iPhone：UIImagePickerController随机无法拍照

Question

I use a UIPickerViewController to take picture. It works 80% but seemingly at random it fails to take a picture. In tracing the code I found out that it occasionally goes to

-PinRecordNewTableViewController:viewDidUnload. 

That is where it fails because it set nil to all ivars.

@interface PinRecordNewTableViewController : UITableViewController {
}
... 
@implementation PinRecordNewTableViewController
...
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
...
        PinRecordNewPicture *pinRecordNewPicture = [[PinRecordNewPicture alloc] initWithNibName:@"PinRecordNewPicture" bundle:nil];
        pinRecordNewPicture.delegate = self;
        [self.navigationController pushViewController:pinRecordNewPicture animated:YES];    
        [pinRecordNewPicture release];  
...             
}
@interface PinRecordNewPicture : UIViewController 
...
@implementation PinRecordNewPicture
...
- (void)picturePicker:(UIImagePickerControllerSourceType)theSource {

UIImagePickerController *picker = [[UIImagePickerController alloc] init];

picker.delegate = self;
picker.sourceType = theSource;
picker.allowsEditing = YES;

[self presentModalViewController:picker animated:YES];

[picker release];
}

- (IBAction) takePicture:(id)sender {

UIImagePickerControllerSourceType source = UIImagePickerControllerSourceTypeCamera;

    if ([UIImagePickerController isSourceTypeAvailable:source]) {

       [self picturePicker:source];

    }

What did I do wrong? Did I miss something that causes it to behave "randomly"?

Thanks in advance for your help.

Answer 1

If it called viewDidUnload , then it is very likely that your app is running out of memory. This could be a problem, or just the result of editing large images in phone.

Answer 2

If you're trying to take multiple pictures, save the current one to the Documents area of the app. It frees up the memory. This way, the memory warning can be avoided.

If ViewDidUnload is being called, you might think about saving the relevant state of the app in didReceiveMemoryWarning and restoring it in viewDidLoad. This is done using NSUserDefaults class