Edit the MainActivity.java file (Creating HTML5 Android WebApp)

package com.thirteenov.lightweightnotetaker;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.Window;
import android.view.WindowManager;
import android.webkit.WebChromeClient;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class MainActivity extends AppCompatActivity {

    WebView browser;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(
                WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN
        );

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        browser = findViewById(R.id.webview);
        browser.setWebChromeClient(new WebChromeClient());
        browser.getSettings().setJavaScriptEnabled(true);
        browser.getSettings().setDomStorageEnabled(true);
        browser.getSettings().setAllowFileAccessFromFileURLs(true);
        browser.getSettings().setAllowUniversalAccessFromFileURLs(true);
        browser.getSettings().setMediaPlaybackRequiresUserGesture(false);

        browser.loadUrl("file:///android_asset/index.html");

        browser.setWebViewClient(new WebViewClient() {
            public boolean shouldOverrideUrlLoading(WebView viewx, String urlx) {
                if(!urlx.contains("http")){
                    viewx.loadUrl(urlx);
                    return false;
                }else{
                    Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(urlx));
                    startActivity(intent);
                    return true;
                }
            }
        });
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        WebView browser = findViewById(R.id.webview);
        if ((keyCode == KeyEvent.KEYCODE_BACK) && browser.canGoBack()) {
            //if Back key pressed and webview can navigate to previous page
            browser.goBack();
            // go back to previous page
            return true;
        }
        else
        {
            finish();
        }
        return super.onKeyDown(keyCode, event);
    }
}