有没有办法在用户已经在 iOS 上拒绝相机访问权限后向他们询问? [英] Is there a way to ask user for Camera access after they have already denied it on iOS?

问题描述

我正在使用此代码，但不幸的是它不起作用.

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

在用户拒绝相机访问后，我想请求他们允许在他们下次尝试加载相机时再次使用相机(在这种情况下，它是使用相机视图的条形码扫描仪).我总是得到 AVAuthorizationStatusDenied 然后 granted 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.

我的许多用户给我发电子邮件说我尝试扫描条形码时屏幕是黑的"，这是因为他们出于某种原因拒绝了相机访问.我希望能够再次提示他们，因为拒绝很可能是一个错误.

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.

有没有办法做到这一点?

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

经过一些研究，看起来你不能做我想做的事.这是我编写的用于弹出对话框并在 iOS 8+ 上自动打开设置"应用程序的替代方法.

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+.

一些注意事项:

• 从 iOS 10 开始，您需要在 Info.plist 中指定 NSCameraUsageDescription 键才能请求相机访问权限，否则您的应用将在运行时崩溃.
• 一旦用户更改了您应用的任何权限，它就会终止您的应用.相应地处理并在用户点击开始"之前保存任何需要的数据.按钮.
• 在 iOS 8 和 11 之间的某个时间点，Apple 不再要求用户触摸设置"应用中的隐私"单元格来访问和更改相机设置.您可能希望根据用户使用的 iOS 版本更改有关用户应该在设置"应用中执行的操作的说明.如果有人想在下方发表评论，告诉我们具体的 iOS 版本发生了哪些变化，那就太好了.
• 截至本答案的最后一次编辑，以下代码适用于 iOS 14.2.

• Since iOS 10 you need to specify NSCameraUsageDescription key in your Info.plist to be able ask for camera access, otherwise your app will crash at runtime.
• Once the user changes any permissions for your app, it will kill your app. Handle accordingly and save any needed data before the user hits that "Go" button.
• At some point between iOS 8 and 11, Apple no longer required the user to touch the Privacy cell in the Setting apps in order to get to and change the Camera settings. You may want to change your instructions on what the user is supposed to do in the Settings app based on what iOS version they are using. If someone wants to leave a comment below telling us all what exact iOS version that changed in, that would be awesome.
• As of the last edit of this answer, the code below is working on iOS 14.2.

Swift 5.2:

在视图控制器的顶部:

import AVFoundation

在打开相机视图之前:

@IBAction func goToCamera()
{
    let status = AVCaptureDevice.authorizationStatus(for: .video)
    switch (status)
    {
    case .authorized:
        self.popCamera()

    case .notDetermined:
        AVCaptureDevice.requestAccess(for: .video) { (granted) in
            if (granted)
            {
                self.popCamera()
            }
            else
            {
                self.camDenied()
            }
        }

    case .denied:
        self.camDenied()

    case .restricted:
        let alert = UIAlertController(title: "Restricted",
                                      message: "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.",
                                      preferredStyle: .alert)

        let okAction = UIAlertAction(title: "OK", style: .default, handler: nil)
        alert.addAction(okAction)
        self.present(alert, animated: true, completion: nil)
    @unknown default:
        fatalError()
    }
}

带有完成块的拒绝警报:

Denial alert with completion block:

func camDenied()
{
    DispatchQueue.main.async
    {
        var 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:

1. Close this app.

2. Open the Settings app.

3. Scroll to the bottom and select this app in the list.

4. Turn the Camera on.

5. Open this app and try again."

        var alertButton = "OK"
        var goAction = UIAlertAction(title: alertButton, style: .default, handler: nil)

        if UIApplication.shared.canOpenURL(URL(string: UIApplication.openSettingsURLString)!)
        {
            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:

1. Touch the Go button below to open the Settings app.

2. Turn the Camera on.

3. Open this app and try again."

            alertButton = "Go"

            goAction = UIAlertAction(title: alertButton, style: .default, handler: {(alert: UIAlertAction!) -> Void in
                UIApplication.shared.open(URL(string: UIApplication.openSettingsURLString)!, options: [:], completionHandler: nil)
            })
        }

        let alert = UIAlertController(title: "Error", message: alertText, preferredStyle: .alert)
        alert.addAction(goAction)
        self.present(alert, animated: true, completion: nil)
    }
}

目标-C:

在视图控制器的顶部:

#import <AVFoundation/AVFoundation.h>

在打开相机视图之前:

- (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:

1. Touch the Go button below to open the Settings app.

2. Turn the Camera on.

3. 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:

1. Close this app.

2. Open the Settings app.

3. Scroll to the bottom and select this app in the list.

4. Turn the Camera on.

5. 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];
}

对 UIAlertView 的委托调用:

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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