EDIT: These problems appear to be fixed as of iOS 7.1 / Xcode 5.1.1. (Possibly earlier, as I haven't been able to test all versions. Definitely after iOS 7.0, since I tested that one.) When you create a popover segue from a UIBarButtonItem
, the segue makes sure that tapping the popover again hides the popover rather than showing a duplicate. It works right for the new UIPresentationController
-based popover segues that Xcode 6 creates for iOS 8, too.
Since my solution may be of historical interest to those still supporting earlier iOS versions, I've left it below.
If you store a reference to the segue's popover controller, dismissing it before setting it to a new value on repeat invocations of prepareForSegue:sender:
, all you avoid is the problem of getting multiple stacking popovers on repeated presses of the button -- you still can't use the button to dismiss the popover as the HIG recommends (and as seen in Apple's apps, etc.)
You can take advantage of ARC zeroing weak references for a simple solution, though:
1: Segue from the button
As of iOS 5, you couldn't make this work with a segue from a UIBarButtonItem
, but you can on iOS 6 and later. (On iOS 5, you'd have to segue from the view controller itself, then have the button's action call performSegueWithIdentifier:
after checking for the popover.)
2: Use a reference to the popover in -shouldPerformSegue...
@interface ViewController
@property (weak) UIPopoverController *myPopover;
@end
@implementation ViewController
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
// if you have multiple segues, check segue.identifier
self.myPopover = [(UIStoryboardPopoverSegue *)segue popoverController];
}
- (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender {
if (self.myPopover) {
[self.myPopover dismissPopoverAnimated:YES];
return NO;
} else {
return YES;
}
}
@end
3: There's no step three!
The nice thing about using a zeroing weak reference here is that once the popover controller is dismissed -- whether programmatically in shouldPerformSegueWithIdentifier:
, or automatically by the user tapping somewhere else outside the popover -- the ivar goes to nil
again, so we're back to our initial state.
Without zeroing weak references, we'd have to also:
- set
myPopover = nil
when dismissing it in shouldPerformSegueWithIdentifier:
, and
- set ourself as the popover controller's delegate in order to catch
popoverControllerDidDismissPopover:
and also set myPopover = nil
there (so we catch when the popover is automatically dismissed).
What I have discovered so far, is that with any segue identifier that is not popover these are the invocations made by iOS:
- prepareForSegue (on source controller)
- viewDidLoad (on destination controller)
while in popover segue the invocation order is:
- viewDidLoad (on destination controller)
- prepareForSegue (on source controller)
just because I put all my logic in viewDidLoad, the controller was not properly initialized, and a crash happened. So this is not exactly true that prepareForSegue is not called, the truth is that I was getting an exception, and I wrongly mistaken as prepareForSegue not getting called.
I couldn't put everything in viewWillAppear because a call to CoreData had to be made and I didn't want to check if entities were ok each time the view display.
How did I solve this ? I created another method in destination controller
-(void)prepareViewController {
// initialization logic...
}
and changing the prepareForSegue method in source controller itself:
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
MyViewController *mvc = (MyViewController*)[segue destinationViewController];
// passing variable
// with segue style other than popover this called first than viewDidLoad
mvc.myProp1=@"prop1";
mvc.myProp2=@"prop2";
// viewWillAppear is not yet called
// so by sending message to controller
// the view is initialized
[mvc prepareViewController];
}
don't know if this is expected behavior with popover, anyway now things are working.
Best Answer
This is the proper way to do what you need to do:
This ensures that the segue will be cancelled if an instance of the popover has already been displayed. You just need to make sure your popover object has an identifier in the storyboard.