【安卓特效】如何给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(一般同学可能只知道background,其实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中根据按下状态绘制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();
}
}