//動(dòng)畫控制器
AnimationController controller;
//AnimationController是一個(gè)特殊的Animation對(duì)象，在屏幕刷新的每一幀，就會(huì)生成一個(gè)新的值，
// 默認(rèn)情況下，AnimationController在給定的時(shí)間段內(nèi)會(huì)線性的生成從0.0到1.0的數(shù)字
//用來(lái)控制動(dòng)畫的開始與結(jié)束以及設(shè)置動(dòng)畫的監(jiān)聽
//vsync參數(shù)，存在vsync時(shí)會(huì)防止屏幕外動(dòng)畫（動(dòng)畫的UI不在當(dāng)前屏幕時(shí)）消耗不必要的資源
//duration 動(dòng)畫的時(shí)長(zhǎng)，這里設(shè)置的 seconds: 2 為2秒，當(dāng)然也可以設(shè)置毫秒 milliseconds：2000.
 controller =
 AnimationController(duration: const Duration(seconds: 2), vsync: this);
 //動(dòng)畫開始、結(jié)束、向前移動(dòng)或向后移動(dòng)時(shí)會(huì)調(diào)用StatusListener
 controller.addStatusListener((status) {
 if (status == AnimationStatus.completed) {
 //動(dòng)畫從 controller.reverse() 反向執(zhí)行 結(jié)束時(shí)會(huì)回調(diào)此方法
 print("status is completed");
 // controller.reset(); 將動(dòng)畫重置到開始前的狀態(tài)
 //開始執(zhí)行
 //controller.forward();
 } else if (status == AnimationStatus.dismissed) {
 //動(dòng)畫從 controller.forward() 正向執(zhí)行 結(jié)束時(shí)會(huì)回調(diào)此方法
 print("status is dismissed");
 //controller.forward();
 }else if (status == AnimationStatus.forward) {
 print("status is forward");
 //執(zhí)行 controller.forward() 會(huì)回調(diào)此狀態(tài)
 }else if (status == AnimationStatus.reverse) {
 //執(zhí)行 controller.reverse() 會(huì)回調(diào)此狀態(tài)
 print("status is reverse");
 }
 });

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_x/base/base_appbar_page.dart';

/**
 * RelativeRectTween 縮放動(dòng)畫
 */
class RelativeRectTweenPage extends StatefulWidget {
 @override
 State<StatefulWidget> createState() {
 return new RelativeRectTweenState();
 }
}

class RelativeRectTweenState extends BaseAppBarPageState<RelativeRectTweenPage>
 with SingleTickerProviderStateMixin {
 //動(dòng)畫控制器
 AnimationController controller;
 Animation<RelativeRect> animation;

 @override
 String buildInitState() {
 buildBackBar("動(dòng)畫", backIcon: Icons.arrow_back_ios);
 controller =
 AnimationController(duration: const Duration(seconds: 2), vsync: this);
 //動(dòng)畫開始、結(jié)束、向前移動(dòng)或向后移動(dòng)時(shí)會(huì)調(diào)用StatusListener
 controller.addStatusListener((status) {
 if (status == AnimationStatus.completed) {
 //動(dòng)畫從 controller.forward() 正向執(zhí)行 結(jié)束時(shí)會(huì)回調(diào)此方法
 print("status is completed");
 //反向執(zhí)行
 //controller.reverse();
 } else if (status == AnimationStatus.dismissed) {
 //動(dòng)畫從 controller.reverse() 反向執(zhí)行 結(jié)束時(shí)會(huì)回調(diào)此方法
 print("status is dismissed");
 //controller.forward();
 } else if (status == AnimationStatus.forward) {
 print("status is forward");
 //執(zhí)行 controller.forward() 會(huì)回調(diào)此狀態(tài)
 } else if (status == AnimationStatus.reverse) {
 //執(zhí)行 controller.reverse() 會(huì)回調(diào)此狀態(tài)
 print("status is reverse");
 }
 });

 // 這個(gè)動(dòng)畫的過程是
 // 子widget 距左邊距離從 10.0 變化 到100.0
 // 子widget 距上邊距離從 10.0 變化 到100.0
 // 子widget 距右邊距離從 10.0 變化 到100.0
 // 子widget 距下邊距離從 10.0 變化 到100.0
 // 四邊同時(shí)變化 相同的距離 倍率，所以看出來(lái)是 中心縮小的動(dòng)畫
 RelativeRectTween rectTween = RelativeRectTween(
 //初始位置設(shè)置
 begin: const RelativeRect.fromLTRB(
  //子widget 距父布局 left 10.0
  10.0,
  //子widget 距父布局 top 10.0
  10.0,
  //子widget 距父布局 right 10.0
  10.0,
  //子widget 距父布局 bottom 10.0
  10.0),
 //結(jié)束位置設(shè)置
 end: RelativeRect.fromLTRB(
  //子widget 距父布局 left 100.0
 100.0,
  //子widget 距父布局 top 100.0
 100.0,
 //子widget 距父布局 right 100.0
 100.0,
 //子widget 距父布局 bottom 100.0
 100.0,
 ),
 );

 //關(guān)聯(lián) controller
 animation = rectTween.animate(controller);

 return null;
 }

 @override
 Widget buildWidget(BuildContext context) {
 return buildSlideTransition();
 }

 @override
 void dispose() {
 super.dispose();
 controller.dispose();
 }

 //漸變動(dòng)畫
 Widget buildSlideTransition() {
 return Stack(
 children: <Widget>[
 //必須作為Stack的子widget
 PositionedTransition(
  rect: animation,
  child: Container(
  color: Colors.grey,
  child: Image.network(
  "http://img5.duitang.com/uploads/item/201411/16/20141116124947_xBNxM.jpeg",
  ),
  ),
 ),
 Positioned(
  bottom: 20,
  left: 20,
  child: FlatButton(
  onPressed: () {
  if (controller.isDismissed) {
   ///正向動(dòng)畫開始
   controller.forward();
  } else if (controller.isCompleted) {
   ///反向動(dòng)畫開始
   controller.reverse();
  } else {
   //停止
   controller.dispose();
   //重置動(dòng)畫
   controller.reset();
  }
  },
  child: Text("開始")),
 )
 ],
 );
 }
}

 RelativeRectTween rectTween = RelativeRectTween(
 //初始位置設(shè)置
 begin: const RelativeRect.fromLTRB(
  50.0,
  50.0,
  50.0,
  50.0),
 //結(jié)束位置設(shè)置
 end: RelativeRect.fromLTRB(
 50.0,
 50.0,
 50.0,
 500.0,
 ),
 );

RelativeRectTween rectTween = RelativeRectTween(
 //初始位置設(shè)置
 begin: const RelativeRect.fromLTRB(
  50.0,
  50.0,
  50.0,
  50.0),
 //結(jié)束位置設(shè)置
 end: RelativeRect.fromLTRB(
 500.0,
 50.0,
 50.0,
 50.0,
 ),
 );