如何查看 Touch ID 的状态？答案

【问题标题】：How to check the status of Touch ID?如何查看 Touch ID 的状态？
【发布时间】：2018-01-16 10:22:55
【问题描述】：

我想知道如何检查 Touch ID 的状态。详细信息：如果触摸 ID 失败超过 3 次，则触摸 ID 被禁用。要激活，我必须在锁定屏幕上输入密码或按 ID 菜单上的密码。我怎么知道touch id的状态是able还是disable？

【问题讨论】：

【解决方案1】：

// Create LA Context
LAContext *myContext = [[LAContext alloc] init];
NSError *authError = nil;
NSString *myLocalizedReasonString = @"Specify why you need TouchID";

// Policy evalivation - start
if ([myContext canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&authError]) {
    [myContext evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics
              localizedReason:myLocalizedReasonString
                        // Reply block - start
                        reply:^(BOOL success, NSError *error) {

                            // success - start
                            if (success) {

                                NSLog(@"User authenticated successfully, take appropriate action");

                                double delayInSeconds = 0.1;
                                dispatch_time_t replaceTab = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
                                dispatch_after(replaceTab, dispatch_get_main_queue(), ^(void){

                                    [self touchIDSuccess];

                                });

                            // success - end
                            // Not successful - start
                            } else {

                                // error != NULL - start
                                if(error != NULL)
                                {
                                    // switch - start
                                    switch (error.code){

                                        case LAErrorUserCancel:

                                            NSLog(@"LAErrorUserCancel");

                                            break;

                                        case LAErrorUserFallback:

                                            NSLog(@"LAErrorUserFallback");

                                            break;
                                        case LAErrorAppCancel:

                                            NSLog(@"LAErrorAppCancel");

                                            break;

                                        case LAErrorAuthenticationFailed:


                                            NSLog(@"kLAErrorAuthenticationFailed");


                                        default:

                                            break;

                                    }// switch - end

                                }// error != NULL - end

                            }// Not success - end

                    }];// Reply block - end

} else {
    // Touch ID was previously used but now Could not evaluate policy , may be because user removed the fingerprint

    NSLog(@"Could not evaluate policy");

}

【讨论】：