实践 - Touch ID 解锁功能

4月 29 2017 4 分钟读完 (约 584 字)

导语

iOS 8 引入了 Touch ID 认证的方式来解决输入密码的麻烦操作，Swift 最低需要 iOS 8*，因此本文会用 *Swift 来实现 Touch ID 功能

环境

macOS Sierra 10.12.4
Xcode 8.3.1
Swift 3.0
iPhone 6S 10.1.1

Touch ID 需要硬件支持

`LocalAuthentication.framework`

Touch ID 认证依赖的框架，引入即可

`LAContext`

Touch ID 认证的上下文对象

有两个方法

能不能?

1	open func canEvaluatePolicy(_ policy: LAPolicy, error: NSErrorPointer) -> Bool

`LAPolicy`

public enum LAPolicy : Int {
/// Device owner was authenticated using a biometric method (Touch ID).
@available(iOS 8.0, *)
    case deviceOwnerAuthenticationWithBiometrics
    
/// Device owner was authenticated by Touch ID or device passcode.
@available(iOS 9.0, *)
    case deviceOwnerAuthentication

具体用那种策略去验证。

`NSErrorPointer`

1	public typealias NSErrorPointer = AutoreleasingUnsafeMutablePointer<NSError?>?

流程(显示什么,结果如何?)

1	open func evaluatePolicy(_ policy: LAPolicy, localizedReason: String, reply: @escaping (Bool, Error?) -> Swift.Void)

`localizedReason`

要求 Touch ID 验证的原因

`reply`

返回的结果后的回调

`LAError`

失败的原因有

认证失败(比如用了未被认证的手指)
用户取消
用户取消选择了输入密码
系统取消(比如另一个程序切换至前台)
未设置密码
设备不支持
未设置 Touch ID (手指没设置)

iOS 9 上又添加了 3 种情况

失败次数过多
被取消 ( 上一次认证过程还未结束 )
LAContext 上下文对象有不合法

具体详情可以查看 LAError 枚举的定义

`Code`

func authenticateUser() {
   // Get the local authentication context.
   let context = LAContext()
   
   // Declare a NSError variable.
   var error: NSError?
   
   // Set the reason string that will appear on the authentication alert.
   let reasonString = "请画押🐾"
   
   if context.canEvaluatePolicy(LAPolicy.deviceOwnerAuthenticationWithBiometrics, error: &error) {
       _ = [context .evaluatePolicy(LAPolicy.deviceOwnerAuthenticationWithBiometrics, localizedReason: reasonString, reply: { (success: Bool, evalPolicyError: Error?) -> Swift.Void in
           
           if success {
               print("Authentication success")
           } else{

               let err : LAError = LAError(_nsError: evalPolicyError! as NSError)
               switch err.code.rawValue {
               case LAError.systemCancel.rawValue:
                   print("Authentication was cancelled by the system")
               case LAError.userCancel.rawValue:
                   print("Authentication was cancelled by the user")
               case LAError.userFallback.rawValue:
                   print("User selected to enter custom password")
               default:
                   print("Authentication failed")
                   break
               }
           }
           
       } )]
   }
}

Demo

总结

　　Touch ID 功能的设计其实比较直观，实现也挺容易的，遇到的干扰主要是 Swift 由于版本迭代语法上的差异。