bottom navigation sets locale on startup and language change. Fixed a bug where the selected fragment changes when rotated.

app/src/main/java/com/a1/nextlocation/MainActivity.java

@@ -30,8 +30,9 @@ import java.io.File;
 import java.util.Arrays;
 import java.util.Locale;
 
-public class MainActivity extends AppCompatActivity {
+public class MainActivity extends AppCompatActivity implements Refreshable{
     private static final String TAG = MainActivity.class.getName();
+    private BottomNavigationView bottomNav;
 
     /**
      * onCreate method that creates the main activity
@@ -40,12 +41,12 @@ public class MainActivity extends AppCompatActivity {
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
+
+        setLocale(loadLocale());
         setContentView(R.layout.activity_main);
-
-        BottomNavigationView bottomNav = findViewById(R.id.navbar);
+        bottomNav = findViewById(R.id.navbar);
         bottomNav.setOnNavigationItemSelectedListener(navListener);
 
-
         /*System.out.println(Arrays.toString(getFilesDir().listFiles()));
         FileIO<Route> fileIO = new FileIO<>();
         fileIO.writeFileData(new Route("TERSTSET"), getApplicationContext());
@@ -59,9 +60,9 @@ public class MainActivity extends AppCompatActivity {
         RouteListManager.INSTANCE.load();
 
         // initialize saved language from sharedPreferences
-        setLocale(loadLocale());
-
-        getSupportFragmentManager().beginTransaction().replace(R.id.fragment_layout, new HomeFragment()).commit();
+        if (savedInstanceState == null) {
+            getSupportFragmentManager().beginTransaction().replace(R.id.fragment_layout, new HomeFragment()).commit();
+        }
     }
 
     /**
@@ -107,4 +108,14 @@ public class MainActivity extends AppCompatActivity {
         getSupportFragmentManager().beginTransaction().replace(R.id.fragment_layout, selectedFragment).commit();
         return true;
     };
+
+    /**
+     * refreshes bottom navigation
+     */
+    @Override
+    public void refresh() {
+        bottomNav.getMenu().clear();
+        bottomNav.inflateMenu(R.menu.navmenu);
+        bottomNav.setSelectedItemId(R.id.settings);
+    }
 }

app/src/main/java/com/a1/nextlocation/Refreshable.java

@@ -0,0 +1,5 @@
+package com.a1.nextlocation;
+
+public interface Refreshable {
+    void refresh();
+}

app/src/main/java/com/a1/nextlocation/fragments/SettingsFragment.java

@@ -19,13 +19,23 @@ import android.widget.Spinner;
 
 import com.a1.nextlocation.MainActivity;
 import com.a1.nextlocation.R;
+import com.a1.nextlocation.Refreshable;
+
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Locale;
 
 public class SettingsFragment extends Fragment {
 
     private SharedPreferences.Editor editor;
-    
+    private Refreshable refreshable;
+
+    @Override
+    public void onAttach(@NotNull Context context) {
+        super.onAttach(context);
+        refreshable = (Refreshable) context;
+    }
+
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -57,15 +67,11 @@ public class SettingsFragment extends Fragment {
             @Override
             public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                 setLocale(dropdownPositionToLanguage(id));
+                // refresh fragment on language change
                 if (id != previousID) {
-                    Fragment currentFragment = getActivity().getSupportFragmentManager().findFragmentById(R.id.fragment_layout);
-                    FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
-                    fragmentTransaction.detach(currentFragment);
-                    fragmentTransaction.attach(currentFragment);
-                    fragmentTransaction.commit();
+                    refresh();
                 }
             }
-
             @Override
             public void onNothingSelected(AdapterView<?> parent) {
             }
@@ -115,6 +121,8 @@ public class SettingsFragment extends Fragment {
         fragmentTransaction.detach(currentFragment);
         fragmentTransaction.attach(currentFragment);
         fragmentTransaction.commit();
+
+        refreshable.refresh();
     }
 
     /**