Flutter: 能够从整个树中删除键盘焦点

重现步骤

我想显示 textField 的提示文本，直到用户触摸其他地方。
接触点可能位于小部件树的深处，我不知道如何获取小部件树中某处的当前聚焦节点以调用 unfocused，以显示 textField 处于非活动状态并隐藏键盘。 这可能只是我对 flutter 的理解的一个问题，或者缺少示例且没有解释如何使用这些模式的文档。

该代码示例显示了在节点上调用 unfocus 的 GestureDetector。 这很简单，因为在同一个小部件中可以轻松访问 focusNode。 这里的问题是如何在嵌套的小部件树中做同样的事情。 这样做的推荐模式是什么？

  <strong i="9">@override</strong>
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          title: new Text(widget.title),
        ),
        body: new Stack(children: <Widget>[
          new GestureDetector(
              excludeFromSemantics: true,
              onTapDown: (_) {
                _focusNode.unfocus();
              }),
          new Column(children: <Widget>[
            new TextField(
                focusNode: _focusNode,
                decoration: new InputDecoration(
                    border: null,
                    hintText: _focusNode.hasFocus ? 'FOCUS' : 'no focus')),
            new RaisedButton(
                child: new Text('Remove Focus'),
                onPressed: () => _focusNode.unfocus())
          ])
        ]));
  }

  final FocusNode _focusNode = new FocusNode();

  <strong i="10">@override</strong>
  void initState() {
    super.initState();
    _focusNode.addListener(() {
      setState(() {});
      print('Has focus: $_focusNode.hasFocus');
    });
  }

颤振医生

[√] Flutter (on Microsoft Windows [Version 10.0.16299.192], locale en-US, channel dev)
    • Flutter version 0.0.21 at c:\sdks\flutter
    • Framework revision 2e449f06f0 (2 days ago), 2018-01-29 14:26:51 -0800
    • Engine revision 6921873c71
    • Tools Dart version 2.0.0-dev.16.0
    • Engine Dart version 2.0.0-edge.da1f52592ef73fe3afa485385cb995b9aec0181a

[√] Android toolchain - develop for Android devices (Android SDK 27.0.2)
    • Android SDK at C:\Users\ride4\AppData\Local\Android\sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-27, build-tools 27.0.2
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b01)

[√] Android Studio (version 3.0)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b01)

[√] IntelliJ IDEA Community Edition (version 2017.2)
    • Flutter plugin version 19.1
    • Dart plugin version 172.4343.25

[√] Connected devices
    • Android SDK built for x86 • emulator-5554 • android-x86 • Android 7.1.1 (API 25) (emulator)