Latitude e Longitude não funcionam

MainActivity.java

package br.uesc.nilton.focoapi14;

import android.Manifest;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.provider.Settings;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements LocationListener {
    private LocationManager locationManager;
    private boolean allowNetwork;

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

    @Override
    protected void onResume() {
        super.onResume();

        allowNetwork = true;

        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

        if((ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) || (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED)) {
            Toast.makeText(this, "A aplicação não tem permição para usar o GPS", Toast.LENGTH_LONG).show();
        }
        else{
            if (!locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
                Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                Toast.makeText(this, "Ative o GPS para continuar", Toast.LENGTH_LONG).show();
                startActivity(intent);
            } else {
                locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, this);
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
            }
        }



    }

    @Override
    protected void onPause() {
        super.onPause();

        if((ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) || (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED)) {
        }
        else{
            locationManager.removeUpdates(this);
        }
    }

    public void tirarFoto(View view) {
        Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
        startActivityForResult(intent, 0);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (data != null) {
            Bundle bundle = data.getExtras();
            if (bundle != null) {
                Bitmap img = (Bitmap) bundle.get("data");

                ImageView iv = (ImageView) findViewById(R.id.imageView);
                iv.setImageBitmap(img);
            }
        }
    }

    @Override
    public void onLocationChanged(Location location) {
        // EVENTO CHAMADO QUANDO O POSICIONAMENTO É ALTERADO

        Log.i("nilton", "Localizacao ok");
        Toast.makeText(this, "onLocationChanged", Toast.LENGTH_LONG).show();

        TextView txtLat = (TextView) findViewById(R.id.txtLatitude);
        TextView txtLng = (TextView) findViewById(R.id.txtLongitude);

        if (location.getProvider().equals(LocationManager.GPS_PROVIDER)) {
            allowNetwork = false;
        }

        //if (allowNetwork || location.getProvider().equals(LocationManager.GPS_PROVIDER)){

            Toast.makeText(this, "Localização ok", Toast.LENGTH_LONG).show();
            txtLat.setText("Latitude: " + location.getLatitude());
            txtLng.setText("Longitude: " + location.getLongitude());

        //}
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // EVENTO DISPARADO QUANDO O STATUS/SINAL DO GPS É ALTERADO

        Toast.makeText(this, "onStatusChanged", Toast.LENGTH_LONG).show();
    }

    @Override
    public void onProviderEnabled(String provider) {
        // EVENTO DISPARADO QUANDO GPS É ATIVADO
        Log.i("log", "GPS ATIVADO");
        Toast.makeText(this, "onProviderEnabled", Toast.LENGTH_LONG).show();
    }

    @Override
    public void onProviderDisabled(String provider) {
        // EVENTO DISPARADO QUANDO GPS É DESATIVADO

        Log.i("log", "GPS DESATIVADO");
        Toast.makeText(this, "onProviderDisabled", Toast.LENGTH_LONG).show();
    }
}