How to wait for a function to execute in Kotlin?

Question

Android

I have a function that is supposed to return the result of whether the biometric check passed or not

fun fingerPrintResult():Boolean
    {
        val executor = Executors.newSingleThreadExecutor()
        val activity: FragmentActivity = this // reference to activity

        var resultReturn:Boolean = false

        val biometricPrompt = BiometricPrompt(activity, executor, object : BiometricPrompt.AuthenticationCallback() {

            override fun onAuthenticationError(errorCode: Int, errString: CharSequence) {
                super.onAuthenticationError(errorCode, errString)
                resultReturn = false
            }

            override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
                super.onAuthenticationSucceeded(result)
                resultReturn = true
            }

            override fun onAuthenticationFailed() {
                super.onAuthenticationFailed()
                resultReturn = false
            }
        })

        val promptInfo = BiometricPrompt.PromptInfo.Builder()
            .setTitle("Подтвердите личность")
            .setNegativeButtonText("Negative Button")
            .build()

         biometricPrompt.authenticate(promptInfo)

        return resultReturn
    }

I call it in one of the buttons OnItemClickListener

ad.setNegativeButton("Удалить", object : DialogInterface.OnClickListener {
                    override fun onClick(dialog: DialogInterface, arg1: Int) {

                        var isTrue: Boolean = false

                        isTrue = fingerPrintResult()

                        if(!isTrue)
                        {
                            Toast.makeText(applicationContext,"Error!", Toast.LENGTH_SHORT).show()
                            return
                        }

                        var value = item["id"].toString()
                        var db = DBHandler(parent.context)
                        db.deleteCountry(Integer.parseInt(value))
                    }
                })

But isTrue does not wait for the test to complete.
How can I make it wait for the result of the function?

Answer 1

Doesn't it bother you at all that you are waiting for the same dialogue and doing something in the callback? The same meaning. In the methods you get the result.

Answer 2

Something like this:

suspend fun fingerPrintResult(): Boolean {
    val executor = Executors.newSingleThreadExecutor()
    val activity: FragmentActivity = this // reference to activity

    return suspendCoroutine { coroutine ->

        val biometricPrompt = BiometricPrompt(activity, executor, object : BiometricPrompt.AuthenticationCallback() {

                override fun onAuthenticationError(errorCode: Int, errString: CharSequence) {
                    super.onAuthenticationError(errorCode, errString)
                    coroutine.resume(false)
                }

                override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
                    super.onAuthenticationSucceeded(result)
                    coroutine.resume(true)
                }

                override fun onAuthenticationFailed() {
                    super.onAuthenticationFailed()
                    coroutine.resume(false)
                }
            })

        val promptInfo = BiometricPrompt.PromptInfo.Builder()
            .setTitle("Подтвердите личность")
            .setNegativeButtonText("Negative Button")
            .build()

        biometricPrompt.authenticate(promptInfo)
    }
}