UIImagePickerController在iOS设备上工作但在iOS模拟器上没有？

我一直在物理iOS设备上运行我的应用程序一段时间没有任何问题.但是现在UI ImagePickerController视图不会出现在模拟器上.我已经使用方法 here将照片保存到模拟器中,并确认它们确实存在于图像库中的模拟器上. Xcode中没有弹出错误.我尝试过使用不同的源类型,但无济于事.知道我可能做错了什么吗？非常感谢！

码

UIImagePickerControllersourceType sourceType;
    if([UIImagePickerController issourceTypeAvailable:UIImagePickerControllersourceTypePhotoLibrary])
            {
                sourceType = UIImagePickerControllersourceTypePhotoLibrary;
            }
            else
            {
                sourceType = UIImagePickerControllersourceTypeSavedPhotosAlbum;
            }
            //Display photo library.
            [self startImagePickerControllerFromViewController: self
                                            usingDelegate: self
                                           withsourceType: sourceType];

...

- (BOOL)startImagePickerControllerFromViewController:(UIViewController*) controller
                                  usingDelegate:(id <UIImagePickerControllerDelegate,UINavigationControllerDelegate>) delegate
                                 withsourceType:(UIImagePickerControllersourceTypE) sourceType
{
    //Insure camera,controller,and delegate exist.
    if (([UIImagePickerController issourceTypeAvailable:
          UIImagePickerControllersourceTypeCamera] == NO)
        || (delegate == nil)
        || (controller == nil))
        return NO;

    //Create the ImagePicker.
    UIImagePickerController *imagePickerUI = [[UIImagePickerController alloc] init];
    imagePickerUI.sourCEType = sourceType;
    //Only allow still images.
    imagePickerUI.mediaTypes = [[NSArray alloc] initWithObjects: (NSString *) kUTTypeImage,nil];
    //Turn off ediTing.
    imagePickerUI.allowsEdiTing = NO;
    //Set the delegate.
    imagePickerUI.delegate = delegate;
    //Present the picker view.
    [controller presentViewController:imagePickerUI animated:YES completion:nil];

    return YES;
}

if (([UIImagePickerController issourceTypeAvailable:
      UIImagePickerControllersourceTypeCamera] == NO)