我创建了一个自定义视图,它是FrameLayout的父类。在我的视图内部,我创建了遮罩层:
function makeBitmapMask(int animationHeight) {
mask = Bitmap.createBitmap(getMeasuredWidth(), getMeasuredHeight(),
Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(mask);
drawable.setBounds(0, animationHeight, getMeasuredWidth(), getMeasuredHeight());
drawable.draw(canvas);
}
并创建了Paint:
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setXfermode(mPorterDuffXferMode);
接下来我要重写 dispatchDraw 方法:
@Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);
paint.setXfermode(mPorterDuffXferMode);
canvas.drawBitmap(mask, 0.0f, 0.0f, mPaint);
paint.setXfermode(null);
}
为了制作遮罩动画,我运行 Handler:
int animationHeight = 0;
private void animateView() {
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
animateView();
animationHeight += 10;
makeBitmapMask(animationHeight);
invalidate();
}
}, 10);
}
它能够工作,但非常缓慢。
使用ValueAnimator得到相同的结果:
ValueAnimator va = ValueAnimator.ofInt(0, getHeight());
int mDuration = 3000;
va.setDuration(mDuration);
va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
public void onAnimationUpdate(ValueAnimator animation) {
Integer value = (Integer) animation.getAnimatedValue();
makeBitmapMask(value);
invalidate();
}
});
va.start();
我认为makeBitmapMask()很慢。 也许我只能改变遮罩的边界或高度,而不需要在每个动画帧上重新创建新的位图? 制作视图遮罩的正确方法是什么?
ValueAnimator
/ObjectAnimator
- pskink