KeyboardUi in EditFunctionDialog

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

@@ -0,0 +1,408 @@
+package org.solovyev.android.calculator;
+
+import android.annotation.SuppressLint;
+import android.content.Context;
+import android.content.res.Resources;
+import android.graphics.Color;
+import android.graphics.PointF;
+import android.os.Build;
+import android.support.annotation.DrawableRes;
+import android.support.annotation.IdRes;
+import android.support.annotation.NonNull;
+import android.text.TextUtils;
+import android.util.TypedValue;
+import android.view.GestureDetector;
+import android.view.HapticFeedbackConstants;
+import android.view.MotionEvent;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.ImageButton;
+import android.widget.ImageView;
+import android.widget.LinearLayout;
+
+import org.solovyev.android.views.dragbutton.DirectionDragButton;
+import org.solovyev.android.views.dragbutton.DragButton;
+import org.solovyev.android.views.dragbutton.DragDirection;
+import org.solovyev.android.views.dragbutton.SimpleDragListener;
+
+import java.util.List;
+
+import static org.solovyev.android.views.dragbutton.DirectionDragButton.Direction.down;
+import static org.solovyev.android.views.dragbutton.DirectionDragButton.Direction.up;
+
+
+public class KeyboardUi {
+    @NonNull
+    private final ButtonHandler buttonHandler = new ButtonHandler();
+    @NonNull
+    private final User user;
+    @NonNull
+    private final List<String> parameterNames;
+    @NonNull
+    private final SimpleDragListener dragListener;
+    private final int textColor;
+    private final int textColorSecondary;
+    private final int sidePadding;
+
+    @SuppressWarnings("deprecation")
+    public KeyboardUi(@NonNull User user, @NonNull List<String> parameterNames) {
+        this.user = user;
+        this.parameterNames = parameterNames;
+        this.dragListener = new SimpleDragListener(buttonHandler, user.getContext());
+        final Resources resources = user.getResources();
+        textColor = resources.getColor(R.color.cpp_button_text);
+        textColorSecondary = resources.getColor(R.color.cpp_button_text);
+        sidePadding = resources.getDimensionPixelSize(R.dimen.cpp_button_padding);
+    }
+
+    public void makeView() {
+        LinearLayout row = makeRow();
+        addButton(row, 0, "7");
+        addButton(row, 0, "8");
+        addButton(row, 0, "9").setText("π", up).setText("e", down);
+        addOperationButton(row, R.id.cpp_kb_button_multiply, Locator.getInstance().getEngine().getMultiplicationSign()).setText("^n", up).setText("^2", down);
+        addButton(row, R.id.cpp_kb_button_clear, "C");
+
+        row = makeRow();
+        addButton(row, 0, "4");
+        addButton(row, 0, "5");
+        addButton(row, 0, "6");
+        addOperationButton(row, R.id.cpp_kb_button_divide, "/").setText("%", up).setText("sqrt", down);
+        final View backspace = addImageButton(row, R.id.cpp_kb_button_backspace, R.drawable.ic_backspace_white_24dp);
+        LongClickEraser.createAndAttach(backspace, user.getEditor());
+
+        row = makeRow();
+        addButton(row, 0, "1");
+        addButton(row, 0, "2");
+        addButton(row, 0, "3");
+        addOperationButton(row, R.id.cpp_kb_button_plus, "+");
+        addImageButton(row, R.id.cpp_kb_button_space, R.drawable.ic_space_bar_white_24dp);
+
+        row = makeRow();
+        addButton(row, R.id.cpp_kb_button_brackets, "( )").setText("(", up).setText(")", down);
+        addButton(row, 0, "0").setText("00", up).setText("000", down);
+        addButton(row, 0, ".").setText(",", up);
+        addOperationButton(row, R.id.cpp_kb_button_minus, "−");
+        addImageButton(row, R.id.cpp_kb_button_keyboard, R.drawable.ic_keyboard_white_24dp);
+
+        row = makeRow();
+        final int parametersCount = parameterNames.size();
+        addButton(row, 0, parametersCount > 0 ? parameterNames.get(0) : "x");
+        addButton(row, 0, parametersCount > 1 ? parameterNames.get(1) : "y");
+        addButton(row, R.id.cpp_kb_button_functions, "f(x)");
+        addButton(row, R.id.cpp_kb_button_constants, "π");
+        addImageButton(row, R.id.cpp_kb_button_close, R.drawable.ic_done_white_24dp);
+    }
+
+    @NonNull
+    private View addImageButton(@NonNull LinearLayout row, @IdRes int id, @DrawableRes int icon) {
+        final LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(0, ViewGroup.LayoutParams.MATCH_PARENT);
+        lp.weight = 1f;
+        final View view = makeImageButton(id, icon);
+        row.addView(view, lp);
+        return view;
+    }
+
+    @NonNull
+    private DirectionDragButton addOperationButton(@NonNull LinearLayout row, @IdRes int id, @NonNull String text) {
+        final DirectionDragButton button = addButton(row, id, text);
+        button.setBackgroundResource(R.drawable.material_button_light_primary);
+        button.setTextColor(Color.WHITE);
+        button.setDirectionTextColor(Color.WHITE);
+        return button;
+    }
+
+    @NonNull
+    private DirectionDragButton addButton(@NonNull LinearLayout row, @IdRes int id, @NonNull String text) {
+        final LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(0, ViewGroup.LayoutParams.MATCH_PARENT);
+        lp.weight = 1f;
+        final DirectionDragButton view = makeButton(id, text);
+        row.addView(view, lp);
+        return view;
+    }
+
+    @NonNull
+    private LinearLayout makeRow() {
+        final LinearLayout row = new LinearLayout(user.getContext());
+        row.setOrientation(LinearLayout.HORIZONTAL);
+        final LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 0);
+        lp.weight = 1f;
+        user.getKeyboard().addView(row, lp);
+        return row;
+    }
+
+    @NonNull
+    private DirectionDragButton makeButton(@IdRes int id, @NonNull String text) {
+        final DirectionDragButton button = new DirectionDragButton(user.getContext());
+        fillButton(button, id);
+        button.setText(text);
+        button.setTextColor(textColor);
+        button.setDirectionTextColor(textColorSecondary);
+        button.setTextSize(TypedValue.COMPLEX_UNIT_DIP, 24);
+        button.setOnDragListener(dragListener);
+        return button;
+    }
+
+    private void fillButton(@NonNull View button, @IdRes int id) {
+        button.setOnClickListener(buttonHandler);
+        button.setId(id);
+        button.setBackgroundResource(R.drawable.material_button_light);
+        button.setPadding(sidePadding, 1, sidePadding, 1);
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            button.setStateListAnimator(null);
+        }
+    }
+
+    @NonNull
+    private View makeImageButton(@IdRes int id, @DrawableRes int icon) {
+        final ImageButton button = new ImageButton(user.getContext());
+        fillButton(button, id);
+        button.setImageResource(icon);
+        button.setScaleType(ImageView.ScaleType.CENTER_INSIDE);
+        return button;
+    }
+
+    public interface User {
+        @NonNull
+        Context getContext();
+
+        @NonNull
+        Resources getResources();
+
+        @NonNull
+        EditText getEditor();
+
+        @NonNull
+        ViewGroup getKeyboard();
+
+        void insertOperator(char operator);
+
+        void insertOperator(@NonNull String operator);
+
+        void showFunctions(@NonNull View v);
+
+        void showConstants(@NonNull View v);
+
+        void insertText(@NonNull CharSequence text, int offset);
+
+        void done();
+
+        void showIme();
+    }
+
+    private class ButtonHandler implements View.OnClickListener, SimpleDragListener.DragProcessor {
+        @Override
+        public void onClick(@NonNull View v) {
+            switch (v.getId()) {
+                case R.id.cpp_kb_button_divide:
+                    user.insertOperator('/');
+                    break;
+                case R.id.cpp_kb_button_plus:
+                    user.insertOperator('+');
+                    break;
+                case R.id.cpp_kb_button_minus:
+                    user.insertOperator('-');
+                    break;
+                case R.id.cpp_kb_button_multiply:
+                    user.insertOperator('*');
+                    break;
+                case R.id.cpp_kb_button_functions:
+                    user.showFunctions(v);
+                    break;
+                case R.id.cpp_kb_button_constants:
+                    user.showConstants(v);
+                    break;
+                case R.id.cpp_kb_button_space:
+                    user.insertText(" ", 0);
+                    break;
+                case R.id.cpp_kb_button_keyboard:
+                    user.showIme();
+                    break;
+                case R.id.cpp_kb_button_clear:
+                    user.getEditor().setText("");
+                    user.getEditor().setSelection(0);
+                    break;
+                case R.id.cpp_kb_button_brackets:
+                    user.insertText("()", -1);
+                    break;
+                case R.id.cpp_kb_button_close:
+                    user.done();
+                    break;
+                default:
+                    onDefaultClick(v);
+                    break;
+            }
+            user.getEditor().requestFocus();
+            v.performHapticFeedback(HapticFeedbackConstants.KEYBOARD_TAP);
+        }
+
+        private void onDefaultClick(@NonNull View v) {
+            user.insertText(((Button) v).getText(), 0);
+        }
+
+        @Override
+        public boolean processDragEvent(@NonNull DragDirection direction, @NonNull DragButton button, @NonNull PointF startPoint, @NonNull MotionEvent e) {
+            switch (button.getId()) {
+                default:
+                    return onDefaultDrag(button, direction);
+            }
+        }
+
+        private boolean onDefaultDrag(@NonNull DragButton button, @NonNull DragDirection direction) {
+            final String text = ((DirectionDragButton) button).getText(direction);
+            if (TextUtils.isEmpty(text)) {
+                return false;
+            }
+            switch (text) {
+                case "sqrt":
+                    user.insertText("sqrt()", -1);
+                    break;
+                case ",":
+                    user.insertText(", ", 0);
+                    break;
+                case "^n":
+                    user.insertOperator('^');
+                    break;
+                case "^2":
+                    user.insertOperator("^ 2");
+                    break;
+                case "?":
+                case ">":
+                case "<":
+                case ">=":
+                case "<=":
+                case ":":
+                    user.insertOperator(text);
+                    break;
+                default:
+                    user.insertText(text, 0);
+                    break;
+            }
+            button.performHapticFeedback(HapticFeedbackConstants.KEYBOARD_TAP);
+            return true;
+        }
+    }
+
+    public static final class LongClickEraser implements View.OnTouchListener, View.OnClickListener {
+
+        @NonNull
+        private final View view;
+
+        @NonNull
+        private final EditText editText;
+
+        @NonNull
+        private final GestureDetector gestureDetector;
+
+        @NonNull
+        private final Eraser eraser = new Eraser();
+
+        private LongClickEraser(@NonNull final View view, @NonNull EditText editText) {
+            this.view = view;
+            this.editText = editText;
+            this.gestureDetector = new GestureDetector(view.getContext(), new GestureDetector.SimpleOnGestureListener() {
+                public void onLongPress(MotionEvent e) {
+                    if (eraser.isTracking()) {
+                        eraser.start();
+                    }
+                }
+            });
+        }
+
+        public static void createAndAttach(@NonNull View view, @NonNull EditText editText) {
+            final LongClickEraser l = new LongClickEraser(view, editText);
+            view.setOnClickListener(l);
+            view.setOnTouchListener(l);
+        }
+
+        private static void erase(@NonNull EditText editText) {
+            final int start = clampSelection(editText.getSelectionStart());
+            final int end = clampSelection(editText.getSelectionEnd());
+            if (start != end) {
+                editText.getText().delete(Math.min(start, end), Math.max(start, end));
+            } else if (start > 0) {
+                editText.getText().delete(start - 1, start);
+            }
+        }
+
+        public static int clampSelection(int selection) {
+            return selection < 0 ? 0 : selection;
+        }
+
+        @SuppressLint("ClickableViewAccessibility")
+        @Override
+        public boolean onTouch(View v, MotionEvent event) {
+            switch (event.getAction()) {
+                case MotionEvent.ACTION_CANCEL:
+                case MotionEvent.ACTION_UP:
+                    eraser.stopTracking();
+                    break;
+                default:
+                    eraser.startTracking();
+                    gestureDetector.onTouchEvent(event);
+                    break;
+            }
+            return false;
+        }
+
+        @Override
+        public void onClick(View v) {
+            erase(editText);
+            v.performHapticFeedback(HapticFeedbackConstants.KEYBOARD_TAP);
+        }
+
+        private class Eraser implements Runnable {
+            private static final int DELAY = 300;
+            private long delay;
+            private boolean erasing;
+            private boolean tracking = true;
+
+            @Override
+            public void run() {
+                erase(editText);
+                if (editText.length() == 0 || clampSelection(editText.getSelectionStart()) == 0) {
+                    stop();
+                    return;
+                }
+                delay = Math.max(50, 2 * delay / 3);
+                view.postDelayed(this, delay);
+            }
+
+            void start() {
+                if (erasing) {
+                    stop();
+                }
+                erasing = true;
+                delay = DELAY;
+                view.removeCallbacks(this);
+                view.performHapticFeedback(HapticFeedbackConstants.KEYBOARD_TAP);
+                run();
+            }
+
+            void stop() {
+                view.removeCallbacks(this);
+                if (!erasing) {
+                    return;
+                }
+
+                erasing = false;
+            }
+
+            public void stopTracking() {
+                stop();
+                tracking = false;
+            }
+
+            public boolean isTracking() {
+                return tracking;
+            }
+
+            public void startTracking() {
+                tracking = true;
+            }
+        }
+    }
+
+}

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

@@ -0,0 +1,105 @@
+package org.solovyev.android.calculator;
+
+import android.app.Dialog;
+import android.content.Context;
+import android.os.IBinder;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+import android.view.Gravity;
+import android.view.View;
+import android.view.Window;
+import android.view.WindowManager;
+import android.view.inputmethod.InputMethodManager;
+import android.widget.EditText;
+import android.widget.LinearLayout;
+import android.widget.PopupWindow;
+
+import java.util.List;
+
+public class KeyboardWindow {
+
+    @Nullable
+    private PopupWindow window;
+    @Nullable
+    private Dialog dialog;
+
+    private static void hideIme(@NonNull View view) {
+        final IBinder token = view.getWindowToken();
+        if (token != null) {
+            InputMethodManager imm = (InputMethodManager) view.getContext().getSystemService(
+                    Context.INPUT_METHOD_SERVICE);
+            imm.hideSoftInputFromWindow(token, 0);
+        }
+    }
+
+    public void hide() {
+        if (!isShown()) {
+            return;
+        }
+        moveDialog(Gravity.CENTER);
+        window.dismiss();
+        window = null;
+        dialog = null;
+    }
+
+    public void show(@NonNull KeyboardUi.User user, @Nullable Dialog dialog, @NonNull List<String> parameterNames) {
+        if (isShown()) {
+            return;
+        }
+        this.dialog = dialog;
+        moveDialog(Gravity.TOP);
+        final EditText editor = user.getEditor();
+        hideIme(editor);
+        final Context context = editor.getContext();
+        final LinearLayout view = new LinearLayout(context);
+        view.setOrientation(LinearLayout.VERTICAL);
+        final int buttonSize = context.getResources().getDimensionPixelSize(R.dimen.cpp_kb_button_size);
+        final int keyboardSize = 5 * buttonSize;
+        window = new PopupWindow(view, keyboardSize, keyboardSize);
+        window.setClippingEnabled(false);
+        window.setOnDismissListener(new PopupWindow.OnDismissListener() {
+            @Override
+            public void onDismiss() {
+                window = null;
+            }
+        });
+        // see http://stackoverflow.com/a/4713487/720489
+        editor.post(new Runnable() {
+            @Override
+            public void run() {
+                if (window == null) {
+                    return;
+                }
+                if (editor.getWindowToken() != null) {
+                    hideIme(editor);
+                    final int inputWidth = editor.getWidth();
+                    final int xOff = (inputWidth - keyboardSize) / 2;
+                    window.setWidth(keyboardSize);
+                    window.showAsDropDown(editor, xOff, 0);
+                } else {
+                    editor.postDelayed(this, 50);
+                }
+            }
+        });
+        new KeyboardUi(user, parameterNames).makeView();
+    }
+
+    public boolean isShown() {
+        return window != null;
+    }
+
+    @SuppressWarnings("unchecked")
+    public <V extends View> V getContentView() {
+        return (V) window.getContentView();
+    }
+
+    public void moveDialog(int gravity) {
+        if (dialog == null) {
+            return;
+        }
+        final Window window = dialog.getWindow();
+        final WindowManager.LayoutParams lp = window.getAttributes();
+        lp.gravity = gravity;
+        window.setAttributes(lp);
+    }
+}

app/src/main/java/org/solovyev/android/calculator/function/EditFunctionFragment.java

@@ -22,9 +22,11 @@
 
 package org.solovyev.android.calculator.function;
 
+import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.content.Intent;
+import android.content.res.Resources;
 import android.os.Bundle;
 import android.os.Parcel;
 import android.os.Parcelable;
@@ -33,8 +35,15 @@ import android.support.design.widget.TextInputLayout;
 import android.support.v4.app.FragmentManager;
 import android.support.v7.app.AlertDialog;
 import android.support.v7.app.AppCompatActivity;
+import android.text.Editable;
+import android.view.ContextMenu;
+import android.view.KeyEvent;
 import android.view.LayoutInflater;
+import android.view.Menu;
+import android.view.MenuItem;
 import android.view.View;
+import android.view.ViewGroup;
+import android.view.inputmethod.InputMethodManager;
 import android.widget.Button;
 import android.widget.EditText;
 
@@ -45,6 +54,8 @@ import org.solovyev.android.calculator.CalculatorEventListener;
 import org.solovyev.android.calculator.CalculatorEventType;
 import org.solovyev.android.calculator.CalculatorUtils;
 import org.solovyev.android.calculator.DisplayState;
+import org.solovyev.android.calculator.KeyboardUi;
+import org.solovyev.android.calculator.KeyboardWindow;
 import org.solovyev.android.calculator.Locator;
 import org.solovyev.android.calculator.R;
 import org.solovyev.android.calculator.math.edit.CalculatorFunctionsActivity;
@@ -52,8 +63,10 @@ import org.solovyev.android.calculator.math.edit.FunctionsFragment;
 import org.solovyev.android.calculator.math.edit.MathEntityRemover;
 import org.solovyev.android.calculator.math.edit.VarEditorSaver;
 import org.solovyev.android.calculator.model.AFunction;
+import org.solovyev.common.math.MathRegistry;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
@@ -66,11 +79,23 @@ import jscl.math.Generic;
 import jscl.math.function.Constant;
 import jscl.math.function.CustomFunction;
 import jscl.math.function.Function;
+import jscl.math.function.IConstant;
 import jscl.math.function.IFunction;
 
-public class EditFunctionFragment extends BaseDialogFragment implements CalculatorEventListener {
+public class EditFunctionFragment extends BaseDialogFragment implements CalculatorEventListener, View.OnClickListener, View.OnFocusChangeListener, View.OnKeyListener {
 
     private static final String ARG_INPUT = "input";
+    private static final int MENU_FUNCTION = Menu.FIRST;
+    private static final int MENU_CONSTANT = Menu.FIRST + 1;
+
+    @NonNull
+    private final MathRegistry<Function> functionsRegistry = Locator.getInstance().getEngine().getFunctionsRegistry();
+    @NonNull
+    private final MathRegistry<IConstant> constantsRegistry = Locator.getInstance().getEngine().getVarsRegistry();
+    @NonNull
+    private final KeyboardWindow keyboardWindow = new KeyboardWindow();
+    @NonNull
+    private final KeyboardUser keyboardUser = new KeyboardUser();
     @Bind(R.id.function_params)
     FunctionParamsView paramsView;
     @Bind(R.id.function_name_label)
@@ -154,6 +179,34 @@ public class EditFunctionFragment extends BaseDialogFragment implements Calculat
         return dialog;
     }
 
+    @Override
+    public void onFocusChange(View v, boolean hasFocus) {
+        if (v.getId() == R.id.function_body) {
+            if (hasFocus) {
+                keyboardWindow.show(keyboardUser, getDialog(), paramsView.getParams());
+            } else {
+                keyboardWindow.hide();
+            }
+        }
+    }
+    @Override
+    public void onClick(View v) {
+        if (v.getId() == R.id.function_body) {
+            keyboardWindow.show(keyboardUser, getDialog(), paramsView.getParams());
+        }
+    }
+
+    @Override
+    public boolean onKey(View v, int keyCode, KeyEvent event) {
+        if (v.getId() == R.id.function_body) {
+            if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK && keyboardWindow.isShown()) {
+                keyboardWindow.hide();
+                return true;
+            }
+        }
+        return false;
+    }
+
     private void tryClose() {
         if (validate()) {
             applyData();
@@ -169,6 +222,9 @@ public class EditFunctionFragment extends BaseDialogFragment implements Calculat
         if (!validateName()) {
             return false;
         }
+        if (!validateBody()) {
+            return false;
+        }
         return true;
     }
 
@@ -182,6 +238,11 @@ public class EditFunctionFragment extends BaseDialogFragment implements Calculat
         return true;
     }
 
+    private boolean validateBody() {
+        return true;
+    }
+
+    @SuppressLint("InflateParams")
     @NonNull
     @Override
     protected View onCreateDialogView(@NonNull Context context, @NonNull LayoutInflater inflater, @Nullable Bundle savedInstanceState) {
@@ -198,6 +259,9 @@ public class EditFunctionFragment extends BaseDialogFragment implements Calculat
             descriptionView.setText(input.getDescription());
             bodyView.setText(input.getContent());
         }
+        bodyView.setOnClickListener(this);
+        bodyView.setOnFocusChangeListener(this);
+        bodyView.setOnKeyListener(this);
 
         return view;
     }
@@ -275,7 +339,7 @@ public class EditFunctionFragment extends BaseDialogFragment implements Calculat
             result.content = in.readString();
             result.description = in.readString();
 
-            final List<String> parameterNames = new ArrayList<String>();
+            final List<String> parameterNames = new ArrayList<>();
             in.readTypedList(parameterNames, STRING_CREATOR);
             result.parameterNames = parameterNames;
 
@@ -310,7 +374,7 @@ public class EditFunctionFragment extends BaseDialogFragment implements Calculat
             result.name = name;
             result.content = value;
             result.description = description;
-            result.parameterNames = new ArrayList<String>(parameterNames);
+            result.parameterNames = new ArrayList<>(parameterNames);
 
             return result;
         }
@@ -323,7 +387,7 @@ public class EditFunctionFragment extends BaseDialogFragment implements Calculat
             final Generic generic = viewState.getResult();
             if (generic != null) {
                 final Set<Constant> constants = CalculatorUtils.getNotSystemConstants(generic);
-                final List<String> parameterNames = new ArrayList<String>(constants.size());
+                final List<String> parameterNames = new ArrayList<>(constants.size());
                 for (Constant constant : constants) {
                     parameterNames.add(constant.getName());
                 }
@@ -372,4 +436,161 @@ public class EditFunctionFragment extends BaseDialogFragment implements Calculat
             out.writeSerializable(function);
         }
     }
+
+    private class KeyboardUser implements KeyboardUi.User, MenuItem.OnMenuItemClickListener {
+        @NonNull
+        @Override
+        public Context getContext() {
+            return getActivity();
+        }
+
+        @NonNull
+        @Override
+        public Resources getResources() {
+            return EditFunctionFragment.this.getResources();
+        }
+
+        @NonNull
+        @Override
+        public EditText getEditor() {
+            return bodyView;
+        }
+
+        @NonNull
+        @Override
+        public ViewGroup getKeyboard() {
+            return keyboardWindow.getContentView();
+        }
+
+        @Override
+        public void insertOperator(char operator) {
+            insertOperator(String.valueOf(operator));
+        }
+
+        public int clampSelection(int selection) {
+            return selection < 0 ? 0 : selection;
+        }
+
+        @Override
+        public void insertOperator(@NonNull String operator) {
+            final int start = clampSelection(bodyView.getSelectionStart());
+            final int end = clampSelection(bodyView.getSelectionEnd());
+            final Editable e = bodyView.getText();
+            e.replace(start, end, getOperator(start, end, e, operator));
+        }
+
+        @NonNull
+        private String getOperator(int start, int end, @NonNull Editable e, @NonNull CharSequence operator) {
+            boolean spaceBefore = true;
+            boolean spaceAfter = true;
+            if (start > 0 && Character.isSpaceChar(e.charAt(start - 1))) {
+                spaceBefore = false;
+            }
+            if (end < e.length() && Character.isSpaceChar(e.charAt(end))) {
+                spaceAfter = false;
+            }
+
+            if (spaceBefore && spaceAfter) {
+                return " " + operator + " ";
+            }
+            if (spaceBefore) {
+                return " " + operator;
+            }
+            if (spaceAfter) {
+                return operator + " ";
+            }
+            return String.valueOf(operator);
+        }
+
+        @Override
+        public void showConstants(@NonNull View v) {
+            bodyView.setOnCreateContextMenuListener(new View.OnCreateContextMenuListener() {
+                @Override
+                public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
+                    final int id = v.getId();
+                    if (id == R.id.function_body) {
+                        menu.clear();
+                        for (String constant : getNamesSorted(constantsRegistry)) {
+                            menu.add(MENU_CONSTANT, Menu.NONE, Menu.NONE, constant).setOnMenuItemClickListener(KeyboardUser.this);
+                        }
+                        unregisterForContextMenu(bodyView);
+                    }
+                }
+            });
+            bodyView.showContextMenu();
+        }
+
+        @Nonnull
+        private List<String> getNamesSorted(@NonNull MathRegistry<?> registry) {
+            final List<String> names = registry.getNames();
+            Collections.sort(names);
+            return names;
+        }
+
+        @Override
+        public void showFunctions(@NonNull View v) {
+            bodyView.setOnCreateContextMenuListener(new View.OnCreateContextMenuListener() {
+                @Override
+                public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
+                    final int id = v.getId();
+                    if (id == R.id.function_body) {
+                        menu.clear();
+                        for (String function : getNamesSorted(functionsRegistry)) {
+                            menu.add(MENU_FUNCTION, Menu.NONE, Menu.NONE, function).setOnMenuItemClickListener(KeyboardUser.this);
+                        }
+                        unregisterForContextMenu(bodyView);
+                    }
+                }
+            });
+            bodyView.showContextMenu();
+        }
+
+        @Override
+        public void insertText(@NonNull CharSequence text, int selectionOffset) {
+            final int start = clampSelection(bodyView.getSelectionStart());
+            final int end = clampSelection(bodyView.getSelectionEnd());
+            final Editable e = bodyView.getText();
+            e.replace(start, end, text);
+            if (selectionOffset != 0) {
+                final int selection = clampSelection(bodyView.getSelectionEnd());
+                final int newSelection = selection + selectionOffset;
+                if (newSelection >= 0 && newSelection < e.length()) {
+                    bodyView.setSelection(newSelection);
+                }
+            }
+        }
+
+        @Override
+        public void done() {
+            keyboardWindow.hide();
+            validateBody();
+        }
+
+        @Override
+        public void showIme() {
+            final InputMethodManager keyboard = (InputMethodManager)
+                    getContext().getSystemService(Context.INPUT_METHOD_SERVICE);
+            keyboard.showSoftInput(getEditor(), InputMethodManager.SHOW_FORCED);
+            keyboardWindow.hide();
+        }
+
+        @Override
+        public boolean onMenuItemClick(MenuItem item) {
+            final int groupId = item.getGroupId();
+            final CharSequence title = item.getTitle();
+            if (groupId == MENU_FUNCTION) {
+                final int argsListIndex = title.toString().indexOf("(");
+                if (argsListIndex < 0) {
+                    keyboardUser.insertText(title + "()", -1);
+                } else {
+                    keyboardUser.insertText(title.subSequence(0, argsListIndex) + "()", -1);
+                }
+            } else if (groupId == MENU_CONSTANT) {
+                keyboardUser.insertText(title.toString(), 0);
+            } else {
+                return false;
+            }
+            return true;
+        }
+    }
 }

app/src/main/java/org/solovyev/android/calculator/function/FunctionParamsView.java

@@ -27,6 +27,8 @@ import android.content.Context;
 import android.os.Build;
 import android.os.Parcel;
 import android.os.Parcelable;
+import android.text.Editable;
+import android.text.TextUtils;
 import android.util.AttributeSet;
 import android.view.View;
 import android.view.ViewGroup;
@@ -38,6 +40,7 @@ import android.widget.TextView;
 
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.App;
+import org.solovyev.android.calculator.R;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -146,6 +149,7 @@ public class FunctionParamsView extends LinearLayout {
         }
         paramView.setInputType(EditorInfo.TYPE_CLASS_TEXT);
         paramView.setId(id);
+        paramView.setHint(R.string.c_function_parameter);
         rowView.addView(paramView, new LayoutParams(0, WRAP_CONTENT, 3));
 
         addView(rowView, new ViewGroup.LayoutParams(MATCH_PARENT, WRAP_CONTENT));
@@ -195,7 +199,10 @@ public class FunctionParamsView extends LinearLayout {
         for (int i = 1; i < getChildCount(); i++) {
             final ViewGroup row = getRowByIndex(i);
             final EditText paramView = (EditText) row.getChildAt(PARAM_VIEW_INDEX);
-            params.add(paramView.getText().toString());
+            final Editable param = paramView.getText();
+            if (!TextUtils.isEmpty(param)) {
+                params.add(param.toString());
+            }
         }
 
         return params;

app/src/main/java/org/solovyev/android/calculator/history/EditHistoryFragment.java

@@ -1,5 +1,6 @@
 package org.solovyev.android.calculator.history;
 
+import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.os.Bundle;
@@ -11,14 +12,16 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.widget.EditText;
 import android.widget.TextView;
-import butterknife.Bind;
-import butterknife.ButterKnife;
+
 import org.solovyev.android.calculator.AppComponent;
 import org.solovyev.android.calculator.BaseDialogFragment;
 import org.solovyev.android.calculator.R;
 
 import javax.inject.Inject;
 
+import butterknife.Bind;
+import butterknife.ButterKnife;
+
 public class EditHistoryFragment extends BaseDialogFragment {
 
     public static final String ARG_STATE = "state";
@@ -81,6 +84,7 @@ public class EditHistoryFragment extends BaseDialogFragment {
         });
     }
 
+    @SuppressLint("InflateParams")
     @NonNull
     @Override
     protected View onCreateDialogView(@NonNull Context context, @NonNull LayoutInflater inflater, @Nullable Bundle savedInstanceState) {

app/src/main/res/values-small/dimens.xml

@@ -29,4 +29,5 @@
 
     <dimen name="cpp_display_text_size">20sp</dimen>
     <dimen name="cpp_display_text_size_mobile">20sp</dimen>
+    <dimen name="cpp_kb_button_size">40dp</dimen>
 </resources>

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

@@ -39,4 +39,5 @@
     <dimen name="cpp_onscreen_main_padding">1dp</dimen>
 
     <dimen name="cpp_dialog_spacing">20dp</dimen>
+    <dimen name="cpp_kb_button_size">50dp</dimen>
 </resources>

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

@@ -60,5 +60,17 @@
     <item name="acl_wizard_prev_button" type="id" />
     <item name="acl_wizard_next_button" type="id" />
     <item name="acl_wizard_content" type="id" />
+    <item name="cpp_kb_button_multiply" type="id" />
+    <item name="cpp_kb_button_clear" type="id" />
+    <item name="cpp_kb_button_divide" type="id" />
+    <item name="cpp_kb_button_backspace" type="id" />
+    <item name="cpp_kb_button_plus" type="id" />
+    <item name="cpp_kb_button_space" type="id" />
+    <item name="cpp_kb_button_brackets" type="id" />
+    <item name="cpp_kb_button_minus" type="id" />
+    <item name="cpp_kb_button_keyboard" type="id" />
+    <item name="cpp_kb_button_functions" type="id" />
+    <item name="cpp_kb_button_constants" type="id" />
+    <item name="cpp_kb_button_close" type="id" />
 
 </resources>

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

@@ -149,6 +149,7 @@
     <string name="c_function_value">Value</string>
     <string name="c_function_description">Description</string>
     <string name="c_function_parameters">Parameters</string>
+    <string name="c_function_parameter">Parameter</string>
     <string name="function_create_function">Create function</string>
     <string name="function_edit_function">Edit function</string>
     <string name="function_name_is_not_valid">Name of function is not valid: name must start with a letter, can contain letters, digits and underscore.</string>