iOS8 Touch ID api接口调用

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Touch ID简介

Touch ID是苹果公司提供的一种将指纹用作密码的简便方式。只需轻触i主屏幕按钮，就能激活Touch ID传感器。主屏幕按钮周围的钢圈检测手指通知 Touch ID读取指纹。Touch ID 不会储存指纹的任何图像。它只存储指纹的数学表达式。

Touch ID的指纹数据存储在A7处理器的一个叫"secure enclave"协处理器上，唯一的Touch ID指纹识别器与唯一单独的A7处理器匹配。也就是说你将Touch ID拆开装到别的iPhone 5s上，Touch ID是无法使用的，因为它无法读取到A7处理器上的指纹数据。

Touch ID接口

使用Touch ID需要导入LocalAuthentication.framework，必须在装有iOS8的真机设备才能编译通过。

导入

[objc] view plaincopy
#import <LocalAuthentication/LAContext.h>  

判断当前是否有可用的Touch ID

    - (BOOL)canEvaluatePolicy      {          LAContext *context = [[LAContext alloc] init];          NSError *error;          BOOL success;                    // test if we can evaluate the policy, this test will tell us if Touch ID is available and enrolled          success = [context canEvaluatePolicy: LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&error];                    return success;      }

判断[context canEvaluatePolicy:error:]；判断当前是否有可用Touch ID，设备没有设备没有TouchID或者TouchID未开启返回false，有TouchID并开启返回true.

调用显示验证界面

    - (void)evaluatePolicy      {          LAContext *context = [[LAContext alloc] init];          __block  NSString *msg;                    // show the authentication UI with our reason string          [context evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics localizedReason:NSLocalizedString(@"UNLOCK_ACCESS_TO_LOCKED_FATURE", nil) reply:           ^(BOOL success, NSError *authenticationError) {               if (success) {                   msg =[NSString stringWithFormat:@"EVALUATE_POLICY_SUCCESS"];               } else {                   msg = [NSString stringWithFormat:@"EVALUATE_POLICY_WITH_ERROR : %@",                          authenticationError];               }               UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:msg message:nil delegate:nil cancelButtonTitle:@"ok" otherButtonTitles:nil];               [alertView show];           }];                }

调用[contextevaluatePolicy:localizedReason:reply]可以显示验证界面，验证完毕后有一个回调。苹果官方文档规定第二个参数localizedReason一定要(shoudbe)使用用户的当前语言呈现。

真机演示(演示指纹识别成功的例子)

在真机测试中，指纹识别3次错误会退出验证界面并输出错误信息；在验证界面点击“输入密码”，也会退出，并输出错误信息。估计这是iOS8 Beta的bug，正常应该是指纹识别失败或者点击“输入密码”要弹出数字键盘。正式发布时，官方应该会处理好这个问题。

测试用的代码片段

- (void)viewDidLoad  {      [super viewDidLoad];      [self.view setBackgroundColor:[UIColor whiteColor]];      UIButton* btn = [[UIButton alloc] init];      [btn setTitle:@"push me!" forState:UIControlStateNormal];      CGRect frame = CGRectMake(self.view.frame.size.width/2 - 60., self.view.frame.size.height/2, 120., 80.);      [btn setFrame:frame];            [btn addTarget:self action:@selector(showTouchId) forControlEvents:UIControlEventTouchUpInside];            [self.view addSubview:btn];        }    - (void)showTouchId  {      if ([self canEvaluatePolicy]) {          [self evaluatePolicy];      } else {          UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"5s ok?" message:nil delegate:nil cancelButtonTitle:@"ok" otherButtonTitles:nil];          [alertView show];      }  }    #pragma mark - Tests    - (BOOL)canEvaluatePolicy  {      LAContext *context = [[LAContext alloc] init];      NSError *error;      BOOL success;            // test if we can evaluate the policy, this test will tell us if Touch ID is available and enrolled      success = [context canEvaluatePolicy: LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&error];            return success;  }    - (void)evaluatePolicy  {      LAContext *context = [[LAContext alloc] init];      __block  NSString *msg;            // show the authentication UI with our reason string      [context evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics localizedReason:NSLocalizedString(@"UNLOCK_ACCESS_TO_LOCKED_FATURE", nil) reply:       ^(BOOL success, NSError *authenticationError) {           if (success) {               msg =[NSString stringWithFormat:@"EVALUATE_POLICY_SUCCESS"];           } else {               msg = [NSString stringWithFormat:@"EVALUATE_POLICY_WITH_ERROR : %@",                      authenticationError];           }           UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:msg message:nil delegate:nil cancelButtonTitle:@"ok" otherButtonTitles:nil];           [alertView show];       }];        }

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