ViewAnimationUtils知识点

今天看到了一个视图慢慢显示出来的动画，心生好奇，决定一探究竟，原来，实现非常简单，使用ViewAnimationUtils. createCircularReveal（）方法可以实现，这个方法返回一个动画器，该动画器可以使剪贴圆具有动画效果。具体代码如下：

    final View view = findViewById(R.id.view);
    view.addOnLayoutChangeListener(new View.OnLayoutChangeListener() {
        @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
        @Override
        public void onLayoutChange(View v, int left, int top, int right, int bottom,
                                   int oldLeft, int oldTop, int oldRight, int oldBottom) {
            int x = (int) (view.getWidth() / 2 );
            int y = (int) (view.getHeight() / 2 );
            // x,y 是动画圆心点
            Animator animator = ViewAnimationUtils.createCircularReveal(view, x, y,
                    0,view.getHeight());
            animator.setDuration(4000);
            animator.start();
            animator.addListener(new Animator.AnimatorListener() {
                @Override
                public void onAnimationStart(Animator animation) { }
    
                @Override
                public void onAnimationEnd(Animator animation) {
                    view.setVisibility(View.GONE);
                }
    
                @Override
                public void onAnimationCancel(Animator animation) { }
    
                @Override
                public void onAnimationRepeat(Animator animation) { }
            });
        }
    });