Number format preferences screen

app/src/main/java/org/solovyev/android/calculator/Engine.java

@@ -22,35 +22,12 @@
 
 package org.solovyev.android.calculator;
 
+import android.content.Context;
 import android.content.SharedPreferences;
+import android.support.annotation.NonNull;
 import android.support.annotation.StringRes;
 import android.text.TextUtils;
-
 import com.squareup.otto.Bus;
-
-import org.solovyev.android.Check;
-import org.solovyev.android.calculator.functions.FunctionsRegistry;
-import org.solovyev.android.calculator.operators.OperatorsRegistry;
-import org.solovyev.android.calculator.operators.PostfixFunctionsRegistry;
-import org.solovyev.android.prefs.BooleanPreference;
-import org.solovyev.android.prefs.CharacterPreference;
-import org.solovyev.android.prefs.IntegerPreference;
-import org.solovyev.android.prefs.Preference;
-import org.solovyev.android.prefs.StringPreference;
-import org.solovyev.common.NumberFormatter;
-import org.solovyev.common.text.EnumMapper;
-import org.solovyev.common.text.NumberMapper;
-
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.concurrent.Executor;
-
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-import javax.inject.Inject;
-import javax.inject.Singleton;
-
 import jscl.AngleUnit;
 import jscl.JsclMathEngine;
 import jscl.MathEngine;
@@ -59,6 +36,25 @@ import jscl.math.operator.Operator;
 import jscl.text.Identifier;
 import jscl.text.Parser;
 import midpcalc.Real;
+import org.solovyev.android.Check;
+import org.solovyev.android.calculator.functions.FunctionsRegistry;
+import org.solovyev.android.calculator.operators.OperatorsRegistry;
+import org.solovyev.android.calculator.operators.PostfixFunctionsRegistry;
+import org.solovyev.android.calculator.preferences.PreferenceEntry;
+import org.solovyev.android.prefs.*;
+import org.solovyev.common.text.CharacterMapper;
+import org.solovyev.common.NumberFormatter;
+import org.solovyev.common.text.EnumMapper;
+import org.solovyev.common.text.NumberMapper;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+import javax.inject.Singleton;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.Executor;
 
 @Singleton
 public class Engine implements SharedPreferences.OnSharedPreferenceChangeListener {
@@ -98,13 +94,6 @@ public class Engine implements SharedPreferences.OnSharedPreferenceChangeListene
         this.mathEngine.setGroupingSeparator(JsclMathEngine.GROUPING_SEPARATOR_DEFAULT);
     }
 
-    private static void migratePreference(@Nonnull SharedPreferences preferences, @Nonnull BooleanPreference preference, @Nonnull String oldKey, @Nonnull SharedPreferences.Editor editor) {
-        if (!preferences.contains(oldKey)) {
-            return;
-        }
-        editor.putBoolean(preference.getKey(), preferences.getBoolean(oldKey, false));
-    }
-
     private static void migratePreference(@Nonnull SharedPreferences preferences, @Nonnull StringPreference<?> preference, @Nonnull String oldKey, @Nonnull SharedPreferences.Editor editor) {
         if (!preferences.contains(oldKey)) {
             return;
@@ -112,15 +101,6 @@ public class Engine implements SharedPreferences.OnSharedPreferenceChangeListene
         editor.putString(preference.getKey(), preferences.getString(oldKey, null));
     }
 
-    private static void migratePreference(@Nonnull SharedPreferences preferences, @Nonnull CharacterPreference preference, @Nonnull String oldKey, @Nonnull SharedPreferences.Editor editor) {
-        if (!preferences.contains(oldKey)) {
-            return;
-        }
-        final String s = preferences.getString(oldKey, null);
-        editor.putInt(preference.getKey(), TextUtils.isEmpty(s) ? 0 : s.charAt(0));
-    }
-
-
     public static boolean isValidName(@Nullable String name) {
         if (!TextUtils.isEmpty(name)) {
             try {
@@ -261,7 +241,7 @@ public class Engine implements SharedPreferences.OnSharedPreferenceChangeListene
         }
     }
 
-    public enum Notation {
+    public enum Notation implements PreferenceEntry {
         dec(Real.NumberFormat.FSE_NONE, R.string.cpp_number_format_dec),
         eng(Real.NumberFormat.FSE_ENG, R.string.cpp_number_format_eng),
         sci(Real.NumberFormat.FSE_SCI, R.string.cpp_number_format_sci);
@@ -274,6 +254,18 @@ public class Engine implements SharedPreferences.OnSharedPreferenceChangeListene
             this.id = id;
             this.name = name;
         }
+
+        @NonNull
+        @Override
+        public CharSequence getName(@NonNull Context context) {
+            return context.getString(name);
+        }
+
+        @NonNull
+        @Override
+        public CharSequence getId() {
+            return name();
+        }
     }
 
     public static class ChangedEvent {
@@ -307,7 +299,7 @@ public class Engine implements SharedPreferences.OnSharedPreferenceChangeListene
         public static class Output {
             public static final StringPreference<Integer> precision = StringPreference.ofTypedValue("engine.output.precision", "5", NumberMapper.of(Integer.class));
             public static final StringPreference<Notation> notation = StringPreference.ofEnum("engine.output.notation", Notation.dec, Notation.class);
-            public static final CharacterPreference separator = CharacterPreference.of("engine.output.separator", JsclMathEngine.GROUPING_SEPARATOR_DEFAULT);
+            public static final StringPreference<Character> separator = StringPreference.ofTypedValue("engine.output.separator", JsclMathEngine.GROUPING_SEPARATOR_DEFAULT, CharacterMapper.INSTANCE);
         }
     }
 }

app/src/main/java/org/solovyev/android/calculator/preferences/NumberFormatExamplesPreference.java

@@ -0,0 +1,59 @@
+package org.solovyev.android.calculator.preferences;
+
+import android.content.Context;
+import android.graphics.Typeface;
+import android.util.AttributeSet;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.TextView;
+import jscl.JsclMathEngine;
+import org.solovyev.android.material.preferences.Preference;
+
+@SuppressWarnings("unused")
+public class NumberFormatExamplesPreference extends Preference {
+    public NumberFormatExamplesPreference(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
+        super(context, attrs, defStyleAttr, defStyleRes);
+    }
+
+    public NumberFormatExamplesPreference(Context context, AttributeSet attrs, int defStyle) {
+        super(context, attrs, defStyle);
+    }
+
+    public NumberFormatExamplesPreference(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    public NumberFormatExamplesPreference(Context context) {
+        super(context);
+    }
+
+    public void update(JsclMathEngine engine) {
+        final StringBuilder examples = new StringBuilder();
+        examples.append("     1/3 = ").append(engine.format(1d / 3)).append("\n");
+        examples.append("      √2 = ").append(engine.format(Math.sqrt(2d))).append("\n");
+        examples.append("\n");
+        examples.append("    1000 = ").append(engine.format(1000d)).append("\n");
+        examples.append(" 1000000 = ").append(engine.format(1000000d)).append("\n");
+        examples.append("   11^10 = ").append(engine.format(Math.pow(11d, 10))).append("\n");
+        examples.append("   10^24 = ").append(engine.format(Math.pow(10d, 24))).append("\n");
+        examples.append("\n");
+        examples.append("   0.001 = ").append(engine.format(0.001d)).append("\n");
+        examples.append("0.000001 = ").append(engine.format(0.000001d)).append("\n");
+        examples.append("  11^−10 = ").append(engine.format(Math.pow(11d, -10))).append("\n");
+        examples.append("  10^−24 = ").append(engine.format(Math.pow(10d, -24)));
+        setSummary(examples);
+    }
+
+    @Override
+    protected View onCreateView(ViewGroup parent) {
+        final View view = super.onCreateView(parent);
+        final View summary = view.findViewById(android.R.id.summary);
+        if (summary instanceof TextView) {
+            final TextView textView = (TextView) summary;
+            textView.setMaxLines(12);
+            textView.setLines(12);
+            textView.setTypeface(Typeface.MONOSPACE);
+        }
+        return view;
+    }
+}

app/src/main/java/org/solovyev/android/calculator/preferences/NumberFormatPreference.java

@@ -1,119 +0,0 @@
-package org.solovyev.android.calculator.preferences;
-
-import android.annotation.TargetApi;
-import android.content.Context;
-import android.content.SharedPreferences;
-import android.os.Build;
-import android.preference.DialogPreference;
-import android.support.annotation.NonNull;
-import android.util.AttributeSet;
-import android.view.View;
-import android.widget.ArrayAdapter;
-import android.widget.Spinner;
-
-import org.solovyev.android.calculator.App;
-import org.solovyev.android.calculator.Engine;
-import org.solovyev.android.calculator.Named;
-import org.solovyev.android.calculator.R;
-import org.solovyev.android.calculator.text.NaturalComparator;
-import org.solovyev.android.views.DiscreteSeekBar;
-import org.solovyev.common.NumberFormatter;
-
-import butterknife.Bind;
-import butterknife.ButterKnife;
-
-import static org.solovyev.android.calculator.Engine.Preferences.Output;
-
-public class NumberFormatPreference extends DialogPreference {
-    @Bind(R.id.nf_notation_spinner)
-    Spinner notationSpinner;
-    ArrayAdapter<Named<Engine.Notation>> notationAdapter;
-    @Bind(R.id.nf_precision_seekbar)
-    DiscreteSeekBar precisionSeekBar;
-    @Bind(R.id.nf_separator_spinner)
-    Spinner separatorSpinner;
-    ArrayAdapter<Named<Character>> separatorAdapter;
-
-    {
-        setPersistent(false);
-        setDialogLayoutResource(R.layout.preference_number_format);
-    }
-
-    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
-    public NumberFormatPreference(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
-        super(context, attrs, defStyleAttr, defStyleRes);
-    }
-
-    public NumberFormatPreference(Context context, AttributeSet attrs, int defStyleAttr) {
-        super(context, attrs, defStyleAttr);
-    }
-
-    public NumberFormatPreference(Context context, AttributeSet attrs) {
-        super(context, attrs);
-    }
-
-    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
-    public NumberFormatPreference(Context context) {
-        super(context);
-    }
-
-    @Override
-    protected void onBindDialogView(View view) {
-        super.onBindDialogView(view);
-        ButterKnife.bind(this, view);
-
-        final SharedPreferences preferences = getSharedPreferences();
-        precisionSeekBar.setMax(NumberFormatter.MAX_PRECISION);
-        precisionSeekBar.setCurrentTick(Math.max(0, Math.min(NumberFormatter.MAX_PRECISION, Output.precision.getPreference(preferences))));
-        notationAdapter = makeNotationAdapter();
-        notationSpinner.setAdapter(notationAdapter);
-        notationSpinner.setSelection(indexOf(notationAdapter, Output.notation.getPreference(preferences)));
-
-        separatorAdapter = makeSeparatorAdapter();
-        separatorSpinner.setAdapter(separatorAdapter);
-        separatorSpinner.setSelection(indexOf(separatorAdapter, Output.separator.getPreference(preferences)));
-    }
-
-    @Override
-    protected void onDialogClosed(boolean save) {
-        super.onDialogClosed(save);
-        if (!save) {
-            return;
-        }
-        final SharedPreferences.Editor editor = getSharedPreferences().edit();
-        Output.precision.putPreference(editor, precisionSeekBar.getCurrentTick());
-        Output.notation.putPreference(editor, notationAdapter.getItem(notationSpinner.getSelectedItemPosition()).item);
-        Output.separator.putPreference(editor, separatorAdapter.getItem(separatorSpinner.getSelectedItemPosition()).item);
-        editor.apply();
-    }
-
-    private <T> int indexOf(ArrayAdapter<Named<T>> adapter, T item) {
-        for (int i = 0; i < adapter.getCount(); i++) {
-            if (adapter.getItem(i).item.equals(item)) {
-                return i;
-            }
-        }
-        return -1;
-    }
-
-    @NonNull
-    private ArrayAdapter<Named<Engine.Notation>> makeNotationAdapter() {
-        final Context context = getContext();
-        final ArrayAdapter<Named<Engine.Notation>> adapter = App.makeSimpleSpinnerAdapter(context);
-        for (Engine.Notation notation : Engine.Notation.values()) {
-            adapter.add(Named.create(notation, notation.name, context));
-        }
-        adapter.sort(NaturalComparator.INSTANCE);
-        return adapter;
-    }
-
-    @NonNull
-    private ArrayAdapter<Named<Character>> makeSeparatorAdapter() {
-        final Context context = getContext();
-        final ArrayAdapter<Named<Character>> adapter = App.makeSimpleSpinnerAdapter(context);
-        adapter.add(Named.create(NumberFormatter.NO_GROUPING, R.string.p_grouping_separator_no, context));
-        adapter.add(Named.create('\'', R.string.p_grouping_separator_apostrophe, context));
-        adapter.add(Named.create(' ', R.string.p_grouping_separator_space, context));
-        return adapter;
-    }
-}

app/src/main/java/org/solovyev/android/calculator/preferences/PrecisionPreference.java

@@ -0,0 +1,72 @@
+package org.solovyev.android.calculator.preferences;
+
+import android.annotation.TargetApi;
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.os.Build;
+import android.preference.DialogPreference;
+import android.util.AttributeSet;
+import android.view.View;
+import butterknife.Bind;
+import butterknife.ButterKnife;
+import org.solovyev.android.calculator.Engine;
+import org.solovyev.android.calculator.R;
+import org.solovyev.android.views.DiscreteSeekBar;
+
+import static org.solovyev.common.NumberFormatter.MAX_PRECISION;
+import static org.solovyev.common.NumberFormatter.MIN_PRECISION;
+
+@SuppressWarnings("unused")
+public class PrecisionPreference extends DialogPreference {
+
+    @Bind(R.id.precision_seekbar)
+    DiscreteSeekBar seekBar;
+
+    {
+        setPersistent(false);
+        setDialogLayoutResource(R.layout.preference_precision);
+    }
+
+    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+    public PrecisionPreference(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
+        super(context, attrs, defStyleAttr, defStyleRes);
+    }
+
+    public PrecisionPreference(Context context, AttributeSet attrs, int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+    }
+
+    public PrecisionPreference(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+    public PrecisionPreference(Context context) {
+        super(context);
+    }
+
+    @Override
+    protected void onBindDialogView(View view) {
+        super.onBindDialogView(view);
+        ButterKnife.bind(this, view);
+
+        final SharedPreferences preferences = getSharedPreferences();
+        seekBar.setMax(MAX_PRECISION - 1);
+        final int precision = Math.max(MIN_PRECISION, Math.min(MAX_PRECISION, Engine.Preferences.Output.precision.getPreference(preferences)));
+        seekBar.setCurrentTick(precision - 1);
+    }
+
+    @Override
+    protected void onDialogClosed(boolean save) {
+        super.onDialogClosed(save);
+        if (!save) {
+            return;
+        }
+        final int precision = seekBar.getCurrentTick() + 1;
+        if (callChangeListener(precision)) {
+            final SharedPreferences.Editor editor = getSharedPreferences().edit();
+            Engine.Preferences.Output.precision.putPreference(editor, precision);
+            editor.apply();
+        }
+    }
+}

app/src/main/java/org/solovyev/android/calculator/preferences/PreferencesActivity.java

@@ -35,6 +35,7 @@ public class PreferencesActivity extends BaseActivity implements SharedPreferenc
 
     static {
         preferenceDefs.append(R.xml.preferences, new PrefDef("screen-main", R.string.cpp_settings));
+        preferenceDefs.append(R.xml.preferences_number_format, new PrefDef("screen-number-format", R.string.c_prefs_calculations_category));
         preferenceDefs.append(R.xml.preferences_calculations, new PrefDef("screen-calculations", R.string.c_prefs_calculations_category));
         preferenceDefs.append(R.xml.preferences_appearance, new PrefDef("screen-appearance", R.string.c_prefs_appearance_category));
         preferenceDefs.append(R.xml.preferences_other, new PrefDef("screen-other", R.string.c_prefs_other_category));

app/src/main/java/org/solovyev/android/calculator/preferences/PreferencesFragment.java

@@ -11,8 +11,11 @@ import android.support.v4.app.FragmentActivity;
 import android.util.SparseArray;
 import android.view.View;
 import android.widget.ListView;
-
+import com.squareup.otto.Bus;
+import com.squareup.otto.Subscribe;
+import jscl.JsclMathEngine;
 import org.solovyev.android.calculator.AdView;
+import org.solovyev.android.calculator.Engine;
 import org.solovyev.android.calculator.Preferences;
 import org.solovyev.android.calculator.Preferences.Gui.Theme;
 import org.solovyev.android.calculator.R;
@@ -22,14 +25,15 @@ import org.solovyev.android.checkout.BillingRequests;
 import org.solovyev.android.checkout.Checkout;
 import org.solovyev.android.checkout.ProductTypes;
 import org.solovyev.android.checkout.RequestListener;
+import org.solovyev.android.prefs.StringPreference;
 import org.solovyev.android.wizard.Wizards;
-
+import org.solovyev.common.text.CharacterMapper;
-import java.util.Arrays;
-import java.util.List;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
+import java.util.Arrays;
+import java.util.List;
 
 import static org.solovyev.android.calculator.App.cast;
 import static org.solovyev.android.calculator.wizard.CalculatorWizards.DEFAULT_WIZARD_FLOW;
@@ -48,11 +52,15 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
     Languages languages;
     @Inject
     Wizards wizards;
+    @Inject
+    JsclMathEngine engine;
+    @Inject
+    Bus bus;
 
     @Nonnull
-    public static PreferencesFragment create(int preferencesResId, int layoutResId) {
+    public static PreferencesFragment create(int preferences, int layout) {
         final PreferencesFragment fragment = new PreferencesFragment();
-        fragment.setArguments(createArguments(preferencesResId, layoutResId, NO_THEME));
+        fragment.setArguments(createArguments(preferences, layout, NO_THEME));
         return fragment;
     }
 
@@ -62,6 +70,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
         cast(this).getComponent().inject(this);
 
         preferences.registerOnSharedPreferenceChangeListener(this);
+        bus.register(this);
     }
 
     private void setPreferenceIntent(int xml, @Nonnull PreferencesActivity.PrefDef def) {
@@ -108,6 +117,11 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
                     }
                 });
             }
+        } else if (preference == R.xml.preferences_number_format) {
+            prepareListPreference(Engine.Preferences.Output.notation, Engine.Notation.class);
+            preparePrecisionPreference();
+            prepareSeparatorPreference();
+            prepareNumberFormatExamplesPreference();
         }
 
         prepareLanguagePreference(preference);
@@ -136,6 +150,73 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
         });
     }
 
+    private void prepareNumberFormatExamplesPreference() {
+        final NumberFormatExamplesPreference preference = (NumberFormatExamplesPreference) preferenceManager.findPreference("numberFormat.examples");
+        if (preference == null) {
+            return;
+        }
+        preference.update(engine);
+    }
+
+    private void prepareSeparatorPreference() {
+        final ListPreference preference = (ListPreference) preferenceManager.findPreference(Engine.Preferences.Output.separator.getKey());
+        preference.setSummary(separatorName(Engine.Preferences.Output.separator.getPreference(preferences)));
+        preference.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
+            @Override
+            public boolean onPreferenceChange(Preference p, Object newValue) {
+                preference.setSummary(separatorName(CharacterMapper.INSTANCE.parseValue(String.valueOf(newValue))));
+                return true;
+            }
+        });
+    }
+
+    private int separatorName(char separator) {
+        switch (separator) {
+            case '\'':
+                return R.string.p_grouping_separator_apostrophe;
+            case ' ':
+                return R.string.p_grouping_separator_space;
+            case 0:
+                return R.string.p_grouping_separator_no;
+        }
+        return R.string.p_grouping_separator_no;
+    }
+
+    private void preparePrecisionPreference() {
+        final PrecisionPreference preference = (PrecisionPreference) preferenceManager.findPreference(Engine.Preferences.Output.precision.getKey());
+        preference.setSummary(String.valueOf(Engine.Preferences.Output.precision.getPreference(preferences)));
+        preference.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
+            @Override
+            public boolean onPreferenceChange(Preference p, Object newValue) {
+                preference.setSummary(String.valueOf(newValue));
+                return true;
+            }
+        });
+    }
+
+    private <E extends Enum<E> & PreferenceEntry> void prepareListPreference(@Nonnull final StringPreference<E> p, @Nonnull Class<E> type) {
+        final ListPreference preference = (ListPreference) preferenceManager.findPreference(p.getKey());
+        if (preference == null) {
+            return;
+        }
+        final E[] entries = type.getEnumConstants();
+        final FragmentActivity activity = getActivity();
+        populate(preference, entries);
+        preference.setSummary(p.getPreference(preferences).getName(activity));
+        preference.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
+            @Override
+            public boolean onPreferenceChange(Preference p, Object newValue) {
+                for (E entry : entries) {
+                    if (entry.getId().equals(newValue)) {
+                        preference.setSummary(entry.getName(activity));
+                        break;
+                    }
+                }
+                return true;
+            }
+        });
+    }
+
     private void prepareLayoutPreference(int preference) {
         if (preference != R.xml.preferences_appearance) {
             return;
@@ -220,6 +301,11 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
     public void onSharedPreferenceChanged(SharedPreferences preferences, String key) {
     }
 
+    @Subscribe
+    public void onEngineChanged(Engine.ChangedEvent e) {
+        prepareNumberFormatExamplesPreference();
+    }
+
     @Override
     public void onResume() {
         super.onResume();
@@ -246,6 +332,7 @@ public class PreferencesFragment extends org.solovyev.android.material.preferenc
 
     @Override
     public void onDestroy() {
+        bus.unregister(this);
         preferences.unregisterOnSharedPreferenceChangeListener(this);
         super.onDestroy();
     }

app/src/main/java/org/solovyev/android/prefs/StringPreference.java

@@ -56,6 +56,11 @@ public final class StringPreference<T> extends AbstractPreference<T> {
         return new StringPreference<T>(key, mapper.parseValue(defaultValue), mapper);
     }
 
+    @Nonnull
+    public static <T> StringPreference<T> ofTypedValue(@Nonnull String key, @Nullable T defaultValue, @Nonnull Mapper<T> mapper) {
+        return new StringPreference<T>(key, defaultValue, mapper);
+    }
+
     @Nonnull
     public static <T extends Enum> StringPreference<T> ofEnum(@Nonnull String key, @Nullable T defaultValue, @Nonnull Class<T> enumType) {
         return new StringPreference<T>(key, defaultValue, EnumMapper.of(enumType));

app/src/main/java/org/solovyev/common/text/CharacterMapper.java

@@ -0,0 +1,27 @@
+package org.solovyev.common.text;
+
+import android.text.TextUtils;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+public class CharacterMapper implements Mapper<Character> {
+
+    @Nonnull
+    public static final CharacterMapper INSTANCE = new CharacterMapper();
+
+    private CharacterMapper() {
+    }
+
+    @Nonnull
+    @Override
+    public String formatValue(@Nullable Character value) throws IllegalArgumentException {
+        return value == null || value == 0 ? "" : String.valueOf(value);
+    }
+
+    @Nonnull
+    @Override
+    public Character parseValue(@Nullable String value) throws IllegalArgumentException {
+        return TextUtils.isEmpty(value) ? 0 : value.charAt(0);
+    }
+}

app/src/main/res/layout/preference_number_format.xml

@@ -1,45 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
-              xmlns:app="http://schemas.android.com/apk/res-auto"
-              android:layout_width="match_parent"
-              android:layout_height="match_parent"
-              android:orientation="vertical"
-              android:padding="@dimen/cpp_dialog_spacing">
-
-    <TextView
-        style="@style/CppLabel"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:text="Notation"/>
-
-    <Spinner
-        android:id="@+id/nf_notation_spinner"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"/>
-
-    <TextView
-        style="@style/CppLabel"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:text="Precision"/>
-
-    <org.solovyev.android.views.DiscreteSeekBar
-        android:id="@+id/nf_precision_seekbar"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        app:labelsColor="?android:attr/textColorSecondary"
-        app:labelsSize="12sp"
-        app:values="@array/cpp_prefs_precisions"/>
-
-    <TextView
-        style="@style/CppLabel"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:text="Separator"/>
-
-    <Spinner
-        android:id="@+id/nf_separator_spinner"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"/>
-
-</LinearLayout>

app/src/main/res/layout/preference_precision.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<org.solovyev.android.views.DiscreteSeekBar android:id="@+id/precision_seekbar"
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:padding="@dimen/cpp_dialog_spacing"
+    app:labelsColor="?android:attr/textColorSecondary"
+    app:labelsSize="12sp"
+    app:values="@array/cpp_prefs_precisions" />

app/src/main/res/values/text_non_translatable.xml

@@ -18,7 +18,6 @@
     <string name="cpp_exponent" translatable="false">E</string>
     <string name="cpp_theme_black" translatable="false">%1$s (AMOLED)</string>
     <string-array name="cpp_prefs_precisions" translatable="false">
-        <item>0</item>
         <item>1</item>
         <item>2</item>
         <item>3</item>

app/src/main/res/xml/preferences.xml

@@ -35,6 +35,10 @@
         a:key="restart_wizard"
         a:title="@string/cpp_restart_wizard" />
 
+    <Preference
+        a:key="screen-number-format"
+        a:title="Number format" />
+
     <Preference
         a:key="screen-calculations"
         a:title="@string/c_prefs_calculations_category" />

app/src/main/res/xml/preferences_calculations.xml

@@ -24,30 +24,6 @@
 
 <PreferenceScreen xmlns:a="http://schemas.android.com/apk/res/android">
 
-    <org.solovyev.android.calculator.preferences.NumberFormatPreference
-        a:key="engine.output.numberFormat"
-        a:title="Number format" />
-
-    <ListPreference
-        a:entries="@array/cpp_prefs_precisions"
-        a:entryValues="@array/cpp_prefs_precisions"
-        a:key="engine.output.precision"
-        a:summary="@string/c_calc_result_precision_summary"
-        a:title="@string/p_calc_result_precision_title" />
-
-    <android.preference.CheckBoxPreference
-        a:defaultValue="false"
-        a:key="engine.output.scientificNotation"
-        a:summary="@string/c_calc_science_notation_summary"
-        a:title="@string/c_calc_science_notation_title" />
-
-    <ListPreference
-        a:entries="@array/p_grouping_separator_names"
-        a:entryValues="@array/p_grouping_separator_values"
-        a:key="engine.groupingSeparator"
-        a:summary="@string/c_calc_grouping_separator_summary"
-        a:title="@string/c_calc_grouping_separator" />
-
     <ListPreference
         a:entries="@array/p_angle_units_names"
         a:entryValues="@array/p_angle_units"

app/src/main/res/xml/preferences_number_format.xml

@@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<!--
+  ~ Copyright 2016 serso aka se.solovyev
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~    http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  ~
+  ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+  ~ Contact details
+  ~
+  ~ Email: se.solovyev@gmail.com
+  ~ Site:  http://se.solovyev.org
+  -->
+
+<PreferenceScreen xmlns:a="http://schemas.android.com/apk/res/android"
+    xmlns:m="http://schemas.android.com/apk/res-auto">
+
+    <org.solovyev.android.material.preferences.ListPreference
+        a:key="engine.output.notation"
+        a:title="Notation"
+        m:materialColor="@color/material_text_selector" />
+
+    <org.solovyev.android.calculator.preferences.PrecisionPreference
+        a:key="engine.output.precision"
+        a:title="@string/p_calc_result_precision_title" />
+
+    <org.solovyev.android.material.preferences.ListPreference
+        a:entries="@array/p_grouping_separator_names"
+        a:entryValues="@array/p_grouping_separator_values"
+        a:key="engine.output.separator"
+        a:title="@string/c_calc_grouping_separator"
+        m:materialColor="@color/material_text_selector" />
+
+    <org.solovyev.android.calculator.preferences.NumberFormatExamplesPreference
+        a:key="numberFormat.examples"
+        a:selectable="false"
+        a:title="Examples" />
+
+</PreferenceScreen>

jscl/src/main/java/org/solovyev/common/NumberFormatter.java

@@ -14,6 +14,7 @@ public class NumberFormatter {
     public static final char NO_GROUPING = 0;
     public static final int NO_ROUNDING = -1;
     public static final int DEFAULT_MAGNITUDE = 5;
+    public static final int MIN_PRECISION = 1;
     public static final int MAX_PRECISION = 15;
 
     private final Real.NumberFormat numberFormat = new Real.NumberFormat();
@@ -39,7 +40,7 @@ public class NumberFormatter {
     }
 
     public void setPrecision(int precision) {
-        this.precision = precision;
+        this.precision = Math.max(MIN_PRECISION, Math.min(precision, MAX_PRECISION));
     }
 
     public void setGroupingSeparator(char groupingSeparator) {