viewWillDisappear not called when calling popToRoo

问题:

I work on a legacy application, and have found out, that my view[Will/Did]Disappear methods are not always fired properly.

The case is, I have a (custom) UIViewController set as rootViewController in AppDelegate. This rootViewController has a UINavigationController, which has two view controllers pushed on it. When the user presses the home button, the user is logged out. When he later returns to the app, the application calls [UINavigationController popToRootViewControllerAnimated:YES] and then displays a modal UIViewController for logging in.

The problem is: When I push/pop on the UINavigationController normally, my viewWillDisappear method is called properly. But when I use the popToRootViewControllerAnimated: method, viewWillDisappear is not called on any of the viewControllers that are popped off.

Searching on the internet has only given two possible reasons:

• If using a UINavigationController as a subview, you must call view[Will/Did]Disappear yourself
• Not calling the proper super methods

None of these suggestions are the case in my app. And I have no idea where to look. Anybody has a suggestion to what has been done wrong in the app?

回答1:

The view probably wasn't onscreen. It has to be onscreen (visible) for the viewWillDisappear: method to be called. If it's coming back from the background, it wasn't visible.

You could try using willMoveToParentViewController: which is called when the view controller is removed from its parent.

回答2:

such useful to me

[nav performSelector:@selector(popToRootViewControllerAnimated:) withObject:nil afterDelay:0.0];

I rewrote UITabBarController

- (void)setSelectedIndex:(NSUInteger)selectedIndex {

    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.01 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        UINavigationController *navigationController = [originalViewController as:[UINavigationController class]];
        if (navigationController.presentedViewController) {
            [navigationController dismissViewControllerAnimated:NO completion:^{
                [navigationController popToRootViewControllerAnimated:NO];
            }];
        }else if (navigationController.topViewController){
            [navigationController popToRootViewControllerAnimated:NO];
        }
    });

}