Handle orientation changes

app/src/main/java/fr/free/nrw/commons/nearby/NearbyActivity.java

@@ -75,6 +75,8 @@ public class NearbyActivity extends NavigationBaseActivity implements LocationUp
     private boolean lockNearbyView; //Determines if the nearby places needs to be refreshed
     private BottomSheetBehavior bottomSheetBehavior; // Behavior for list bottom sheet
     private BottomSheetBehavior bottomSheetBehaviorForDetails; // Behavior for details bottom sheet
+    private NearbyMapFragment nearbyMapFragment;
+    private static final String TAG_RETAINED_FRAGMENT = "RetainedFragment";
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
@@ -82,6 +84,7 @@ public class NearbyActivity extends NavigationBaseActivity implements LocationUp
         sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
         setContentView(R.layout.activity_nearby);
         ButterKnife.bind(this);
+        resumeFragment();
         bundle = new Bundle();
 
         initBottomSheetBehaviour();
@@ -91,6 +94,21 @@ public class NearbyActivity extends NavigationBaseActivity implements LocationUp
         initViewState();
     }
 
+    private void resumeFragment() {
+        // find the retained fragment on activity restarts
+        android.support.v4.app.FragmentManager fm = getSupportFragmentManager();
+        nearbyMapFragment = (NearbyMapFragment) fm.findFragmentByTag(TAG_RETAINED_FRAGMENT);
+
+        // create the fragment and data the first time
+        if (nearbyMapFragment == null) {
+            // add the fragment
+            nearbyMapFragment = new NearbyMapFragment();
+            fm.beginTransaction().add(nearbyMapFragment, TAG_RETAINED_FRAGMENT).commit();
+            // load data from a data source or perform any calculation
+        }
+
+    }
+
     private void initViewState() {
         if (sharedPreferences.getBoolean(MAP_LAST_USED_PREFERENCE, false)) {
             viewMode = NearbyActivityMode.MAP;
@@ -307,6 +325,19 @@ public class NearbyActivity extends NavigationBaseActivity implements LocationUp
         checkGps();
     }
 
+    @Override
+    public void onPause() {
+        super.onPause();
+        // this means that this activity will not be recreated now, user is leaving it
+        // or the activity is otherwise finishing
+        if(isFinishing()) {
+            android.support.v4.app.FragmentManager fm = getSupportFragmentManager();
+            // we will not need this fragment anymore, this may also be a good place to signal
+            // to the retained fragment object to perform its own cleanup.
+            fm.beginTransaction().remove(nearbyMapFragment).commit();
+        }
+    }
+
 
 
     /**

app/src/main/java/fr/free/nrw/commons/nearby/NearbyMapFragment.java

@@ -92,6 +92,7 @@ public class NearbyMapFragment extends android.support.v4.app.Fragment {
         Mapbox.getInstance(getActivity(),
                 getString(R.string.mapbox_commons_app_token));
         MapboxTelemetry.getInstance().setTelemetryEnabled(false);
+        setRetainInstance(true);
     }
 
     @Override