Flutter：关闭DropdownButton（DropdownMenu）

Question

有没有办法在执行 onTap 函数时关闭包含所有 DropdownMenuItems的DropdownButton的选择菜单（DropdownMenuItem 内的 GestureDetector）？

这是我对 Alperen Baskaya 方法的实现（稍微简化的版本，以便于理解）。然而，这种方法还不起作用，我不确定是因为我错误地实施了它，还是因为该方法不适用于我的问题。

class _BoatSelectionState extends State<BoatSelection> {
  FocusNode focusNode;
  
  @override
  void initState() {
    super.initState();
    focusNode = FocusNode();
  }

  @override
  Widget build(BuildContext context) {
    return Row(
      children: [
        Expanded(
          child: 
            DropdownButtonHideUnderline(
              child: DropdownButton<Boat>(
                focusNode: focusNode,
                icon: Icon(
                  Icons.keyboard_arrow_down_rounded,
                  color: Colors.black,
                ),
                isExpanded: true,
                value: selectedBoat,
                onChanged: (Boat _boat) => Provider.of<BoatStreamsCubit>(context, listen: false).setBoat(_boat),
                selectedItemBuilder: (BuildContext context) {
                  return widget.boats.map<Widget>((Boat boat) {
                    return Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: [
                        BoatClassLogo(boat: boat),
                        Expanded(
                          child: Padding(
                            padding: const EdgeInsets.only(left: DesignValues.paddingMd),
                            child: BoatInformation(boat: boat),
                          ),
                        ),
                      ],
                    );
                  }).toList();
                },
                items: widget.boats.map<DropdownMenuItem<Boat>>((Boat _boat) {
                  return DropdownMenuItem<Boat>(
                    value: _boat,
                    child: Row(
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: [
                        Padding(
                          padding: const EdgeInsets.only(right: DesignValues.paddingMd),
                          child: BoatClassLogo(boat: _boat),
                        ),
                        Expanded(
                          child: BoatInformation(boat: _boat),
                        ),
                        GestureDetector(
                          onTap: () {
                            focusNode.unfocus();
                            Navigator.push(context, MaterialPageRoute(builder: (context) => BoatForm(CreationState.edit, _boat)));
                          },
                          child: Padding(
                            padding: const EdgeInsets.symmetric(horizontal: 5.0),
                            child: Icon(
                              Icons.edit,
                              color: AppColors.primary,
                            ),
                          ),
                        ),
                      ],
                    ),
                  );
                }).toList(),
              ),
          ),
        ),
      ],
    );
  }
}

Answer 1

我查了一下Dart中DropdownMenu的内部实现。

DropdownMenu 的弹出窗口是通过使用创建的Navigator.push()。它等待用户单击某个项目并返回带有 的值Navigator.pop()。因此，我们可以通过 获取下拉菜单的上下文来手动弹出弹出窗口GlobalKey。

late GlobalKey dropdownKey;  

@override
void initState() {
    super.initState();
    dropdownKey = GlobalKey();
}

...

DropdownButton<Boat>(
    key: dropdownKey,
    ...)

并使用删除它Navigator.pop()

GestureDetector(
    onTap: () {
        Navigator.pop(dropdownKey.currentContext);

完整代码：

class _BoatSelectionState extends State<BoatSelection> {
  GlobalKey dropdownKey;
  
  @override
  void initState() {
    super.initState();
    dropdownKey = GlobalKey(); // Init GlobalKey, allows to close the DropdownButton
  }

  @override
  Widget build(BuildContext context) {
    return Row(
      children: [
        Expanded(
          child: 
            DropdownButtonHideUnderline(
              child: DropdownButton<Boat>(
                key: dropdownKey,
                icon: Icon(
                  Icons.keyboard_arrow_down_rounded,
                  color: Colors.black,
                ),
                isExpanded: true,
                value: selectedBoat,
                onChanged: (Boat _boat) => Provider.of<BoatStreamsCubit>(context, listen: false).setBoat(_boat),
                selectedItemBuilder: (BuildContext context) {
                  return widget.boats.map<Widget>((Boat boat) {
                    return Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: [
                        BoatClassLogo(boat: boat),
                        Expanded(
                          child: Padding(
                            padding: const EdgeInsets.only(left: DesignValues.paddingMd),
                            child: BoatInformation(boat: boat),
                          ),
                        ),
                      ],
                    );
                  }).toList();
                },
                items: widget.boats.map<DropdownMenuItem<Boat>>((Boat _boat) {
                  return DropdownMenuItem<Boat>(
                    value: _boat,
                    child: Row(
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: [
                        Padding(
                          padding: const EdgeInsets.only(right: DesignValues.paddingMd),
                          child: BoatClassLogo(boat: _boat),
                        ),
                        Expanded(
                          child: BoatInformation(boat: _boat),
                        ),
                        GestureDetector(
                          onTap: () {
                            Navigator.pop(dropdownKey.currentContext); // Closes the dropdown
                            Navigator.push(context, MaterialPageRoute(builder: (context) => BoatForm(CreationState.edit, _boat)));
                          },
                          child: Padding(
                            padding: const EdgeInsets.symmetric(horizontal: 5.0),
                            child: Icon(
                              Icons.edit,
                              color: AppColors.primary,
                            ),
                          ),
                        ),
                      ],
                    ),
                  );
                }).toList(),
              ),
          ),
        ),
      ],
    );
  }
}