UIImagePickerController error: Snapshotting a view

问题:

I am getting this error only in iOS 7 and the application crashed. In iOS 6, I never get any error, just once of memory warning when opening the camera.

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.

Here is what I am doing.

imagePicker = [[UIImagePickerController alloc] init];
[imagePicker setDelegate:self];
[imagePicker setSourceType:UIImagePickerControllerSourceTypeCamera];
[imagePicker setAllowsEditing:YES];

[self presentModalViewController:imagePicker animated:YES];

I did tried to delay the presentModalViewController, but I am still getting the same message. After few seconds (7-10), the application crashed.

This error is only present in iOS 7.

Anybody has the clue? Thank you in advance.

回答1:

The problem in iOS7 has to do with transitions. It seems that if a previous transition didn't complete and you launch a new one, iOS7 messes the views, where iOS6 seems to manage it correctly.

You should initialize your Camera in your UIViewController, only after the view has Loaded and with a timeout:

- (void)viewDidAppear:(BOOL)animated 
{
    [super viewDidAppear:animated];
    //show camera...
    if (!hasLoadedCamera)
        [self performSelector:@selector(showcamera) withObject:nil afterDelay:0.3];
}

and here is the initialization code

- (void)showcamera {
    imagePicker = [[UIImagePickerController alloc] init];
    [imagePicker setDelegate:self];
    [imagePicker setSourceType:UIImagePickerControllerSourceTypeCamera];
    [imagePicker setAllowsEditing:YES];

    [self presentModalViewController:imagePicker animated:YES];
}

回答2:

This error also showed up for me with Apple's PhotoPicker sample code project.

I was using Xcode Version 5.0 and iOS 7.0.3 on an iPhone 4.

Steps to Reproduce:

1. Download Apple's PhotoPicker sample project at https://developer.apple.com/library/ios/samplecode/PhotoPicker/Introduction/Intro.html

2. In APLViewController.m comment out line 125

   //imagePickerController.showsCameraControls = NO;

3. In APLViewController.m comment out lines 130-133

   //[[NSBundle mainBundle] loadNibNamed:@"OverlayView" owner:self options:nil];
// self.overlayView.frame = imagePickerController.cameraOverlayView.frame;
// imagePickerController.cameraOverlayView = self.overlayView;
// self.overlayView = nil;

4. Build and launch the app.

5. Once launched, rotate device to Landscape mode.

6. Click Camera icon to open UIImagePickerController in Camera mode.

7. View the console output.

Console output

PhotoPicker[240:60b] 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.

showsCameraControls property

The problem occurs for me when this has a value of YES (the default).

Setting this to NO eliminated the message.

Bug report

I just filed a bug report with Apple.

I've tried many of the suggestions that have been made in different posts, but have not found a satisfactory workaround.

回答3:

I got the problem when I tried to present the camera view inside of a popover. Under iOS6 this was no problem but in iOS7 I got the message

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.

as well.

However after I changed the presentation of the camera view to fullscreen as described in Taking Pictures and Movies, iOS Developer Library everything went fine again and the message never appeared again. However I had to make sure that depending on in which mode the app is (i.e., presenting camera view or photo roll) I had to either dismiss the popover or the view controller whenever the method - (void) imagePickerControllerDidCancel: (UIImagePickerController *) picker was called.

回答4:

create a property

@property (nonatomic) UIImagePickerController *imagePickerController;

Then

UIImagePickerController *picker = [[UIImagePickerController alloc] init];
picker.delegate = self;
picker.modalPresentationStyle = UIModalPresentationCurrentContext;
picker.sourceType = UIImagePickerControllerSourceTypeCamera;
picker.allowsEditing = YES;
self.imagePickerController = picker;
[self presentViewController:self.imagePickerController animated:YES completion:nil];

This should solve the problem

回答5:

I used this code to workaround the problem:

UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
[imagePicker setSourceType:UIImagePickerControllerSourceTypeCamera];
[imagePicker setDelegate:self];

if ([self respondsToSelector:@selector(presentViewController:animated:completion:)]){
    [imagePicker setShowsCameraControls:NO];
    [self presentViewController:imagePicker animated:YES completion:^{
        [imagePicker setShowsCameraControls:YES];
    }];
} else {
    [imagePicker setShowsCameraControls:YES];
    [self presentModalViewController:imagePicker animated:YES];
}

回答6:

I have the same issue and found a solve. I think, that error related with orientation of your application. My application uses only landscape mode, but UIImagePickerController use portrait mode. I add try-catch block to main.m, and get real exception:

Supported orientations has no common orientation with the application, and shouldAutorotate is returning YES

How i solve this problem:

1) Recheck device orientation in Target->General, or .plist file: Supported interface orientations : Landscape left, Landscape right.

2) Add in AppDelegate.m:

- (NSUInteger)application:(UIApplication *)application supportedInterfaceOrientationsForWindow:(UIWindow *)window {
    return UIInterfaceOrientationMaskLandscape | UIInterfaceOrientationMaskPortrait;
}

After this step UIImagePickerController works properly, but my viewcontrollers can be rotated to portrait mode. So, to solve this:

3) Create a category for UINavigationController, (supportedInterfaceOrientations moved from UIViewController to UINavigationController in iOS6):

@implementation UINavigationController (RotationIOS6)

- (NSUInteger)supportedInterfaceOrientations {
    return UIInterfaceOrientationMaskLandscape;
}

@end

This solution works properly on iOS 6.0, 6.1, 7.0. Hope this helps.

回答7:

I get this error when building app with iOS SDK 6.1, deployment target iOS 6.1 and running app on iOS 7 powered iPhone. App doesn't crash but implementing UIViewController shouldAutorotate method helps me to remove error message.

- (BOOL)shouldAutorotate {
    return YES;
}

回答8:

I had the same issue when I was trying to modify the demo app that come with the Avirary SDK, in the demo app, it can only edit the photo picked from the camera roll. To try to edit the photo by capturing from camera, I first added the following code in the UIViewcontroller.m file:

#pragma mark - Take Picture from Camera
- (void)showCamera
{
//[self launchPhotoEditorWithImage:sampleImage highResolutionImage:nil];

    if ([self hasValidAPIKey]) {
        UIImagePickerController * imagePicker = [UIImagePickerController new];
        [imagePicker setSourceType:UIImagePickerControllerSourceTypeCamera];
        [imagePicker setDelegate:self];
        [imagePicker setAllowsEditing:YES]; //important, must have

        if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) {
            [self presentViewController:imagePicker animated:YES completion:nil];
        }else{
            [self presentViewControllerInPopover:imagePicker];
        }
    }
}

Then when I run the app, the error occurred:

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.

To solve the error, modified the UIImagePicker delegate in your UIViewContooler.m file as shown below:

#pragma mark - UIImagePicker Delegate

- (void) imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    NSURL * assetURL = [info objectForKey:UIImagePickerControllerReferenceURL];

    void(^completion)(void)  = ^(void){

        [[self assetLibrary] assetForURL:assetURL resultBlock:^(ALAsset *asset) {
            if (asset){
                [self launchEditorWithAsset:asset];
            }
        } failureBlock:^(NSError *error) {
            [[[UIAlertView alloc] initWithTitle:@"Error" message:@"Please enable access to your device's photos." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil] show];
        }];

        UIImage * editedImage = [info objectForKey:UIImagePickerControllerEditedImage];
        if(editedImage){
            [self launchPhotoEditorWithImage:editedImage highResolutionImage:editedImage];
        }

    };

    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) {
        [self dismissViewControllerAnimated:YES completion:completion];
    }else{
        [self dismissPopoverWithCompletion:completion];
    }

}    

Then the error disappeared and the app works!

回答9:

Try this, use

[self performSelector:@selector(presentCameraView) withObject:nil afterDelay:1.0f];

and function

-(void)presentCameraView{
    [self presentViewController:imagePicker animated:YES completion:nil];
}

to replace. [self presentModalViewController:imagePicker animated:YES]; and of cause make imagePicker as a global variable.

回答10:

This is what fixed it for me on my app, ymmv

first off it is a iPhone - iPad app

in appname-Info.plist. in the Supported interface orientations(iPad) showed 4 orientations.

in the Supported interface orientations showed 3 orientations. I added the fourth and ran the app, no debug output.

Hope this helps.

回答11:

I've just encountered the same issue. In my case the problem was that I had some non-ARC code and I've migrated it to ARC. When I did the migration, I didn't hold a strong reference to the UIImagePickerController and that was the reason for the crash.

Hope it helps :)

回答12:

I had same issue in iOS 8, But the Camera Access was Disable inside Settings--> Privacy for my App. Just Enabled it, and It was working.

回答13:

I spent long time try to find the solution, and surprisingly I have found it at the end and it was just very funny once I discovered it.

Here is what you will do to retrieve the image you picked and resume working :)

-(void)imagePickerController:(UIImagePickerController*)picker didFinishPickingMediaWithInfo:(NSDictionary*)info
{
    UIImage* pickedImage = [info objectForKey:@"UIImagePickerControllerOriginalImage"];
    [composeImageView setImage:pickedImage];
[picker dismissViewControllerAnimated:YES completion:nil];
 }

Yes, to solve the issue, you only need to dismiss the picker normally as it seems this message: "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." stops the picker from being responsive but you can dismiss it and retrieve the image normally.

回答14:

In my case it was related with a layout change: the VC presenting the UIImagePickerViewController has the status bar hidden, but the UIImagePickerViewController hasn't.

So, I solved it hiding the status bar in the UIImagePickerViewController as it's shown in this answer.

回答15:

Not directly answering your question but you mentioned you had a memory warning ,you might be storing the raw image in a property which can lead to a memory warning. This is because the raw image takes up roughly 30MB of memory. I noticed a similar memory warning when testing apps on iOS6 which were on the iPhone 4 series. I still got this warning when the devices were upgraded to iOS7. There is no memory warning when testing on iPhone 5 series on iOS7.

回答16:

Changing

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

to

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

fixed the issue for me.