有没有办法要求用户的相机访问，他们已经拒绝了iOS 8？ [英] Is there a way to ask user for Camera access after they have already denied it on iOS 8?

问题描述

我正在使用此代码，但很遗憾，它无法正常工作。

I am using this code, but unfortunately it doesn't work.

用户拒绝相机访问后，我想要求他们获得使用下次他们尝试加载它（在这种情况下，它是一个条形码扫描仪使用相机视图）。我总是得到 AVAuthorizationStatusDenied ，然后授予总是自动返回 NO 即使我在代码中再次要求它。

After a user has denied camera access, I want to ask them for permission to use the camera again the next time they try to load it (in this case it's a barcode scanner using the camera view). I always get AVAuthorizationStatusDenied and then granted always automatically returns NO even though I ask for it again in code.

我的许多用户都通过电子邮件通知我我尝试扫描条码时我的屏幕是黑色的，这是因为他们由于某种原因拒绝相机访问。

Many of my users are e-mailing me saying "my screen is black when I try to barcode scan" and it's because they have denied camera access for some reason. I want to be able to prompt them again because most likely the denial was a mistake.

有没有可能的方法来做这个？

Is there a possible way to do this?

    AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
    if(authStatus == AVAuthorizationStatusAuthorized)
    {
        NSLog(@"%@", @"You have camera access");
    }
    else if(authStatus == AVAuthorizationStatusDenied)
    {
        NSLog(@"%@", @"Denied camera access");

        [AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
            if(granted){
                NSLog(@"Granted access to %@", AVMediaTypeVideo);
            } else {
                NSLog(@"Not granted access to %@", AVMediaTypeVideo);
            }
        }];
    }
    else if(authStatus == AVAuthorizationStatusRestricted)
    {
        NSLog(@"%@", @"Restricted, normally won't happen");
    }
    else if(authStatus == AVAuthorizationStatusNotDetermined)
    {
        NSLog(@"%@", @"Camera access not determined. Ask for permission.");

        [AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
            if(granted){
                NSLog(@"Granted access to %@", AVMediaTypeVideo);
            } else {
                NSLog(@"Not granted access to %@", AVMediaTypeVideo);
            }
        }];
    }
    else
    {
        NSLog(@"%@", @"Camera access unknown error.");
    }

推荐答案

你不能做我想要的。这是我编码的替代方案，我编码为弹出一个对话框，并打开设置应用程序自动如果在iOS 8 +。

After some research it looks like you can't do what I'd like. Here is the alternative that I coded to pop a dialog and open the Settings app automatically if on iOS 8+.

- (IBAction)goToCamera
{
    AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
    if(authStatus == AVAuthorizationStatusAuthorized)
    {
        [self popCamera];
    }
    else if(authStatus == AVAuthorizationStatusNotDetermined)
    {
        NSLog(@"%@", @"Camera access not determined. Ask for permission.");

        [AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted)
        {
            if(granted)
            {
                NSLog(@"Granted access to %@", AVMediaTypeVideo);
                [self popCamera];
            }
            else
            {
                NSLog(@"Not granted access to %@", AVMediaTypeVideo);
                [self camDenied];
            }
        }];
    }
    else if (authStatus == AVAuthorizationStatusRestricted)
    {
        // My own Helper class is used here to pop a dialog in one simple line.
        [Helper popAlertMessageWithTitle:@"Error" alertText:@"You've been restricted from using the camera on this device. Without camera access this feature won't work. Please contact the device owner so they can give you access."];
    }
    else
    {
        [self camDenied];
    }
}

拒绝警报：

- (void)camDenied
{
    NSLog(@"%@", @"Denied camera access");

    NSString *alertText;
    NSString *alertButton;

    BOOL canOpenSettings = (&UIApplicationOpenSettingsURLString != NULL);
    if (canOpenSettings)
    {
        alertText = @"It looks like your privacy settings are preventing us from accessing your camera to do barcode scanning. You can fix this by doing the following:\n\n1. Touch the Go button below to open the Settings app.\n\n2. Touch Privacy.\n\n3. Turn the Camera on.\n\n4. Open this app and try again.";

        alertButton = @"Go";
    }
    else
    {
        alertText = @"It looks like your privacy settings are preventing us from accessing your camera to do barcode scanning. You can fix this by doing the following:\n\n1. Close this app.\n\n2. Open the Settings app.\n\n3. Scroll to the bottom and select this app in the list.\n\n4. Touch Privacy.\n\n5. Turn the Camera on.\n\n6. Open this app and try again.";

        alertButton = @"OK";
    }

    UIAlertView *alert = [[UIAlertView alloc]
                          initWithTitle:@"Error"
                          message:alertText
                          delegate:self
                          cancelButtonTitle:alertButton
                          otherButtonTitles:nil];
    alert.tag = 3491832;
    [alert show];
}

代表调用UIAlertView：

Delegate call for the UIAlertView:

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
{
    if (alertView.tag == 3491832)
    {
        BOOL canOpenSettings = (&UIApplicationOpenSettingsURLString != NULL);
        if (canOpenSettings)
            [[UIApplication sharedApplication] openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]];
    }
}

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