iOS应用程序-试图从图库中获取iOS照片但出现错误

Question

I'm new to iOS coding, so my apologies in advance. I know this topic has been covered many times (I searched) however I can't seem to resolve my problem, which is why I am posting.

I am trying to access the iOS photo gallery but I keep getting two errors:

One is 'Application tried to present a nil modal view controller on target .'

Edit: The above error was fixed by initing the _picker in ChooseExsisting, as was suggested in the comments.

The other

[CameraController ChooseExsiting:]: unrecognized selector sent to instance 0x157e11330'

My code is as follows:

- (IBAction)ChooseExsiting {
UIImagePickerController *pickerController = [[UIImagePickerController alloc]
                                             init];
pickerController.delegate = self;
[self.picker setSourceType:UIImagePickerControllerSourceTypePhotoLibrary];
[self presentViewController:_picker animated:YES completion:NULL]; }

I imagine my ChooseExsisting code is incorrect. Would anyone have any suggestions? I would greatly appreciate it.

Answer 1

In your ChooseExisting method, you instantiate a controller into a local variable, but then call present with _picker property variable which is probably nil. Either present the controller from the local variable or init the property like in TakePhoto method.

EDIT: As for the second part, both your IBActions have a wrong method signature if you are connecting them to Tap handlers in the Storyboard for example. They should look like this:

- (IBAction) TakePhoto:(id)sender

- (IBAction) ChooseExsiting:(id)sender

Answer 2

Change your ChooseExisitng method to below one:

- (IBAction)ChooseExsiting:(id) sender {
    UIImagePickerController *pickerController = [[UIImagePickerController alloc]
                                         init];
    pickerController.delegate = self;
    [pickerController setSourceType:UIImagePickerControllerSourceTypePhotoLibrary];
    [self presentViewController:pickerController animated:YES completion:NULL]; }

or

- (IBAction)ChooseExsiting:(id) sender {
    self.picker = [[UIImagePickerController alloc]
                                         init];
    self.picker.delegate = self;
    [self.picker setSourceType:UIImagePickerControllerSourceTypePhotoLibrary];
    [self presentViewController:self.picker animated:YES completion:NULL]; }

Answer 3

 You can try this . It work for me
 Follow below three steps1.First of all you need to add below delegate in .h file (UIImagePickerControllerDelegate,UIPickerViewDelegate)
 2.Add below three methods in your controller
 3. On button click call below methods
 here choose photo for open gallary. so on button click call choose photo method
 - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
   CGSize newSize=CGSizeMake(150, 150);
   UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [[info objectForKey:UIImagePickerControllerEditedImage] drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();
   img_profile_pic.image = newImage;
   [self dismissViewControllerAnimated:YES completion:nil];
   isProfilePic=TRUE;
}
- (void)showImagePickerForSourceType:(UIImagePickerControllerSourceType)sourceType
{
    UIImagePickerController *imagePickerController = [[UIImagePickerController alloc] init];
    imagePickerController.allowsEditing = YES;
    imagePickerController.modalPresentationStyle = UIModalPresentationCurrentContext;
    imagePickerController.sourceType = sourceType;
    imagePickerController.delegate = self;
    imagePickerController = imagePickerController;
    [self presentViewController:imagePickerController animated:YES completion:nil];
 }

  - (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
  {
      [self dismissViewControllerAnimated:YES completion:nil];
   }


  -(void) takePhoto{
       [self showImagePickerForSourceType:UIImagePickerControllerSourceTypeCamera];
   }
  -(void) choosePhoto{
     [self showImagePickerForSourceType:UIImagePickerControllerSourceTypePhotoLibrary];
   }

Answer 4

Instead of doing

    if ([UIImagePickerController isSourceTypeAvailable:!UIImagePickerControllerSourceTypeCamera]) {

    self.picker = [[UIImagePickerController alloc] init];
    self.picker.delegate = self;
    [self.picker setSourceType:UIImagePickerControllerSourceTypeCamera];
    [self presentViewController:_picker animated:YES completion:NULL];
    } }

You should do this

    if ([UIImagePickerController isSourceTypeAvailable:!UIImagePickerControllerSourceTypeCamera]) {
    if(!_picker){
    _picker = [[UIImagePickerController alloc] init];
    _picker.delegate = self;
    [_picker setSourceType:UIImagePickerControllerSourceTypeCamera];
    [self presentViewController:_picker animated:YES completion:NULL];

    }else{

    [self presentViewController:_picker animated:YES completion:NULL];

    }}}

You should initialize _picker property before presenting it, right now you're trying to initialize local property of VC or you can also present self.picker instead of _picker in your code.