试试这个

       -(IBAction)buttonpressed{ 
        UIImagePickerController *anImagePickerController = [UIImagePickerController new];
        anImagePickerController.delegate = self;
        anImagePickerController.sourceType = UIImagePickerControllerSourceTypeCamera;

        UIImageView *anImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"overlay_320x427.png"]];
        anImageView.frame = CGRectMake(0, 1, 320, 427);
        anImageView.hidden = YES;
        anImagePickerController.cameraOverlayView = anImageView;

        [self presentModalViewController:anImagePickerController animated:YES];
        [anImagePickerController release];

        [NSTimer scheduledTimerWithTimeInterval:0.1
                                         target:self
                                       selector:@selector(timerFireMethod:)
                                       userInfo:anImageView
                                        repeats:NO];
        [anImageView release];
    }
    - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(NSDictionary *)info {




 /* Do something here*/
        [self dismissModalViewControllerAnimated:YES];




    }

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