如何检测何时在 Flutter 中选择了 TextField? [英] How to detect when a TextField is selected in Flutter?

问题描述

我有一个 Flutter TextField，当该字段被选中时，它会被软键盘覆盖.显示键盘时，我需要向上滚动字段并移开.这是一个非常常见的问题，StackOverflow 中提供了解决方案发帖.

I have a Flutter TextField which gets covered by the soft keyboard when the field is selected. I need to scroll the field up and out of the way when the keyboard is displayed. This is a pretty common problem and a solution is presented in this StackOverflow post.

我想我已经弄清楚了 ScrollController 部分，但是如何检测何时选择了 TextField?似乎没有任何事件方法(例如 onFocus()、onSelected()、onTap() 等).

I think I have the ScrollController part figured out but how do I detect when the TextField has been selected? There doesn't appear to be any event method (e.g. onFocus(), onSelected(), onTap(), etc).

我尝试将 TextField 包装在 GestureDetector 中，但这也不起作用 - 显然该事件从未被捕获.

I tried wrapping the TextField in a GestureDetector but that didn't work either -- apparently the event was never captured.

new GestureDetector(
  child: new TextField(
    decoration: const InputDecoration(labelText: 'City'),
  ),
  onTap: () => print('Text Selected'),
),

这是一个基本要求，我知道必须有一个简单的解决方案.

This is such a basic requirement that I know there must be an easy solution.

推荐答案

我想你正在寻找 FocusNode.

I suppose you are looking for FocusNode.

要监听焦点变化，您可以在 FocusNode 中添加一个监听器，并将 focusNode 指定到 TextField.

To listen to focus change, you can add a listner to the FocusNode and specify the focusNode to TextField.

例子:

class TextFieldFocus extends StatefulWidget {
  @override
  _TextFieldFocusState createState() => _TextFieldFocusState();
}

class _TextFieldFocusState extends State<TextFieldFocus> {
  FocusNode _focus = FocusNode();

  TextEditingController _controller = TextEditingController();

  @override
  void initState() {
    super.initState();
    _focus.addListener(_onFocusChange);
  }

  @override
  void dispose() {
    super.dispose();
    _focus.removeListener(_onFocusChange);
    _focus.dispose();
  }

  void _onFocusChange() {
    debugPrint("Focus: ${_focus.hasFocus.toString()}");
  }
  
  @override
  Widget build(BuildContext context) {
    return new Container(
      color: Colors.white,
      child: new TextField(
        focusNode: _focus,
      ),
    );
  }
}

这个要点表示如何确保焦点节点在 ui 上可见.

This gist represents how to ensure a focused node to be visible on the ui.

希望对你有帮助！

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