iOS 8 – Glitch when presenting view controller quickly after setting key window or dismissing and instanly presenting another

Question

Since testing my app on iOS 8, I find a work around view controllers initialization and presentation really baaadly slow.

I used to work with a code similar to this on iOS 6 & 7:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    ....

    [self.window setRootViewController:_rootController];
    [self.window makeKeyAndVisible];

    // Conditions

    if (#first launch condition#) {
        // quite small controller containing Welcome showcase
        WelcomeViewController *w = ....
        [_rootViewController presentViewController:w animated:NO];
    }

    else if (#last opened item condition#) {
        // pretty big container, root view controller contains
        // a grid view which opens Item detail container the same way
        ItemDetailController *item = ....
        [_rootViewController presentViewController:item animated:NO];
    }

}

This became a really sluggish hell with iOS 8. Root view controller now appears visible for 0.5-1 second and then instantly redraws the screen with presented one. Moreover, the slowness of the presentation began to cause an Unbalanced calls to begin/end appearance transitions _rootViewController warning.

Initial quick hint was to move both conditions with calls to another function and call it with a zero-delay so it's processed in next main run loop:

[self performSelector:@selector(postAppFinishedPresentation) withObject:nil afterDelay:0];

or something like that. This fixes the unballanced calls issue, but the visual gap (rootviewcontroller, gap, presented one) becomes (obviously) even bigger.

The slowness of the presentation is also obvious when you call something usual as:

// Example: Delegate caught finished Sign In dialog,
//          dismiss it and instantly switch to Profile controller

-(void)signInViewControllerDidFinishedSuccessfully
{
    [self dismissViewControllerAnimated:NO completion:^{
         UserProfileViewController *userProfile = ...
         [self presentViewController:userProfile animated:NO];
    }];
}

which should be completely fair piece of code, which used to perform direct transition without a visible flick of parent view controller on iOS 7. Now, same thing – parent flicks during the transition, even it's both handled without animation.

Does anybody face this as an issue? Any solutions? I'd love to solve this without a need to do some hilarious magic with UIWindows for each thing I need to transit flawlessly.

Answer 1

I am not sure the requirement is restricted to have root view controller and present anything over there.

But according to your code it's have welcome view controller thing and I think in this case, this logic is more useful.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Conditions

    if (#first launch condition#) {
        // quite small controller containing Welcome showcase
        WelcomeViewController *w = ....

        //It can be navigation or tab bar controller which have "w" as rootviewcontroller
        [self.window setRootViewController:w];
    }

    else if (#last opened item condition#) {
        // pretty big container, root view controller contains
        // a grid view which opens Item detail container the same way
        ItemDetailController *item = ....
        //It can be navigation or tab bar controller which have "item" as rootviewcontroller
        [self.window setRootViewController:item];
    }

    [self.window makeKeyAndVisible];

}