How to Create an Alert Dialog Box in Android?

Alert Dialog shows the Alert message and gives the answer in the form of yes or no. Alert Dialog displays the message to warn you and then according to your response, the next step is processed. Android Alert Dialog is built with the use of three fields: Title, Message area, and Action Button.

Alert Dialog code has three methods:

• setTitle() method for displaying the Alert Dialog box Title
• setMessage() method for displaying the message
• setIcon() method is used to set the icon on the Alert dialog box.

Then we add the two Buttons, setPositiveButton and setNegativeButton to our Alert Dialog Box as shown below.

Example:

Step By Step Implementation

Step 1: Create a New Project in Android Studio

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. The code for that has been given in both Java and Kotlin Programming Language for Android.

Step 2: Working with the XML Files

Next, go to the activity_main.xml file, which represents the UI of the project. Below is the code for the activity_main.xml file. Comments are added inside the code to understand the code in more detail.

XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="180dp"
        android:gravity="center_horizontal"
        android:text="Press The Back Button of Your Phone."
        android:textSize="30dp"
        android:textStyle="bold" />
</RelativeLayout>

Step 3: Working with the MainActivity File

Go to the MainActivity File and refer to the following code. Below is the code for the MainActivity File. Comments are added inside the code to understand the code in more detail.

Java

import android.content.DialogInterface;
import android.os.Bundle;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    // Declare the onBackPressed method when the back button is pressed this method will call
    @Override
    public void onBackPressed() {
        // Create the object of AlertDialog Builder class
        AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);

        // Set the message show for the Alert time
        builder.setMessage("Do you want to exit ?");

        // Set Alert Title
        builder.setTitle("Alert !");

        // Set Cancelable false for when the user clicks on the outside the Dialog Box then it will remain show
        builder.setCancelable(false);

        // Set the positive button with yes name Lambda OnClickListener method is use of DialogInterface interface.
        builder.setPositiveButton("Yes", (DialogInterface.OnClickListener) (dialog, which) -> {
            // When the user click yes button then app will close
            finish();
        });

        // Set the Negative button with No name Lambda OnClickListener method is use of DialogInterface interface.
        builder.setNegativeButton("No", (DialogInterface.OnClickListener) (dialog, which) -> {
            // If user click no then dialog box is canceled.
            dialog.cancel();
        });

        // Create the Alert dialog
        AlertDialog alertDialog = builder.create();
        // Show the Alert Dialog box
        alertDialog.show();
    }
}

Kotlin

import android.os.Bundle
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }

    // Declare the onBackPressed method when the back button is pressed this method will call
    override fun onBackPressed() {
        // Create the object of AlertDialog Builder class
        val builder = AlertDialog.Builder(this)

        // Set the message show for the Alert time
        builder.setMessage("Do you want to exit ?")

        // Set Alert Title
        builder.setTitle("Alert !")

        // Set Cancelable false for when the user clicks on the outside the Dialog Box then it will remain show
        builder.setCancelable(false)

        // Set the positive button with yes name Lambda OnClickListener method is use of DialogInterface interface.
        builder.setPositiveButton("Yes") {
            // When the user click yes button then app will close
                dialog, which -> finish()
        }

        // Set the Negative button with No name Lambda OnClickListener method is use of DialogInterface interface.
        builder.setNegativeButton("No") {
            // If user click no then dialog box is canceled.
                dialog, which -> dialog.cancel()
        }

        // Create the Alert dialog
        val alertDialog = builder.create()
        // Show the Alert Dialog box
        alertDialog.show()
    }
}

Output: