Android的GridView控件点击图片变暗效果

 @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));

 }