ios7.1后setting中没有开启相机服务应用程序相机预览黑屏问题

if ( [[[UIDevice currentDevice] systemVersion] floatValue] >= 7.0){
                
                //check whether the permission open for user in settings
                AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
                if (authStatus == AVAuthorizationStatusRestricted || authStatus == AVAuthorizationStatusDenied)
                    
                {
                    CMAlertView *alert = [[CMAlertView alloc]init];
                    [alert setAlertViewFrameWithX:self.localView.frame.size.width/8 withY:self.localView.bounds.size.height/2 withW:self.localView.frame.size.width - self.localView.frame.size.width/4 withH:100];
                    [alert setImage:@"[email protected]" withOrignalx:20 withY:30 withW:30 withH:30];
                    [alert setLabelWithText:NSLocalizedStringFromTable(@"alert_view_please_open_camera_visit_permission", @"StringInfo", nil) withX:50 withY:15 withW:180 withH:50];
                    [alert setFont:[UIFont systemFontOfSize:18.0f] withColor:[UIColor whiteColor]];
                    [alert setAlertViewBackgroundColor:[UIColor colorWithRed:68/255.0f green:153/255.0f blue:181/255.0f alpha:1.0]];
                    [alert setAlertViewDisplayType:@"Info"];
                    [alert show];
                    [alert release];
                    
                }
                else{
                    //present the camera view
                    UIImagePickerController *picker = [[UIImagePickerController alloc] init];//initial
                    self.imagePickerController = picker;
                    [picker release];
                    self.imagePickerController.delegate = self;
                    self.imagePickerController.allowsEditing = YES;//set editable
                    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]){
                        self.imagePickerController.sourceType = UIImagePickerControllerSourceTypeCamera;
                        
                    }else{
                        
                        self.imagePickerController.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
                        
                        
                    }
                    [self presentViewController:self.imagePickerController animated:YES completion:nil];//enter camera
                }