iOS：警告：試圖在演示文稿正在進行時在<ViewController>上呈現<ModalViewController>

Question

我試圖在從圖像選取器中選取圖像後創建模式視圖控制器。我使用的代碼：

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

    NSLog(@"Picker has returned"); 
    [self dismissModalViewControllerAnimated:YES]; 



    // TODO: make this all threaded? 
    // crop the image to the bounds provided 
    img = [info objectForKey:UIImagePickerControllerOriginalImage]; 
    NSLog(@"orig image size: %@", [[NSValue valueWithCGSize:img.size] description]); 

    // save the image, only if it's a newly taken image: 
    if([picker sourceType] == UIImagePickerControllerSourceTypeCamera){ 
     UIImageWriteToSavedPhotosAlbum(img, nil, nil, nil); 
    } 

    // self.image_View.image=img; 
    //self.image_View.contentMode = UIViewContentModeScaleAspectFit; 


    ModalViewController *sampleView = [[ModalViewController alloc] init]; 
    [self presentModalViewController:sampleView animated:YES]; 
} 

不過，我收到警告：

Warning: Attempt to present <ModalViewController: 0x7561600> on <ViewController: 0x75a72e0> while a presentation is in progress! 

和模態視圖不出現。

我在做什麼錯？

Answer 1

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

    // TODO: make this all threaded? 
    // crop the image to the bounds provided 
    img = [info objectForKey:UIImagePickerControllerOriginalImage]; 
    NSLog(@"orig image size: %@", [[NSValue valueWithCGSize:img.size] description]); 

    // save the image, only if it's a newly taken image: 
    if ([picker sourceType] == UIImagePickerControllerSourceTypeCamera) { 
     UIImageWriteToSavedPhotosAlbum(img, nil, nil, nil); 
    } 

    // self.image_View.image = img; 
    // self.image_View.contentMode = UIViewContentModeScaleAspectFit; 

    NSLog(@"Picker has returned"); 
    [self dismissViewControllerAnimated:YES 
          completion:^{ 
           ModalViewController *sampleView = [[ModalViewController alloc] init]; 
           [self presentModalViewController:sampleView animated:YES]; 
          }]; 
} 

Answer 2

這裏發生問題的原因是，您首先解僱了UIImagePicker，並立即將另一個視圖顯示爲模態視圖。這就是你得到這個錯誤的原因。

請與下面的代碼：

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

[self dismissViewControllerAnimated:NO completion:^{ 

    img = [info objectForKey:UIImagePickerControllerOriginalImage]; 
    NSLog(@"orig image size: %@", [[NSValue valueWithCGSize:img.size] description]); 

    if([picker sourceType] == UIImagePickerControllerSourceTypeCamera) 
    { 
     UIImageWriteToSavedPhotosAlbum(img, nil, nil, nil); 
    } 

    ModalViewController *sampleView = [[ModalViewController alloc] init]; 
    [self presentModalViewController:sampleView animated:YES]; 
    }]; 
}