未调用 dismissViewController 完成处理程序

Question

尝试使用 link 中第一个答案中的代码（来自 Kampai）： How to use UIAlertController to replace UIActionSheet?

但是，我的代码甚至没有调用完成处理程序。

警报操作 sheet 可以在按下两个按钮后解除，但完成处理程序中的任何内容都不起作用。知道可能是什么问题吗？我刚开始使用完成处理程序并尝试在网上找到答案，但很少有人遇到与我相同的问题。

- (IBAction)takePhotoButtonPressed:(UIButton *)sender {
pressedButtonTagNumber = sender.tag;

UIAlertController *actionSheet = [UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleActionSheet];

[actionSheet addAction:[UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {

    // Cancel button tappped
    [self dismissViewControllerAnimated:YES completion:^{
    }];
}]];

[actionSheet addAction:[UIAlertAction actionWithTitle:@"Take a Photo" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
    NSLog(@"!");
    // Take a Photo button tapped
    [self dismissViewControllerAnimated:YES completion:^{
        NSLog(@"0"); // NOT CALLED
        // Initialize UIImagePickerController
        UIImagePickerController *takePhotoImagePickerController = [[UIImagePickerController alloc] init];            takePhotoImagePickerController.delegate = self;
        takePhotoImagePickerController.allowsEditing = YES;
        NSLog(@"1");
        // Check and assign image source
        if (![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
            NSLog(@"2");
            UIAlertController *noCameraErrorSheet = [UIAlertController alertControllerWithTitle:@"Camera is not available" message:nil preferredStyle:UIAlertControllerStyleActionSheet];
            [noCameraErrorSheet addAction:[UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {
                // Cancel button tappped
                [self dismissViewControllerAnimated:YES completion:^{
                }];
            }]];
        } else {
            takePhotoImagePickerController.sourceType = UIImagePickerControllerSourceTypeCamera;
            // Present UIImagePickerController
            [self presentViewController:takePhotoImagePickerController animated:YES completion:NULL];
        }

    }];
}]];

解法：

@Paulw11 解决方案效果很好：

1) 无需为 UIAlertController 关闭 ViewController。 2）如果包装正在解除（显然），则无法调用新的 UIAlertController。 3) 最好提前检查并禁用按钮。

UIAlertController *actionSheet = [UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleActionSheet];

[actionSheet addAction:[UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {
}]];

UIAlertAction *takePhotoActionButton = [UIAlertAction actionWithTitle:@"Take Photo" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
    [self takePhoto];
}];
UIAlertAction *uploadPhotoActionButton = [UIAlertAction actionWithTitle:@"Upload from Library" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
    [self uploadPhoto];
}];

// Disable take a photo button if source not available
if (![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
    [takePhotoActionButton setEnabled:FALSE];
}
// Disable upload a photo button if source not available
if (![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]) {
    [uploadPhotoActionButton setEnabled:FALSE];
}

[actionSheet addAction:takePhotoActionButton];
[actionSheet addAction:uploadPhotoActionButton];

// Present action sheet.
[self presentViewController:actionSheet animated:YES completion:nil];

Answer 1

您无需从操作处理程序中调用 dismissViewController:animated: 即可删除警报。 UIAlertController 在调用操作处理程序代码之前调用它以关闭自身。

在您的操作处理程序中，您只需执行该操作 selected 时应该执行的任何操作：

在这种情况下：

在您的取消操作中，您不需要做任何事情
在您的 "take a photo" 操作中您拍了一张照片

此外，从用户体验的角度来看，最好禁用 "take a photo" 或在他们 select 时立即发出警报，而不是在他们尝试后发出警报拍照；换句话说，更早而不是更晚地指出问题

未调用 dismissViewController 完成处理程序

dismissViewController completion handler not called

ios

objective-c

uiviewcontroller

completionhandler

ios-camera