Iphone – UIImagePickerController weirdness

iphoneuiimagepickercontroller

UIImagePickerController is easy to use, but i'm all of a sudden finding it exasperating when I didn't find it so before. What's happening is that sometimes the imagePickerController:didFinishPickingImage:editingInfo delegate method does not seem to work — the image will not show in the UIImageView even after the assignment was made. Sometimes it will, sometimes not, and furthermore, every single bit of example code i've tried (from the web, from the "Beginning iPhone 3 Development" book, etc.) exhibits the same problem. I'm at a loss as to why, and the problem happens on both my iPhone 3G as well as my 3GS, so I doubt that it's a hardware issue. These devices are running OS 3.1.2. The view controller is loaded from a xib file that contains one button and the UIImageView. I'd really like someone to tell me what stupid thing i'm obviously doing wrong 🙂

Here is the code — i've tried to make the smallest app I could that exhibits the problem:

#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>

@interface imagepickerViewController : UIViewController <UINavigationControllerDelegate, UIImagePickerControllerDelegate>
{
    IBOutlet UIButton *button;
    IBOutlet UIImageView *imageView;    
}

@property (nonatomic, retain) UIImageView *imageView;

- (IBAction)takepic;
- (void)usePic:(UIImage *)pic;

@end




#import "imagepickerViewController.h"

@implementation imagepickerViewController

@synthesize imageView;

- (IBAction)takepic 
{
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera])
    {
        UIImagePickerController *picker = [[UIImagePickerController alloc] init];
        picker.sourceType = UIImagePickerControllerSourceTypeCamera;        
        picker.delegate = self;

        [self presentModalViewController:picker animated:YES];
        [picker release];
    }
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(NSDictionary *)info
{
    [self usePic:image];
    [picker dismissModalViewControllerAnimated:YES];

    // after this method returns, the UIImageView should show the image -- yet very often it does not ...
}

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
{
    [picker dismissModalViewControllerAnimated:YES];
}

- (void)usePic:(UIImage *)picture
{
    imageView.image = picture;
}

@end

Best Solution

I came accross this issue recently too. My solution was to dismiss the modal UIImagePickerController view prior to using the image.

By dismissing the image picker, the previous view controller's view is reloaded, and the UIImageView which was to be the recipient of the chosen image is reloaded and no longer nil.

i.e. I changed from this:

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
    // Wrong! imageView has been released by the UIViewController after a low memory warning and is now nil.
    [imageView setImage:image];
    [self dismissModalViewControllerAnimated:YES];
}

to this:

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
    // Dismis the image picker first which causes the UIViewController to reload it's view (and therefore also imageView)
    [self dismissModalViewControllerAnimated:YES];
    [imageView setImage:image];
}
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