.NET MAUI Android - Unable to create service: class not found exception

Question

I'm building a call screener app for Android using the CallScreeningService API. When I run the app, it registers the service OK but when I call the emulator, I get the following exception:

Java.Lang.RuntimeException: 'Unable to create service com.katoapps.callblocker.CallBlockerService: java.lang.ClassNotFoundException: Didn't find class "com.katoapps.callblocker.CallBlockerService" on path: DexPathList[[zip file "/data/app/~~OvboC6Rbk2k7eFeBnJFlKg==/com.katoapps.callblocker-aJoY2QavLWrfwVyoFIXSMA==/base.apk"],nativeLibraryDirectories=[/data/app/~~OvboC6Rbk2k7eFeBnJFlKg==/com.katoapps.callblocker-aJoY2QavLWrfwVyoFIXSMA==/lib/x86_64, /data/app/~~OvboC6Rbk2k7eFeBnJFlKg==/com.katoapps.callblocker-aJoY2QavLWrfwVyoFIXSMA==/base.apk!/lib/x86_64, /system/lib64, /system_ext/lib64]]'

Here's CallBlockerService (located in /Platforms/Android/CallBlockerService.cs)

namespace CallBlocker;

using Android.App;
using Android.Telecom;

[Service(Exported = true, Permission = "android.permission.BIND_SCREENING_SERVICE")]
[IntentFilter(new string[] { "android.telecom.CallScreeningService" })]
public class CallBlockerService : CallScreeningService
{
    public override void OnScreenCall(Call.Details callDetails)
    {
    }
}

The main activity that registers the service:

using Android.App;
using Android.App.Roles;
using Android.Content;
using Android.Content.PM;
using Android.OS;

namespace CallBlocker;

[Activity(Theme = "@style/Maui.SplashTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize | ConfigChanges.Density)]
public class MainActivity : MauiAppCompatActivity
{
    private static int REQUEST_ID = 1;

    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        RoleManager roleManager = (RoleManager)GetSystemService(RoleService);
        Intent intent = roleManager.CreateRequestRoleIntent(RoleManager.RoleCallScreening);
        StartActivityForResult(intent, REQUEST_ID);
    }

    protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
    {
        if (requestCode == REQUEST_ID)
        {
            if (resultCode == Result.Ok)
            {
                // Your app is now the call screening app
            }
            else
            {
                // Your app is not the call screening app
            }
        }
    }
}

The android manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.katoapps.callblocker">
    <application android:allowBackup="true" android:icon="@mipmap/appicon" android:roundIcon="@mipmap/appicon_round" android:supportsRtl="true" android:label="Call Blocker">
        <service android:name=".CallBlockerService"
                android:exported="true"
                android:permission="android.permission.BIND_SCREENING_SERVICE">
            <intent-filter>
                <action android:name="android.telecom.CallScreeningService" />
            </intent-filter>
        </service>
    </application>
    <uses-sdk android:minSdkVersion="29" />

</manifest>

And the project info (not sure if it's relevant)

<Project Sdk="Microsoft.NET.Sdk">

    <PropertyGroup>
        <TargetFrameworks>net7.0-android;</TargetFrameworks>
        <OutputType>Exe</OutputType>
        <RootNamespace>CallBlocker</RootNamespace>
        <UseMaui>true</UseMaui>
        <SingleProject>true</SingleProject>
        <ImplicitUsings>enable</ImplicitUsings>

        <!-- Display name -->
        <ApplicationTitle>CallBlocker</ApplicationTitle>

        <!-- App Identifier -->
        <ApplicationId>com.katoapps.callblocker</ApplicationId>
        <ApplicationIdGuid>025a85bb-9e56-4624-a3cf-3797a5a01bd2</ApplicationIdGuid>

        <!-- Versions -->
        <ApplicationDisplayVersion>1.0</ApplicationDisplayVersion>
        <ApplicationVersion>1</ApplicationVersion>

        <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android'">29.0</SupportedOSPlatformVersion>
    </PropertyGroup>

    <PropertyGroup Condition="'$(Configuration)|$(TargetFramework)|$(Platform)'=='Debug|net7.0-android|AnyCPU'">
      <ApplicationId>com.katoapps.callblocker</ApplicationId>
    </PropertyGroup>

    <PropertyGroup Condition="'$(Configuration)|$(TargetFramework)|$(Platform)'=='Release|net7.0-android|AnyCPU'">
      <ApplicationId>com.katoapps.callblocker</ApplicationId>
    </PropertyGroup>

    <ItemGroup>
        <!-- App Icon -->
        <MauiIcon Include="Resources\AppIcon\appicon.svg" ForegroundFile="Resources\AppIcon\appiconfg.svg" Color="#512BD4" />

        <!-- Splash Screen -->
        <MauiSplashScreen Include="Resources\Splash\splash.svg" Color="#512BD4" BaseSize="128,128" />

        <!-- Images -->
        <MauiImage Include="Resources\Images\*" />
        <MauiImage Update="Resources\Images\dotnet_bot.svg" BaseSize="168,208" />

        <!-- Custom Fonts -->
        <MauiFont Include="Resources\Fonts\*" />

        <!-- Raw Assets (also remove the "Resources\Raw" prefix) -->
        <MauiAsset Include="Resources\Raw\**" LogicalName="%(RecursiveDir)%(Filename)%(Extension)" />
    </ItemGroup>

    <ItemGroup>
        <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="7.0.0" />
    </ItemGroup>

</Project>

Why is the app not finding my CallBlockerService?

Answer 1

Decompiling the APK revealed this Android manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" android:compileSdkVersion="33" android:compileSdkVersionCodename="13" package="com.katoapps.callblocker" platformBuildVersionCode="33" platformBuildVersionName="13">
    <application android:label="Call Blocker" android:icon="@mipmap/appicon" android:name="crc6474c5bb46df487c36.MainApplication" android:debuggable="true" android:allowBackup="true" android:supportsRtl="true" android:extractNativeLibs="true" android:roundIcon="@mipmap/appicon_round" android:appComponentFactory="androidx.core.app.CoreComponentFactory">
        <service android:name="com.katoapps.callblocker.CallBlockerService" android:permission="android.permission.BIND_SCREENING_SERVICE" android:exported="true">
            <intent-filter>
                <action android:name="android.telecom.CallScreeningService"/>
            </intent-filter>
        </service>
        <service android:name="crc6474c5bb46df487c36.CallBlockerService" android:permission="android.permission.BIND_SCREENING_SERVICE" android:exported="true">
            <intent-filter>
                <action android:name="android.telecom.CallScreeningService"/>
            </intent-filter>
        </service>
...
    </application>
</manifest>

The compiler modifies the Android manifest and adds the service automatically under a GUID name, so the fix was to simply remove my service from the manifest.