iOS:请求访问摄像头

Question

我有一个带有二维码扫描仪的应用程序，它工作得很好，但在iOS 8上，对摄像头的默认访问是“拒绝”。因此，我必须进入设置并手动为应用程序提供使用摄像头的权限。我如何才能使提示符显示类似于“您是否要授予此应用程序使用摄像头的访问权限”？

这是我的代码示例，检查相机权限，然后在用户没有提供权限的情况下请求权限。但是，授予权限的链接从未出现，最终只显示了UIAlertView。当我测试时，状态确实是拒绝的，那么它不请求权限有什么原因吗？谢谢!

我还有#import AVFoundation/AVFoundation.h，所以这不是问题所在。

-(void) checkCameraAuthorization {

AVAuthorizationStatus status = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];

if(status == AVAuthorizationStatusAuthorized) { // authorized
    NSLog(@"camera authorized");
}
else if(status == AVAuthorizationStatusDenied){ // denied
    if ([AVCaptureDevice respondsToSelector:@selector(requestAccessForMediaType: completionHandler:)]) {
        [AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
            // Will get here on both iOS 7 & 8 even though camera permissions weren't required
            // until iOS 8. So for iOS 7 permission will always be granted.

            NSLog(@"DENIED");

            if (granted) {
                // Permission has been granted. Use dispatch_async for any UI updating
                // code because this block may be executed in a thread.
                dispatch_async(dispatch_get_main_queue(), ^{
                    //[self doStuff];
                });
            } else {
                // Permission has been denied.
                UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Not Authorized" message:@"Please go to Settings and enable the camera for this app to use this feature." delegate:self cancelButtonTitle:nil otherButtonTitles:@"OK", nil];
                [alert show];
            }
        }];
    }
}
else if(status == AVAuthorizationStatusRestricted){ // restricted
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Not Authorized" message:@"Please go to Settings and enable the camera for this app to use this feature." delegate:self cancelButtonTitle:nil otherButtonTitles:@"OK", nil];
    [alert show];
}
else if(status == AVAuthorizationStatusNotDetermined){ // not determined

    [AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
        if(granted){ // Access has been granted ..do something
            NSLog(@"camera authorized");
        } else { // Access denied ..do something
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Not Authorized" message:@"Please go to Settings and enable the camera for this app to use this feature." delegate:self cancelButtonTitle:nil otherButtonTitles:@"OK", nil];
            [alert show];
        }
    }];
}
}

Answer 1

听起来这个应用程序已经被拒绝访问摄像头。在这种情况下，您不能再次提示。每次安装只能提示用户访问一次。在此之后，您需要将用户定向到设置。

将用户发送到您的设置，在您的设置中，可以使用以下设置启用摄像头(在iOS8上)：

[[UIApplication sharedApplication] openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]];

如果您正在测试，请尝试从手机中删除该应用程序，然后重新安装并运行它。这会使您返回到AVAuthorizationStatusNotDetermined状态。

Answer 2

对于swift 3：

UIApplication.shared.openURL(URL(string: UIApplicationOpenSettingsURLString)!)

有关更多信息，请查看此视频https://www.youtube.com/watch?v=Btd1XH-gHKM