Flutter RawKeyboardListener收听了两次？

Z时代
2024-01-10
分类：问答

我想要实现的是在查看此小部件时，RawKeyboardListener当TextField未选中/焦点对准时立即开始收听。它运行HandleKey

function来处理我要处理的问题keyCode。

我遇到的问题是第一次运行该应用程序时，handleKey function似乎运行了两次。因此，在下面的示例中，why does this run

twice $_keyCode当我仅输入1键时，它将打印TWICE。我认为它监听keyUp和keyDown。我想要的结果是它只能运行一次…

但是，当我选择TextField并使用模拟器键盘进行常规提交时，代码也可以正常工作。

我正在努力理解为什么它仅在与TextField交互后才有问题。我觉得它需要一个Future或await某个地方？但我不知道

请帮忙。

    import 'package:flutter/material.dart';
    import 'package:flutter/services.dart';
    import 'dart:async';
    class KeyboardListener extends StatefulWidget {
        KeyboardListener();
        @override
        _RawKeyboardListenerState createState() => new _RawKeyboardListenerState();
    }
    class _RawKeyboardListenerState extends State<KeyboardListener> {
        TextEditingController _controller = new TextEditingController();
        FocusNode _textNode = new FocusNode();
        @override
            initState() {
            super.initState();
        }
        //Handle when submitting
        void _handleSubmitted(String finalinput) {
            setState(() {
                SystemChannels.textInput.invokeMethod('TextInput.hide'); //hide keyboard again
                _controller.clear();
            });
        }
        handleKey(RawKeyEventDataAndroid key) {
            String _keyCode;
            _keyCode = key.keyCode.toString(); //keycode of key event (66 is return)
            print("why does this run twice $_keyCode");
        }
        _buildTextComposer() {
            TextField _textField = new TextField(
                controller: _controller,
                onSubmitted: _handleSubmitted,
            );
            FocusScope.of(context).requestFocus(_textNode);
            return new RawKeyboardListener(
                focusNode: _textNode,
                onKey: (key) => handleKey(key.data),
                child: _textField
            );
        }
      @override
      Widget build(BuildContext context) {
        return new Scaffold(
          appBar: new AppBar(title: new Text("Search Item")),
          body: _buildTextComposer(),
        );
      }
    }

回答：

使用以下类的实例会同时为keydown和keyup事件调用回调：

RawKeyDownEvent

RawKeyUpEvent

您可以将整个对象传递给handleKey，并根据对象的运行时类型进行过滤。例如

  handleKey(RawKeyEvent key) {
    print("Event runtimeType is ${key.runtimeType}");
    if(key.runtimeType.toString() == 'RawKeyDownEvent'){
        RawKeyEventDataAndroid data = key.data as RawKeyEventDataAndroid;
        String _keyCode;
        _keyCode = data.keyCode.toString(); //keycode of key event (66 is return)
        print("why does this run twice $_keyCode");
    }
  }
  _buildTextComposer() {
      TextField _textField = new TextField(
          controller: _controller,
          onSubmitted: _handleSubmitted,
      );
      FocusScope.of(context).requestFocus(_textNode);
      return new RawKeyboardListener(
          focusNode: _textNode,
          onKey: handleKey,
          child: _textField
      );
  }