我需要有自動警報視圖和動作的幫助

Question

好的，所以當用戶第一次啓動我的應用程序時，我想要一個警報視圖，它將彈出2個選擇。我使用下面的方法：

- (void) displayWelcomeScreen 
{ 
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults]; 
    NSString *alreadyRun = @"already-run"; 
    if ([prefs boolForKey:alreadyRun]) 
     return; 
    [prefs setBool:YES forKey:alreadyRun]; 
    UIAlertView *alert = [[UIAlertView alloc] 
     initWithTitle:@"…" 
     message:@"…" 
     delegate:nil cancelButtonTitle:nil otherButtonTitles:@"OK", nil]; 
    [alert show]; 
    [alert release]; 
} 

當我第一次啓動應用程序時，沒有警報視圖彈出。難道我做錯了什麼？順便說一句，我希望它只顯示在應用程序的第一次啓動。它不能顯示任何其他時間。提前致謝。

Answer 1

試試這個：

(void)viewDidLoad{ 

NSLog(@"In viewDidLoad"); 
[self displayWelcomeScreen]; 

} 

在displayWelcom中eScreen編寫代碼：

- (void) displayWelcomeScreen 
{ 
    NSLog(@"In displayWelcomeScreen"); 
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults]; 
    NSString *alreadyRun = @"already-run"; 
    if ([prefs boolForKey:alreadyRun]) 
     return; 
    [prefs setBool:YES forKey:alreadyRun]; 
    UIAlertView *alert = [[UIAlertView alloc] 
     initWithTitle:@"…" 
     message:@"…" 
     delegate:nil cancelButtonTitle:nil otherButtonTitles:@"OK", nil]; 
    [alert show]; 
    [alert release]; 
} 

並檢查控制檯是否顯示在displayWelcomeScreen中。

Answer 2

嘗試使用這些。我只是對你的代碼做了一些改動。

- (void) displayWelcomeScreen 
{ 
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults]; 

    if ([prefs objectForKey:@"alreadyRun"]) 
    { 
     return; 
    } 
    else 
    { 
     [prefs setObject:@"YES" forKey:@"alreadyRun"]; 
     [prefs synchronize]; 
     UIAlertView *alert = [[UIAlertView alloc] 
     initWithTitle:@"…" 
     message:@"…" 
     delegate:nil cancelButtonTitle:nil otherButtonTitles:@"OK", nil]; 
     [alert show]; 
     [alert release]; 
    } 
} 

Answer 3

在你的appDelegate didFinishLaunchingWithOptions

，加入這樣的事情

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; 
if (![defaults boolForKey:@"everLaunched"]) { 
    [defaults setBool:YES forKey:@"everLaunched"]; 
    [defaults setBool:YES forKey:@"firstLaunch"]; 
} 
else{ 
    [defaults setBool:NO forKey:@"firstLaunch"]; 
} 

檢查，如果你需要顯示歡迎信息：

- (void) displayWelcomeScreen 
{ 
    if ([[NSUserDefaults standardUserDefaults] boolForKey:@"firstLaunch"]) 
     { 
      NSLog(@"I should display alert view now with two selections"); 
      //what to you want to to here now? show alert view? with two choices? 
      //you might want to remember the selected choice from user 
     } 
    else { 
     NSLog(@"the user already made his choice, this is not a first launch"); 
     //what do you want to do here now? show home screen? let the user use the app? 
     //the user has already made his choice 
     } 
}