FocusNode - 为什么 requestFocus() 不起作用？

Question

以下是相关代码。onFieldSubmitted: 中的 debugPrint() 正在运行，所以代码到了这里，但焦点没有改变。焦点不变。

 _createItemHeadingWidget() {
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: TextFormField(
        controller: _controllerItemHed,
        autofocus: true,
        focusNode: _focusNodeItemHed,
        textInputAction: TextInputAction.next,
        onFieldSubmitted: (v) {
          debugPrint("ItemHeading submitted");
          FocusScope.of(context).requestFocus(_focusNodeItemDetail);
        },
        decoration: InputDecoration(
          labelText: "Item Heading",
          hintText: "Enter item heading",
          border: OutlineInputBorder(borderRadius: BorderRadius.circular(20.0)),
        ),
      ),
    );
  }

  Widget _createItemDetailWidget() {
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: TextFormField(
        controller: _controllerItemDetail,
        maxLength: 75,
        focusNode: _focusNodeItemDetail,
        textInputAction: TextInputAction.next,
        onFieldSubmitted: (v) {
          debugPrint("ItemDetail submitted");
          FocusScope.of(context).requestFocus(_focusNodeItemPrice);
        },
        decoration: InputDecoration(
          labelText: "Item Detail",
          hintText: "Enter item detail",
          border: OutlineInputBorder(borderRadius: BorderRadius.circular(20.0)),
        ),
      ),
    );
  }

class DataEntryState extends State<DataEntry> {
  final TextEditingController _controllerItemHed = TextEditingController();
  final TextEditingController _controllerItemDetail = TextEditingController();
  final TextEditingController _controllerItemPrice = TextEditingController();
  final TextEditingController _controllerSeller = TextEditingController();
  final TextEditingController _controllerContactNr = TextEditingController();
  final TextEditingController _controllerLocation = TextEditingController();

  final FocusNode _focusNodeItemHed = FocusNode();
  final FocusNode _focusNodeItemDetail = FocusNode();
  final FocusNode _focusNodeItemPrice = FocusNode();
  final FocusNode _focusNodeSeller = FocusNode();
  final FocusNode _focusNodeContactNr = FocusNode();
  final FocusNode _focusNodeLocation = FocusNode();

Answer 1

在尝试了许多不起作用的方法之后，我能找到的唯一解决方案如下：

  _changeFocus(BuildContext context, FocusNode focusNodeCurrent,
      FocusNode focusNodeNext) {
    focusNodeCurrent.unfocus();
    setState(() => _focusNodeCurrent = focusNodeNext);
  }

debugPrint() 显示在 _changeFocus() 中，unfocus() 确实有效，而 requestFocus() 则不起作用。

在构建中：

    if (_focusNodeCurrent != null)
      FocusScope.of(context).requestFocus(_focusNodeCurrent);

其他相关代码（其中一些可能是多余的）：

 TextFormField _createItemHeadingWidget(BuildContext context) {
    FocusScope.of(context).reparentIfNeeded(_focusNodeItemHed);
    return TextFormField(
      controller: _controllerItemHed,
      maxLength: 50,
      keyboardType: TextInputType.text,
      autofocus: _dataRec == null,
      focusNode: _focusNodeItemHed,
      textInputAction: TextInputAction.next,
      onFieldSubmitted: (v) {
        _changeFocus(context, _focusNodeItemHed, _focusNodeItemDetail);
      },
      decoration: InputDecoration(
        labelText: "Item Heading",
        hintText: "Enter item heading",
        border: OutlineInputBorder(borderRadius: BorderRadius.circular(20.0)),
      ),
    );
  }