Android编程之书架效果背景图处理方法

public class myGridView extends GridView {
 private Bitmap background;
 private Bitmap newBackGround;
 public myGridView(Context context, AttributeSet attrs) {
  super(context, attrs);
  //加载做为背景的图片
  background = BitmapFactory.decodeResource(getResources(), R.drawable.bookcase_bg);
 }
 protected void dispatchDraw(Canvas canvas) {
  //取得加载的背景图片高，宽
  int width = background.getWidth();
  int height = background.getHeight();
  //取得手机屏幕的高，宽，这里要注意，不要在构造方法中写，因为那样取到的值是0
  int scWidth = this.getWidth();
  int scHeight = this.getHeight();
  //计算缩放率，新尺寸除原始尺寸,我这里因为高不用变，所以就是原大小的比例1
  //这里一定要注意，这里的值是比例，不是值。
  float scaleWidth = ((float) scWidth) / width;
  float scaleHeight = 1;
  //Log.v("info", "width:" + width + "height:" + height + "scWidth:" + scWidth + "scaleWidth:" + scaleWidth + "scaleHeight:" + scaleHeight);
  // 创建操作图片用的matrix对象
  Matrix matrix = new Matrix();
  // 缩放图片动作
  matrix.postScale(scaleWidth, scaleHeight);
  //生成新的图片
  newBackGround = Bitmap.createBitmap(background, 0, 0,
    width, height, matrix, true);
  int count = getChildCount();
  //Log.v("myGridView-Count", count + "");
  int top = 185;
  //Log.v("getChildAt", getChildAt(0).getTop() + "");
  int backgroundWidth = newBackGround.getWidth();
  int backgroundHeight = newBackGround.getHeight();
  for (int y = top; y<scHeight; y += 223){
   //for (int x = 0; x<scWidth; x += backgroundWidth){
    canvas.drawBitmap(newBackGround, 0, y, null);
   //}
  }
  super.dispatchDraw(canvas);
 }
 //禁止滚动 条滚动
 public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
   int expandSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2,
    MeasureSpec.AT_MOST);
   super.onMeasure(widthMeasureSpec, expandSpec);
  }
}