android + google map api v2 + current location

Question

i am creating an app with a google map view and i want this app to detect the current location of the user and display the lat and long with a marker on the map but all i can do until now is the display of the google map and the detection of current location without any marker displayed and without any text appear to display the lat and long

i did not add a marker until now because i do not know where to put it in the code and what is the best practice to do that

can anyone help me ??? this is the code of the:

manifest file

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="in.wptrafficanalyzer.locationgooglemapv2demo"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="16" />

    <permission
        android:name="in.wptrafficanalyzer.LocationGoogleMapV2Demo.permission.MAPS_RECEIVE"
        android:protectionLevel="signature" />

    <uses-permission android:name="in.wptrafficanalyzer.LocationGoogleMapV2Demo.permission.MAPS_RECEIVE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="true" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="in.wptrafficanalyzer.locationgooglemapv2demo.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

        <meta-data
            android:name="com.google.android.maps.v2.API_KEY"
            android:value="API KEY" />
    </application>

</manifest>

xml file

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/tv_location"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <fragment
        android:id="@+id/map"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        class="com.google.android.gms.maps.SupportMapFragment" />

</RelativeLayout>

java file

package in.wptrafficanalyzer.locationgooglemapv2demo;

import android.app.Dialog;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import android.widget.TextView;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;

public class MainActivity extends FragmentActivity implements LocationListener {

    GoogleMap googleMap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // Getting Google Play availability status
        int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getBaseContext());

        // Showing status
        if(status!=ConnectionResult.SUCCESS){ // Google Play Services are not available

            int requestCode = 10;
            Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status, this, requestCode);
            dialog.show();

        }else { // Google Play Services are available

            // Getting reference to the SupportMapFragment of activity_main.xml
            SupportMapFragment fm = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);

            // Getting GoogleMap object from the fragment
            googleMap = fm.getMap();

            // Enabling MyLocation Layer of Google Map
            googleMap.setMyLocationEnabled(true);

            // Getting LocationManager object from System Service LOCATION_SERVICE
            LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

            // Creating a criteria object to retrieve provider
            Criteria criteria = new Criteria();

            // Getting the name of the best provider
            String provider = locationManager.getBestProvider(criteria, true);

            // Getting Current Location
            Location location = locationManager.getLastKnownLocation(provider);

            if(location!=null){
                onLocationChanged(location);
            }
            locationManager.requestLocationUpdates(provider, 20000, 0, this);
        }
    }
    @Override
    public void onLocationChanged(Location location) {

        TextView tvLocation = (TextView) findViewById(R.id.tv_location);

        // Getting latitude of the current location
        double latitude = location.getLatitude();

        // Getting longitude of the current location
        double longitude = location.getLongitude();

        // Creating a LatLng object for the current location
        LatLng latLng = new LatLng(latitude, longitude);

        // Showing the current location in Google Map
        googleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));

        // Zoom in the Google Map
        googleMap.animateCamera(CameraUpdateFactory.zoomTo(15));

        // Setting latitude and longitude in the TextView tv_location
        tvLocation.setText("Latitude:" +  latitude  + ", Longitude:"+ longitude );

    }

    @Override
    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
}

Answer 1

First check the documentation here, it gives good indication on best strategies for getting user position.

Personally I usually start the map with a marker placed at the position retrivied with

Location lastKnownLocation = locationManager.getLastKnownLocation(locationProvider);

and then I start listening for position update and move the marker.

It also depend on how accurate position you need for the pourpose of your application, if you don't need really accurate position but the area is sufficient maybe you can just use thelastKnownLocation.

You can try something like this

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // Getting Google Play availability status
    int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getBaseContext());

    // Showing status
    if(status!=ConnectionResult.SUCCESS){ // Google Play Services are not available

        int requestCode = 10;
        Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status, this, requestCode);
        dialog.show();

    }else { // Google Play Services are available

        // Getting reference to the SupportMapFragment of activity_main.xml
        SupportMapFragment fm = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);

        // Getting GoogleMap object from the fragment
        googleMap = fm.getMap();

        // Enabling MyLocation Layer of Google Map
        googleMap.setMyLocationEnabled(true);

        // Getting LocationManager object from System Service LOCATION_SERVICE
        LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

        // Creating a criteria object to retrieve provider
        Criteria criteria = new Criteria();

        // Getting the name of the best provider
        String provider = locationManager.getBestProvider(criteria, true);

        // Getting Current Location
        Location location = locationManager.getLastKnownLocation(provider);

        LocationListener locationListener = new LocationListener() {
          void onLocationChanged(Location location) {
          // redraw the marker when get location update.
          drawMarker(location);
        }

        if(location!=null){
           //PLACE THE INITIAL MARKER              
           drawMarker(location);
        }
        locationManager.requestLocationUpdates(provider, 20000, 0, locationListener);
    }
}

private void drawMarker(Location location){
    // Remove any existing markers on the map
    googleMap.clear();
    LatLng currentPosition = new LatLng(location.getLatitude(),location.getLongitude());
    googleMap.addMarker(new MarkerOptions()
    .position(currentPosition)
    .snippet("Lat:" + location.getLatitude() + "Lng:"+ location.getLongitude())
    .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_AZURE))
    .title("ME"));
}

Also you don't need the Activity class to implements LocationListener, you can just define a listener and register it as I did above

P.S. I don't have an editor son my code can contain typo

Hope this helps, cheers