flutter 设置某个输入框为第一响应

  FocusNode _codefocusNode =  FocusNode();


设置textfile 的 FocusNode
  child: CupertinoTextField(
        autofocus: _codefocusNode,
      ),

设置为第一响应者
  FocusScope.of(context).requestFocus(_codefocusNode);