private void updateShaderMatrix() {
 float scale;
 float dx = 0;
 float dy = 0;
 mShaderMatrix.set(null);
 if (mBitmapWidth * mDrawableRect.height() > mDrawableRect.width()
  * mBitmapHeight) {
 scale = mDrawableRect.height() / (float) mBitmapHeight;
 dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f;
 } else {
 scale = mDrawableRect.width() / (float) mBitmapWidth;
 dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f;
 }
 mShaderMatrix.setScale(scale, scale);
 mShaderMatrix.postTranslate((int) (dx 0.5f) mBorderWidth,
 (int) (dy 0.5f) mBorderWidth);

 mBitmapShader.setLocalMatrix(mShaderMatrix);
}

public boolean onTouchEvent(MotionEvent event) {
 ViewGroup parent = getScrollableParent();
 switch (event.getAction()) {
 case MotionEvent.ACTION_DOWN:
 mHolderEventFlag = !CoverManager.getInstance().isRunning();
 if (mHolderEventFlag) {
  parent.requestDisallowInterceptTouchEvent(true);
  CoverManager.getInstance().start(this, event.getRawX(), 
  event.getRawY(), mOnDragCompeteListener);
 }
 break;
 case MotionEvent.ACTION_MOVE:
 if (mHolderEventFlag) {
  CoverManager.getInstance().update(event.getRawX(),
  event.getRawY());
 }
 break;
 case MotionEvent.ACTION_UP:
 case MotionEvent.ACTION_CANCEL:
 if (mHolderEventFlag) {
  parent.requestDisallowInterceptTouchEvent(false);
  CoverManager.getInstance().finish(this, event.getRawX(),
  event.getRawY());
 }
 break;
 }
 return true;
}