1、优化MyPageAppBar属性(showBack是否展示默认的返回箭头)

lib/widget/my_app_bar.dart

 import 'package:flutter/material.dart';
 
 class MyPageAppBar extends StatelessWidget implements PreferredSizeWidget {
-  final String? title;
-  final Color? backgroundColor;
-  final Color? foregroundColor;
-  final bool showBack;
+  final String? title; // 标题
+  final Color? backgroundColor; // 背景颜色
+  final Color? foregroundColor; // 前景颜色
+  final bool showBack;  // 是否展示返回箭头
   final bool primary;
-  final Function()? onBack;
-  final List<Widget>? actions;
-  final bool exitApp;
-  final Widget? leading;
-  final double? elevation;
-  final Widget? titleWidget;
+  final List<Widget>? actions; // 右侧widget
+  final Widget? leading; // 左侧widget
+  final double? elevation; // 阴影
+  final Widget? titleWidget; // 自定义标题widget
 
   const MyPageAppBar({
     Key? key,
@@ -20,9 +18,7 @@ class MyPageAppBar extends StatelessWidget implements PreferredSizeWidget {
     this.foregroundColor,
     this.showBack = true,
     this.primary = true,
-    this.onBack,
     this.actions,
-    this.exitApp = false,
     this.leading,
     this.elevation = 0,
     this.titleWidget,
@@ -40,6 +36,7 @@ class MyPageAppBar extends StatelessWidget implements PreferredSizeWidget {
       actions: actions,
       leading: leading,
       elevation: elevation,
+      automaticallyImplyLeading: showBack,
     );
   }