[ShareLocation] Added Re-Center logic

If currently following another user, and the map gets moved,
enable a recenter button to update the location to the currently
selected location of the user.

app/src/main/java/com/aldo/apps/familyhelpers/ShareLocationActivity.java

@@ -35,6 +35,7 @@ import com.google.android.gms.maps.model.LatLng;
 import com.google.android.gms.maps.model.MapStyleOptions;
 import com.google.android.gms.maps.model.Marker;
 import com.google.android.gms.maps.model.MarkerOptions;
+import com.google.android.material.floatingactionbutton.FloatingActionButton;
 import com.google.android.material.materialswitch.MaterialSwitch;
 import com.google.firebase.auth.FirebaseAuth;
 import com.google.firebase.auth.FirebaseUser;
@@ -144,11 +145,23 @@ public class ShareLocationActivity extends AppCompatActivity implements OnMapRea
      */
     private RecyclerView mActiveShares;
 
+    /**
+     * The {@link FloatingActionButton} to recenter the camera on the followed location.
+     */
+    private FloatingActionButton mRecenterFollowBtn;
+
+    private LocationObject mCurrentlyFollowingLocation;
+
     /**
      * The {@link ActiveShareAdapter} to populate the activeShare view.
      */
     private ActiveShareAdapter mActiveShareAdapter;
 
+    /**
+     * Flag indicating whether currently the user wants to be following another user or not.
+     */
+    private boolean mIsFollowing;
+
     @Override
     protected void onCreate(final Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -165,10 +178,12 @@ public class ShareLocationActivity extends AppCompatActivity implements OnMapRea
         mInfoBoxTimeStamp = findViewById(R.id.share_location_info_timestamp);
         mNoActiveShares = findViewById(R.id.tv_no_active_shares);
         mActiveShares = findViewById(R.id.active_share_layout);
+        mRecenterFollowBtn = findViewById(R.id.fab_recenter_on_follower);
 
         mActiveShares.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false));
         mActiveShareAdapter = new ActiveShareAdapter(this);
 
+        mRecenterFollowBtn.setOnClickListener(v -> startFollowingAndCenterCamera());
         mActiveShares.setAdapter(mActiveShareAdapter);
         mapFragment.getMapAsync(this);
         mDbHelper = new DatabaseHelper();
@@ -270,6 +285,11 @@ public class ShareLocationActivity extends AppCompatActivity implements OnMapRea
         updateExistingOrCreateValidMarkers(locationObjectMap);
     }
 
+    /**
+     * Helper method to update the active share fragment with all available sharing users.
+     *
+     * @param locationObjectMap The {@link Map} of ids and {@link LocationObject}s.
+     */
     private void updateActiveShares(final Map<String, LocationObject> locationObjectMap) {
         final List<User> activeShares = new ArrayList<>();
         for (final String shareId : locationObjectMap.keySet()) {
@@ -298,6 +318,8 @@ public class ShareLocationActivity extends AppCompatActivity implements OnMapRea
             if (TextUtils.equals(removeKey, mCurrentlyFollowing)) {
                 clearInfoBox();
                 mCurrentlyFollowing = null;
+                mIsFollowing = false;
+                mCurrentlyFollowingLocation = null;
             }
             mMarkerMap.remove(removeKey);
         }
@@ -315,14 +337,6 @@ public class ShareLocationActivity extends AppCompatActivity implements OnMapRea
             final LatLng receivedLocation = new LatLng(newReceived.getLatitude(), newReceived.getLongitude());
             final String sharingId = locationSet.getKey();
             final User locationUser = mDbHelper.getUserForId(sharingId);
-
-            if (TextUtils.equals(mCurrentlyFollowing, sharingId)) {
-                final LocationObject locationObject = locationSet.getValue();
-                updateInfoBox(locationObject);
-                mGmap.animateCamera(CameraUpdateFactory.newLatLngZoom(
-                        new LatLng(locationObject.getLatitude(), locationObject.getLongitude()),
-                        15.0f));
-            }
             if (mMarkerMap.containsKey(sharingId)) {
                 final Marker existing = mMarkerMap.get(sharingId);
                 if (existing == null) {
@@ -339,6 +353,14 @@ public class ShareLocationActivity extends AppCompatActivity implements OnMapRea
                         .title(locationUser == null ? "" : locationUser.getDisplayName()));
                 mMarkerMap.put(locationSet.getKey(), marker);
             }
+            if (TextUtils.equals(mCurrentlyFollowing, sharingId)) {
+                final LocationObject locationObject = locationSet.getValue();
+                mCurrentlyFollowingLocation = locationObject;
+                updateInfoBox(locationObject);
+                if (mIsFollowing) {
+                    startFollowingAndCenterCamera();
+                }
+            }
         }
     }
 
@@ -422,6 +444,7 @@ public class ShareLocationActivity extends AppCompatActivity implements OnMapRea
     private void handleCurrentlyFollowingChanged(final String shareId) {
         Log.d(TAG, "onCreate: Currently selected = [" + shareId + "]");
         mCurrentlyFollowing = shareId;
+        mIsFollowing = !TextUtils.isEmpty(mCurrentlyFollowing);
         // Re-setup the subscription.
         if (mLocationUpdateSubscription != null) {
             mLocationUpdateSubscription.dispose();
@@ -439,6 +462,18 @@ public class ShareLocationActivity extends AppCompatActivity implements OnMapRea
         Log.e(TAG, "handleUserSubscriptionFailed: Subscription to all users failed, keep cached state");
     }
 
+    /**
+     * Helper method to start following and recenter the camera on the location followed.
+     */
+    private void startFollowingAndCenterCamera() {
+        mIsFollowing = true;
+        mGmap.animateCamera(CameraUpdateFactory.newLatLngZoom(
+                new LatLng(mCurrentlyFollowingLocation.getLatitude(),
+                        mCurrentlyFollowingLocation.getLongitude()),
+                15.0f));
+        mRecenterFollowBtn.setVisibility(View.GONE);
+    }
+
     @Override
     public void onMapReady(@NonNull final GoogleMap googleMap) {
         mGmap = googleMap;
@@ -456,6 +491,14 @@ public class ShareLocationActivity extends AppCompatActivity implements OnMapRea
         } else {
             mGmapsMarker.setPosition(defaultHome);
         }
+        mGmap.setOnCameraMoveStartedListener(reason -> {
+            if (GoogleMap.OnCameraMoveStartedListener.REASON_GESTURE == reason
+                    && !TextUtils.isEmpty(mCurrentlyFollowing)) {
+                Log.d(TAG, "onCameraMoveStarted: User moved map, set following to false.");
+                mIsFollowing = false;
+                mRecenterFollowBtn.setVisibility(View.VISIBLE);
+            }
+        });
         mGmap.moveCamera(CameraUpdateFactory.newLatLngZoom(defaultHome, 8.0f));
     }
 }

app/src/main/res/layout/activity_share_location.xml

@@ -31,6 +31,17 @@
 
     </androidx.constraintlayout.widget.ConstraintLayout>
 
+    <com.google.android.material.floatingactionbutton.FloatingActionButton
+        android:id="@+id/fab_recenter_on_follower"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:src="@android:drawable/ic_menu_compass"
+        app:layout_constraintBottom_toBottomOf="@id/map"
+        app:layout_constraintEnd_toEndOf="@id/map"
+        android:layout_marginBottom="25dp"
+        android:layout_marginEnd="25dp"
+        android:visibility="gone"/>
+
     <androidx.fragment.app.FragmentContainerView
         android:id="@+id/map"
         android:name="com.google.android.gms.maps.SupportMapFragment"