[Android]: App behavior when receiving notifications on the splash screen and main screen

I'm using flutter and I'm a bad understand native android development very well. I'm using 2 Activities in my project:

1. SplashActivity - visible 1 time at the time of launching the app.
2. MainActivity - the main part of the application.

The problem is that when receiving push-notification from Firebase and when clicking on the notification, the program is completely restarted starting from SlashActivity. I added isTaskRoot to my SplashActivity, but it turned out not to be true, because my notification, when clicked, stopped calling a callback(), only expands the app or opens it starting with SplashActivity.

How it should work:

1. If MainActivity already exists (either in the background or foreground), open that same instance.
2. If MainActivity was destroyed (the user previously pressed Back), then open the SplashActivity. The splash activity will redirect you itself to MainActivity.
3. Notification should be targeted at the MainActivity and changed flow (callback), in depend on the previous points.

@SuppressLint("CustomSplashScreen")
public class SplashActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        supportRequestWindowFeature(Window.FEATURE_NO_TITLE);
        super.onCreate(savedInstanceState);

        // bad decision
        if (!isTaskRoot()) {
            finish();
            return;
        }

        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.launch_screen);

        new Handler().postDelayed(() -> {
            Intent intent = new Intent(SplashActivity.this, MainActivity.class);
            intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            intent.setFlags(Intent.FLAG_ACTIVITY_NO_USER_ACTION);
            intent.setFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
            startActivity(intent);
            overridePendingTransition(0, 0);
            finish();
        }, 2000);
    }
}

import io.flutter.embedding.android.FlutterFragmentActivity

class MainActivity: FlutterFragmentActivity() {
}

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.app">
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.INTERNET" />
   <application
        android:label="example"
        android:name="${applicationName}"
        android:icon="@mipmap/ic_launcher">
        <activity
            android:name=".SplashActivity"
            android:parentActivityName=".MainActivity"
            android:exported="true"
            android:allowBackup="true"
            android:launchMode="singleTask"
            android:theme="@style/AppTheme"
            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
            android:hardwareAccelerated="true"
            android:windowSoftInputMode="adjustResize">
            <meta-data
                android:name="io.flutter.embedding.android.SplashScreenDrawable"
                android:resource="@drawable/launch_background"
                />
            <meta-data
              android:name="io.flutter.embedding.android.NormalTheme"
              android:resource="@style/NormalTheme"
              />
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
       <activity
           android:name=".MainActivity"
           android:exported="true"
           android:launchMode="singleTop"
           android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
           android:hardwareAccelerated="true"
           android:windowSoftInputMode="adjustResize"
           android:theme="@style/LaunchTheme">
           <meta-data
               android:name="io.flutter.embedding.android.NormalTheme"
               android:resource="@style/NormalTheme"
               />
           <intent-filter>
               <action android:name="android.intent.action.MAIN"/>
               <category android:name="android.intent.category.LAUNCHER"/>
           </intent-filter>
           <intent-filter>
               <action android:name="FLUTTER_NOTIFICATION_CLICK" />
               <category android:name="android.intent.category.DEFAULT" />
           </intent-filter>
       </activity>
        <meta-data
            android:name="flutterEmbedding"
            android:value="2" />
       <meta-data
           android:name="com.google.firebase.messaging.default_notification_channel_id"
           android:value="high_importance_channel" />
       <meta-data
           android:name="com.google.firebase.messaging.default_notification_icon"
           android:resource="@drawable/ic_notification" />
       <meta-data
           android:name="com.google.firebase.messaging.default_notification_color"
           android:resource="@color/colorNotification" />
    </application>
    <queries>
        <intent>
            <action android:name="android.intent.action.VIEW" />
            <category android:name="android.intent.category.BROWSABLE" />
            <data android:scheme="https" />
        </intent>
        <intent>
            <action android:name="android.intent.action.SENDTO" />
            <data android:scheme="mailto" />
        </intent>
    </queries>
</manifest>

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