在iOS 8中,我有从相机捕捉图像的问题,直到现在我正在使用这段代码

UIImagePickerController *controller=[[UIImagePickerController alloc] init];
controller.videoQuality=UIImagePickerControllerQualityTypeMedium;
controller.delegate=(id)self;
controller.sourceType=UIImagePickerControllerSourceTypeCamera;
[self presentViewController:controller animated:YES completion:nil];

但在iOS 8中,我得到了这个:

Snapshotting a view that has not been rendered results in an empty snapshot. Ensure your view has been rendered at least once before snapshotting or snapshot after screen updates.

我已经尝试了本文提供的解决方案

@property (strong,nonatomic)UIImagePickerController *controller;

_controller=[[UIImagePickerController alloc] init];
_controller.videoQuality=UIImagePickerControllerQualityTypeMedium;
_controller.delegate=(id)self;
_controller.sourceType=UIImagePickerControllerSourceTypeCamera;
_[self presentViewController:controller animated:YES completion:nil];

...
controller.modalPresentationStyle=UIModalPresentationFullScreen;
or
controller.modalPresentationStyle=UIModalPresentationCurrentContext;
...

double delayInSeconds = 0.1;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    [self presentViewController:controller animated:YES completion:nil];
});

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

[self presentViewController:controller animated:YES completion:^{

}];

任何想法?


当前回答

我遇到过这个问题。当我们调用相机并释放视图时就产生了这个问题。举个例子,调用一个相机并在viewDidDisappear方法中设置视图为nil,这个错误将会出现,因为没有相机事件的回调。对于这个错误,也要确认一下。

其他回答

在我的情况下(XCode 7和iOS 9),我使用UINavigationController“隐藏”,所以我必须添加UINavigationControllerDelegate来呈现相机或滚动,它的工作就像它应该做的!和pickerControllerDelegate。Self也不显示错误!

对于任何人来说,在图像捕捉后看到黑色预览的问题,隐藏状态栏后显示UIPickerController似乎可以解决这个问题。

UIImagePickerControllerSourceType source = [UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera] ? UIImagePickerControllerSourceTypeCamera : UIImagePickerControllerSourceTypeSavedPhotosAlbum;
UIImagePickerController *cameraController = [[UIImagePickerController alloc] init];
        cameraController.delegate = self;
        cameraController.sourceType = source;
        cameraController.allowsEditing = YES;
        [self presentViewController:cameraController animated:YES completion:^{
            //iOS 8 bug.  the status bar will sometimes not be hidden after the camera is displayed, which causes the preview after an image is captured to be black
            if (source == UIImagePickerControllerSourceTypeCamera) {
                [[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation:UIStatusBarAnimationNone];
            }
        }];

我发现了同样的问题,并尝试了所有方法。我有两个不同的应用程序,一个在objective-C和一个在swift -两者都有同样的问题。错误消息出现在调试器中,屏幕在第一张照片之后变黑。这只发生在iOS >= 8.0,显然这是一个错误。

我找到了一个困难的变通办法。用imagePicker关闭相机控制。showsCameraControls = false并创建自己的overlayView,其中有缺失的按钮。关于如何做到这一点,有各种各样的教程。 奇怪的错误信息保留了下来,但至少屏幕不会变黑,而且你有一个工作的应用程序。

或者,考虑使用drawviewherarchyinrect:

迅速:

extension UIImage{

    class func renderUIViewToImage(viewToBeRendered: UIView) -> UIImage
    {
        UIGraphicsBeginImageContextWithOptions(viewToBeRendered.bounds.size, true, 0.0)
        viewToBeRendered.drawViewHierarchyInRect(viewToBeRendered.bounds, afterScreenUpdates: true)
        viewToBeRendered.layer.renderInContext(UIGraphicsGetCurrentContext()!)

        let finalImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return finalImage
    }
}

objective - c:

- (UIImage *)snapshot:(UIView *)view
{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, YES, 0);
    [view drawViewHierarchyInRect:view.bounds afterScreenUpdates:YES];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;
}

还看到:

https://developer.apple.com/library/ios/qa/qa1817/_index.html 如何捕获UIView到UIImage而不损失视网膜显示的质量

I don't have enough reputation points to comment on @greg's answer above, so will add my observations here. I have a Swift project for both iPad and iPhone. I have a method inside my main view controller (relevant bit below). When I test this on a phone, everything works properly and no warnings are generated. When I run it on an iPad, everything works properly but I see the warning about snapshotting the view. The interesting bit, however, is that when I run on an iPad without using the popover controller, everything works properly with no warning. Unfortunately, Apple mandates that the image picker must be used within a popover on iPad, if the camera is not being used.

    dispatch_async(dispatch_get_main_queue(), {
        let imagePicker: UIImagePickerController = UIImagePickerController();
        imagePicker.sourceType = UIImagePickerControllerSourceType.SavedPhotosAlbum;
        imagePicker.mediaTypes = [kUTTypeImage];
        imagePicker.allowsEditing = false;
        imagePicker.delegate = self;

        if(UIDevice.currentDevice().userInterfaceIdiom == .Pad){ // on a tablet, the image picker is supposed to be in a popover
            let popRect: CGRect = buttonRect;
            let popover: UIPopoverController = UIPopoverController(contentViewController: imagePicker);
            popover.presentPopoverFromRect(popRect, inView: self.view, permittedArrowDirections: UIPopoverArrowDirection.Up, animated: true);
        }else{
            self.presentViewController(imagePicker, animated: true, completion: nil);
        }
    });