Question

我创建两个UIAlertcontroller按钮：

One Button - "OpenCamera"
Two button - "OpenGallery"

当我点击其中一个时，我无法理解我是如何创建动作的。

- (IBAction)takePic:(id)sender {


UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil
                                                               message:nil
                                                        preferredStyle:UIAlertControllerStyleActionSheet]; // 1
UIAlertAction *openCamrea = [UIAlertAction actionWithTitle:@"open camrea"
                                                      style:UIAlertActionStyleDefault handler:^(UIAlertAction * action) {
                                                      }];
UIAlertAction *openGallery = [UIAlertAction actionWithTitle:@"open gallery"
                                                       style:UIAlertActionStyleDefault handler:^(UIAlertAction * action) {
                                                       }];

[alert addAction:openCamrea];
[alert addAction:openGallery];

[self presentViewController:alert animated:YES completion:nil];
}

Answer 1

处理程序是在选择项目时执行的块。

UIAlertAction *openGallery = [UIAlertAction
    actionWithTitle:@"open gallery"
    style:UIAlertActionStyleDefault
    handler:^(UIAlertAction * action) {
        // Code to run when the open gallery option is pressed.
    }];

顺便说一句，我认为问题中长期不间断的行确实没有帮助，因为它们有效地隐藏了关键参数。

Answer 2

完整代码：

- (IBAction)takePic:(id)sender {


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

  UIAlertAction *openCamrea = [UIAlertAction actionWithTitle:@"open camrea"
                                                      style:UIAlertActionStyleDefault handler:^(UIAlertAction * action)
  {
    if (![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {

        UIAlertView *myAlertView = [[UIAlertView alloc] initWithTitle:@"Error"message:@"Device has no camera"delegate:nil cancelButtonTitle:@"OK"otherButtonTitles: nil];

        [myAlertView show];
    }
    else
    {
       UIImagePickerController *picker = [[UIImagePickerController alloc] init];
       picker.delegate = self;
       picker.allowsEditing = YES;
       picker.sourceType = UIImagePickerControllerSourceTypeCamera;

       [self presentViewController:picker animated:YES completion:NULL];
    }
  }];
  UIAlertAction *openGallery = [UIAlertAction actionWithTitle:@"open gallery"
                                                       style:UIAlertActionStyleDefault handler:^(UIAlertAction * action)
  {
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.delegate = self;
    picker.allowsEditing = YES;
    picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

    [self presentViewController:picker animated:YES completion:NULL];
  }];

  [alert addAction:openCamrea];
  [alert addAction:openGallery];

  [self presentViewController:alert animated:YES completion:nil];
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

  UIImage *chosenImage = info[UIImagePickerControllerEditedImage];
  self.img.image = chosenImage;

  [picker dismissViewControllerAnimated:YES completion:NULL];

}

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {

  [picker dismissViewControllerAnimated:YES completion:NULL];

}

Answer 3

将代码放入要传递到handler

的[UIAlertAction actionWithTitle:style:handler:]块中

例如：

UIAlertAction *openCamrea = [UIAlertAction actionWithTitle:@"open camrea"
                                                      style:UIAlertActionStyleDefault handler:^(UIAlertAction * action) {

                                                          // openCamera action code goes here

                                                  }];

UIAlertAction *openGallery = [UIAlertAction actionWithTitle:@"open gallery"
                                                   style:UIAlertActionStyleDefault handler:^(UIAlertAction * action) {

                                                       // openGallery action code goes here

                                                   }];

单击按钮而不是UIAlertcontroller时创建操作

3 个答案: