UITabBarController + UINavigationController and blacker screen display
I am currently working on updating one of my applications and I am facing a very strange issue related to UITabBarController.
In my storyboard I have about 8 view controllers, and in my UITabBarController subclass I add 4 more view controllers that are loaded programmatically. Most of these views need to have a UINavigationController to maintain consistency when pivoting, as some views go out of the Advanced tab on the main line, to do this I nested them in the UINavigationController.
If you select view 6 in portrait and rotate the UINavigationController, it turns black when the view gets its own button in the tab bar, however, when it reverts to "larger", the view returns. In my examination of this data, it seems that the UINavigationController has lost the UIViewController as the root view controller.
Work as expected in a view that is not in the Advanced tab: imgur.com/gVB8wTF
Black screen if the view appears on the More tab: http://imgur.com/WaoNoL1
I made a quick example of a project that has this problem: https://github.com/joshluongo/UITabBarController-Issues
Any ideas on how to fix this?
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I found a workaround that seems to work around this issue.
By overriding UITraitCollection
in a subclass UITabBarController
, you can force to horizontalSizeClass
always be UIUserInterfaceSizeClassCompact
. This will result in UITabBar
only having 5 elements regardless of orientation.
Here's some sample Objective-C code:
- (UITraitCollection *)traitCollection {
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) {
// Workaround to fix the iPhone 6 Plus roatation issue.
UITraitCollection *curr = [super traitCollection];
UITraitCollection *compact = [UITraitCollection traitCollectionWithHorizontalSizeClass:UIUserInterfaceSizeClassCompact];
return [UITraitCollection traitCollectionWithTraitsFromCollections:@[curr, compact]];
}
return [super traitCollection];
}
Then, if you need access to real traits, override -traitCollection
in UIViewController
to return traits with [UIScreen mainScreen]
.
Here is some sample Objective-C code for that:
- (UITraitCollection *)traitCollection {
return [UIScreen mainScreen].traitCollection;
}
It's not a perfect solution, but until Apple decides to fix this bug, this will get the job done.
I hope this helps someone.
rdar: // 21297168
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I faced the same problem.
I was able to come up with a workaround that works really well. I pushed it to Github: https://github.com/jfahrenkrug/UITabBarControllerMoreBugWorkaround
Any improvements are appreciated.
The error occurs because the stack of your UINavigationController is removed from it and pushed into the private UIMoreNavigationController. But when pivoting back to regular width, this stack is not properly pushed back to the original UINavigationViewController.
The solution is to subclass UITabBarController and replace it willTransitionToTraitCollection:withTransitionCoordinator:
with this:
- (void)willTransitionToTraitCollection:(UITraitCollection *)newCollection withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
{
//#define MORE_TAB_DEBUG 1
#ifdef MORE_TAB_DEBUG
#define MoreTabDLog(fmt, ...) NSLog((@"[More Tab Debug] " fmt), ##__VA_ARGS__);
#else
#define MoreTabDLog(...)
#endif
MoreTabDLog(@"-- before willTransitionToTraitCollection");
/*
There is a bug when going in and out of the compact size class when a tab bar
controller has more than 5 tabs. See http://www.openradar.me/25393521
It comes down to this: When you have more than 5 tabs and a view controller on a tab
beyond the 4th tab is a UINavigationController, you have a problem.
When you are on this tab in compact and push one or more VCs onto the stack and then
change back to regular width, only the top most view controller will be added back onto the
stack.
This happens because the stack of your UINavigationController is taken out of that NavVC and put
into the private UIMoreNavigationController. But upon rotating back to regular, that stack is not
correctly put back into your own NavVC.
We have 3 cases we have to handle:
1) We are on the "More" tab in compact and are looking at the UIMoreListController and then change to
regular size.
2) While in compact width, we are on a tab greater than the 4th and are changing to regular width.
3) While in regular width, we are on a tab greater than the 4th and are changing to compact width.
*/
if ((self.traitCollection.horizontalSizeClass != newCollection.horizontalSizeClass) ||
(self.traitCollection.verticalSizeClass != newCollection.verticalSizeClass))
{
/*
Case 1: We are on the "More" tab in compact and are looking at the UIMoreListController and then change to regular size.
*/
if ([self.selectedViewController isKindOfClass:[UINavigationController class]] && [NSStringFromClass([self.selectedViewController class]) hasPrefix:@"UIMore"]) {
// We are on the root of the MoreViewController in compact, going into regular.
// That means we have to pop all the viewControllers in the MoreViewController to root
#ifdef MORE_TAB_DEBUG
UINavigationController *moreNavigationController = (UINavigationController *)self.selectedViewController;
UIViewController *moreRootViewController = [moreNavigationController topViewController];
MoreTabDLog(@"-- going OUT of compact while on UIMoreList");
MoreTabDLog(@"moreRootViewController: %@", moreRootViewController);
#endif
for (NSInteger overflowVCIndex = 4; overflowVCIndex < [self.viewControllers count]; overflowVCIndex++) {
if ([self.viewControllers[overflowVCIndex] isKindOfClass:[UINavigationController class]]) {
UINavigationController *navigationController = (UINavigationController *)self.viewControllers[overflowVCIndex];
MoreTabDLog(@"popping %@ to root", navigationController);
[navigationController popToRootViewControllerAnimated:NO];
}
}
} else {
BOOL isPotentiallyInOverflow = [self.viewControllers indexOfObject:self.selectedViewController] >= 4;
MoreTabDLog(@"isPotentiallyInOverflow: %i", isPotentiallyInOverflow);
if (isPotentiallyInOverflow && [self.selectedViewController isKindOfClass:[UINavigationController class]]) {
UINavigationController *selectedNavController = (UINavigationController *)self.selectedViewController;
NSArray<UIViewController *> *selectedNavControllerStack = [selectedNavController viewControllers];
MoreTabDLog(@"Selected Nav: %@, selectedNavStack: %@", selectedNavController, selectedNavControllerStack);
UIViewController *lastChildVCOfTabBar = [[self childViewControllers] lastObject];
if ([lastChildVCOfTabBar isKindOfClass:[UINavigationController class]] && [NSStringFromClass([lastChildVCOfTabBar class]) hasPrefix:@"UIMore"]) {
/*
Case 2: While in compact width, we are on a tab greater than the 4th and are changing to regular width.
We are going OUT of compact
*/
UINavigationController *moreNavigationController = (UINavigationController *)lastChildVCOfTabBar;
NSArray *moreNavigationControllerStack = [moreNavigationController viewControllers];
MoreTabDLog(@"--- going OUT of compact");
MoreTabDLog(@"moreNav: %@, moreNavStack: %@, targetNavStack: %@", moreNavigationController, moreNavigationControllerStack, selectedNavControllerStack);
if ([moreNavigationControllerStack count] > 1) {
NSArray *fixedTargetStack = [moreNavigationControllerStack subarrayWithRange:NSMakeRange(1, moreNavigationControllerStack.count - 1)];
MoreTabDLog(@"fixedTargetStack: %@", fixedTargetStack);
dispatch_async(dispatch_get_main_queue(), ^{
NSArray *correctVCList = [NSArray arrayWithArray:self.viewControllers];
[selectedNavController willMoveToParentViewController:self];
[selectedNavController setViewControllers:fixedTargetStack animated:NO];
// We need to do this because without it, the selectedNavController doesn't
// have a parentViewController anymore.
[self addChildViewController:selectedNavController];
// We need to do this because otherwise the previous call will cause the given
// Tab to show up twice in the UIMoreListController.
[self setViewControllers:correctVCList];
});
} else {
MoreTabDLog(@"popping to root");
dispatch_async(dispatch_get_main_queue(), ^{
[selectedNavController popToRootViewControllerAnimated:NO];
});
}
} else {
/*
Case 3: While in regular width, we are on a tab greater than the 4th and are changing to compact width.
We are going INTO compact
*/
MoreTabDLog(@"-- going INTO compact");
if ([selectedNavControllerStack count] > 0) {
[coordinator animateAlongsideTransition:^(id<UIViewControllerTransitionCoordinatorContext> _Nonnull context) {
// no op
} completion:^(id<UIViewControllerTransitionCoordinatorContext> _Nonnull context) {
UIViewController *parentViewControllerOfTopVC = [[selectedNavControllerStack lastObject] parentViewController];
MoreTabDLog(@"parentViewControllerOfTopVC: %@", parentViewControllerOfTopVC);
if ([parentViewControllerOfTopVC isKindOfClass:[UINavigationController class]] && [NSStringFromClass([parentViewControllerOfTopVC class]) hasPrefix:@"UIMore"]) {
UINavigationController *moreNavigationController = (UINavigationController *)parentViewControllerOfTopVC;
NSArray *moreNavigationControllerStack = [moreNavigationController viewControllers];
BOOL isOriginalRootVCInMoreStack = [moreNavigationControllerStack containsObject:[selectedNavControllerStack firstObject]];
MoreTabDLog(@"moreNav: %@, moreNavStack: %@, isOriginalRootVCInMoreStack: %i", moreNavigationController, moreNavigationControllerStack, isOriginalRootVCInMoreStack);
if (!isOriginalRootVCInMoreStack) {
NSArray *fixedMoreStack = [@[moreNavigationControllerStack[0]] arrayByAddingObjectsFromArray:selectedNavControllerStack];
MoreTabDLog(@"fixedMoreStack: %@", fixedMoreStack);
[selectedNavController setViewControllers:selectedNavControllerStack animated:NO];
dispatch_async(dispatch_get_main_queue(), ^{
[moreNavigationController setViewControllers:fixedMoreStack animated:NO];
});
}
}
}];
}
}
}
}
}
[super willTransitionToTraitCollection:newCollection withTransitionCoordinator:coordinator];
MoreTabDLog(@"-- after willTransitionToTraitCollection");
}
Enjoy!
Johannes
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