iphone - How to check if UIDocumentInteractionController will fail to open document due to missing external application on iPad?

Question

I am using UIDocumentInteractionController for showing popover menu "Open In..." so that user can open a document in other application.

Method presentOpenInMenuFromBarButtonItem:animated: returns NO in case there is no application able to open given document (menu will not show). But it is too late for me to wait until getting so far. I would like to disable the button initiating that opening if it is not possible instead of raising expectations of an user and then say "sorry, it is not possible to open it".

Is it possible to query system to see if there is at least one application registered for particular document type? I have checked canPreviewItem: in QLPreviewController, but it seems it doesn't support the same document types which UIDocumentInteractionController can handle.

Answer 1

[EDIT] Not working for iOS 6.0 (see comment)

It seems that dismissMenuAnimated (with no animation at all) is the key:

-(BOOL)canOpenDocumentWithURL:(NSURL*)url inView:(UIView*)view {
    BOOL canOpen = NO;
    UIDocumentInteractionController* docController = [UIDocumentInteractionController 
                                                   interactionControllerWithURL:url];
    if (docController)
    {
        docController.delegate = self;
        canOpen = [docController presentOpenInMenuFromRect:CGRectZero
                                   inView:self.view animated:NO];                   
        [docController dismissMenuAnimated:NO];
    }
    return canOpen;
}

It will return YES if at least one application is able to open the file pointed by url. At least it's working in my case (KMZ files), testing with/without Dropbox app on iPhone iOS 4.3.
Actually, it seems to work even if url is not pointing to an actual file (i.e. @"test.kmz"), but I wouldn't rely on it for all file types.