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Beginner 10 min Java Full project

Alert Dialog in Android Studio (Java)

Show an alert dialog that asks the user to confirm something, with Yes and No buttons that do different things.

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What you'll learn

Build a dialog with AlertDialog.Builder
Add title, message and buttons
Respond to Yes and No

Before you start

Android Studio (any recent version)
An emulator or an Android phone

How it fits together

1Button tap
2MaterialAlertDialogBuilder
3User picks a button
4Your code reacts

Build it step by step

1. Create the project

In Android Studio choose New Project → Empty Views Activity, with Language Java and Minimum SDK API 24.

2. Add two buttons

In activity_main.xml, add Delete a file and Choose a colour, plus a TextView that shows what the user picked.

3. A Yes/No dialog

MaterialAlertDialogBuilder builds a Material 3 dialog step by step: setTitle, setMessage, setIcon, then the buttons. Each button gets a small block of code that runs when it's tapped. Call show() at the end.

4. A list to choose from

setSingleChoiceItems shows radio buttons. Remember the tapped item, and apply it when the user taps OK.

5. Ask before leaving

Add an OnBackPressedCallback. When the user presses Back, show an "Leave the app?" dialog; Exit calls finish().

6. Run it

Try each button, then press Back.

Tips

Put dialog text in strings.xml, so it's easy to change or translate.
Use dialogs only for decisions that matter; too many annoy users.

What's improved over the video

Material 3 dialogs, a single-choice list, an exit confirmation using the current Back API, and all text in strings.xml.

Files affected

Check what to add and what to replace before copying code.

app/src/main/java/com/example/alertdialog/MainActivity.javaReplace file
app/src/main/res/layout/activity_main.xmlReplace file
app/src/main/java/com/example/alertdialog/Screens.javaAdd these lines
app/src/main/res/values/strings.xmlReplace file

Application code

Select a file to see its code and where it belongs.

This code uses package com.example.alertdialog. Change that first line to your own package, the one at the top of your MainActivity.

Replace fileapp/src/main/java/com/example/alertdialog/MainActivity.java

Shows a confirm dialog, a single-choice list, and an exit dialog on Back.

MainActivity.java

package com.example.alertdialog;

import android.os.Bundle;
import android.widget.Button;
import android.widget.TextView;

import androidx.activity.OnBackPressedCallback;
import androidx.appcompat.app.AppCompatActivity;

import com.google.android.material.dialog.MaterialAlertDialogBuilder;

/**
 * Three common dialogs: a Yes/No confirmation, a single-choice list, and "Exit the app?" on Back.
 * MaterialAlertDialogBuilder gives them the Material 3 look.
 */
public class MainActivity extends AppCompatActivity {
    private static final String[] COLOURS = {"Purple", "Coral", "Sky blue", "Mint"};
    private int chosenColour = 0;
    TextView result;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Screens.setUp(this, R.layout.activity_main);
        result = findViewById(R.id.textResult);

        Button confirm = findViewById(R.id.btnConfirm);
        confirm.setOnClickListener(v -> new MaterialAlertDialogBuilder(this)
                .setTitle(R.string.delete_title)
                .setMessage(R.string.delete_message)
                .setIcon(R.drawable.ic_warning)
                .setNegativeButton(R.string.cancel, (dialog, which) -> result.setText(R.string.result_kept))
                .setPositiveButton(R.string.delete, (dialog, which) -> result.setText(R.string.result_deleted))
                .show());

        Button choose = findViewById(R.id.btnChoose);
        choose.setOnClickListener(v -> new MaterialAlertDialogBuilder(this)
                .setTitle(R.string.choose_title)
                // The radio list remembers the current choice; OK confirms it.
                .setSingleChoiceItems(COLOURS, chosenColour, (dialog, which) -> chosenColour = which)
                .setNegativeButton(R.string.cancel, null)
                .setPositiveButton(R.string.ok, (dialog, which) -> result.setText(getString(R.string.result_colour, COLOURS[chosenColour])))
                .show());

        // Ask before leaving the app with the Back button.
        getOnBackPressedDispatcher().addCallback(this, new OnBackPressedCallback(true) {
            @Override
            public void handleOnBackPressed() {
                new MaterialAlertDialogBuilder(MainActivity.this)
                        .setTitle(R.string.exit_title)
                        .setMessage(R.string.exit_message)
                        .setCancelable(true)
                        .setNegativeButton(R.string.stay, null)
                        .setPositiveButton(R.string.exit, (dialog, which) -> finish())
                        .show();
            }
        });
    }
}

Full source code

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