getLastKnownLocation() working on 4.* but crashes on 2.3.4

Question

I am using SupportMapFrgment to ensure backwards compatibility for the Google Maps API in my application.

It seems to load the map just fine on 4.1 but i get a crash on 2.3.4.

Here's my code:

 private String getCurrentLocation() {
        LocationManager service = (LocationManager) getSystemService(LOCATION_SERVICE);
        Criteria criteria = new Criteria();
        String provider = service.getBestProvider(criteria, false);
        Location location = service.getLastKnownLocation(provider);



        LatLng userLocation = new LatLng(location.getLatitude(),
                location.getLongitude());

        Geocoder geocoder = new Geocoder(this, Locale.getDefault());
        List<Address> addresses = null;
        String addressText = "";
        try {
            while (addresses == null) {
                addresses = geocoder.getFromLocation(userLocation.latitude,
                        userLocation.longitude, 1);
            }

            if (addresses != null && addresses.size() > 0) {
                Address address = addresses.get(0);
                addressText = String.format(
                        "%s, %s, %s",
                        address.getMaxAddressLineIndex() > 0 ? address
                                .getAddressLine(0) : "", address.getLocality(),
                        address.getCountryName());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return addressText;
    }

This is where i retrieve the map:

map = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                .getMap();

The XML layout:

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/location_stuff"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/greenish"
    android:orientation="vertical" >

    <RelativeLayout
        android:id="@+id/location_header"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:background="@color/greenish" >

        <RelativeLayout
            android:id="@+id/cancel_btn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_centerVertical="true"
            android:layout_marginLeft="20dp"
            android:background="@drawable/done_rounded_btn"
            android:gravity="center" >

            <TextView
                android:id="@+id/retake_txt"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerInParent="true"
                android:layout_marginTop="10dp"
                android:gravity="center"
                android:paddingLeft="7dp"
                android:paddingRight="7dp"
                android:text="@string/cancel"
                android:textAllCaps="true"
                android:textColor="#FFFFFF"
                android:textSize="16sp" />
        </RelativeLayout>

        <TextView
            android:id="@+id/location_txt"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_centerVertical="true"
            android:gravity="center_vertical"
            android:text="@string/location_map"
            android:textAllCaps="true"
            android:textColor="@color/done_color"
            android:textSize="16sp" />
    </RelativeLayout>

    <fragment
        android:layout_weight="6"
        android:id="@+id/map"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        class="com.google.android.gms.maps.SupportMapFragment"/>


    <RelativeLayout
        android:id="@+id/save_location_layout"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:background="@color/greenish" >

        <LinearLayout
            android:id="@+id/delete_btn"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_centerVertical="true"
            android:layout_marginLeft="25dp"
            android:layout_marginRight="25dp"
            android:background="@drawable/done_rounded_btn"
            android:orientation="horizontal"
            android:paddingBottom="7dip"
            android:paddingTop="7dip"
            android:weightSum="7" >

            <TextView
                android:id="@+id/delete_txt"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="6"
                android:background="@null"
                android:paddingLeft="10dp"
                android:text="@string/save_location"
                android:textAllCaps="true"
                android:textColor="@color/white"
                android:textSize="18sp" />

            <ImageView
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:layout_weight="1"
                android:contentDescription="@string/hello_world"
                android:paddingLeft="10dp"
                android:paddingRight="10dp"
                android:src="@drawable/input_map_white" />
        </LinearLayout>
    </RelativeLayout>

</LinearLayout>

and the stack trace:

09-06 10:15:14.366: E/AndroidRuntime(10352): FATAL EXCEPTION: main
09-06 10:15:14.366: E/AndroidRuntime(10352): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.captoom/ro.gebs.captoom.activities.LocationActivity}: java.lang.NullPointerException
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1653)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1669)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.os.Handler.dispatchMessage(Handler.java:99)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.os.Looper.loop(Looper.java:130)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread.main(ActivityThread.java:3737)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at java.lang.reflect.Method.invokeNative(Native Method)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at java.lang.reflect.Method.invoke(Method.java:507)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:894)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:652)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at dalvik.system.NativeStart.main(Native Method)
09-06 10:15:14.366: E/AndroidRuntime(10352): Caused by: java.lang.NullPointerException
09-06 10:15:14.366: E/AndroidRuntime(10352):    at ro.gebs.captoom.activities.LocationActivity.getCurrentLocation(LocationActivity.java:131)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at ro.gebs.captoom.activities.LocationActivity.retrieveLocation(LocationActivity.java:98)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at ro.gebs.captoom.activities.LocationActivity.onCreate(LocationActivity.java:80)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1617)
09-06 10:15:14.366: E/AndroidRuntime(10352):    ... 11 more
09-06 10:15:14.366: E/AndroidRuntime(10352): [Blue Error Handler] Make Debugging Report file for main
09-06 10:15:14.366: E/AndroidRuntime(10352): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.captoom/ro.gebs.captoom.activities.LocationActivity}: java.lang.NullPointerException
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1653)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1669)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.os.Handler.dispatchMessage(Handler.java:99)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.os.Looper.loop(Looper.java:130)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread.main(ActivityThread.java:3737)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at java.lang.reflect.Method.invokeNative(Native Method)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at java.lang.reflect.Method.invoke(Method.java:507)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:894)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:652)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at dalvik.system.NativeStart.main(Native Method)
09-06 10:15:14.366: E/AndroidRuntime(10352): Caused by: java.lang.NullPointerException
09-06 10:15:14.366: E/AndroidRuntime(10352):    at ro.gebs.captoom.activities.LocationActivity.getCurrentLocation(LocationActivity.java:131)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at ro.gebs.captoom.activities.LocationActivity.retrieveLocation(LocationActivity.java:98)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at ro.gebs.captoom.activities.LocationActivity.onCreate(LocationActivity.java:80)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
09-06 10:15:14.366: E/AndroidRuntime(10352):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1617)
09-06 10:15:14.366: E/AndroidRuntime(10352):    ... 11 more

Any help much appreciated.

EDIT

the problem was with the device settings, i just had to enable:

Settings -> Application Settings -> Development -> Allow Mock Location

Settings -> Location & Security -> Use Wireless Networks

Thanks for all your answers.

Answer 1

The getLastKnownLocation method will return the last cached location,so it will return null until the provider you specify has gotten at least one update. You need to have an application requesting (and receive) updates at least once in your session before you call getLastKnownLocation().

So you need to handle this situation.

Try following ,

    location = locationManager.getLastKnownLocation(provider);
    LatLng userLocation = null;
    if (location != null) {

        old_latitude=location.getLatitude();
        old_longitude=location.getLongitude();

        userLocation = new LatLng(old_latitude,old_longitude); 

        this.onLocationChanged(location);
    }    

Answer 2

getLastKnownLocation doesn't create a crash.

As we can see from your stacktrace

09-06 10:15:14.366: E/AndroidRuntime(10352): Caused by: java.lang.NullPointerException
09-06 10:15:14.366: E/AndroidRuntime(10352):    at ro.gebs.captoom.activities.LocationActivity.getCurrentLocation(LocationActivity.java:131)

you are trying to call a method on a reference that points to nothing or null.

getLastKnownLocation can return null if last location is not known. You have to handle that.