聊天界面中，键盘遮挡了文本输入框的问题。

可以使用监听键盘高度的方式，当键盘弹出时，根据键盘高度动态调整聊天界面的布局，使得文本输入框不被键盘遮挡。具体示例代码如下：

class ChatScreen extends StatefulWidget {
  @override
  _ChatScreenState createState() => _ChatScreenState();
}

class _ChatScreenState extends State<ChatScreen> {
  double _keyboardHeight = 0;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) {
      final double screenHeight = MediaQuery.of(context).size.height;
      final double appBarHeight =
          AppBar().preferredSize.height + MediaQuery.of(context).padding.top;
      final double maxTextFieldHeight =
          screenHeight - appBarHeight - kToolbarHeight;
      final double defaultTextFieldHeight = 50;
      final double extraSpaceHeight = maxTextFieldHeight - defaultTextFieldHeight;
      final double keyboardHeight = extraSpaceHeight / 2;

      _keyboardHeight = keyboardHeight;
      setState(() {});
    });

    _addListenerForKeyboard();
  }

  @override
  void dispose() {
    _removeListenerForKeyboard();
    super.dispose();
  }

  void _addListenerForKeyboard() {
    WidgetsBinding.instance.addPersistentFrameCallback((_) {
      final currentKeyboardHeight =
          MediaQuery.of(context).viewInsets.bottom;
      if (currentKeyboardHeight != _keyboardHeight) {
        setState(() {
          _keyboardHeight = currentKeyboardHeight;
        });
      }
    });
  }

  void _removeListenerForKeyboard() {
    WidgetsBinding.instance.removePersistentCallbacks(_addListenersForKeyboard);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('聊天'),
      ),
      body: Stack(
        children: [
          //聊天记录列表
          ListView(
            padding: const EdgeInsets.only(bottom: kToolbarHeight),
            children: [
              //聊天记录
            ],
          ),
          //输入框
          Positioned(
            bottom: _keyboardHeight,
            left: 0,
            right: 0,
            child: TextField