NSUserDefaults无法完全在应用程序中进行设置

Question

I have a settings view in my app that will give the user the option of one of the Tabs showing either a feed of mp3s from a podcast or mov from a podcast. I set it up on the first time running the app to display an AlertView asking what they prefer. I do that with this in the applicationDidFinishLaunching:

 NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
if (! [defaults boolForKey:@"notFirstRun"]) {
    UIAlertView *firstrun = [[UIAlertView alloc] initWithTitle:@"Sermon Preference" message:@"Do you prefer audio only, or video sermons?  (This setting can be changed at any time in the Settings Page.)" delegate:self cancelButtonTitle:nil otherButtonTitles:@"Audio", @"Video", nil];
    [firstrun show];
    [firstrun release];
    [defaults setBool:YES forKey:@"notFirstRun"];
}

Then I set this in the AppDelegate

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
    if (buttonIndex == 0)       {   
        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
        NSString *nope = @"Audio";
        [defaults setObject:nope forKey:@"videosermons"];
        [defaults synchronize];


    }
    if (buttonIndex == 1)        {
        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
        NSString *yup = @"Video";
        [defaults setObject:yup forKey:@"videosermons"];
        [defaults synchronize];        }

    }

On the Root View (Which is the audio listing of sermons) of the Navigation Controller for sermons I set this in viewWillAppear:

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];


NSString *currently = [defaults objectForKey:@"videosermons"];
if ([currently isEqualToString:@"Video"]) {
    self.videoView = [[[VideoPodcastTableView alloc] initWithNibName:@"VideoPodcastTableView" bundle:[NSBundle mainBundle]] autorelease];


    [self.navigationController pushViewController:_videoView animated:NO];    }
if ([currently isEqualToString:@"Audio"]) {
}

I also set up a Settings Tab with a segmentControl to reflect what has been selected. This is the issue:

If I click on Video in the firstRun popup, and then go straight to the Sermons tab, it stays on Audio Sermons. I can then navigate to the Settings Tab and it will show Video selected. Now, without selecting anything, I can go once more to the Sermons tab, and it will now go to the Video Sermons. Why is it that it is not getting the message to change until after I go to the settings?

Answer 1

The problem is that you're already loading your root view before the UIAlertView clickedButtonAtIndex: selector is called. After you launch your UIAlertView in your AppDelegate, your application continues loading your root view in the background.

viewWillAppear will have already run by the time a UIAlertView option has been selected.

To solve this, I'd recommend having another root view as your initial view. If you're using storyboards, have one segue going to a view controller that launches your alert view, and another segue going to your tab page. On first launch, segue to the alert view page, and otherwise segue to the tab page. This way your NSUserDefaults @"videosermons" key can be set before the tab view is loaded.