AlertDialog in Android

Dialogs are the most popular and easiest ways of interactions with users. Almost every application contains some dialogs in it. In Android, Dialog is a small window that implies users to decide or enable them to enter particular details. A dialog does not occupy the entire screen and is used for events requiring users to proceed further in the application. 

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One of the most popular implementations of Dialog in Android is AlertDialog. It is used to alert the user before performing a particular task. For example, suppose you want to delete some pictures from the Gallery. In that case, the Gallery application will alert you about pressing the delete button, which is the positive button to perform the action in this case, and the image will be deleted permanently.

In this blog, you’ll learn everything about Android AlertDialog, its methods, and how to create it with an example. So, let’s get started.

Android Dialogs

Android contains various dialogs as listed below:

Android AlertDialog

In Android, AlertDialog prompts a dialog to the user with messages and buttons to perform an action to proceed further in the application. It displays the Alert message to warn users, and according to their response(yes/no), the next step is processed.

Android AlertDIalog is the sub-class of Dialog class.

AlertDialog in Android application comprises three regions: Title, Content area (Message), Action Button.

• Title - In Android Alerts, you can display a title with up to 3 buttons, a custom layout, a list of selectable items, or a message based on the need. And the title is optional. If you want to present a simple message or question, then the title is not required.

• Content Area - This displays a message. It can be a list or custom layouts depending on the necessities.

• Action Button - This displays action buttons for user interaction. There should not be more than three action buttons in AlertDialog, and they are positive, negative, and neutral. Positive is used to accept and continue with the action. Negative to cancel the action. Neutral is used when the user wants to proceed with the action but unnecessarily intends to cancel.

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Methods of Android AlertDialog

AlertDialogs in Android can be build using different methods in the activity file.

To create AlertDialog, you need to make an object of AlertDialog.Builder class provides APIs that allow you to work with any kind of content, including a custom layout.

Syntax: 

AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);

Then you need to set the positive (yes) or negative (no) or neutral button to the AlertDialog box. 

Syntax:

alertDialogBuilder.setPositiveButton(CharSequence text,
  DialogInterface.OnClickListener listener)
alertDialogBuilder.setNegativeButton(CharSequence text,
  DialogInterface.OnClickListener listener)
alertDialogBuilder.setNeutralButton(CharSequence text, DialogInterface.OnClickListener listener);

After creating and setting the dialog builder, you will create an alert dialog by calling the create() method of the builder class. 

Syntax

This will create the alert dialog and will show it on the screen.

Android AlertDialog Example

Follow the below steps to create an Android AlertDialog application.

• Step 1: Create a new Android application using Android Studio and name it as MyApp.

• Step 2: Next, you’ll have a Java and XML file. Open XML file and text message.

• Step 3: Now open an activity_main.xml file from reslayout path and write the code like as shown below

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent">
      <Button
        android:id="@+id/getBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="150dp"
        android:layout_marginTop="200dp"
        android:text="Show Alert" />
</RelativeLayout>

We have defined one-button control in RelativeLayout to display the alert dialog on the Button click in the XML layout file.

• Step 4:   Now load the XML layout resource from the activity onCreate() callback method.

For that, open the main activity file MainActivity.java from javacom.Mindmajix.MyApp path and write the code like as shown below.

MainActivity.java 

package com.Mindmajix.MyApp;
import android.content.DialogInterface;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn = (Button)findViewById(R.id.getBtn);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                builder.setTitle("Login Alert")
                        .setMessage("Are you sure, you want to continue ?")
                        .setCancelable(false)
                        .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                Toast.makeText(MainActivity.this,"Selected Option: YES",Toast.LENGTH_SHORT).show();
                            }
                        })
                        .setNegativeButton("No", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                Toast.makeText(MainActivity.this,"Selected Option: No",Toast.LENGTH_SHORT).show();
                            }
                        });
                //Creating dialog box
                AlertDialog dialog = builder.create();
                dialog.show();
            }
        });
    }
}

• Step5: From the above code, you might notice that setContentView is used to call the layout in the form of R.layout.layout_file_name. And the activity_main file is used to show AlertDialog on Button click.

The output of AlertDialog Example:

When the above code is executed using Android Virtual Device (AVD), you’ll get the result as shown below.

This is how you can use AlertDialog control in Android applications to show AlertDialog based on the requirement.

Conclusion:

This brings us to the end of this blog. You’ve learned what Android AlertDialog is and how to create an AlertDialog application. We hope the information shared is informative.

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