Fixed multiple instatiation of the SidebarMainFragment and its

presenter. Subscribing to each room change on different connected
servers.

app/src/main/java/chat/rocket/android/activity/AbstractAuthedActivity.java

@@ -205,4 +205,18 @@ abstract class AbstractAuthedActivity extends AbstractFragmentActivity {
             )
     );
   }
+
+  protected void subscribeToNewConfigChanges() {
+    compositeDisposable.add(
+            rocketChatCache.getSelectedRoomIdPublisher()
+                    .map(Optional::get)
+                    .distinctUntilChanged()
+                    .subscribeOn(Schedulers.io())
+                    .observeOn(AndroidSchedulers.mainThread())
+                    .subscribe(
+                            this::updateRoomIdIfNeeded,
+                            Logger::report
+                    )
+    );
+  }
 }

app/src/main/java/chat/rocket/android/activity/AbstractFragmentActivity.java

@@ -75,10 +75,22 @@ abstract class AbstractFragmentActivity extends RxAppCompatActivity {
         .commit();
   }
 
+  protected void showFragmentWithTag(Fragment fragment, String tag) {
+    getSupportFragmentManager().beginTransaction()
+            .replace(getLayoutContainerForFragment(), fragment, tag)
+            .addToBackStack(null)
+            .commit();
+  }
+
   protected void showFragmentWithBackStack(Fragment fragment) {
     getSupportFragmentManager().beginTransaction()
         .replace(getLayoutContainerForFragment(), fragment)
         .addToBackStack(null)
         .commit();
   }
+
+  @Nullable
+  protected Fragment findFragmentByTag(String tag) {
+    return getSupportFragmentManager().findFragmentByTag(tag);
+  }
 }

app/src/main/java/chat/rocket/android/activity/MainActivity.java

@@ -197,9 +197,17 @@ public class MainActivity extends AbstractAuthedActivity implements MainContract
 
   private void updateSidebarMainFragment() {
     closeSidebarIfNeeded();
+    String selectedServerHostname = new RocketChatCache(this).getSelectedServerHostname();
+    Fragment sidebarFragment = findFragmentByTag(selectedServerHostname);
+    if (sidebarFragment == null) {
+      sidebarFragment = SidebarMainFragment.create(selectedServerHostname);
+    }
+    subscribeToNewConfigChanges();
     getSupportFragmentManager().beginTransaction()
-        .replace(R.id.sidebar_fragment_container, SidebarMainFragment.create(hostname))
+        .replace(R.id.sidebar_fragment_container, sidebarFragment, selectedServerHostname)
+        .addToBackStack(null)
         .commit();
+    getSupportFragmentManager().executePendingTransactions();
   }
 
   @Override
@@ -220,7 +228,11 @@ public class MainActivity extends AbstractAuthedActivity implements MainContract
 
   @Override
   public void showRoom(String hostname, String roomId) {
-    showFragment(RoomFragment.create(hostname, roomId));
+    Fragment roomFragment = findFragmentByTag(roomId);
+    if (roomFragment == null) {
+      roomFragment = RoomFragment.create(hostname, roomId);
+    }
+    showFragmentWithTag(roomFragment, roomId);
     closeSidebarIfNeeded();
     KeyboardHelper.hideSoftKeyboard(this);
   }
@@ -311,7 +323,6 @@ public class MainActivity extends AbstractAuthedActivity implements MainContract
     if (!hostname.equalsIgnoreCase(serverHostname)) {
       RocketChatCache rocketChatCache = new RocketChatCache(getApplicationContext());
       rocketChatCache.setSelectedServerHostname(serverHostname);
-      onHostnameUpdated();
     }
   }
 

app/src/main/java/chat/rocket/android/fragment/sidebar/SidebarMainFragment.java

@@ -8,7 +8,9 @@ import android.support.v4.app.DialogFragment;
 import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.support.v7.widget.SearchView;
+import android.view.LayoutInflater;
 import android.view.View;
+import android.view.ViewGroup;
 import android.widget.CompoundButton;
 import android.widget.TextView;
 
@@ -100,15 +102,29 @@ public class SidebarMainFragment extends AbstractFragment implements SidebarMain
     );
   }
 
+  @Nullable
+  @Override
+  public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
+    View view = super.onCreateView(inflater, container, savedInstanceState);
+    presenter.bindView(this);
+    return view;
+  }
+
+  @Override
+  public void onDestroyView() {
+    presenter.release();
+    super.onDestroyView();
+  }
+
   @Override
   public void onResume() {
     super.onResume();
-    presenter.bindView(this);
+
   }
 
   @Override
   public void onPause() {
-    presenter.release();
+
     super.onPause();
   }
 
@@ -287,7 +303,7 @@ public class SidebarMainFragment extends AbstractFragment implements SidebarMain
     ));
 
     roomListHeaders.add(new LivechatRoomListHeader(
-            getString(R.string.fragment_sidebar_main_livechat_title)
+        getString(R.string.fragment_sidebar_main_livechat_title)
     ));
 
     roomListHeaders.add(new ChannelRoomListHeader(