旋转UIView后检查UIButton的位置

Question

我有一个按钮，我在UIImageView上添加。当用户触摸屏幕 时，UIImageView将旋转，我想知道是否有方法在旋转完成后获取按钮的新位置。

现在，我让所有的时间用这种方法原来的位置：

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { 

    NSLog(@"Xposition : %f", myButton.frame.origin.x); 
    NSLog(@"Yposition : %f", myButton.frame.origin.y); 

} 

感谢，

Answer 1

这是一个棘手的问题。参考UIView关于帧属性的文档，它指出：

警告：如果transform属性不是标识转换，则此属性的值是未定义的，因此应该忽略。

所以诀窍是找到一个解决方法，它取决于你确切的需要。如果你只需要一个近似值，或者如果你的旋转总是90度的倍数，那么CGRectApplyAffineTransform()函数可能工作得很好。将它传递给感兴趣的UIButton的（未转换的）框架，以及按钮的当前转换，它会给你一个转换矩形。请注意，由于rect被定义为原点，宽度和高度，因此无法定义边长不平行于屏幕边的矩形。在不平行的情况下，它将返回旋转矩形的最小可能的边界矩形。

现在，如果你需要知道一个或全部转化点的精确坐标，我已经写代码之前计算它们，但它是一个有点更复杂：

- (void)computeCornersOfTransformedView:(UIView*)transformedView relativeToView:(UIView*)parentView { 
    /* Computes the coordinates of each corner of transformedView in the coordinate system 
    * of parentView. Each is corner represented by an independent CGPoint. Doesn't do anything 
    * with the transformed points because this is, after all, just an example. 
    */ 

    // Cache the current transform, and restore the view to a normal position and size. 
    CGAffineTransform cachedTransform = transformedView.transform; 
    transformedView.transform = CGAffineTransformIdentity; 

    // Note each of the (untransformed) points of interest. 
    CGPoint topLeft = CGPointMake(0, 0); 
    CGPoint bottomLeft = CGPointMake(0, transformedView.frame.size.height); 
    CGPoint bottomRight = CGPointMake(transformedView.frame.size.width, transformedView.frame.size.height); 
    CGPoint topRight = CGPointMake(transformedView.frame.size.width, 0); 

    // Re-apply the transform. 
    transformedView.transform = cachedTransform; 

    // Use handy built-in UIView methods to convert the points. 
    topLeft = [transformedView convertPoint:topLeft toView:parentView]; 
    bottomLeft = [transformedView convertPoint:bottomLeft toView:parentView]; 
    bottomRight = [transformedView convertPoint:bottomRight toView:parentView]; 
    topRight = [transformedView convertPoint:topRight toView:parentView]; 

    // Do something with the newly acquired points. 
} 

请原谅任何轻微代码中的错误，我写在浏览器中。不是最有用的IDE ...