Question

I have a question regarding view controller navigations in Three20. I have a TTTableView “Gallery” and TTPhotoViewController “Photos”. When I touch inside one table view item, the app will navigate to a photo view.

Here are the code I used:

In the AppDelegate.m - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions method,

TTNavigator *navigator = [TTNavigator navigator];
navigator.supportsShakeToReload = NO;
navigator.persistenceMode = TTNavigatorPersistenceModeAll;


TTURLMap *map = navigator.URLMap;
[map from:@"*" toViewController:[TTWebController class]];

[map from:@"tt://launcher" toSharedViewController:[LauncherViewController class]];

[map from:@"tt://photos" parent:@"tt://gallery" toViewController:[PhotoViewController class] selector:nil transition:0];
[map from:@"tt://gallery" parent:@"tt://launcher" toViewController:[GalleryViewController class] selector:nil transition:0];

The GalleryViewController is a tableview Controller

@interface GalleryViewController : TTTableViewController
@end

In the GalleryViewController.m

-(void)createModel
{
    self.dataSource = [TTListDataSource dataSourceWithObjects:
                   [TTTableSubtitleItem itemWithText:@"Album One" subtitle:nil imageURL:@"http://example.image.url" URL:@"tt://photos"]
                   ,
                   [TTTableSubtitleItem itemWithText:@"Album Two" subtitle:nil imageURL:@"http://example.image.url2" URL:@"tt://photos"],
                   nil];
}

I copied this code from the TTCatalog.xcodeproj sample project. But I cannot drill into the photo view and got the following from the console when I try to navigate to photo view from the table view item.

nested push animation can result in corrupted navigation bar 
Finishing up a navigation transition in an Navigation Bar subview tree might get corrupted.
Unbalanced calls to begin/end appearance transitions for <PhotoViewController: 0x6c5d8f0>.

So I don’t know how to solve this question. Thanks!

——–Update:———-

I figured out how to solve the problem. In the AppDelegate methods, use

[map from:@"tt://launcher" toSharedViewController:[LauncherViewController class]];

[map from:@"tt://photos" parent:@"tt://gallery" toSharedViewController:[PhotoViewController class] selector:nil];
[map from:@"tt://gallery" parent:@"tt://launcher" toSharedViewController:[GalleryViewController class] selector:nil];

instead of the [map from: parent: toViewController: selector: transition:]

But here comes another question, can someone explain why the toSharedViewController can solve this problem?

Answer 1

For your intended use, you don’t even need to use - from:parent:toSharedViewController:, just try - from:toViewController:. The reason for this is that your way to the PhotoViewController is straight forward (Launcher -> Gallery -> Photo).

For the case that you want to navigate to the PhotoViewController directly from the LauncherViewController while having the GalleryViewControllerin between (i.e. having a back-button on the top left of your PhotoViewController pointing to the GalleryViewController), you want to call - from:parent:toSharedViewController:.

Currently, you are calling - from:parent:toSharedViewController:, which will reuse the shared controller, thus not generating the “nested push”-warnings:

Controllers created with the “share” mode, meaning that it will be
created once and re-used until it is destroyed.