我试图在UI
ImageView中使用特定图像绘制一些圆圈.这就是我想要做的事情：
UIGraphicsBeginImageContext(self.view.bounds.size); CGContextRef contextRef = UIGraphicsGetCurrentContext(); CGContextSetLineWidth(contextRef,2.0); CGContextSetStrokeColorWithColor(contextRef,[color CGColor]); CGRect circlePoint = (CGRectMake(coordsFinal.x,coordsFinal.y,50.0,50.0)); CGContextStrokeEllipseInRect(contextRef,circlePoint); UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); [photoView addSubview:image];
圆圈绘制得很好,但我希望PhotoView充当它的遮罩.因此,例如,如果我使用动画将UIImageView移出UIView,我希望圆圈随之移动.重要的是坐标相对于整个屏幕.
解决方法
请改用Core Animation的形状图层.
CAShapeLayer *circleLayer = [CAShapeLayer layer];
// Give the layer the same bounds as your image view
[circleLayer setBounds:CGRectMake(0.0f,0.0f,[photoView bounds].size.width,[photoView bounds].size.height)];
// Position the circle anywhere you like,but this will center it
// In the parent layer,which will be your image view's root layer
[circleLayer setPosition:CGPointMake([photoView bounds].size.width/2.0f,[photoView bounds].size.height/2.0f)];
// Create a circle path.
UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:
CGRectMake(0.0f,50.0f,50.0f)];
// Set the path on the layer
[circleLayer setPath:[path CGPath]];
// Set the stroke color
[circleLayer setStrokeColor:[[UIColor redColor] CGColor]];
// Set the stroke line width
[circleLayer setLineWidth:2.0f];
// Add the sublayer to the image view's layer tree
[[photoView layer] addSublayer:circleLayer];
现在,如果您为包含此图层的UIImageView设置动画,该图层将随之移动,因为它是子图层.现在没有必要覆盖drawRect：.
