Android : Java.Lang.RuntimeException with intent

I am developing two apps on Android: app A which when a button is pressed should open app B which should return a value to app A, like "OK". To do this, app A sends an intent with the action "com.intent.test", but when it receives the intent, app B crashes with the following error message:

Java.Lang.RuntimeException: 'Unable to instantiate activity ComponentInfo{com.example.newdemo/com.example.newdemo.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.example.demointent.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.demointent-SsbNhZc7TrVyMjaIbZDfVw==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.demointent-SsbNhZc7TrVyMjaIbZDfVw==/lib/arm64, /data/app/com.example.demointent-SsbNhZc7TrVyMjaIbZDfVw==/base.apk!/lib/arm64-v8a, /system/lib64, /system/product/lib64]]'

AndroidManifest.xml app B :

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="com.example.demointent" android:installLocation="auto">
    <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="33" />
    <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme">
        <activity android:name=".MainActivity" android:label="@string/app_name" android:exported="true" android:enabled="true">
            <intent-filter>
                <action android:name="com.intent.test" />
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
    </application>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
</manifest>

MainActivity app B:

namespace NewDemo
{
    [Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
    public class MainActivity : AppCompatActivity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            try
            {
                base.OnCreate(savedInstanceState);
                Xamarin.Essentials.Platform.Init(this, savedInstanceState);
                SetContentView(Resource.Layout.activity_main);

                Intent receivedIntent = Intent;
                if (receivedIntent == null) return;

                var dataReceived = receivedIntent.GetStringExtra("key");
                var action = receivedIntent.Action;

                var intent = new Intent();
                switch (action)
                {
                    case "com.intent.test":
                        intent.PutExtra("result", "OK");
                        break;
                }

                SetResult(Result.Ok, intent);
                Toast.MakeText(this, "My app is started. Data: " + dataReceived, ToastLength.Short)?.Show();
                Finish();
            }
            catch (Exception ex)
            {
                Toast.MakeText(this, "error: " + ex.Message, ToastLength.Short)?.Show();
            }

        }
    }
}

MainActivity app A:

      protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            SetContentView(Resource.Layout.activity_main);
            var btnstartWithAction = FindViewById<TextView>(Resource.Id.btnstartWithAction);
            if (btnstartWithAction != null)
            {
                btnstartWithAction.Click += (sender, e) =>
                {
                    var intent = new Intent();
                    var action = "com.intent.test";
                    intent.SetAction(action);
                    intent.PutExtra("key", "keytest");

                    StartActivityForResult(Intent.CreateChooser(intent, "App"), 3);
                };
            }
        }

This error appears when I use the intent with action. When app A call App B with the package name, I don't have a problem. Like this :

                   Intent launchIntent = ApplicationContext.PackageManager.GetLaunchIntentForPackage("com.example.newdemo");
                    launchIntent?.SetFlags(0);
                    launchIntent?.SetAction("com.intent.test");
                    launchIntent?.PutExtra("key", "12345");
                    StartActivityForResult(Intent.CreateChooser(launchIntent, ""), 12);

I have already cleaned and built my project several times. I'm coding in c# with Xamarin and visual studio 2022. does anyone have any idea what is going on?
Thanks.

> Java.Lang.RuntimeException: 'Unable to instantiate activity
> ComponentInfo{com.example.newdemo/com.example.newdemo.MainActivity}:
> java.lang.ClassNotFoundException: Didn't find class
> "com.example.demointent.MainActivity"

On Xamarin.Android, by default, generates the Java wrappers using MD5-based class names to avoid Java class name clashing, such as:

 md579731053346ff64fcf21847b09163ce1.MainActivity 

You have hard-coded a activity android:name=".MainActivity" in your manifest but the generated class will be MD5-based by default.

You should avoid to mix up declarative attributes and manually writing the AndroidManifest.xml.

[Activity (Label = "MyApp", MainLauncher = true, Icon = "@mipmap/ic_launcher")] is generating a piece of code in the actual used (generated) AndroidManifest.xml that looks like:

  <activity android:icon="@drawable/icon" android:label="AndroidApp1" android:name="md5c178831cd46fc53bebc42cf953f78ced.MainActivity">
  <intent-filter>
    <action android:name="android.intent.action.MAIN" />
    <category android:name="android.intent.category.LAUNCHER" />
  </intent-filter>
</activity>

and your code will be somewhere else. You can find the generated AndroidManifest.xml in the output folder .\obj\Debug\android.

So,try to remove the manual edits from your manifest file and add your stuff via attributes if you need.

For example:

[Activity(Label = "SearchBarDemos", Icon = "@mipmap/icon", Theme = "@style/MainTheme", MainLauncher = true,Exported =true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)] 
    [
    IntentFilter
    (
        new[] { Android.Content.Intent.ActionView },
        Categories = new[]
            {
                Android.Content.Intent.CategoryDefault,
                Android.Content.Intent.CategoryBrowsable
            },
        DataSchemes = new[] { "myapp" }
    )
]
    public class MainActivity:Activity
 {

 }