getting location in WebView via js

I am not sure why, but now it works. There is code for simply app with webView which use gps location.
MainActivity:

package com.qiteq.gpswebview;

import android.Manifest;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.webkit.GeolocationPermissions;
import android.webkit.WebChromeClient;
import android.webkit.WebView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        WebView wv = new WebView(this);
        wv.loadUrl("http://qiteq.pl/stack/index.html");
        setContentView(wv);

        ActivityCompat.requestPermissions(this, new String[]{
                Manifest.permission.ACCESS_FINE_LOCATION,
                Manifest.permission.ACCESS_COARSE_LOCATION
        }, 0);

        wv.getSettings().setJavaScriptEnabled(true);


        wv.setWebChromeClient(new WebChromeClient() {
            @Override
            public void onGeolocationPermissionsShowPrompt(String origin, GeolocationPermissions.Callback callback) {
                callback.invoke(origin, true, false);
            }
        });


    }
}

Manifest:

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

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

And index.html:

<script>
function getLocationConstant()
{
  if(navigator.geolocation)
  {
   navigator.geolocation.getCurrentPosition(onGeoSuccess,onGeoError);
  } else {
   alert("No GPS support");
  }
}


function onGeoSuccess(event)
{
    document.getElementById("location").value =  event.coords.latitude+", "+event.coords.longitude;
    alert("Success: "+event.coords.latitude+", "+event.coords.longitude);
}


function onGeoError(event)
{
  alert("Error code " + event.code + ". " + event.message);
}


</script>

<input type="text" name="location" id="location" style="width:278px;">
<button onclick="getLocationConstant()" >Click</button>