implementation of view-viewmodel pattern MVVM - kotlin

Question

I am new to development and I want to learn how to use the MVVM pattern. I have a problem with the fact that I need to implement the methods that I have in SignUpFragment in the ViewModel class. Please help me understand how to finally do this. I will be very grateful! Thanks in advance
please do not send links to materials, I want to understand my example, thanks
My fragment
class SignUpFragment : Fragment() {
private val viewModel: SignUpViewModel by activityViewModels()
private val binding: FragmentSignUpBinding? = null
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val viewModel:SignUpViewModel = ViewModelProviders.of(this)[SignUpViewModel::class.java]
val binding: FragmentSignUpBinding =
DataBindingUtil.inflate(
inflater, R.layout.fragment_sign_up, container, false
)
return binding.root
}
// call next sign up screen window
fun callNextSignUpScreen(view: View) {
//validate form
if (!(validateFullName() || validateUserName() as Boolean || validateEmail() as Boolean || validatePassword() as Boolean)) {
return
} else {
binding?.signupNextBtn?.setOnClickListener {
findNavController()
.navigate(
R.id.action_signUpFragment_to_signUpSecondFragment
)
}
}
//add transition
val pairs: Array<Pair<*, *>?> = arrayOfNulls(4)
pairs[0] = Pair<View, String>(binding?.signupBackButton, "transition_back_arrow_btn")
pairs[1] = Pair<View, String>(binding?.signupLoginBtn, "transition_login_btn")
pairs[2] = Pair<View, String>(binding?.signupNextBtn, "transition_next_btn")
pairs[3] = Pair<View, String>(binding?.signupTitleText, "transition_title_btn")
}
//validate field full name
private fun validateFullName(): Boolean {
val validName: String = binding!!.signupFullname.editText?.text.toString().trim()
return if (validName.isEmpty()) {
binding.signupFullname.error = "field can not be Empty"
false
} else {
binding.signupFullname.error = null
binding.signupFullname.isErrorEnabled = false
true
}
}
//validate field user name
private fun validateUserName(): Any {
val userName: String = binding!!.signupUserName.editText?.text.toString().trim()
val checksPaces: Regex = "[a-zA-Z0-9._-]+#[a-z]+\\.++[a-z]+".toRegex()
return if (userName.isEmpty()) {
binding.signupUserName.error = "field can not be Empty"
false
} else (if (userName.length > 20) {
binding.signupUserName.error = "Username is too large!"
false
} else if (!userName.matches(checksPaces)) {
binding.signupEmail.error = "Invalid Email"
} else {
binding.signupUserName.error = null
binding.signupUserName.isErrorEnabled = false
true
})
}
//validate field email
private fun validateEmail(): Any {
val email: String = binding!!.signupEmail.editText?.text.toString().trim()
val checkEmail: Regex = "[a-zA-Z0-9._-]+#[a-z]+\\.++[a-z]+".toRegex()
return if (email.isEmpty()) {
binding.signupEmail.error = "field can not be Empty"
false
} else if (!email.matches(checkEmail)) {
binding.signupEmail.error = "Invalid Email"
} else {
binding.signupEmail.error = null
binding.signupEmail.isErrorEnabled = false
true
}
}
//validate field password
private fun validatePassword(): Any {
val password: String = binding!!.signupPassword.editText?.text.toString().trim()
val checkPassword: Regex =
"^(?=.*[0-9])(?=.*[a-z])(?=.*[A-Z])(?=.*[##\$%^&+=])(?=\\S+\$).{8,}\$".toRegex()
return if (password.isEmpty()) {
binding.signupPassword.error = "Password should contain4 characters!"
false
} else if (!password.matches(checkPassword)) {
binding.signupPassword.error = "Invalid Email"
} else {
binding.signupPassword.error = null
binding.signupPassword.isErrorEnabled = false
true
}
}