Question

当我尝试从我的代码加载相机时，相机预览为黑色。如果我等待10-20秒，它将显示真实的相机预览。我发现了几个问题，其中一些问题表明在后台运行其他代码应该是这个问题的原因。但是我没有在后台运行任何代码。我该如何解决这个问题？

这是我运行相机的代码

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

photoPicker.delegate = self;
photoPicker.sourceType = UIImagePickerControllerSourceTypeCamera;
[self presentViewController:photoPicker animated:YES completion:NULL];

Answer 1

大约5个月前，我的团队在iOS7中发现了UIImageViewController的内存泄漏。每个实例化都以指数方式减慢app（即第一个alloc-init延迟1秒，第二个延迟2秒，第三个延迟5秒）。最终，我们有30-60次延迟（类似于您所遇到的情况）。

我们通过继承UIImagePickerController并使其成为Singleton解决了这个问题。这样它只被初始化一次。现在我们的延迟很小，我们避免泄漏。如果子类化不是一个选项，请在viewController中尝试一个class属性，然后像这样延迟加载它。

-(UIImagePickerController *)imagePicker{
    if(!_imagePicker){
        _imagePicker = [[UIImagePickerController alloc]init];
        _imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
    }
    return _imagePicker;
}

然后你可以稍后再称它为：

[self presentViewController:self.imagePicker animated:YES completion:nil];

Answer 2

如果有这个问题 - 如果主调度线程上正在运行某些东西会发生这种情况 - 您是否有机会调整图像大小？

它将预览放到主线程上，如果有什么东西使用它，你会得到一个黑屏。这是一个错误，解决方法是接管主线程或禁用照片选择器直到队列空闲

Answer 3

这应该适合你：

    - (void)cameraViewPickerController:(UIImagePickerController *)picker
{
    [self startCameraControllerFromViewController: picker
                                    usingDelegate: self];
}


- (BOOL) startCameraControllerFromViewController: (UIViewController*) controller
                                   usingDelegate: (id <UIImagePickerControllerDelegate,
                                                   UINavigationControllerDelegate>) delegate {

    if (([UIImagePickerController isSourceTypeAvailable:
          UIImagePickerControllerSourceTypeCamera] == NO)
        || (delegate == nil)
        || (controller == nil))
        return NO;


    UIImagePickerController *cameraUI = [[UIImagePickerController alloc] init];
    cameraUI.sourceType = UIImagePickerControllerSourceTypeCamera;

    // Displays a control that allows the user to choose movie capture
    cameraUI.mediaTypes = [[NSArray alloc] initWithObjects: (NSString *) kUTTypeImage, (NSString *) kUTTypeMovie,nil];

    // Hides the controls for moving & scaling pictures, or for
    // trimming movies. To instead show the controls, use YES.
    cameraUI.allowsEditing = NO;

    cameraUI.delegate = delegate;

    [controller presentViewController:cameraUI animated:YES completion:nil];
    return YES;
}

iOS 7 UIImagePicker预览黑屏

3 个答案: