content: /*
   * Copyright (C) 2010 Daniel Nilsson
   *
   * 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.androzic.ui;
  
  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 that draws 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 mPaintWhite = new Paint();
  	private Paint mPaintGray = new Paint();
  
  	/**
  	 * Bitmap in which the pattern will be cached.
  	 */
  	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(), null);
  	}
  
  	@Override
  	public int getOpacity() {
  		return 0;
  	}
  
  	@Override
  	public void setAlpha(int alpha) {
  		throw new UnsupportedOperationException("Alpha is not supported by this drawable.");
  	}
  
  	@Override
  	public void setColorFilter(ColorFilter cf) {
  		throw new UnsupportedOperationException("ColorFilter is not supported by this drawable.");
  	}
  
  	@Override
  	protected void onBoundsChange(Rect bounds) {
  		super.onBoundsChange(bounds);
  		generatePatternBitmap();
  	}
  
  	/**
  	 * This will generate a bitmap with the pattern
  	 * as big as the rectangle we were allow to draw on.
  	 * We do this to cache the bitmap so we don't need to
  	 * recreate it each time draw() is called since it
  	 * takes a few milliseconds.
  	 */
  	private void generatePatternBitmap()
  	{
  		int height = getBounds().height();
  		int width = getBounds().width();
  
  		if (width <= 0 || height <= 0)
  			return;
  
  		int numRectanglesHorizontal = (int) Math.ceil((width / mRectangleSize));
  		int numRectanglesVertical = (int) Math.ceil(height / mRectangleSize);
  
  		mBitmap = Bitmap.createBitmap(width, 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;
  
  		}
  
  	}
  
  }