Android Clip机制实现扩展动画

原创
2022/08/20 11:10
阅读数 94

Clip可以避免with和height被扭曲,利用clip机制,可以实现卷轴、圆圈扩散、前一页翻页动画等。

 

public class ClipTransitionLayout extends FrameLayout implements ViewTreeObserver.OnPreDrawListener, ValueAnimator.AnimatorUpdateListener {
    private static final String TAG = "ClipTransitionLayout";
    private final Rect mClipRect;
    private float mRoundRadius;
    private Path path = new Path();
    private ValueAnimator valueAnimator;

    public ClipTransitionLayout(Context context) {
        this(context,null);
    }

    public ClipTransitionLayout(Context context, AttributeSet attrs) {
        this(context, attrs,0);
    }

    public ClipTransitionLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        setClipChildren(true);
        mClipRect = new Rect(0, 0, 0, 0);

    }



    @Override
    public boolean onPreDraw() {
        mRoundRadius = Math.min(getWidth(),getHeight())/2;
        getViewTreeObserver().removeOnPreDrawListener(this);
        valueAnimator = ValueAnimator.ofFloat(0, 1);
        valueAnimator.setInterpolator(new AccelerateInterpolator());
        valueAnimator.setDuration(1000L);
        valueAnimator.addUpdateListener(this);
        valueAnimator.start();
        return false;
    }

    @Override
    public void onAnimationUpdate(ValueAnimator animation) {
        float fraction = animation.getAnimatedFraction();
        mClipRect.left = 0;
        mClipRect.top = 0;
        mClipRect.right = (int) (getWidth()*fraction);
        mClipRect.bottom = getHeight();
        if(fraction==1){
            mRoundRadius = 0;
        }
        postInvalidate();

    }
//硬件加速时,虽然每个View都通过自己的RenderNode获得和其他View无交集的Canvas,但是在合成View时,依然遵循了由Parent->Child的合成逻辑,因此dispatchDraw中,
//clipath在合成时自动处理,保证父布局可以“裁剪”子view的绘制区域
    @Override
    protected void dispatchDraw(Canvas canvas) {
        if(isInEditMode()){
            mRoundRadius = Math.min(getWidth(),getHeight())/2;
            mClipRect.right = getWidth()/2;
        }
        int saveCount = 0;

        if(canvas.isHardwareAccelerated()) {
             saveCount = canvas.save(); 
//硬件加速时,android官方不推荐使用saveLayer离屏渲染
        }else{
//离屏渲染
             saveCount = canvas.saveLayer(0,0,getWidth(),getHeight(),null,Canvas.ALL_SAVE_FLAG);
        }
        if(mRoundRadius==0) {
            canvas.clipRect(mClipRect);
        }else{
            path.reset();
            path.addRoundRect(new RectF(mClipRect.left,mClipRect.top,mClipRect.right,mClipRect.bottom),
                    new float[]{0,0,0,0,mRoundRadius,mRoundRadius,0,0},
                    Path.Direction.CCW);
            canvas.clipPath(path);
        }
        super.dispatchDraw(canvas);
        canvas.restoreToCount(saveCount);
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        getViewTreeObserver().addOnPreDrawListener(this);
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        getViewTreeObserver().removeOnPreDrawListener(this);
        if(valueAnimator!=null){
            valueAnimator.cancel();
        }
    }

}
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