UIView Positioning for iPhone: Any concept of "Z-Index"?
I know if I want to add a black background to a UIImageView, I can create an UIImageView that is a bit smaller than the UIView it's contained in. If I do this, the UIImageView is positioned on top of the black background.
Just hypotheti开发者_如何学Gocally speaking, suppose I want the black background UIView on TOP of the UIImageView (so that it covers the image), how do I do this? Is there a concept of a z-index?
Here's my code to add a black background to an image:
UIView *blackBG = [[UIView alloc] initWithFrame:CGRectMake(0,0,100,100)];
blackBG.backgroundColor = [UIColor blackColor];
UIImageView *myPicture = [[UIImageView alloc] initWithImage:
[UIImage imageNamed: @"myPicture.jpg"]];
int borderWidth = 10;
myPicture.frame = CGRectMake(borderWidth,
borderWidth,
blackBG.frame.size.width-borderWidth*2,
blackBG.frame.size.height-borderWidth*2)];
[blackBG addSubview: myPicture];
Subviews are layered, you can send a subview to the back with...
[myView sendSubviewToBack:mySubView];
or bringSubviewToFront etc.
You can also do one of these...
[myView insertSubview:mySubview atIndex:0]; //Places it at the bottom
[myView insertSubview:mySubview belowSubview:anotherSubview]; //Places it below anotherSubview
As soon as you add a view as a subview to another view however, the parent view is the bottom of the stack. You can play around with CALayer z orders but you are bypassing the general approach of views and subviews.
Create a single view as a parent for both the bg view and the imageview, then you can order them how you like.
UPDATE: I have a UIView+Layout category which has nice [subview sendToBack];
and [subview bringToFront];
which you may find useful.... article here
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