当用户允许iOS中的摄像头访问警报时如何获得通知？

Question

I want to record a video after a count down 3 2 1. But on first time without allowing the camera the video has started recording without showing to camera . I want to call the recording code in the block which is called when the user allow to camera on camera access alert.

self.recordingManager.previewLayer.frame = CGRectMake(47, 2000, 280, 154);

// set code for count down
imageArr = [[NSArray alloc]initWithObjects:@"countdown_three",@"countdown_two",@"countdown_one", nil];
[_countImageView setImage:[UIImage imageNamed:[imageArr objectAtIndex:0]]];
[_countImageView setHidden:NO];
NSLog(@"%@",[imageArr objectAtIndex:0]);
count = 4;
timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(setCountDownDuration) userInfo:nil repeats:YES];

// customize progressbar
_captureProgress.hidden = NO;
_captureProgress.progress = 0.0;
_captureProgress.layer.borderWidth = 0.2;
_captureProgress.layer.borderColor = [UIColor colorWithRed:167.0f/255 green:188.0f/255 blue:219.0f/255 alpha:1].CGColor;
CGAffineTransform transform = CGAffineTransformMakeScale(1.6f, 8.0f);
_captureProgress.transform = transform;

count--;

if (count == 3) {
    [self.progressStatusLbl setText:@"GET READY"];
    [_countImageView setImage:[UIImage imageNamed:[imageArr objectAtIndex:0]]];
}
if (count == 2) {
    [_countImageView setImage:[UIImage imageNamed:[imageArr objectAtIndex:1]]];
}

if (count == 1) {
    [_countImageView setImage:[UIImage imageNamed:[imageArr objectAtIndex:2]]];
}

if (count == 0) {
    [timer invalidate];
    timer = nil;
    AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
    if(authStatus == AVAuthorizationStatusAuthorized)
    {
        [self.progressStatusLbl setText:@"RECORDING"];
        [self openCamera];
    }
    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.progressStatusLbl setText:@"RECORDING"];
                 [self openCamera];
             }
             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."];
        [Utils showAlertMessageWithTitle:@"Error" msg:@"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."  firstButtonTitle:@"Ok" secontButtonTitle:nil];
    }
    else
    {
        [self camDenied];
    }

Answer 1

For AVAuthorizationStatusNotDetermined state, add observer for a key (boolean), and update this flag in completion of requestAccessForMediaType then start camera or call camDenied deoending on user's actions.

So you code should look like as below:

Add a new private property in your class

@property (nonatomic, strong) NSNumber *granted;

then add following methods

- (void)askForPermission {
    NSLog(@"%@", @"Camera access not determined. Ask for permission.");
    [self addObserver:self forKeyPath:@"granted" options:NSKeyValueObservingOptionNew context:nil];
    [AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted)
     {
         self.granted = @(granted);

     }];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([keyPath isEqualToString:@"granted"]) {
        BOOL granted = [object boolValue];
        if(granted)
        {
            NSLog(@"Granted access to %@", AVMediaTypeVideo);

            [self.progressStatusLbl setText:@"RECORDING"];
            [self openCamera];
        }
        else
        {
            NSLog(@"Not granted access to %@", AVMediaTypeVideo);
            [self camDenied];
        }
    } else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}

call askForPermission in AVAuthorizationStatusNotDetermined case.