触摸ID屏幕显示两次

Question

我已经实现了一个锁定屏幕，每隔3分钟就会启动一个密码屏幕。如果用户具有触摸ID，则我启动Touch ID。

 OCTouchIdManager *touchManager = [[OCTouchIdManager alloc]init];


 if([touchManager isTouchIdAvilable] &&(userEabled) && passphraseLockStatusValue ){
        [touchManager authenticateUserSuccess:^(void){

            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

                dispatch_async(dispatch_get_main_queue(), ^{
                    [self proceedOnSuccess];
                });

            });



        }
                                fallBackBlock:^(NSInteger error){

                                    //if error 1 then fall back (either the user clicked cancel or enter password)
                                    //if error 2 then touch id fail (wrong finger)

                                    if(error==1){
                                        // do nothing, assume that the user will now user the mass passphase lock to verify.
                                    }else if (error ==2){
                                        [self showInvalidPasswordAlert];
                                    }

                                }];
    }

和我的touchIDManager

-(void)authenticateUserSuccess:(TouchIdSuccessBlock)successBlock fallBackBlock:(TouchIdFallBackBlock)fallbackBlock{
    self.laContext.localizedFallbackTitle=@"Enter Passphrase";
    [self.laContext evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics
                   localizedReason:@"Please Login With your Touch ID to continue."
                             reply:^(BOOL success, NSError *error) {

                                 if (error) {
                                     //There was a problem verifying your identity"
                                     fallbackBlock(1);
                                     return;
                                 }
                                 if (success) {
                                     successBlock();

                                 } else {
                                     //"You are not the device owner."

                                     fallbackBlock(2);
                                 }
                             }];
}

但是在某些设备中有时会出现两次触摸ID屏幕。意思是，有一个小闪烁。 这个问题很小，但它仍然让许多用户感到恼火。还有其他人有问题吗？我该如何解决呢。