Hello list, I have the following view hierarchy in an iPhone test app:
window
status bar
view managed by a tab bar with 2 tabs
view for tab 0: some view, managed by some view controller
view for tab 1: one of a set of views, managed by a navigation controller
tab bar
In more detail, MainWindow.xib has a UIViewController (tabBarVC) masquerading
as a UITabBarController, that is, the view it's responsible for has a UITabBar
along with a "content" view (held by an ivar called 'dataView') which is where
the tab bar puts the contents of each tab.
[ Yes, I know I could (and possibly/probably should) use a bona-fide
UITabBarController but I need to be able to manipulate the tab bar in some
ways, which is something you can't do with the tab bar attached to a tab bar
controller. Regardless of the wisdom (or lack thereof) of this design, the
problem I'm having is not due to using a stand-alone tab bar, as you'll see in
a moment. ]
The view managed by tabBarVC is loaded from a nib file (TabBarVC.xib) and
contains the view itself (with the tab bar and dataView as subviews) and two
view controllers, one for each tab (SomeVC and NavVC). The views they manage
(some view and the root view for the navigation controller) are loaded from
separate nib files.
It's all very straight-forward, actually, except that both tabs display 20
pixels below the bottom of the status bar - please see the picture. Clearly,
this is a problem of setting the appropriate auto-resizing masks for views and
the various other related properties.
And that's where I'm stuck. I already tried all options that I think make sense
but I'm obviously missing something (read: a better grasp of the conditions
under which sizes and positions get set and changed by IB when I'm not looking).
Here's what the properties are for the pictures in question:
In MainWindow.xib, the tabBarVC has the "resize view from NIB" selected and a
status bar set in the simulated UI elements panel.
In TabBarVC.xib, both view controllers and the root view controller of the
navigation controller all have the "resize view from NIB" selected. SomeVC has
a status bar and a tab bar in the simulated UI elements panel while NavVC has
those as well as a navigation bar. The view in this nib has a status bar in the
simulated panel, scale to fill for its mode, autoresize its subviews, (0, 0,
320, 460) for its frame, and top and left anchors for its autosizing mask.
The dataView subview (it's red in the pics) has scale to fill and autoresize
its subviews both selected, (0, 0, 320, 411) for its frame, and a full
autosizing mask (all anchors and both horizontal and vertical stretchers).
The views in NavRootVC.xib and SomeVC.xib both have scale to fill, autoresize
subviews, top and left anchors, and status bar and tab bar in the simulated
panel. The view in SomeVC.xib has a frame (0, 0, 320, 411) and the view in
NavRootVC.xib has (0, 0, 320, 367) and a navigation bar set in the simulated
panel.
Incidentally, according to the docs, the simulated UI elements panel has no
actual effect on any object saved in the nib but that's not entirely true since
view sizes get changed when you set those simulated elements and those view
sizes are saved along with the view, aren't they?
To summarize, I'm puzzled because both subviews of dataView are sized correctly
but positioned incorrectly, despite the fact that their autosizing masks are
set to anchor them at their top positions and both of them have their top
positions set to vertical zero. Somewhere, something is deciding to slide (by
the height of the status bar) any view added as a subview of dataView. I just
can't see where that is happening. I NSLogged the frame of any view added as a
subview to dataView and, sure enough, it has its vertical top set to 20 before
it's added as a subview, so it's been changed from the vertical zero displayed
by IB even before its superview-to-be has a chance to change its frame.
More than just a "do X to fix it" I'd greatly appreciate some insight on why
this is happening (beyond the obvious "because views need to be resized and
repositioned to fit the space they're allotted to by their view controllers").
This isn't my first time getting frustrated by IB's propensity to
resize/reposition views when no one is looking and the docs haven't been
particularly helpful in this regard. I'm sure I'm not alone in this, either.
If you feel up to playing with the test app, its project can be downloaded from
here: http://www.restlessbrain.com/NavTest.zip
Thank you in advance for any help and apologies for the long message.
WT
<<inline: tabs.png>>
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