Webview last session destroyed after minimizing tab

Question

This is my first time creating a webview application using Android Studio. So i have a website that contain login pages.I need to develop applications by using webview. The problem was when the app was newly installed then open it up, then the user change tab, the webview rollback to its main webview url. But after of that it doesn't bother anymore its completely working.I want that to remove so the user can changing tab on the first place without destroying it's current activities. This is mainactivity codes. I don't use any fragments.

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.app.Activity;
import android.content.Context;
import android.content.DialogInterface;
import android.support.design.widget.CoordinatorLayout;
import android.support.v7.app.AlertDialog;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private Context mContext;
    private Activity mActivity;
    private CoordinatorLayout mCLayout;
    private WebView mWebView;
    boolean isHomePage = false;


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


        // Get the application context for back button and exit
        mContext = getApplicationContext();
        mActivity = MainActivity.this;
        mCLayout = (CoordinatorLayout) findViewById(R.id.coordinator_layout);
        mWebView = (WebView) findViewById(R.id.webview);

        // Zoom out of the website to mobile view.
        WebView browser = (WebView) findViewById(R.id.webview);
        browser.getSettings().setLoadWithOverviewMode(true);
        browser.getSettings().setUseWideViewPort(true);
        // >>> Enable zoom IN and OUT.
        browser.getSettings().setBuiltInZoomControls(true);
        browser.getSettings().setDisplayZoomControls(false);

        // Enabling Javascript.
        final WebView myWebView = (WebView) findViewById(R.id.webview);
        WebSettings webSettings = myWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);

        // Loading the URL to Webview.
        mWebView.getSettings().setCacheMode(WebSettings.LOAD_CACHE_ELSE_NETWORK);
        mWebView.loadUrl("url");

        // Enabling DOM Storage most IMPORTANT one
        mWebView.getSettings().setDomStorageEnabled(true);

        // Enabling Automatic Javascript when opening windows not needed just to make sure
        mWebView.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);


        // Preventing to load on browser - it keeps loading to the same webview even the link is targeting to other.


        myWebView.setWebViewClient(new WebViewClient() {
            public boolean shouldOverrideUrlLoading(WebView viewx, String urlx) {
                viewx.loadUrl(urlx);
                return false;
            }

        });


        mWebView.setWebViewClient(new WebViewClient() {
                                      @Override
                                      public boolean shouldOverrideUrlLoading(WebView view, String url) {
                                          view.loadUrl(url);

                                          if (url.contains("url")) {
                                              isHomePage = true;


                                              return true;
                                          } else
                                              isHomePage = false;
                                          return false;
                                      }

                                  }
        );



        // Hiding Status and Dock bar when opening the applications
        View decorView = getWindow().getDecorView();
// Hide both the navigation bar and the status bar.
// SYSTEM_UI_FLAG_FULLSCREEN is only available on Android 4.1 and higher, but as
// a general rule, you should design your app to hide the status bar whenever you
// hide the navigation bar.
        int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                | View.SYSTEM_UI_FLAG_FULLSCREEN;
        decorView.setSystemUiVisibility(uiOptions);
    }


    protected void showAppExitDialog() {


        AlertDialog.Builder builder = new AlertDialog.Builder(mActivity);

        builder.setTitle("Please confirm");
        builder.setMessage("Do you want to exit the app?");
        builder.setCancelable(true);

        builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialogInterface, int i) {
                // Do something when user want to exit the app
                // Let allow the system to handle the event, such as exit the app
                MainActivity.super.onBackPressed();
            }
        });

        builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialogInterface, int i) {
                // Do something when want to stay in the app
                Toast.makeText(mContext, "thank you", Toast.LENGTH_LONG).show();
            }
        });

        // Create the alert dialog using alert dialog builder
        AlertDialog dialog = builder.create();

        // Finally, display the dialog when user press back button
        dialog.show();
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (event.getAction() == KeyEvent.ACTION_DOWN) {
            switch (keyCode) {
                case KeyEvent.KEYCODE_BACK:
                    String url = new String("url");
                    String webUrl = new String(mWebView.getUrl());

                    if (url.equals(webUrl)) {
                        Toast.makeText(this, "You are logged in. Please Logout if you want to exit.",
                                Toast.LENGTH_SHORT).show();



                    } else if (isHomePage == false) {
                        if (mWebView.canGoBack()) {
                            Toast.makeText(this, "DoubleBack",
                                    Toast.LENGTH_SHORT).show();
                            mWebView.goBack();
                            mWebView.goBack();
                            isHomePage = true;
                        }
                    }else{
                        url = new String("url");
                        webUrl = new String(mWebView.getUrl());

                        if (url.equals(webUrl)) {
                            Toast.makeText(this, "Access Denied",
                                    Toast.LENGTH_SHORT).show();
                        }
                        else
                        if (mWebView.canGoBack()) {
                            Toast.makeText(this, "Back",
                                    Toast.LENGTH_SHORT);
                            mWebView.goBack();
                        }
                    }
                    return true;
                default:
            }

        }
        return super.onKeyDown(keyCode, event);
    }

    }

This is my 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.test"
    android:installLocation="auto"
    android:versionCode="3210"
    android:versionName="1.1.0"
    >
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-sdk android:targetSdkVersion="10"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme"
        android:usesCleartextTraffic="true"
        android:isGame="false"

        >

        <activity
            android:name=".MainActivity"
            android:configChanges="orientation|keyboard|keyboardHidden|screenSize"
            android:windowSoftInputMode="adjustNothing|adjustPan"
            android:label="@string/app_name">  <!--Prevent Reloading when changing screen rotation-->
            <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
        </activity>
    </application>

</manifest>