在iPhone应用程序在后台运行时显示弹出窗口(UIAlertView)

Question

我是iphone app开发的新手.

我的问题是,当我的应用程序在后台运行时,如何显示弹出窗口(UIAlertView)？我正在使用xcode 4.2 for ios 6我无法通过互联网找到满意的答案.有人可以帮我这个吗？

    - (void)applicationDidEnterBackground:(UIApplication *)application
      {
         UIApplication* app = [UIApplication sharedApplication];
         bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
            [app endBackgroundTask:bgTask];
            bgTask = UIBackgroundTaskInvalid;
         }];

         dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
         NSTimer* t = [NSTimer scheduledTimerWithTimeInterval:5 target:self selector:@selector(doBackgroundProcessing) userInfo:nil repeats:YES];
        [[NSRunLoop currentRunLoop] addTimer:t forMode:NSDefaultRunLoopMode];
        [[NSRunLoop currentRunLoop] run];
    });

}

    - (void) doBackgroundProcessing
    {
        global = [lMGlobal getInstance];

        while(TRUE)
        {
            [self showAlertFor:@"Hello" andMessage:@"Wake up"];

            [NSThread sleepUntilDate:[lMGlobal getSleepDuration]];

        }

    }

    - (void) showAlertFor:(NSString *)title andMessage:(NSString*)message
      {
          UIAlertView *alertDialog;
          alertDialog = [[UIAlertView alloc]
               initWithTitle:title
               message:message
               delegate: self
               cancelButtonTitle: nil
               otherButtonTitles: @"Mute", nil];

          [alertDialog
          performSelector:@selector(show)
          onThread:[NSThread mainThread]
          withObject:nil
          waitUntilDone:NO];
          [alertDialog release];
      }

Answer 1

虽然您无法显示UIAlertView,但您可以显示UILocalNotification.您的代码可能如下所示:

backupAlarm = [[UILocalNotification alloc] init];

backupAlarm.fireDate = alarmTime;
backupAlarm.timeZone = [NSTimeZone systemTimeZone];

backupAlarm.alertBody = @"Good morning, time to wake up.";
backupAlarm.alertAction = @"Show me";
backupAlarm.soundName = UILocalNotificationDefaultSoundName;