如何将子视图添加到另一个子视图并使其显示？

Question

What I am doing it creating a UIImageView and hope to add it to a UIScrollingView as its scrolling content, but it never appears. So I tried the following code and the problem is now pretty clear to me. How can I add a subview to another subview?

 //in myViewController.m
 @synthesize scrollView = _scrollView;
 - (void) viewDidLoad{ 
     UIView* simpleView = [[UIView alloc] initWithFrame:CGRectMake(0,0,300,200)];
     [simpleView setBackgroundColor: [UIColor BlueColor]];
     [self.view addSubview: simpleView]  //this would work, the simple view appears
     [self.scrollView addSubview: simpleView]  //this would not work, the simple view doesn't appear
 }

the scrollView property is hooked up with ScollView in the storyboard, which is the only thing in that controller

Answer 1

You need to do this:

[self.view addSubview: scrollview]  
[self.scrollView addSubview: simpleView] 

Basically add one on top of the other not everything is being stacked on the view. Image on top of view on top of self pretty much

Answer 2

One possibility: The scroll view might not be linked to the scrollView property from your xib/storyboard. Set a breakpoint in this method and check it.

Answer 3

A view can only have one superView.

So when you do this:

[self.view addSubview: simpleView];
[self.scrollView addSubview: simpleView];

You just set the simpleView superView to self.view then you replace it by self.scrollView. simpleView is no longer the subview of self.view.

As said by ECEsurfer, stack your views:

[self.view addSubview: scrollview];
[self.scrollView addSubview: simpleView];

Hope it helps !