RectF oval = new RectF(x, y, x1, y1);
paint.setColor(Color.WHITE);//設定圓環的顏色
paint.setStyle(Paint.Style.STROKE);//設定空心
paint.setAntiAlias(true);//消除鋸齒
paint.setStrokeWidth(Utils.dip2px(getContext(), 2));
paint.setAlpha(255 - alpha);
canvas.drawArc(oval, -90, circle, false, paint);//根據進度畫圓弧 

ValueAnimator animator = ValueAnimator.ofFloat
 
(0, 360);
animator.setDuration((long) 1000).setRepeatCount(0);
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
    @Override
public void onAnimationUpdate(ValueAnimator animation) {
        Float angle = (Float) animation.getAnimatedValue();
        circle = angle;
        invalidate();
    }
});
animator.addListener(new 
 
AnimatorListenerAdapter() {
    @Override
public void onAnimationEnd(Animator animation) {
        AlphaMax();
    }
});
// 自定義開始減速到0後加速到初始值的Interpolator
animator.setInterpolator(new LinearInterpolator());
animator.start();