feat:value change animtion

Author: LiuL0703

lib/main.dart

@@ -28,6 +28,7 @@ import 'view/gestures.dart';
 import 'view/media_query.dart';
 import 'view/styled_text.dart';
 import 'view/animation/easeing.dart';
+import 'view/animation/valuechange.dart';
 // import 'package:flutter_examples_code/view/navigation_drawer/screens/home.dart';
 import 'package:flutter_examples_code/view/navigation_drawer/screens/account.dart';
 import 'package:flutter_examples_code/view/navigation_drawer/screens/setting.dart';
@@ -82,6 +83,7 @@ class MyApp extends StatelessWidget {
         "gestures_demo":(context)=> new GestureDemo(),
         "media_query": (context)=> new MediaQueryDemo(),
         "styled_text": (context)=> new StyleTextDemo(),
+        "value_change_animation": (context)=> new ValueChangeAnimation(),
       },
       home: MyHomePage(title: '首页'),
     );
@@ -127,6 +129,7 @@ class _MyHomePageState extends State<MyHomePage> {
     "Media Query Demo": "media_query",
     "Styled Text Demo": "styled_text",
     "Easing Animation Demo": "easing_animation",
+    "Value Change Animation": "value_change_animation",
   };
   Drawer getNavDrawer(BuildContext context){
     var headChild = new DrawerHeader(child: 

lib/view/animation/valuechange.dart

@@ -0,0 +1,55 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
+
+class ValueChangeAnimation extends StatefulWidget {
+  @override
+  _ValueChangeAnimationState createState() => _ValueChangeAnimationState();
+}
+
+class _ValueChangeAnimationState extends State<ValueChangeAnimation> 
+    with TickerProviderStateMixin {
+
+  AnimationController controller;
+  Animation animation;
+  @override
+  void initState() {
+    super.initState();
+    controller = AnimationController(
+      duration: new Duration(milliseconds: 1000), vsync: this);
+    final Animation curve = CurvedAnimation(
+      parent: controller, curve: Curves.easeOut);
+    animation = IntTween(begin: 0, end: 10).animate(curve)
+      ..addStatusListener((status){
+        if(status == AnimationStatus.completed){
+          controller.reverse();
+        }
+
+        if(status == AnimationStatus.dismissed){
+          Navigator.pop(context);
+        }
+      });
+  }
+  @override
+  Widget build(BuildContext context) {
+    controller.forward();
+    return AnimatedBuilder(
+      animation: controller,
+      builder: (BuildContext context, Widget child){
+        return Scaffold(
+          body: new Center(
+            child: new Text(
+              animation.value.toString(),
+              style: TextStyle(fontSize: 48.0)
+            ),
+          ),
+        );
+      },
+    );
+  }
+
+  @override
+  void dispose() { 
+    controller.dispose();
+    super.dispose();
+  }
+}