想做一个点击下拉变成input框的搜索组件

代码是这样的

Widget build(BuildContext context) {
    return GestureDetector(
      onTap: handle_drop,
      child: Container(
        child: _isDrop?SearchInput():FocusButton(),
      ),
    );
  }

通过_isDrop来判断是渲染input还是渲染展开按钮
onTap是点击调用handle_drop

bool _isDrop = false;
void handle_drop() {
    setState(() {
      _isDrop = !_isDrop;
    });
  }

我想改成这样

class _SearchButtonState extends State<SearchButton> {
  bool _isDrop = false;
  void handle_drop(bool boolean) {
    setState(() {
      _isDrop = boolean;
    });
  }
  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: handle_drop(true),
      child: Container(
        child: _isDrop?SearchInput():FocusButton(),
      ),
    );
  }
}

然后onTap就报错了

The expression here has a type of 'void', and therefore cannot be used.

我要怎么做才能onTap的时候带着参数值？