Android Handle Logged In/Out State on Startup

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.android">

    ...

    <application
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name">

        <activity
            android:name=".onboarding.StartupActivity"
            android:label="@string/app_name"
            android:launchMode="singleInstance"
            android:theme="android:style/Theme.NoDisplay">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:launchMode="singleTop" />
            
        <activity
            android:name=".authentication.controller.AuthenticationActivity"
            android:label="@string/title_sign_in"
            android:launchMode="singleTask"
            android:windowSoftInputMode="adjustResize|stateHidden" />
         
         ....
    </application>

</manifest>

StartupActivity.java

package com.example.android.onboarding;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;

import com.example.android.MainActivity;
import com.example.android.R;

import com.example.android.authentication.controller.AuthenticationActivity;

import com.example.android.util.ResourceUtils;

public class StartupActivity extends Activity {
    private static final AUTHENTICATION_REQUEST_CODE = 1000;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        if (isLoggedIn()) {
            Intent startupIntent = new Intent(this, MainActivity.class);
            startupIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP);
            startActivity(startupIntent);
            finish();
        } else {
            Intent startupIntent = new Intent(this, AuthenticationActivity.class);
            startActivityForResult(startupIntent, AUTHENTICATION_REQUEST_CODE);
        }

        super.onCreate(savedInstanceState);
    }

    private boolean isLoggedIn() {
        // Check SharedPreferences or wherever you store login information
        return this.getSharedPreferences("my_app_preferences", Context.MODE_PRIVATE).getBoolean("loggedIn", false);
    }
  
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == AUTHENTICATION_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
            Intent startupIntent = new Intent(this, MainActivity.class);
            startupIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP);
            startActivity(startupIntent);
        }

        finish();
    }
}