private final int captionId;
+
+        private final int tabOrder;
+
+        Category(int captionId, int tabOrder) {
+            this.captionId = captionId;
+            this.tabOrder = tabOrder;
+        }
+
+        public int getCaptionId() {
+            return captionId;
+        }
+
+        abstract boolean isInCategory(@NotNull Var var);
+
+        @NotNull
+        public static List<Category> getCategoriesByTabOrder() {
+            final List<Category> result = CollectionsUtils.asList(Category.values());
+
+            Collections.sort(result, new Comparator<Category>() {
+                @Override
+                public int compare(Category category, Category category1) {
+                    return category.tabOrder - category1.tabOrder;
+                }
+            });
+
+            return result;
+        }
+    }
 
 	void load(@Nullable Context context, @Nullable SharedPreferences preferences);
 

src/main/java/org/solovyev/android/calculator/model/AndroidVarsRegistryImpl.java

@@ -234,4 +234,25 @@ class AndroidVarsRegistryImpl implements AndroidVarsRegistry {
 			return null;
 		}
 	}
+
+    @Override
+    public String getDescription(@NotNull Context context, @NotNull String mathEntityName) {
+        final Var var = get(mathEntityName);
+        if (var != null) {
+            return var.getDescription();
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public String getCategory(@NotNull Var var) {
+        for (Category category : Category.values()) {
+            if ( category.isInCategory(var) ) {
+                return category.name();
+            }
+        }
+
+        return null;
+    }
 }

src/main/java/org/solovyev/android/view/prefs/AndroidUtils.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2009-2011. Created by serso aka se.solovyev.
+ * For more information, please, contact se.solovyev@gmail.com
+ * or visit http://se.solovyev.org
+ */
+
+package org.solovyev.android.view.prefs;
+
+import android.view.Gravity;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.TabHost;
+import android.widget.TextView;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * User: serso
+ * Date: 12/21/11
+ * Time: 11:54 PM
+ */
+public final class AndroidUtils {
+
+    // not intended for instantiation
+    private AndroidUtils() {
+        throw new AssertionError();
+    }
+
+    public static void centerAndWrapTabsFor(@NotNull TabHost tabHost) {
+        int tabCount = tabHost.getTabWidget().getTabCount();
+        for (int i = 0; i < tabCount; i++) {
+            final View view = tabHost.getTabWidget().getChildTabViewAt(i);
+            if ( view != null ) {
+                if (view.getLayoutParams().height > 0) {
+                    // reduce height of the tab
+                    view.getLayoutParams().height *= 0.8;
+                }
+
+                //  get title text view
+                final View textView = view.findViewById(android.R.id.title);
+                if ( textView instanceof TextView) {
+                    // just in case check the type
+
+                    // center text
+                    ((TextView) textView).setGravity(Gravity.CENTER);
+                    // wrap text
+                    ((TextView) textView).setSingleLine(false);
+
+                    // explicitly set layout parameters
+                    textView.getLayoutParams().height = ViewGroup.LayoutParams.FILL_PARENT;
+                    textView.getLayoutParams().width = ViewGroup.LayoutParams.WRAP_CONTENT;
+                }
+            }
+        }
+    }
+}