How to achieve image shadow effect on Android

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public class ShaderEffect extends Activity {
  @Override
  public void onCreate(Bundle savedInstanceState) {
    (savedInstanceState);
    setContentView(new ImageEffect(this));
  }
  class ImageEffect extends View{
    Paint paint; 
    public ImageEffect (Context context){
      super(context);
      paint = new Paint();//Initialize the brush to use for the shadow effect behind it.      (true);//Remove jagging.      (5f, 5.0f, 5.0f, );//Set the shadow layer, this is the key.      (new PorterDuffXfermode(Mode.SRC_IN));
    }
    @Override
    public void onDraw(Canvas canvas){
      (canvas);
      int posX = 20;
      int posY = 50;
      int PicWidth,PicHegiht; 
      Drawable drawable = getResources().getDrawable();
      Drawable dbe = getResources().getDrawable().mutate();//If the mutate method is not called, the original image will also be changed, because the callee resource is the same and all objects are in a shared state.      Drawable drawTest = getResources().getDrawable();
      Bitmap bmp = (getResources(), );
      PicWidth = ();
      PicHegiht = ();
      (posX, (2 * posY) + PicHegiht, posX + PicWidth, (2 * posY) + 2 * PicHegiht );
      (posX,posY,posX+PicWidth,posY+PicHegiht);
      (0, 0, PicWidth, PicHegiht);
      ();//Set the canvas color      (Canvas.MATRIX_SAVE_FLAG);
      (0x7f000000,.SRC_IN);
      (posX + (int)(0.9 * PicWidth/2), posY + PicHegiht/2);//The image translation is to form a shadow effect just after the original image.      (-0.9F, 0.0F);//Image tilt effect.      (1.0f, 0.5f);//The image (actually a canvas) is scaled, and the Y direction is reduced to 1/2.      (canvas);//This is the shadow rendering of the original image. If you draw it first before the original image, it will be in the lower layer.      ();
      ();
      (Canvas.MATRIX_SAVE_FLAG);
      (canvas);//This is the original image of the painting. Since canvas has a layered effect, it will be covered on the shadow.      ();
      //The default effect original image      (Canvas.MATRIX_SAVE_FLAG);
      (canvas);
      ();
      //Picture Shadow Effect      (Canvas.MATRIX_SAVE_FLAG);
      //Rect rect = new Rect(2*posX + PicWidth, 2*posY + PicHegiht, 2*posX + 2*PicWidth, 2*posY + 2*PicHegiht);//This is the theoretical shadow graph coordinate      Rect rect = new Rect(2*posX + PicWidth + 3, 2*posY + PicHegiht + 3, 2*posX + 2*PicWidth - 2, 2*posY + 2*PicHegiht - 2);
      //Because the actual size of the picture is larger than the displayed image, the size needs to be changed appropriately to achieve better results      RectF rectF = new RectF(rect);
      (rectF, 10f, 10f, paint);//Draw a rounded rectangle based on the original rectangle, and it also has a shadow layer.      (bmp, 2*posX + PicWidth, 2*posY + PicHegiht, null);//Draw the original picture.      ();
    }
  }
}