fix: Hide FAB in new chat page if textfield has focus

lib/pages/new_private_chat/new_private_chat.dart

@@ -18,14 +18,34 @@ class NewPrivateChat extends StatefulWidget {
 }
 
 class NewPrivateChatController extends State<NewPrivateChat> {
-  TextEditingController controller = TextEditingController();
+  final TextEditingController controller = TextEditingController();
+  final FocusNode textFieldFocus = FocusNode();
   final formKey = GlobalKey<FormState>();
   bool loading = false;
+  bool hideFab = false;
 
   static const Set<String> supportedSigils = {'@', '!', '#'};
 
   static const String prefix = 'https://matrix.to/#/';
 
+  void setHideFab() {
+    if (textFieldFocus.hasFocus != hideFab) {
+      setState(() => hideFab = textFieldFocus.hasFocus);
+    }
+  }
+
+  @override
+  void initState() {
+    super.initState();
+    textFieldFocus.addListener(setHideFab);
+  }
+
+  @override
+  void dispose() {
+    textFieldFocus.removeListener(setHideFab);
+    super.dispose();
+  }
+
   void submitAction([_]) async {
     controller.text = controller.text.trim();
     if (!formKey.currentState.validate()) return;

lib/pages/new_private_chat/new_private_chat_view.dart

@@ -81,6 +81,7 @@ class NewPrivateChatView extends StatelessWidget {
                   controller: controller.controller,
                   autocorrect: false,
                   textInputAction: TextInputAction.go,
+                  focusNode: controller.textFieldFocus,
                   onFieldSubmitted: controller.submitAction,
                   validator: controller.validateForm,
                   decoration: InputDecoration(
@@ -105,7 +106,7 @@ class NewPrivateChatView extends StatelessWidget {
           ],
         ),
       ),
-      floatingActionButton: PlatformInfos.isMobile
+      floatingActionButton: PlatformInfos.isMobile && !controller.hideFab
           ? FloatingActionButton.extended(
               onPressed: controller.openScannerAction,
               label: Text(L10n.of(context).scanQrCode),