import ‘package:flutter/material.dart‘;
class BottomNavigationWidget extends StatefulWidget {
  _BottomNavigationWidgetState createState() => _BottomNavigationWidgetState();
}
class _BottomNavigationWidgetState extends State<BottomNavigationWidget> {
  final _bottomNavColor = Colors.blue;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        bottomNavigationBar: BottomNavigationBar(
          items: [
            BottomNavigationBarItem(
              icon: Icon(
                Icons.home,
                color: _bottomNavColor,
              ),
              title: Text(
                ‘home‘,
                style: TextStyle(color: _bottomNavColor),
              )
            ),
              BottomNavigationBarItem(
              icon: Icon(
                Icons.email,
                color: _bottomNavColor,
              ),
              title: Text(
                ‘Email‘,
                style: TextStyle(color: _bottomNavColor),
              )
            ),
              BottomNavigationBarItem(
              icon: Icon(
                Icons.airplay,
                color: _bottomNavColor,
              ),
              title: Text(
                ‘Airplay‘,
                style: TextStyle(color: _bottomNavColor),
              )
            ),
              BottomNavigationBarItem(
              icon: Icon(
                Icons.scanner,
                color: _bottomNavColor,
              ),
              title: Text(
                ‘Scnner‘,
                style: TextStyle(color: _bottomNavColor),
              )
            )
 
          ],
        ),
    );
  }
}
 
//底部导航栏
final _变量名a = Color.bule;
BottomNavigationBarItem(
 item:[
  BottomNavigationBarItem(
   icon:Icon(
    Icons.xxx //系统样式
    color:_变量名a
   )
  )
 
 ]
)
 
在当前目录下 例如 lib 新建一个dart文件 右键 file  xxx.dart
引用其他文件 ,先import 文件 即可直接使用新文件下的class 
 
继承Statefulwidge 动态继承 ????和 statlessWidget的区别 没搞明白