create interface for onBackendConnected

src/main/java/eu/siacs/conversations/ui/ConversationsActivity.java

@@ -63,6 +63,7 @@ import eu.siacs.conversations.databinding.ActivityConversationsBinding;
 import eu.siacs.conversations.entities.Account;
 import eu.siacs.conversations.entities.Conversation;
 import eu.siacs.conversations.services.XmppConnectionService;
+import eu.siacs.conversations.ui.interfaces.OnBackendConnected;
 import eu.siacs.conversations.ui.interfaces.OnConversationArchived;
 import eu.siacs.conversations.ui.interfaces.OnConversationRead;
 import eu.siacs.conversations.ui.interfaces.OnConversationSelected;
@@ -258,8 +259,8 @@ public class ConversationsActivity extends XmppActivity implements OnConversatio
 
 	private void notifyFragmentOfBackendConnected(@IdRes int id) {
 		final Fragment fragment = getFragmentManager().findFragmentById(id);
-		if (fragment != null && fragment instanceof XmppFragment) {
+		if (fragment != null && fragment instanceof OnBackendConnected) {
-			((XmppFragment) fragment).onBackendConnected();
+			((OnBackendConnected) fragment).onBackendConnected();
 		}
 	}
 

src/main/java/eu/siacs/conversations/ui/ConversationsOverviewFragment.java

@@ -145,7 +145,7 @@ public class ConversationsOverviewFragment extends XmppFragment implements Enhan
 	}
 
 	@Override
-	void onBackendConnected() {
+	public void onBackendConnected() {
 		refresh();
 	}
 

src/main/java/eu/siacs/conversations/ui/XmppFragment.java

@@ -32,9 +32,9 @@ package eu.siacs.conversations.ui;
 import android.app.Activity;
 import android.app.Fragment;
 
-public abstract class XmppFragment extends Fragment {
+import eu.siacs.conversations.ui.interfaces.OnBackendConnected;
 
-	abstract void onBackendConnected();
+public abstract class XmppFragment extends Fragment implements OnBackendConnected {
 
 	abstract void refresh();
 

src/main/java/eu/siacs/conversations/ui/interfaces/OnBackendConnected.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2018, Daniel Gultsch All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation and/or
+ * other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors
+ * may be used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package eu.siacs.conversations.ui.interfaces;
+
+public interface OnBackendConnected {
+
+	void onBackendConnected();
+
+}

src/main/java/eu/siacs/conversations/utils/UIHelper.java

@@ -418,13 +418,15 @@ public class UIHelper {
 	public static String concatNames(List<MucOptions.User> users, int max) {
 		StringBuilder builder = new StringBuilder();
 		final boolean shortNames = users.size() >= 3;
-		for (int i = 0; i < Math.max(users.size(), max); ++i) {
+		for (int i = 0; i < Math.min(users.size(), max); ++i) {
 			if (builder.length() != 0) {
 				builder.append(", ");
 			}
 			final String name = UIHelper.getDisplayName(users.get(i));
+			if (name != null) {
 				builder.append(shortNames ? name.split("\\s+")[0] : name);
 			}
+		}
 		return builder.toString();
 	}