fix thread error

src/main/java/fr/insa/clavardator/ui/chat/ChatController.java

@@ -67,8 +67,10 @@ public class ChatController implements Initializable {
 
 	private void onMessageAdded(PeerUser user, Message message) {
 		Log.v(this.getClass().getSimpleName(), "Message added: " + message.getText());
-		messageList.getItems().add(message);
-		Platform.runLater(() -> messageList.scrollTo(messageList.getItems().size() - 1));
+		Platform.runLater(() -> {
+			messageList.getItems().add(message);
+			messageList.scrollTo(messageList.getItems().size() - 1);
+		});
 	}
 
 	private void setState(State state) {

src/main/java/fr/insa/clavardator/ui/users/UserListController.java

@@ -59,13 +59,8 @@ public class UserListController implements Initializable {
 		Platform.runLater(() -> peerUserListView.getItems().add(user));
 	}
 
-	private void onUserDisconnected(PeerUser user) {
-		Log.v(this.getClass().getSimpleName(), "Remove user from UI");
-		Platform.runLater(() -> peerUserListView.getItems().remove(user));
-	}
-
 	public void setUserList(UserList userList) {
 		this.userList = userList;
-		userList.addActiveUsersObserver(this::onUserConnected, this::onUserDisconnected);
+		userList.addNewUserObserver(this::onUserConnected);
 	}
 }

src/main/java/fr/insa/clavardator/users/UserList.java

@@ -19,8 +19,7 @@ public class UserList {
 	private final Map<Integer, PeerUser> inactiveUsers = new HashMap<>();
 	private final Map<Integer, PeerUser> activeUsers = new HashMap<>();
 
-	private final ArrayList<UserConnectionCallback> userConnectionObservers = new ArrayList<>();
-	private final ArrayList<UserDisconnectionCallback> userDisconnectionObservers = new ArrayList<>();
+	private final ArrayList<UserConnectionCallback> newUsersObservers = new ArrayList<>();
 
 	private final DatabaseController db = new DatabaseController();
 	private final NetDiscoverer netDiscoverer = new NetDiscoverer();
@@ -33,30 +32,19 @@ public class UserList {
 	 * Discover all active users over the network. Observers are notified for each user discovered.
 	 *
 	 * @param errorCallback The function to call on error
-	 * @see UserList#addActiveUsersObserver(UserConnectionCallback, UserDisconnectionCallback)
+	 * @see UserList#addNewUserObserver(UserConnectionCallback)
 	 */
 	public void discoverActiveUsers(ErrorCallback errorCallback) {
 		netDiscoverer.discoverActiveUsers("CLAVARDATOR_BROADCAST", (ipAddr, data) -> {
 			int id = getIdFromIp(ipAddr);
 			Log.v(this.getClass().getSimpleName(), "Discovered new user: " + id);
-
-			// If already connected, do not modify
-			if (activeUsers.containsKey(id)) {
-				return;
+			final PeerUser finalUser = createNewUser(id);
+			if (finalUser != null) {
+				finalUser.connect(ipAddr, () -> {
+					notifyNewUserObservers(finalUser);
+					finalUser.addObserver(evt -> userChangeObserver(finalUser, evt));
+				}, errorCallback);
 			}
-
-			PeerUser user = inactiveUsers.get(id);
-			if (user == null) {
-				// Username is set on TCP connection start
-				user = new PeerUser(id, "");
-				inactiveUsers.put(id, user);
-			}
-			PeerUser finalUser = user;
-			user.connect(ipAddr, () -> {
-				notifyConnectionObservers(finalUser);
-				finalUser.addObserver(evt -> userChangeObserver(finalUser, evt));
-			}, errorCallback);
-
 		}, errorCallback);
 	}
 
@@ -68,32 +56,39 @@ public class UserList {
 	}
 
 	public void startUserListening(ErrorCallback errorCallback) {
-		connectionListener.acceptConnection(clientSocket -> {
-			int id = getIdFromIp(clientSocket.getInetAddress());
-			Log.v(this.getClass().getSimpleName(), "new connection from user: " + id);
+		connectionListener.acceptConnection(
+				(clientSocket) -> {
+					int id = getIdFromIp(clientSocket.getInetAddress());
+					Log.v(this.getClass().getSimpleName(), "new connection from user: " + id);
+					final PeerUser finalUser = createNewUser(id);
+					if (finalUser != null) {
+						finalUser.connect(clientSocket, () -> {
+							notifyNewUserObservers(finalUser);
+							finalUser.addObserver(evt -> userChangeObserver(finalUser, evt));
+						}, errorCallback);
+					}
+				},
+				errorCallback);
+	}
 
-			// If already connected, warn and return
-			if (activeUsers.containsKey(id)) {
-				Log.w(getClass().getSimpleName(), "An already connected user tried to initiate a new connection: user id " + id);
-				return;
-			}
+	private PeerUser createNewUser(int id) {
+		// If already connected, warn and return
+		if (activeUsers.containsKey(id)) {
+			Log.w(getClass().getSimpleName(),
+					"An already connected user tried to initiate a new connection: user id " + id);
+			return null;
+		}
 
-			// Get the user if already existing
-			PeerUser user = inactiveUsers.get(id);
-			// else create it
-			if (user == null) {
-				// Username is set on TCP connection start
-				user = new PeerUser(id, "");
-				inactiveUsers.put(id, user);
-			}
+		// Get the user if already existing
+		PeerUser user = inactiveUsers.get(id);
+		// else create it
+		if (user == null) {
+			// Username is set on TCP connection start
+			user = new PeerUser(id, "");
+			inactiveUsers.put(id, user);
+		}
 
-			PeerUser finalUser = user;
-			user.connect(clientSocket, () -> {
-				notifyConnectionObservers(finalUser);
-				finalUser.addObserver(evt -> userChangeObserver(finalUser, evt));
-			}, errorCallback);
-
-		}, errorCallback);
+		return user;
 	}
 
 	private void userChangeObserver(PeerUser user, PropertyChangeEvent evt) {
@@ -117,11 +112,8 @@ public class UserList {
 
 				inactiveUsers.remove(id);
 				activeUsers.put(id, user);
-				notifyConnectionObservers(user);
 				Log.v(getClass().getSimpleName(), "State of user " + id + " updated from " +
 						oldState.toString() + " to " + newState.toString());
-
-
 			} else if (oldState == PeerUser.State.CONNECTED &&
 					(newState == PeerUser.State.DISCONNECTED || newState == PeerUser.State.CONNECTING)) {
 				// Disconnection
@@ -136,25 +128,18 @@ public class UserList {
 
 				activeUsers.remove(id);
 				inactiveUsers.put(id, user);
-				notifyDisconnectionObservers(user);
-
 				Log.v(getClass().getSimpleName(), "State of user " + id + " updated from " +
 						oldState.toString() + " to " + newState.toString());
 			}
 		}
 	}
 
-	public void addActiveUsersObserver(UserConnectionCallback connectionCallback, UserDisconnectionCallback disconnectionCallback) {
-		userConnectionObservers.add(connectionCallback);
-		userDisconnectionObservers.add(disconnectionCallback);
+	public void addNewUserObserver(UserConnectionCallback connectionCallback) {
+		newUsersObservers.add(connectionCallback);
 	}
 
-	private void notifyConnectionObservers(PeerUser user) {
-		userConnectionObservers.forEach(callback -> callback.onUserConnected(user));
-	}
-
-	private void notifyDisconnectionObservers(PeerUser user) {
-		userDisconnectionObservers.forEach(callback -> callback.onUserDisconnected(user));
+	private void notifyNewUserObservers(PeerUser user) {
+		newUsersObservers.forEach(callback -> callback.onUserConnected(user));
 	}
 
 	/**