android {
   // add this
    buildFeatures {
        dataBinding = true
    }
}

plugins {
    alias(libs.plugins.android.application)
    alias(libs.plugins.kotlin.android)
    alias(libs.plugins.google.gms.google.services)
    id("kotlin-kapt") // add this
}

مرحله ۳: ایجاد کلاس Model

یک کلاس جدید به نام Model ایجاد کنید که شناسه ایمیل و رمز عبور وارد شده توسط کاربر را در خود نگه دارد. در زیر کد لازم برای پیاده‌سازی کلاس Model مناسب آمده است.

package org.geeksforgeeks.demo;

public class Model {

    private String email;
    private String password;

    public Model(String email, String password) {
        this.email = email;
        this.password = password;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

package org.geeksforgeeks.demo

data class Model (
    var email: String?,
    var password: String?
)

package org.geeksforgeeks.demo;

import android.util.Patterns;

import androidx.databinding.BaseObservable;
import androidx.databinding.Bindable;

public class ViewModel extends BaseObservable {

    // Creating an instance of the Model class
    private Model model = new Model("", "");

    // String variables for toast messages
    private final String successMessage = "Login successful";
    private final String errorMessage = "Email or Password is not valid";

    // String variable for toast message
    private String toastMessage;

    @Bindable
    public String getToastMessage() {
        return toastMessage;
    }

    private void setToastMessage(String toastMessage) {
        this.toastMessage = toastMessage;
        notifyPropertyChanged(BR.toastMessage);
    }

    // Getter and setter methods for email variable
    @Bindable
    public String getUserEmail() {
        return model.getEmail();
    }

    public void setUserEmail(String email) {
        model.setEmail(email);
        notifyPropertyChanged(BR.userEmail);
    }

    // Getter and setter methods for password variable
    @Bindable
    public String getUserPassword() {
        return model.getPassword();
    }

    public void setUserPassword(String password) {
        model.setPassword(password);
        notifyPropertyChanged(BR.userPassword);
    }

    // Actions to be performed when the user clicks the LOGIN button
    public void onButtonClicked() {
        setToastMessage(isValid() ? successMessage : errorMessage);
    }

    // Method to ensure fields are not empty and email/password validation
    private boolean isValid() {
        return !getUserEmail().isEmpty() && Patterns.EMAIL_ADDRESS.matcher(getUserEmail()).matches()
                && !getUserPassword().isEmpty() && getUserPassword().length() > ۵;
    }
}

package org.geeksforgeeks.demo

import android.util.Patterns
import androidx.databinding.BaseObservable
import androidx.databinding.Bindable

class ViewModel : BaseObservable() {

    // Creating an instance of the Model class
    private var model: Model = Model("", "")

    // String variables for toast messages
    private val successMessage = "Login successful"
    private val errorMessage = "Email or Password is not valid"

    // String variable for toast message
    @get:Bindable
    var toastMessage: String? = null
        private set(value) {
            field = value
            notifyPropertyChanged(BR.toastMessage)
        }

    // Getter and setter methods for email variable
    @get:Bindable
    var userEmail: String?
        get() = model.email
        set(value) {
            model.email = value
            notifyPropertyChanged(BR.userEmail)
        }

    // Getter and setter methods for password variable
    @get:Bindable
    var userPassword: String?
        get() = model.password
        set(value) {
            model.password = value
            notifyPropertyChanged(BR.userPassword)
        }

    // Actions to be performed when the user clicks the LOGIN button
    fun onButtonClicked() {
        toastMessage = if (isValid()) successMessage else errorMessage
    }

    // Method to ensure fields are not empty and email/password validation
    private fun isValid(): Boolean {
        return !userEmail.isNullOrEmpty() && Patterns.EMAIL_ADDRESS.matcher(userEmail!!).matches()
                && !userPassword.isNullOrEmpty() && userPassword!!.length > ۵
    }
}

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:bind="http://schemas.android.com/tools">

    <data>
        <variable
            name="viewModel"
            type="org.geeksforgeeks.demo.ViewModel" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:padding="16dp"
        android:orientation="vertical">

        <EditText
            android:id="@+id/inEmail"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="10dp"
            android:layout_marginEnd="10dp"
            android:layout_marginBottom="20dp"
            android:hint="Enter your Email ID"
            android:inputType="textEmailAddress"
            android:padding="8dp"
            android:text="@={viewModel.userEmail}" />

        <EditText
            android:id="@+id/inPassword"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="10dp"
            android:layout_marginEnd="10dp"
            android:hint="Enter your password"
            android:inputType="textPassword"
            android:padding="8dp"
            android:text="@={viewModel.userPassword}" />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="32dp"
            android:onClick="@{()-> viewModel.onButtonClicked()}"
            android:text="Login"
            android:textSize="24sp"
            bind:toastMessage="@{viewModel.toastMessage}" />

    </LinearLayout>
</layout>

package org.geeksforgeeks.demo;

import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.BindingAdapter;
import androidx.databinding.DataBindingUtil;

import org.geeksforgeeks.demo.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // ViewModel updates the Model after observing changes in the View
        // Model will also update the View via the ViewModel
        ActivityMainBinding activityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main);

        // Assigning the ViewModel to the binding
        ViewModel viewModel = new ViewModel();
        activityMainBinding.setViewModel(viewModel);

        // Executes pending bindings immediately
        activityMainBinding.executePendingBindings();
    }

    // BindingAdapter to show the toast message
    @BindingAdapter("toastMessage")
    public static void runMe(View view, String message) {
        if (message != null && !message.isEmpty()) {
            Toast.makeText(view.getContext(), message, Toast.LENGTH_SHORT).show();
        }
    }
}

package org.geeksforgeeks.demo

import android.os.Bundle
import android.view.View
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.databinding.BindingAdapter
import androidx.databinding.DataBindingUtil
import org.geeksforgeeks.demo.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // ViewModel updates the Model after observing changes in the View
        // Model will also update the View via the ViewModel
        val activityMainBinding: ActivityMainBinding =
            DataBindingUtil.setContentView(this, R.layout.activity_main)

        activityMainBinding.viewModel = ViewModel()
        activityMainBinding.executePendingBindings()
    }

    companion object {
        @JvmStatic
        @BindingAdapter("toastMessage")
        fun runMe(view: View, message: String?) {
            message?.let {
                Toast.makeText(view.context, it, Toast.LENGTH_SHORT).show()
            }
        }
    }
}