如何在iOS中从后台线程拨打电话

Question

我从后台线程调用一个方法如下。

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    UIApplication *app = [UIApplication sharedApplication];

    //create new uiBackgroundTask
    __block UIBackgroundTaskIdentifier bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
        [app endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }];

    //and create new timer with async call: 
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        //run function methodRunAfterBackground
        NSTimer* t = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(methodRunAfterBackground) userInfo:nil repeats:YES];
        [[NSRunLoop currentRunLoop] addTimer:t forMode:NSDefaultRunLoopMode];
        [[NSRunLoop currentRunLoop] run];
    });
}

15秒后，我必须打电话给一个号码。我使用[[UIApplication sharedApplication] openURL:[NSURL URLWithString:[NSString stringWithFormat:@"tel://%@",_number]]];但在应用程序处于后台状态时无法拨打电话。我们可以从后台状态拨打电话吗？如果是，怎么样？