【安卓特效】怎样给ImageView加上遮罩,点击时泛黑、或泛白、？

基本思路:

方法1.遮罩可直接叠加一层带alpha的纯白、或纯黑View,可直接在ImageView外套一层FrameLayout,其foreground(一般同学可能仅仅知道background,事实上framelayout还有foreground)给定一个selector(按下时给0x33000000,即泛黑),到位。

方法2.重写imageView,按下状态改变时invalidate(触发onDraw),onDraw中依据按下状态绘制0x33000000。注意imageView.setClickable(true),或imageView.setOnClickListener时才可触发dispatchSetPressed。

@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		// 取id
		// imgTest = (ImageView) findViewById(R.id.imgTest);
		loMain = (RelativeLayout) findViewById(R.id.loMain);

		findViewById(R.id.btn1).setOnClickListener(this);
		findViewById(R.id.btn2).setOnClickListener(this);

		MyImg myImg = new MyImg(this);
		myImg.setImageResource(R.drawable.meinv);
		myImg.setClickable(true);
		loMain.addView(myImg);
	}

	private class MyImg extends ImageView {

		public MyImg(Context context) {
			super(context);
		}

		@Override
		protected void onDraw(Canvas canvas) {
			// TODO Auto-generated method stub
			super.onDraw(canvas);

			if (isPressed())
				canvas.drawColor(0x33000000);
		}

		@Override
		protected void dispatchSetPressed(boolean pressed) {
			// TODO Auto-generated method stub
			super.dispatchSetPressed(pressed);
			invalidate();
		}
	}

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