iOS 7 UIImagePicker preview black screen - ios

Question

When i try to load camera from my code, camera preview is black. If I wait for 10-20 seconds it will show real camera preview. I found several questions and some of them suggest that running some other code in background should be the reason for this. However I don't have any code running in background.
How should I fix this?
This is my code where I run camera
UIImagePickerController *photoPicker = [[UIImagePickerController alloc] init];
photoPicker.delegate = self;
photoPicker.sourceType = UIImagePickerControllerSourceTypeCamera;
[self presentViewController:photoPicker animated:YES completion:NULL];

Answer 1

About 5 months ago my team discovered a memory leak with UIImageViewController in iOS7. Each instantiation slowed down the app exponentially (i.e. first alloc-init had a 1 second delay, second had a 2 second delay, third had a 5 second delay). Eventually, we were having 30-60 delays (similar to what you're experiencing).
We resolved the issue by subclassing UIImagePickerController and making it a Singleton. That way it was only ever initialized once. Now our delay is minimal and we avoid the leak. If subclassing isn't an option, try a class property in your viewController and just lazy load it like so.
-(UIImagePickerController *)imagePicker{
if(!_imagePicker){
_imagePicker = [[UIImagePickerController alloc]init];
_imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
}
return _imagePicker;
}
Then you can just call it later like:
[self presentViewController:self.imagePicker animated:YES completion:nil];

Answer 2

Had this myself - it happens if something is running on the main dispatch thread - are you resizing images by any chance?
It puts the preview onto the main thread and if something is using it, you get a black screen. It's a bug and the workaround is to either take over the main thread or to disable the photo picker until the queue is free

Answer 3

This Should work for you:
- (void)cameraViewPickerController:(UIImagePickerController *)picker
{
[self startCameraControllerFromViewController: picker
usingDelegate: self];
}
- (BOOL) startCameraControllerFromViewController: (UIViewController*) controller
usingDelegate: (id <UIImagePickerControllerDelegate,
UINavigationControllerDelegate>) delegate {
if (([UIImagePickerController isSourceTypeAvailable:
UIImagePickerControllerSourceTypeCamera] == NO)
|| (delegate == nil)
|| (controller == nil))
return NO;
UIImagePickerController *cameraUI = [[UIImagePickerController alloc] init];
cameraUI.sourceType = UIImagePickerControllerSourceTypeCamera;
// Displays a control that allows the user to choose movie capture
cameraUI.mediaTypes = [[NSArray alloc] initWithObjects: (NSString *) kUTTypeImage, (NSString *) kUTTypeMovie,nil];
// Hides the controls for moving & scaling pictures, or for
// trimming movies. To instead show the controls, use YES.
cameraUI.allowsEditing = NO;
cameraUI.delegate = delegate;
[controller presentViewController:cameraUI animated:YES completion:nil];
return YES;
}