本来想将appBar组件里面的内容 写在其他地方。但是写在其他地方报错
HomeHeade’ is not a subtype of type 'PreferredSizeWidget

HomeHeade代码:

class HomeHeade extends StatelessWidget  {

  @override
  Widget build(BuildContext context) {
    return AppBar(
      centerTitle:true,
      title:Text('生存日记',style: TextStyle(color: Color(0xFF02020D))),
      flexibleSpace: Container(
        decoration: BoxDecoration(
          gradient: LinearGradient(colors: [
            Color(0xFFFAD956),
            Colors.white,
          ], begin: Alignment.topCenter, end: Alignment.bottomCenter),
        ),
      ),
    );
  }
}`

支架需要将实现 PreferredSizeWidget的类作为appbar`
implements PreferredSizeWidget
更改代码。执行成功:

class HomeHeade extends StatelessWidget implements PreferredSizeWidget {

  @override
  Size get preferredSize => const Size.fromHeight(50);
  Widget build(BuildContext context) {
    return AppBar(
      centerTitle:true,
      title:Text('生存日记',style: TextStyle(color: Color(0xFF02020D))),
      flexibleSpace: Container(
        decoration: BoxDecoration(
          gradient: LinearGradient(colors: [
            Color(0xFFFAD956),
            Colors.white,
          ], begin: Alignment.topCenter, end: Alignment.bottomCenter),
        ),
      ),
    );
  }
}