Table of Contents
Introduction
You might have noticed that in many Android apps, you need to tap the back button twice to exit. When you tap it once, a message pops up. But if you tap it twice at the same time, you can close the app.
Before Android 13 (which is like the newest version), we used to make this work by changing how the back button behaves in the main part of the app (we call it “MainActivity”). But now, with Android 13, the way we used to do this is not recommended anymore. They have a new method that’s better.
Quick Links:
Project Setup:
-
Launch Visual Studio 2022, and in the start window click Create a new
project to create a new project.
-
In the Create a new project window, select MAUI in the All project types
drop-down, select the .NET MAUI App template, and click the Next button:
-
In the configure your new project window, name your project, choose a
suitable location for it, and click the Next button:
-
In the Additional information window, click the Create button:
-
Once the project is created, we can able to see the Android, iOS, Windows
and other running options in the toolbar. Press the emulator or run button
to build and run the app
Implementation
- This new method lets you see what will happen if you press the back button before you actually do it. This helps you decide if you want to go back or not. For example, you might choose to stay in the app, go back to the Home screen, or return to a previous page in a web browser.
- To use this new method, Android 13 has added something called the “OnBackInvokedCallback”. This is like a tool that helps you do this new back button behavior. It takes the place of the old way we used to change the back button behavior.
- Now, instead of using the old way, we have the “OnBackPressedDispatcher” which takes care of handling when you press the back button. It works with the new method we just talked about.
class BackPress : OnBackPressedCallback
private readonly Activity activity;
private long backPressed;
public BackPress(Activity activity) : base(true)
this.activity = activity;
public override void HandleOnBackPressed()
var navigation = Microsoft.Maui.Controls.Application.Current?.MainPage?.Navigation;
if (navigation is not null && navigation.NavigationStack.Count <= 1 && navigation.ModalStack.Count <= 0)
const int delay = 2000;
if (backPressed + delay > DateTimeOffset.UtcNow.ToUnixTimeMilliseconds())
activity.FinishAndRemoveTask();
Process.KillProcess(Process.MyPid());
else
Toast.MakeText(activity, "Close", ToastLength.Long)?.Show();
backPressed = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
protected override void OnCreate(Bundle? savedInstanceState)
base.OnCreate(savedInstanceState);
OnBackPressedDispatcher.AddCallback(this, new BackPress(this));
Full Code:
using Android.App;
using Android.Content.PM;
using Android.OS;
using Android.Widget;
using AndroidX.Activity;
namespace MauiOnBackPressed;
[Activity(Theme = "@style/Maui.SplashTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize | ConfigChanges.Density)]
public class MainActivity : MauiAppCompatActivity
protected override void OnCreate(Bundle? savedInstanceState)
base.OnCreate(savedInstanceState);
OnBackPressedDispatcher.AddCallback(this, new BackPress(this));
class BackPress : OnBackPressedCallback
private readonly Activity activity;
private long backPressed;
public BackPress(Activity activity) : base(true)
this.activity = activity;
public override void HandleOnBackPressed()
var navigation = Microsoft.Maui.Controls.Application.Current?.MainPage?.Navigation;
if (navigation is not null && navigation.NavigationStack.Count <= 1 && navigation.ModalStack.Count <= 0)
const int delay = 2000;
if (backPressed + delay > DateTimeOffset.UtcNow.ToUnixTimeMilliseconds())
activity.FinishAndRemoveTask();
Process.KillProcess(Process.MyPid());
else
Toast.MakeText(activity, "Close", ToastLength.Long)?.Show();
backPressed = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
Download Code:
You can download the code from
GitHub. If you have
any doubts, feel free to post a comment. If you liked this article, and it
is useful to you, do like, share the article & star the repository on
GitHub.
GitHub. If you have
any doubts, feel free to post a comment. If you liked this article, and it
is useful to you, do like, share the article & star the repository on
GitHub.
References
https://developer.android.com/reference/androidx/activity/OnBackPressedDispatcher
