转自：NsstringFromName

支持系统和机型

iOS系统的指纹识别功能最低支持的机型为iPhone 5s，最低支持系统为iOS 8，虽然安装iOS 7系统的5s机型可以使用系统提供的指纹解锁功能，但由于API并未开放，所以理论上第三方软件不可使用。

依赖框架

LocalAuthentication.framework

#import <LocalAuthentication/LocalAuthentication.h>

注意事项

做iOS 8以下版本适配时，务必进行API验证，避免调用相关API引起崩溃。

使用类

LAContext 指纹验证操作对象

代码

 1 - (void)authenticateUser
 2 {
 3     //初始化上下文对象
 4     LAContext* context = [[LAContext alloc] init];
 5     //错误对象
 6     NSError* error = nil;
 7     NSString* result = @"Authentication is needed to access your notes.";
 8
 9     //首先使用canEvaluatePolicy 判断设备支持状态
10     if ([context canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&error]) {
11         //支持指纹验证
12         [context evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics localizedReason:result reply:^(BOOL success, NSError *error) {
13             if (success) {
14                 //验证成功，主线程处理UI
15             }
16             else
17             {
18                 NSLog(@"%@",error.localizedDescription);
19                 switch (error.code) {
20                     case LAErrorSystemCancel:
21                     {
22                         NSLog(@"Authentication was cancelled by the system");
23                         //切换到其他APP，系统取消验证Touch ID
24                         break;
25                     }
26                     case LAErrorUserCancel:
27                     {
28                         NSLog(@"Authentication was cancelled by the user");
29                         //用户取消验证Touch ID
30                         break;
31                     }
32                     case LAErrorUserFallback:
33                     {
34                         NSLog(@"User selected to enter custom password");
35                         [[NSOperationQueue mainQueue] addOperationWithBlock:^{
36                             //用户选择输入密码，切换主线程处理
37                         }];
38                         break;
39                     }
40                     default:
41                     {
42                         [[NSOperationQueue mainQueue] addOperationWithBlock:^{
43                            //其他情况，切换主线程处理
44                         }];
45                         break;
46                     }
47                 }
48             }
49         }];
50     }
51     else
52     {
53         //不支持指纹识别，LOG出错误详情
54
55         switch (error.code) {
56             case LAErrorTouchIDNotEnrolled:
57             {
58                 NSLog(@"TouchID is not enrolled");
59                 break;
60             }
61             case LAErrorPasscodeNotSet:
62             {
63                 NSLog(@"A passcode has not been set");
64                 break;
65             }
66             default:
67             {
68                 NSLog(@"TouchID not available");
69                 break;
70             }
71         }
72
73         NSLog(@"%@",error.localizedDescription);
74     }
75 }

 1 typedef NS_ENUM(NSInteger, LAError)
 2 {
 3     //授权失败
 4     LAErrorAuthenticationFailed = kLAErrorAuthenticationFailed,
 5
 6     //用户取消Touch ID授权
 7     LAErrorUserCancel           = kLAErrorUserCancel,
 8
 9     //用户选择输入密码
10     LAErrorUserFallback         = kLAErrorUserFallback,
11
12     //系统取消授权(例如其他APP切入)
13     LAErrorSystemCancel         = kLAErrorSystemCancel,
14
15     //系统未设置密码
16     LAErrorPasscodeNotSet       = kLAErrorPasscodeNotSet,
17
18     //设备Touch ID不可用，例如未打开
19     LAErrorTouchIDNotAvailable  = kLAErrorTouchIDNotAvailable,
20
21     //设备Touch ID不可用，用户未录入
22     LAErrorTouchIDNotEnrolled   = kLAErrorTouchIDNotEnrolled,
23 } NS_ENUM_AVAILABLE(10_10, 8_0);

操作流程

首先判断系统版本，iOS 8及以上版本执行-(void)authenticateUser方法，方法自动判断设备是否支持和开启Touch ID。

iOS 9

 1  /// Authentication was not successful, because there were too many failed Touch ID attempts and
 2     /// Touch ID is now locked. Passcode is required to unlock Touch ID, e.g. evaluating
 3     /// LAPolicyDeviceOwnerAuthenticationWithBiometrics will ask for passcode as a prerequisite.
 4     LAErrorTouchIDLockout   NS_ENUM_AVAILABLE(10_11, 9_0) = kLAErrorTouchIDLockout,
 5
 6     /// Authentication was canceled by application (e.g. invalidate was called while
 7     /// authentication was in progress).
 8     LAErrorAppCancel        NS_ENUM_AVAILABLE(10_11, 9_0) = kLAErrorAppCancel,
 9
10     /// LAContext passed to this call has been previously invalidated.
11     LAErrorInvalidContext   NS_ENUM_AVAILABLE(10_11, 9_0) = kLAErrorInvalidContext

其中，LAErrorTouchIDLockout是在8.0中也会出现的情况，但并未归为单独的错误类型，这个错误出现，源自用户多次连续使用Touch ID失败，Touch ID被锁，需要用户输入密码解锁，这个错误的交互LocalAuthentication.framework已经封装好了，不需要开发者关心。

LAErrorAppCancel和LAErrorSystemCancel相似，都是当前软件被挂起取消了授权，但是前者是用户不能控制的挂起，例如突然来了电话，电话应用进入前台，APP被挂起。后者是用户自己切到了别的应用，例如按home键挂起。

LAErrorInvalidContext很好理解，就是授权过程中,LAContext对象被释放掉了，造成的授权失败