Android ImageView.draw（）留下痕迹

Question

我正在实现图像裁剪功能。

我正在绘制裁剪矩形并突出显示，如下面的代码示例。这个aproach适用于android 2.x.x.但随着4.x我不得不硬件加速，因为Canvas.clipPath没有按预期工作。

之后，我得到了这些痕迹。我对画布很新，我会很感激任何帮助。

代码示例

Rect viewDrawingRect = new Rect(); 
imageView.getDrawingRect(viewDrawingRect); 

path.addRect(new RectF(drawRect), Path.Direction.CW); 
canvas.clipPath(path, Region.Op.DIFFERENCE); 
canvas.drawRect(viewDrawingRect, hasFocus() ? focusPaint : noFocusPaint); 

canvas.restore(); 
canvas.drawPath(path, outlinePaint); 

int left = drawRect.left; 
int right = drawRect.right; 
int top = drawRect.top; 
int bottom = drawRect.bottom; 

int widthWidth = resizeDrawableWidth.getIntrinsicWidth()/2; 
int widthHeight = resizeDrawableWidth.getIntrinsicHeight()/2; 
int heightHeight = resizeDrawableHeight.getIntrinsicHeight()/2; 
int heightWidth = resizeDrawableHeight.getIntrinsicWidth()/2; 

int xMiddle = drawRect.left + ((drawRect.right - drawRect.left)/2); 
int yMiddle = drawRect.top + ((drawRect.bottom - drawRect.top)/2); 

resizeDrawableWidth.setBounds(left - widthWidth, 
    yMiddle - widthHeight, 
    left + widthWidth, 
    yMiddle + widthHeight); 
resizeDrawableWidth.draw(canvas); 

resizeDrawableWidth.setBounds(right - widthWidth, 
    yMiddle - widthHeight, 
    right + widthWidth, 
    yMiddle + widthHeight); 
resizeDrawableWidth.draw(canvas); 

resizeDrawableHeight.setBounds(xMiddle - heightWidth, 
    top - heightHeight, 
    xMiddle + heightWidth, 
    top + heightHeight); 
resizeDrawableHeight.draw(canvas); 

resizeDrawableHeight.setBounds(xMiddle - heightWidth, 
    bottom - heightHeight, 
    xMiddle + heightWidth, 
    bottom + heightHeight); 
resizeDrawableHeight.draw(canvas); 

Answer 1

尝试拉伸前调用invalidate（）方法。这将更新视图。请参考这http://developer.android.com/reference/android/view/View.html#invalidate()