1、SearchAppBar：增加属性，①margin(搜索框外边距) ②automaticallyImplyLeading(设置返回箭头展示隐藏)

lib/widget/search_app_bar.dart

@@ -20,6 +20,8 @@ class SearchAppBar extends StatefulWidget implements PreferredSizeWidget {
   final String? rightText;
   final Function? onRightBtnCallback;
   final Widget? leftWidget;
+  final EdgeInsetsGeometry? margin;
+  final bool automaticallyImplyLeading;
 
   const SearchAppBar({
     Key? key,
@@ -39,6 +41,8 @@ class SearchAppBar extends StatefulWidget implements PreferredSizeWidget {
     this.searchIconColor,
     this.searchIconSize,
     this.leftWidget,
+    this.margin,
+    this.automaticallyImplyLeading = true,
   }) : super(key: key);
 
   @override
@@ -74,10 +78,12 @@ class _SearchAppBarState extends State<SearchAppBar> {
         titleSpacing: 0.0,
         primary: widget.primary,
         leading: widget.leading,
+        automaticallyImplyLeading: widget.automaticallyImplyLeading,
         title: Row(
           children: <Widget>[
             Expanded(
               child: Container(
+                margin: widget.margin,
                 decoration: BoxDecoration(
                   borderRadius: const BorderRadius.all(Radius.circular(20.0)),
                   color: