form validation with kotlin flow, stateflow

MainActivity.kt

package com.mustafayigit.formvalidationwithkotlinflow

import android.content.res.ColorStateList
import android.graphics.Color
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.core.widget.doOnTextChanged
import androidx.lifecycle.lifecycleScope
import com.google.android.material.snackbar.Snackbar
import com.mustafayigit.formvalidationwithkotlinflow.databinding.ActivityMainBinding
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.flow.combine
import kotlinx.coroutines.launch

class MainActivity : AppCompatActivity() {
    private lateinit var mBinding: ActivityMainBinding

    private val defaultButtonTintColor = "#1B1717"
    private val onFormValidButtonTintColor = "#4F774F"
    private var errorMessage: String? = null

    private val email = MutableStateFlow("")
    private val password = MutableStateFlow("")
    private val passwordAgain = MutableStateFlow("")

    private val formIsValid = combine(
        email,
        password,
        passwordAgain
    ) { email, password, passwordAgain ->
        mBinding.txtErrorMessage.text = ""
        val emailIsValid = email.length > 6
        val passwordIsValid = password.length in 7..15
        val passwordAgainIsValid = passwordAgain == password
        errorMessage = when {
            emailIsValid.not() -> "email not valid"
            passwordIsValid.not() -> "Password not valid"
            passwordAgainIsValid.not() -> "Passwords do not match"
            else -> null
        }
        errorMessage?.let {
            mBinding.txtErrorMessage.text = it
        }
        emailIsValid and passwordIsValid and passwordAgainIsValid
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        mBinding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(mBinding.root)

        // onCreate
        with(mBinding) {

            txtEmail.doOnTextChanged { text, _, _, _ ->
                email.value = text.toString()
            }
            txtPassword.doOnTextChanged { text, _, _, _ ->
                password.value = text.toString()
            }
            txtPasswordAgain.doOnTextChanged { text, _, _, _ ->
                passwordAgain.value = text.toString()
            }
        }

        val snackBar = Snackbar.make(mBinding.root, "Login Successfully", Snackbar.LENGTH_LONG)

        mBinding.btnLogin.setOnClickListener { snackBar.show() }

        lifecycleScope.launch {
            formIsValid.collect {
                mBinding.btnLogin.apply {
                    backgroundTintList = ColorStateList.valueOf(
                        Color.parseColor(
                            if (it) onFormValidButtonTintColor else defaultButtonTintColor
                        )
                    )
                    isClickable = it
                }
            }
        }


    }
}