Question

我正在尝试检查用户是否已登录Facebook。如果是，我想将它们转移到另一个视图。

我遇到的问题是loginViewFetchedUserInfo和loginViewShowingLoggedInUser都在视图实际加载之前被调用。

因此，当调用[self showWelcome:self]时，我会收到“尝试在转换正在进行时开始模态转换”错误。

在将视图发送到新视图之前，我似乎无法想出等待视图加载的方法。

- (void)loginViewShowingLoggedInUser:(FBLoginView *)loginView {

    // Set flag
    isFirstLoginDone = YES;

    NSLog(@"User is logged in");
}

- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView
                        user:(id<FBGraphUser>)user {

    // Check first login
    if(isFirstLoginDone) {
         [self showWelcome:self];
    }

    // clear the flag
    isFirstLoginDone = NO;

}

- (IBAction)showWelcome:(id)sender
{
    UIStoryboard *mainStoryboard = [UIStoryboard storyboardWithName:@"WelcomeStoryboard" bundle:nil];
    UIViewController *vc = [mainStoryboard instantiateViewControllerWithIdentifier:@"WelcomeController"];
    [self presentViewController:vc animated:YES completion:nil];
}

Answer 1

是的，当一个viewController存在时，当你呈现另一个viewController时会发生这种情况。为此，创建一个虚拟方法，如下面的代码，并用很小的时间间隔激活它。

- (IBAction)showWelcome:(id)sender{
   [self someMethod];
}

-(void)someMethod{
    if(self.isBeingPresented){
        [self performSelector:@selector(someMethod) withObject:nil afterDelay:.1];
    }
    else{
        UIStoryboard *mainStoryboard = [UIStoryboard storyboardWithName:@"WelcomeStoryboard" bundle:nil];
        UIViewController *vc = [mainStoryboard instantiateViewControllerWithIdentifier:@"WelcomeController"];
        [self presentViewController:vc animated:YES completion:nil];
    }
}

在过渡期间尝试开始模态转换

1 个答案: