相机应用程序显示白色屏幕

Question

我对Objective-C很新，我想创建一个应用程序，最终用相机拍照，但图像覆盖。但我想我会从一个简单的相机应用程序开始，只是为了获得它的基础。我已经按照教程创建了一个可以拍照并访问图像库的应用程序。但是当我将它构建到我的iPhone 4s时，它只会加载一个白色屏幕。如果有人可以看看代码，但我认为它是正确的，并提供答案，非常感谢。

//ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

<UIImagePickerControllerDelegate, UINavigationControllerDelegate>


@property (strong, nonatomic) IBOutlet UIImageView *imageView;

- (IBAction)takePhoto:(UIButton *)sender;

- (IBAction)selectPhoto:(UIButton *)sender;


@end

// ViewController.m

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    if (![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {

        UIAlertView *myAlertView = [[UIAlertView alloc] initWithTitle:@"Error"
                                                              message:@"Device has no camera"
                                                             delegate:nil
                                                    cancelButtonTitle:@"OK"
                                                    otherButtonTitles: nil];

        [myAlertView show];

    }

}

- (void)viewDidAppear:(BOOL)animated {

    [super viewDidAppear:animated];

}

- (IBAction)takePhoto:(UIButton *)sender {

    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.delegate = self;
    picker.allowsEditing = YES;
    picker.sourceType = UIImagePickerControllerSourceTypeCamera;

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

}

- (IBAction)selectPhoto:(UIButton *)sender {

    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.delegate = self;
    picker.allowsEditing = YES;
    picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

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


}

#pragma mark - Image Picker Controller delegate methods

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    UIImage *chosenImage = info[UIImagePickerControllerEditedImage];
    self.imageView.image = chosenImage;

    [picker dismissViewControllerAnimated:YES completion:NULL];

}

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {

    [picker dismissViewControllerAnimated:YES completion:NULL];

}

@end