Android Open Source - wally Alpha Pattern Drawable

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License

The source code is released under:

Apache License

Java Source Code

/*
 * Copyright (C) 2010 Daniel Nilsson// w w w . j a v  a  2s  . c o  m
 *
 * 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 net.margaritov.preference.colorpicker.drawable;

import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;

/**
 * This drawable will draw a simple white and gray chessboard pattern.
 * It's pattern you will often see as a background behind a 
 * partly transparent image in many applications.
 * @author Daniel Nilsson
 */
public class AlphaPatternDrawable extends Drawable {
  
  private int mRectangleSize = 10;

  private Paint mPaint = new Paint();
  private Paint mPaintWhite = new Paint();
  private Paint mPaintGray = new Paint();

  private int numRectanglesHorizontal;
  private int numRectanglesVertical;

  /**
   * Bitmap in which the pattern will be cached. 
   * This is so the pattern will not have to be recreated each time draw() gets called.
   * Because recreating the pattern i rather expensive. I will only be recreated if the
   * size changes.
   */
  private Bitmap    mBitmap;
  
  public AlphaPatternDrawable(int rectangleSize) {
    mRectangleSize = rectangleSize;
    mPaintWhite.setColor(0xffffffff);
    mPaintGray.setColor(0xffcbcbcb);
  }

  @Override
  public void draw(Canvas canvas) {
    canvas.drawBitmap(mBitmap, null, getBounds(), mPaint);
  }

  @Override
  public int getOpacity() {
    return 0;
  }

  @Override
  public void setAlpha(int alpha) {
    throw new UnsupportedOperationException("Alpha is not supported by this drawwable.");
  }

  @Override
  public void setColorFilter(ColorFilter cf) {
    throw new UnsupportedOperationException("ColorFilter is not supported by this drawwable.");
  }

  @Override
  protected void onBoundsChange(Rect bounds) {
    super.onBoundsChange(bounds);

    int height = bounds.height();
    int width = bounds.width();

    numRectanglesHorizontal = (int) Math.ceil((width / mRectangleSize));
    numRectanglesVertical = (int) Math.ceil(height / mRectangleSize);

    generatePatternBitmap();

  }
  
  /**
   * This will generate a bitmap with the pattern 
   * as big as the rectangle we were allow to draw on.
   * We do this to chache the bitmap so we don't need to
   * recreate it each time draw() is called since it 
   * takes a few milliseconds.
   */
  private void generatePatternBitmap(){
    
    if(getBounds().width() <= 0 || getBounds().height() <= 0){
      return;
    }
    
    mBitmap = Bitmap.createBitmap(getBounds().width(), getBounds().height(), Config.ARGB_8888);      
    Canvas canvas = new Canvas(mBitmap);
    
    Rect r = new Rect();
    boolean verticalStartWhite = true;
    for (int i = 0; i <= numRectanglesVertical; i++) {

      boolean isWhite = verticalStartWhite;
      for (int j = 0; j <= numRectanglesHorizontal; j++) {

        r.top = i * mRectangleSize;
        r.left = j * mRectangleSize;
        r.bottom = r.top + mRectangleSize;
        r.right = r.left + mRectangleSize;
        
        canvas.drawRect(r, isWhite ? mPaintWhite : mPaintGray);

        isWhite = !isWhite;
      }

      verticalStartWhite = !verticalStartWhite;

    }
    
  }
  
}

Java Source Code List

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