Android LocationListener return null value

Question

Main Java File:

public class MainActivity extends Activity implements LocationListener {
    TextView tv;
    TextView tv2;
    TextView tv3;
    LocationListener locationListener;
    static final String tag="********MAIN********";
    LocationManager lm;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lm = (LocationManager) getSystemService(LOCATION_SERVICE);
    }
    @Override
    protected void onResume() {
        super.onResume();
        lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,0,0,locationListener);
    }
    @Override
    public void onLocationChanged(Location location) {
        Log.i(tag,"Location Changed Method Called");
        String lat= String.valueOf(location.getLatitude());
        String log= String.valueOf(location.getLongitude());
        tv.setText(lat+ " " + log);
    }
    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }
    @Override
    public void onProviderEnabled(String provider) {
    }
    @Override
    public void onProviderDisabled(String provider) {
    }
}

Manifest File:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="p2p.boysjoys.com.alpha" >

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"></uses-permission>
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >


        <activity
            android:name=".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>
    </application>

</manifest>

Error Log:

05-21 18:51:53.970 22842-22842/p2p.boysjoys.com.alpha E/AndroidRuntime﹕ FATAL EXCEPTION: main java.lang.RuntimeException: Unable to resume activity {p2p.boysjoys.com.alpha/p2p.boysjoys.com.alpha.MainActivity}: java.lang.IllegalArgumentException: listener==null at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2596) at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2624) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2101) at android.app.ActivityThread.access$600(ActivityThread.java:138) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1207) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:213) at android.app.ActivityThread.main(ActivityThread.java:4787) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.IllegalArgumentException: listener==null at android.location.LocationManager.requestLocationUpdates(LocationManager.java:510) at p2p.boysjoys.com.alpha.MainActivity.onResume(MainActivity.java:38) at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1184) at android.app.Activity.performResume(Activity.java:5082) at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2586) at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2624) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2101) at android.app.ActivityThread.access$600(ActivityThread.java:138) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1207) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:213) at android.app.ActivityThread.main(ActivityThread.java:4787) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556) at dalvik.system.NativeStart.main(Native Method)

I m trying to get location as soon as app opens and it will set to TextView, but i get an error on line no.38 as pointed out to LogCat

That line is:

lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,0,0,locationListener);

I tried both gps and network on phone and also on emulator but it still giving same error java.lang.IllegalArgumentException: listener==null

Answer 1

Change:

lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,0,0,locationListener);

with this:

lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,0,0,this);

Your class already implements LocationListener. Just use it. (however, in your code you try to use locationListener without initialize it)