In this tutorial, we show you how to display an alert box in Android. See flowing Steps :

  1. First, use the AlertDialog.Builder to create the alert box interface, like title, message to display, buttons, and button onclick function
  2. Later attach above builder to AlertDialog and display it.
  3. Done.

P.S This project is developed in Eclipse 3.7, and tested with Android 2.3.3.

1 Android Layout Files

Simpel layout file, display a button on screen.

File : res/layout/main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
 
    <Button
        android:id="@+id/buttonAlert"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Show Alert Box" />
 
</LinearLayout>

2. Activity

When user click on this button, display the alert box, with your pre-defined alert dialog interface.

File : MainActivity.java

package com.mkyong.android;
 
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
 
public class MainActivity extends Activity {
 
	final Context context = this;
	private Button button;
 
	public void onCreate(Bundle savedInstanceState) {
 
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
 
		button = (Button) findViewById(R.id.buttonAlert);
 
		// add button listener
		button.setOnClickListener(new OnClickListener() {
 
		@Override
		public void onClick(View arg0) {
 
			AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
				context);
 
			// set title
			alertDialogBuilder.setTitle("Your Title");
 
			// set dialog message
			alertDialogBuilder
				.setMessage("Click yes to exit!")
				.setCancelable(false)
				.setPositiveButton("Yes",new DialogInterface.OnClickListener() {
					public void onClick(DialogInterface dialog,int id) {
						// if this button is clicked, close
						// current activity
						MainActivity.this.finish();
					}
				  })
				.setNegativeButton("No",new DialogInterface.OnClickListener() {
					public void onClick(DialogInterface dialog,int id) {
						// if this button is clicked, just close
						// the dialog box and do nothing
						dialog.cancel();
					}
				});
 
				// create alert dialog
				AlertDialog alertDialog = alertDialogBuilder.create();
 
				// show it
				alertDialog.show();
			}
		});
	}
}

3. Demo

Start it, display a button.

android alert box example

When button is clicked, display the alert box

android alert box example

If “Yes” button is clicked, close the activity and return back to your Android main screen.

android alert box example

Download Source Code

Download it – Android-Alert-Dialogl-Example.zip (16 KB)

References

  1. Android AlertDialog Javadoc
  2. Android Dialog example
Tags :
Founder of Mkyong.com and HostingCompass.com, love Java and open source stuff. Follow him on Twitter, or befriend him on Facebook or Google Plus. If you like my tutorials, consider making a donation to this charity, thanks.

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