警告:在调用通知时尝试呈现模态

Question

我正在使用调用viewDidAppear上的presentModal方法

[[NSNotificationCenter defaultCenter] addObserver:self         
                                             selector:@selector(presentModal)         
                                                 name:@"xxxxxxx"         
                                               object:nil];
-(void)presentModal 
{
    PickerModalViewController *pickerModalViewController = [Appdelegate.window.rootViewController.storyboard instantiateViewControllerWithIdentifier:@"PickerModalViewController"];
    pickerType = 2;
    pickerModalViewController.choices = self.localArray;
    pickerModalViewController.buttonTag = pickerType;
    pickerModalViewController.delegate = self;
    self.pickerPresenter = self;
    if (self.pickerPresenter) {
        [self.pickerPresenter presentViewController:pickerModalViewController animated:YES completion:nil];
    }
}

当选择器出现时，它会在设备和模拟器中发出警告

警告：Attempt to present PickerModalViewController: 0x10ec7280 on UINavigationController: 0x90ad610 while a presentation is in progress!

Answer 1

警告会告诉您，出了什么问题。为了避免此警告，您可以使用UINavigationController的delegate属性并实现

- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated