feat: add appbar‘

Author: wanwusangzhi

docs/widget/navigator/appbar/index.md

@@ -1 +1,32 @@
-## **AppBar**
+## **AppBar**
+> 创建导航栏，
+
+### 构造函数
+```
+AppBar({
+  Key key,
+  Widget leading,
+  bool automaticallyImplyLeading: true,
+  Widget title,
+  List<Widget> actions,
+  Widget flexibleSpace,
+  PreferredSizeWidget bottom,
+  double elevation,
+  Color backgroundColor,
+  Brightness brightness,
+  IconThemeData iconTheme,
+  TextTheme textTheme,
+  bool primary: true,
+  bool centerTitle,
+  double titleSpacing: NavigationToolbar.kMiddleSpacing,
+  double toolbarOpacity: 1.0,
+  double bottomOpacity: 1.0
+})
+```
+
+### 属性介绍
+- leading: 导航栏左侧图标
+- title: 导航栏标题
+- actions: 导航栏右侧扩展图标，可添加PopupMenuButton，点开有下拉展开更多按钮。
+- automaticallyImplyLeading: 默认true, 当有上一级页面时，默认显示back按钮
+- bottom: 通过与Tabbar使用

lib/widget/navigator/appbar/demo.dart

@@ -19,7 +19,7 @@ class _IndexState extends State<Index> {
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        title: Text('My Fancy Dress'),
+        title: Text('AppBar'),
         actions: <Widget>[
           IconButton(
             icon: Icon(Icons.playlist_play),
@@ -37,7 +37,10 @@ class _IndexState extends State<Index> {
             onPressed: _repairDress,
           ),
         ],
-      )
+      ),
+      body: Center(
+        child: Image.network('https://flutter.github.io/assets-for-api-docs/assets/material/app_bar.png', fit: BoxFit.contain,),
+      ),
     );
   }
 }