mod: 图片预览

lib/common/widgets/appbar.dart

@@ -0,0 +1,33 @@
+import 'package:flutter/material.dart';
+
+class AppBarWidget extends StatelessWidget implements PreferredSizeWidget {
+  const AppBarWidget({
+    required this.child,
+    required this.controller,
+    required this.visible,
+    Key? key,
+  }) : super(key: key);
+
+  final PreferredSizeWidget child;
+  final AnimationController controller;
+  final bool visible;
+
+  @override
+  // TODO: implement preferredSize
+  Size get preferredSize => child.preferredSize;
+
+  @override
+  Widget build(BuildContext context) {
+    visible ? controller.reverse() : controller.forward();
+    return SlideTransition(
+      position: Tween<Offset>(
+        begin: Offset.zero,
+        end: const Offset(0, -1),
+      ).animate(CurvedAnimation(
+        parent: controller,
+        curve: Curves.easeInOutBack,
+      )),
+      child: child,
+    );
+  }
+}