WebsiteActivity.java

import android.content.DialogInterface;
import android.content.Intent;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.Window;
import android.webkit.WebResourceRequest;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class WebsiteActivity extends AppCompatActivity {

    String url = "http://www.oimtrust.net/";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_website);

        getSupportActionBar().hide();

        WebView siteWeb = (WebView) findViewById(R.id.showWebView);

        siteWeb.getSettings().setJavaScriptEnabled(true);
        siteWeb.getSettings().setLoadWithOverviewMode(true);
        siteWeb.getSettings().setUseWideViewPort(true);

        siteWeb.setWebViewClient(new MyWebViewClient());
        siteWeb.loadUrl(url);
    }

    public void exit(){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("Anda yakin untuk keluar?")
                .setCancelable(false)
                .setPositiveButton("Iya", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        Intent intent = new Intent(Intent.ACTION_MAIN);
                        intent.addCategory(Intent.CATEGORY_HOME);
                        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                        startActivity(intent);
                    }
                })
                .setNegativeButton("Tidak", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                    }
                });
        AlertDialog alert = builder.create();
        alert.show();
    }

    public boolean onKeyDown(int keyCode, KeyEvent event){
        if (keyCode == KeyEvent.KEYCODE_BACK){
            exit();
        }
        return super.onKeyDown(keyCode, event);
    }

    private class MyWebViewClient extends WebViewClient {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
            view.loadUrl(url);
            return true;
        }
    }
}