UI fixes.

1. After sending the app with MessageVC on top into background,
   upon wakeup the app wouldn't connect and display new messages.
2. In ChatListVC the app wouldn't display latest messages.

Tinodios/AppDelegate.swift

@@ -260,7 +260,7 @@ extension AppDelegate: UNUserNotificationCenterDelegate {
         }
         DispatchQueue.global(qos: .userInitiated).async {
             if !SharedUtils.connectAndLoginSync(using: tinode, inBackground: false) {
-                UiUtils.logoutAndRouteToLoginVC()
+                DispatchQueue.main.async { UiUtils.showToast(message: "Failed to connect to server") }
             } else {
                 UiUtils.routeToMessageVC(forTopic: topicName)
             }

Tinodios/ChatListInteractor.swift

@@ -63,20 +63,23 @@ class ChatListInteractor: ChatListBusinessLogic, ChatListDataStore {
             super.init(connected: connected)
             self.interactor = interactor
         }
-        func onLogin(code: Int, text: String) {
+        override func onLogin(code: Int, text: String) {
+            super.onLogin(code: code, text: text)
             self.interactor?.attachToMeTopic()
         }
         override func onDisconnect(byServer: Bool, code: URLSessionWebSocketTask.CloseCode, reason: String) {
             super.onDisconnect(byServer: byServer, code: code, reason: reason)
             // Update presence indicators (all should be off).
             self.interactor?.loadAndPresentTopics()
         }
-        func onDataMessage(data: MsgServerData?) {
+        override func onDataMessage(data: MsgServerData?) {
+            super.onDataMessage(data: data)
             if let topic = data?.topic {
                 interactor?.updateChat(topic)
             }
         }
-        func onInfoMessage(info: MsgServerInfo?) {
+        override func onInfoMessage(info: MsgServerInfo?) {
+            super.onInfoMessage(info: info)
             if info?.what != "call", let topic = info?.src {
                 interactor?.updateChat(topic)
             }

Tinodios/MessageInteractor.swift

@@ -81,7 +81,9 @@ class MessageInteractor: DefaultComTopic.Listener, MessageBusinessLogic, Message
             super.init(connected: connected)
             self.interactor = interactor
         }
-        func onLogin(code: Int, text: String) {
+
+        override func onLogin(code: Int, text: String) {
+            super.onLogin(code: code, text: text)
             _ = UiUtils.attachToMeTopic(meListener: nil)
             _ = interactor?.attachToTopic(interactively: false)
         }

Tinodios/MessageViewController.swift

@@ -257,6 +257,7 @@ class MessageViewController: UIViewController {
     func appBecameActive() {
         self.interactor?.setup(topicName: topicName, sendReadReceipts: self.sendReadReceipts)
         self.interactor?.attachToTopic(interactively: true)
+        self.interactor?.loadMessagesFromCache(scrollToMostRecentMessage: false)
     }
     @objc
     func appGoingInactive() {

Tinodios/UiUtils.swift

@@ -18,6 +18,18 @@ class UiTinodeEventListener: TinodeEventListener {
     init(connected: Bool) {
         self.connected = connected
     }
+
+    // Empty handlers. Otherwise, methods of subclasses of UiTinodeEventListener
+    // won't be called.
+    func onLogin(code: Int, text: String) {}
+    func onMessage(msg: ServerMessage?) {}
+    func onRawMessage(msg: String) {}
+    func onCtrlMessage(ctrl: MsgServerCtrl?) {}
+    func onDataMessage(data: MsgServerData?) {}
+    func onInfoMessage(info: MsgServerInfo?) {}
+    func onMetaMessage(meta: MsgServerMeta?) {}
+    func onPresMessage(pres: MsgServerPres?) {}
+
     func onConnect(code: Int, reason: String, params: [String: JSONValue]?) {
         connected = true
     }