Android studio hide white screen flash on every page load

I am developing an app that uses local files. In index.html file i have multiple links to different local files like: settings.html, add.html, edit.html and ... Problem is when i run app in android studio and smart phone, when i click on any link, before loading content a fast screen flash with white background shows up. Look at this gif:

How can i disable this white flash?

MainActivity.java:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    WebView webView=findViewById(R.id.webView);
    webView.getSettings().setJavaScriptEnabled(true);
    webView.getSettings().setDomStorageEnabled(true);
    webView.loadUrl("file:///android_asset/index.html");

    getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<WebView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/webView"/>

</LinearLayout>