view.superView.bringToFront(view)。这样的间接让一部分人（包括我自己）感觉到不习惯，为此我们可以给UIView添加一个Z-Order相关的Category以避免了这种间接，这样我们就可以用我们习惯的方式来控制视图的Z-Order了。
UIView的Z-Order Category的代码如下：
声明：
@interface UIView (Z-Order)
-(int)getSubviewIndex;
-(void)bringToFront;
-(void)sendToBack;
-(void)bringOneLevelUp;
-(void)sendOneLevelDown;
-(BOOL)isInFront;
-(BOOL)isAtBack;
-(void)swapDepthsWithView:(UIView*)swapView;
@end
实现：
@implementation UIView(Z-Order)
-(int)getSubviewIndex
{
return [self.superview.subviews indexOfObject:self];
}
-(void)bringToFront
{
[self.superview bringSubviewToFront:self];
}
-(void)sendToBack
{
[self.superview sendSubviewToBack:self];
}
-(void)bringOneLevelUp
{
int currentIndex = [self getSubviewIndex];
[self.superview exchangeSubviewAtIndex:currentIndex withSubviewAtIndex:currentIndex+1];
}
-(void)sendOneLevelDown
{
int currentIndex = [self getSubviewIndex];
[self.superview exchangeSubviewAtIndex:currentIndex withSubviewAtIndex:currentIndex-1];
}
-(BOOL)isInFront
{
return ([self.superview.subviews lastObject]==self);
}
-(BOOL)isAtBack
{
return ([self.superview.subviews objectAtIndex:0]==self);
}
-(void)swapDepthsWithView:(UIView*)swapView
{
[self.superview exchangeSubviewAtIndex:[self getSubviewIndex] withSubviewAtIndex:[swapView getSubviewIndex]];
}
@end