ios - How to move custom view to different superview after it was displayed by UIBarButtonItem?

Question

This is the original layout: A UIBarButtonItem displays a custom view inside a UIToolbar:

+-- main view --------------+
|                           |
|                           |
| +-- toolbar ------------+ |
| | +-- custom view ----+ | |
| | |                   | | |
| | +-------------------+ | |
| +-----------------------+ |
+---------------------------+

Here is how I am doing this:

UIBarButtonItem* button = [[[UIBarButtonItem alloc] initWithCustomView:self.customView] autorelease];
NSArray* items =  [NSArray arrayWithObject:button];
self.toolbar.items = items;

After some user interaction I want to remove the custom view from the toolbar and display it somewhere else, in this example directly as a subview of the main view:

+-- main view --------------+
|                           |
| +-- custom view ----+     |
| |                   |     |
| +-------------------+     |
|                           |
| +-- toolbar ------------+ |
| |                       | |
| +-----------------------+ |
+---------------------------+

I am trying to do this like so (self is a view controller):

self.toolbar.items = [NSArray array];
CGRect frame = self.customView.frame;
frame.origin.x = 10;
frame.origin.y = 10;
self.customView.frame = frame;
[self.view addSubview:self.customView];

This does not work. For some reason the custom view is not displayed after I move it to its new superview. I must be doing something wrong here, but I don't know what it is. Any hints?