停止/取消指纹监听器

Question

我是Android Fingerprint Listener的新手，并且自己学习。我面临取消指纹监听器的问题！

我已经建立了一个辅助课程，如下：

@RequiresApi(Build.VERSION_CODES.M)
class FingerprintHandler : FingerprintManager.AuthenticationCallback {

    private var context: Context? = null

    constructor(context: Context) {
        this.context = context
    }

    fun startAuth(manager: FingerprintManager,  context: Context, cancellationSignal: CancellationSignal) {
        manager.authenticate(null, cancellationSignal, 0, this, null)
    }

    override fun onAuthenticationError(errorCode: Int, errString: CharSequence?) {
        super.onAuthenticationError(errorCode, errString)
        Toast.makeText(context!!, "Finger Print Authentication Error", Toast.LENGTH_SHORT).show()
    }

    override fun onAuthenticationSucceeded(result: FingerprintManager.AuthenticationResult?) {
        super.onAuthenticationSucceeded(result)

        Toast.makeText(context, context!!.resources.getString(R.string.success), Toast.LENGTH_SHORT).show()

    }

    override fun onAuthenticationHelp(helpCode: Int, helpString: CharSequence?) {
        super.onAuthenticationHelp(helpCode, helpString)
    }

    override fun onAuthenticationFailed() {
        super.onAuthenticationFailed()
        Toast.makeText(context!!, "Finger Print Authentication Failed", Toast.LENGTH_SHORT).show()
    }
}

在我的活动中，我有：

private var cancellationSignal: CancellationSignal? = null
override fun onPause() {
    stopAuthentication()
    fingerprintManager = null
    super.onPause()
}

    private fun stopAuthentication() {
        if (cancellationSignal != null) {
            cancellationSignal!!.cancel()

 cancellationSignal!!.setOnCancelListener {
            object : CancellationSignal.OnCancelListener {
                override fun onCancel() {
                    Toast.makeText(applicationContext, "Signal Cancelled", Toast.LENGTH_SHORT).show()
                }
            }
        }
        }
    }

主要问题是，每当我想停止监听器时，我都会调用stopAuthentication方法，但由于没有弹出Toast而无法停止它！

我仍然可以使用指纹扫描仪

我在做错什么，有人可以帮我！

我的测试设备是华为Mate 10 Oreo 8.0