Android编程实现GridView控件点击图片变暗效果的方法

@Override
public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  grid = (GridView) findViewById(R.id.grid);
  grid.setAdapter(new GridAdapter());
  grid.setOnItemClickListener(new OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
        long arg3) {
      Toast.makeText(MainActivity.this, "ddd", 1000).show();
    }
  });
}
class GridAdapter extends BaseAdapter {
  @Override
  public int getCount() {
    return imgs.length;
  }
  @Override
  public Object getItem(int arg0) {
    return arg0;
  }
  @Override
  public long getItemId(int arg0) {
    return arg0;
  }
  @Override
  public View getView(int arg0, View view, ViewGroup arg2) {
    if (view == null) {
      holder = new ViewHolder();
      view = LayoutInflater.from(MainActivity.this).inflate(
          R.layout.imgs, null);
      holder.view = (ImageView) view.findViewById(R.id.gridimg);
      view.setTag(holder);
    } else {
      holder = (ViewHolder) view.getTag();
    }
    holder.view.setImageResource(imgs[arg0]);
    holder.view.setOnTouchListener(onTouchListener);
    return view;
  }
  class ViewHolder {
    ImageView view;
  }
  public OnTouchListener onTouchListener = new View.OnTouchListener() {
    @Override
    public boolean onTouch(View view, MotionEvent event) {
      switch (event.getAction()) {
      case MotionEvent.ACTION_UP:
        changeLight((ImageView) view, 0);
        // onclick
        break;
      case MotionEvent.ACTION_DOWN:
        changeLight((ImageView) view, -80);
        break;
      case MotionEvent.ACTION_MOVE:
        // changeLight(view, 0);
        break;
      case MotionEvent.ACTION_CANCEL:
        changeLight((ImageView) view, 0);
        break;
      default:
        break;
      }
      return true;
    }
  };
}
private void changeLight(ImageView imageview, int brightness) {
  ColorMatrix matrix = new ColorMatrix();
  matrix.set(new float[] { 1, 0, 0, 0, brightness, 0, 1, 0, 0,
      brightness, 0, 0, 1, 0, brightness, 0, 0, 0, 1, 0 });
  imageview.setColorFilter(new ColorMatrixColorFilter(matrix));
}