Question

对于我的视图控制器的viewDidLoad方法实现，它会要求用户进行地址簿访问。我需要做到这一点，以便用户点击“不允许＆＃34;警报视图窗口上的按钮，然后我们将它们转到另一个视图控制器。

我的问题是segue永远不会发生并在控制台中显示此输出：

Warning: Attempt to present <MediaCaptureVC: 0x156788c0> on <AddFriendsViewController: 0x15670dd0> whose view is not in the window hierarchy!

我尝试了几件没有帮助的事情：

使用我的segue代码添加viewDidAppear方法实现，并在我的viewDidLoad＆＃39; s if语句中调用[self viewDidAppear]。
将我的segue代码移到viewDidLoad的最底部。

但没有任何作用。我需要一种方法来触发segue，即使视图在技术上正在加载，因为如果他们拒绝访问他们的地址簿，那么他们绝对没有理由留在视图控制器上。

以下是我viewDidLoad方法实现的开始，我要求通讯录访问，然后if(accessGranted == NO)的if语句包含我的segue代码[self performSegueWithIdentifier:@"addFriendsToMediaCaptureSegue" sender:self];

- (void)viewDidLoad

{

[super viewDidLoad];

// Do any additional setup after loading the view.

[self.navigationController setNavigationBarHidden:YES];

self.currentUser = [PFUser currentUser];



self.tableView.dataSource = self;
self.tableView.delegate = self;


//Asks for access to Address Book.

ABAddressBookRef m_addressbook =  ABAddressBookCreateWithOptions(NULL, NULL);



ABAddressBookCopyArrayOfAllPeople(m_addressbook);


__block BOOL accessGranted = NO;
if (ABAddressBookRequestAccessWithCompletion != NULL) { // we're on iOS 6
    dispatch_semaphore_t sema = dispatch_semaphore_create(0);
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        @autoreleasepool {
            // Write your code here...
            // Fetch data from SQLite DB
        }
    });

    ABAddressBookRequestAccessWithCompletion(m_addressbook, ^(bool granted, CFErrorRef error)

    {
        accessGranted = granted;

        NSLog(@"Has access been granted?: %hhd", accessGranted);


        if(accessGranted == NO) {

            [self performSegueWithIdentifier:@"addFriendsToMediaCaptureSegue" sender:self];


        }

        NSLog(@"Has there been an error? %@", error);


        dispatch_semaphore_signal(sema);
    });
    dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);

Answer 1

在viewDidLoad:

中

double delayInSeconds = 0.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
    SecondViewController *vc = [storyboard instantiateViewControllerWithIdentifier:@"SecondViewController"];
    [self presentViewController:vc animated:YES completion:nil];
});;

Answer 2

一定要（在你的storyBoard中），从当前的ViewController到destinationVC定义一个名为addFriendsToMediaCaptureSegue的segue。
您可以尝试移动您的performSegueWithIdentifier：像这样

dispatch_async(dispatch_get_main_queue(), ^{ [self performSegueWithIdentifier:@"addFriendsToMediaCaptureSegue" sender:self]; });

无法使用segue与viewDidLoad或viewDidAppear一起使用

2 个答案: