How customize theme in .NET9 Android Application project?

[eworker2003]

Hi,
I have created "Android Application" project, .NET 9 (Visual Studio 2022 - see screen) which supports Android 15.

To hide App bar (ActionBar) the xml-code was added:

<style name="AppTheme" parent="Theme.AppCompat.Light"> .. <style name="AppTheme.NoActionBar">

<item name="windowActionBar">false</item>

<item name="windowNoTitle">true</item>

</style>

MainActivity.cs:

using AndroidX.AppCompat.App; ... [Activity(Label = "@string/ApplicationName", MainLauncher = true, Theme = "@style/AppTheme.NoActionBar")] public class MainActivity : AppCompatActivity {

I have installed the package xamarin.androidx.appcompat\1.7.1\ (for AndroidX.AppCompat.App using)

But I have warning:
Detected package version outside of dependency constraint: Xamarin.AndroidX.Lifecycle.Process 2.8.7.4 requires Xamarin.AndroidX.Lifecycle.Runtime (>= 2.8.7.4 && < 2.8.8) but version Xamarin.AndroidX.Lifecycle.Runtime 2.9.1 was resolved.

When I run app I have error:

System.TypeLoadException: 'Could not resolve type with token 0100003f from typeref (expected class 'AndroidX.SavedState.ISavedStateRegistryOwner' in assembly 'Xamarin.AndroidX.SavedState, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null') assembly:Xamarin.AndroidX.SavedState, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null ...

Please help - "Android Application" project type is work? Is it possible to use it for build app for Android 15?

[rokmeglic71]

In your project file, you have to define specific version of "Xamarin.AndroidX.Lifecycle.Runtime". At least, this was something I had to do, for similar error on a different reference library. Check the first point in CoPilot AI answer.

[eworker2003]

The link "first point in CoPilot AI answer" returns 403 error. Could you explain - how define specific version? In my project (.csproj) only one reference

<ItemGroup>
  <PackageReference Include="Xamarin.AndroidX.AppCompat" Version="1.7.1" />
</ItemGroup>

[eworker2003]

What is the "Android Application" project type purpose? Why MainActivity is not AppCompatActivity by default like in MAUI or in Xamarin Native? May be it it a bug?

[rokmeglic71]

The problem is in "Xamarin.AndroidX.Lifecycle.Runtime (>= 2.8.7.4 && < 2.8.8) but version Xamarin.AndroidX.Lifecycle.Runtime 2.9.1 was resolved". You have to define lower version of Xamarin.AndroidX.Lifecycle.Runtime and try again.

Xamarin.AndroidX.Lifecycle.Runtime - 2.8.7

<ItemGroup>
  <PackageReference Include="Xamarin.AndroidX.Lifecycle.Runtime" Version="2.8.7" />
</ItemGroup>

This might not be optimal, as you will have older version of Xamarin.AndroidX.Lifecycle.Runtime. It is just to get the error gone.
I do not fully understand what you want and why you added xamarin.androidx.appcompat\1.7.1\ (for AndroidX.AppCompat.App using) which produces this error.

[eworker2003]

I do not fully understand what you want and why you added xamarin.androidx.appcompat

The goal is for MainActivity to inherit from the AppCompatActivity class.
public class MainActivity : AppCompatActivity

By default, when you create a "Android Application" project, MainActivity inherits from the Activity class and in this case I don't see a way to change the theme.
public class MainActivity : Activity

As I understand for using AppCompatActivity I should add xamarin.androidx.appcompat package.

[rokmeglic71]

Can you please make a screenshot of what you are trying to hide (App bar (ActionBar))?

[rokmeglic71]

@eworker2003 can you give me a link to documentation or blog where you have read to inherit AppCompatActivity. The more I think and check with CoPilot AI, I think you can solve all the above problems without inherit AppCompatActivity. Please check the CoPilot AI link and let me know if it helps in anyway. If not, let's start with focusing on one problem and I can provide you with code / blog references.

[eworker2003]

Hi, I have checked Copilot answer - it is not help for this. My project type is native android app, in VS it is ".NET for Android Application" project kind. It looks like Xamarine Native, but it is new, based on .NET.

In MAUI project MainActivity already inherits from MauiAppCompatActivity (as say copilot), but in Android Application project MainActivity inherits from Activity.

give me a link to documentation or blog where you have read to inherit AppCompatActivity.

It is described here:
https://developer.android.com/develop/ui/views/theming/themes

"Styles and themes"

If I try something like this:

<style name="AppTheme" parent="Theme.AppCompat.Light"> true @color/colorPrimary @color/colorPrimaryDark @color/colorAccent </style>

I have the compiler error:
resource style/Theme.AppCompat.Light (....:style/Theme.AppCompat.Light) not found.

So I think it is need to add package Xamarin.AndroidX.AppCompat.

Upd. Now it looks like I have found the solution - I have installed
Xamarin.AndroidX.AppCompat version 1.7.0.7 (not last), with Xamarin.AndroidX.Lifecycle.Runtime (>= 2.8.7.4 && < 2.8.8). It is work, AppCompat is available :)

[rokmeglic71]

Great @eworker2003 , I just found this questionable for future use. Just for your information, how to remove title bar in MAUI, how to remove app bar, edge to edge support and Theme an app (official doc).

[eworker2003]

Thanks, nice link about edge to edge support! This app is not MAUI. it is native Android app, it is more faster than MAUI. I think I will use MAUI too, for creating iOS app and Android too.

PS. For information, in Android Application .NET9 to use AppBarLayout it is need to add package Xamarin.Google.Android.Material

and use this tags:

  <com.google.android.material.appbar.AppBarLayout
    android:theme="@style/AppTheme.AppBarOverlay"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:theme="@style/AppTheme.AppBarOverlay" />

    </com.google.android.material.appbar.AppBarLayout>

[rokmeglic71]

@eworker2003 MAUI 10, preview 7, has also improvements on SafeArea which includes some edge to edge work - at least this is what writes in the release notes.