Android example source code file (CandidateView.java)

This example Android source code file (CandidateView.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, arraylist, candidateview, drawing, empty_list, gesturedetector, graphics, max_suggestions, motionevent, out_of_bounds, override, paint, rect, resources, scroll_pixels, softkeyboard, string, ui, view, x_gap

The CandidateView.java Android example source code

/*
 * Copyright (C) 2008-2009 Google Inc.
 * 
 * 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.
 */

package com.example.android.softkeyboard;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;

import java.util.ArrayList;
import java.util.List;

public class CandidateView extends View {

    private static final int OUT_OF_BOUNDS = -1;

    private SoftKeyboard mService;
    private List<String> mSuggestions;
    private int mSelectedIndex;
    private int mTouchX = OUT_OF_BOUNDS;
    private Drawable mSelectionHighlight;
    private boolean mTypedWordValid;
    
    private Rect mBgPadding;

    private static final int MAX_SUGGESTIONS = 32;
    private static final int SCROLL_PIXELS = 20;
    
    private int[] mWordWidth = new int[MAX_SUGGESTIONS];
    private int[] mWordX = new int[MAX_SUGGESTIONS];

    private static final int X_GAP = 10;
    
    private static final List<String> EMPTY_LIST = new ArrayList();

    private int mColorNormal;
    private int mColorRecommended;
    private int mColorOther;
    private int mVerticalPadding;
    private Paint mPaint;
    private boolean mScrolled;
    private int mTargetScrollX;
    
    private int mTotalWidth;
    
    private GestureDetector mGestureDetector;

    /**
     * Construct a CandidateView for showing suggested words for completion.
     * @param context
     * @param attrs
     */
    public CandidateView(Context context) {
        super(context);
        mSelectionHighlight = context.getResources().getDrawable(
                android.R.drawable.list_selector_background);
        mSelectionHighlight.setState(new int[] {
                android.R.attr.state_enabled,
                android.R.attr.state_focused,
                android.R.attr.state_window_focused,
                android.R.attr.state_pressed
        });

        Resources r = context.getResources();
        
        setBackgroundColor(r.getColor(R.color.candidate_background));
        
        mColorNormal = r.getColor(R.color.candidate_normal);
        mColorRecommended = r.getColor(R.color.candidate_recommended);
        mColorOther = r.getColor(R.color.candidate_other);
        mVerticalPadding = r.getDimensionPixelSize(R.dimen.candidate_vertical_padding);
        
        mPaint = new Paint();
        mPaint.setColor(mColorNormal);
        mPaint.setAntiAlias(true);
        mPaint.setTextSize(r.getDimensionPixelSize(R.dimen.candidate_font_height));
        mPaint.setStrokeWidth(0);
        
        mGestureDetector = new GestureDetector(new GestureDetector.SimpleOnGestureListener() {
            @Override
            public boolean onScroll(MotionEvent e1, MotionEvent e2,
                    float distanceX, float distanceY) {
                mScrolled = true;
                int sx = getScrollX();
                sx += distanceX;
                if (sx < 0) {
                    sx = 0;
                }
                if (sx + getWidth() > mTotalWidth) {                    
                    sx -= distanceX;
                }
                mTargetScrollX = sx;
                scrollTo(sx, getScrollY());
                invalidate();
                return true;
            }
        });
        setHorizontalFadingEdgeEnabled(true);
        setWillNotDraw(false);
        setHorizontalScrollBarEnabled(false);
        setVerticalScrollBarEnabled(false);
    }
    
    /**
     * A connection back to the service to communicate with the text field
     * @param listener
     */
    public void setService(SoftKeyboard listener) {
        mService = listener;
    }
    
    @Override
    public int computeHorizontalScrollRange() {
        return mTotalWidth;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int measuredWidth = resolveSize(50, widthMeasureSpec);
        
        // Get the desired height of the icon menu view (last row of items does
        // not have a divider below)
        Rect padding = new Rect();
        mSelectionHighlight.getPadding(padding);
        final int desiredHeight = ((int)mPaint.getTextSize()) + mVerticalPadding
                + padding.top + padding.bottom;
        
        // Maximum possible width and desired height
        setMeasuredDimension(measuredWidth,
                resolveSize(desiredHeight, heightMeasureSpec));
    }

    /**
     * If the canvas is null, then only touch calculations are performed to pick the target
     * candidate.
     */
    @Override
    protected void onDraw(Canvas canvas) {
        if (canvas != null) {
            super.onDraw(canvas);
        }
        mTotalWidth = 0;
        if (mSuggestions == null) return;
        
        if (mBgPadding == null) {
            mBgPadding = new Rect(0, 0, 0, 0);
            if (getBackground() != null) {
                getBackground().getPadding(mBgPadding);
            }
        }
        int x = 0;
        final int count = mSuggestions.size(); 
        final int height = getHeight();
        final Rect bgPadding = mBgPadding;
        final Paint paint = mPaint;
        final int touchX = mTouchX;
        final int scrollX = getScrollX();
        final boolean scrolled = mScrolled;
        final boolean typedWordValid = mTypedWordValid;
        final int y = (int) (((height - mPaint.getTextSize()) / 2) - mPaint.ascent());

        for (int i = 0; i < count; i++) {
            String suggestion = mSuggestions.get(i);
            float textWidth = paint.measureText(suggestion);
            final int wordWidth = (int) textWidth + X_GAP * 2;

            mWordX[i] = x;
            mWordWidth[i] = wordWidth;
            paint.setColor(mColorNormal);
            if (touchX + scrollX >= x && touchX + scrollX < x + wordWidth && !scrolled) {
                if (canvas != null) {
                    canvas.translate(x, 0);
                    mSelectionHighlight.setBounds(0, bgPadding.top, wordWidth, height);
                    mSelectionHighlight.draw(canvas);
                    canvas.translate(-x, 0);
                }
                mSelectedIndex = i;
            }

            if (canvas != null) {
                if ((i == 1 && !typedWordValid) || (i == 0 && typedWordValid)) {
                    paint.setFakeBoldText(true);
                    paint.setColor(mColorRecommended);
                } else if (i != 0) {
                    paint.setColor(mColorOther);
                }
                canvas.drawText(suggestion, x + X_GAP, y, paint);
                paint.setColor(mColorOther); 
                canvas.drawLine(x + wordWidth + 0.5f, bgPadding.top, 
                        x + wordWidth + 0.5f, height + 1, paint);
                paint.setFakeBoldText(false);
            }
            x += wordWidth;
        }
        mTotalWidth = x;
        if (mTargetScrollX != getScrollX()) {
            scrollToTarget();
        }
    }
    
    private void scrollToTarget() {
        int sx = getScrollX();
        if (mTargetScrollX > sx) {
            sx += SCROLL_PIXELS;
            if (sx >= mTargetScrollX) {
                sx = mTargetScrollX;
                requestLayout();
            }
        } else {
            sx -= SCROLL_PIXELS;
            if (sx <= mTargetScrollX) {
                sx = mTargetScrollX;
                requestLayout();
            }
        }
        scrollTo(sx, getScrollY());
        invalidate();
    }
    
    public void setSuggestions(List<String> suggestions, boolean completions,
            boolean typedWordValid) {
        clear();
        if (suggestions != null) {
            mSuggestions = new ArrayList<String>(suggestions);
        }
        mTypedWordValid = typedWordValid;
        scrollTo(0, 0);
        mTargetScrollX = 0;
        // Compute the total width
        onDraw(null);
        invalidate();
        requestLayout();
    }

    public void clear() {
        mSuggestions = EMPTY_LIST;
        mTouchX = OUT_OF_BOUNDS;
        mSelectedIndex = -1;
        invalidate();
    }
    
    @Override
    public boolean onTouchEvent(MotionEvent me) {

        if (mGestureDetector.onTouchEvent(me)) {
            return true;
        }

        int action = me.getAction();
        int x = (int) me.getX();
        int y = (int) me.getY();
        mTouchX = x;

        switch (action) {
        case MotionEvent.ACTION_DOWN:
            mScrolled = false;
            invalidate();
            break;
        case MotionEvent.ACTION_MOVE:
            if (y <= 0) {
                // Fling up!?
                if (mSelectedIndex >= 0) {
                    mService.pickSuggestionManually(mSelectedIndex);
                    mSelectedIndex = -1;
                }
            }
            invalidate();
            break;
        case MotionEvent.ACTION_UP:
            if (!mScrolled) {
                if (mSelectedIndex >= 0) {
                    mService.pickSuggestionManually(mSelectedIndex);
                }
            }
            mSelectedIndex = -1;
            removeHighlight();
            requestLayout();
            break;
        }
        return true;
    }
    
    /**
     * For flick through from keyboard, call this method with the x coordinate of the flick 
     * gesture.
     * @param x
     */
    public void takeSuggestionAt(float x) {
        mTouchX = (int) x;
        // To detect candidate
        onDraw(null);
        if (mSelectedIndex >= 0) {
            mService.pickSuggestionManually(mSelectedIndex);
        }
        invalidate();
    }

    private void removeHighlight() {
        mTouchX = OUT_OF_BOUNDS;
        invalidate();
    }
}