custom_app_bar_before.dart

// Inside the build() method of our ChatRoom() widget
return Scaffold(
      backgroundColor: Color(0xFFECE5DD),
      appBar: AppBar(
        title: , // <-- we will do the trick here
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.videocam),
            onPressed: () {},
          ),
          // ...and 2 other icons
        ],
      ),
      body: Column(
        children: <Widget>[
          Expanded(
            child: _chatThreads,
          ),
          _inputBar,
        ],
     // closing tags below