//動(dòng)畫(huà)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(huà)的開(kāi)始與結(jié)束以及設(shè)置動(dòng)畫(huà)的監(jiān)聽(tīng)
 //vsync參數(shù)，存在vsync時(shí)會(huì)防止屏幕外動(dòng)畫(huà)（動(dòng)畫(huà)的UI不在當(dāng)前屏幕時(shí)）消耗不必要的資源
 //duration 動(dòng)畫(huà)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(huà)開(kāi)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(huà)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(huà)重置到開(kāi)始前的狀態(tài)
  //開(kāi)始執(zhí)行
  //controller.forward();
  } else if (status == AnimationStatus.dismissed) {
  //動(dòng)畫(huà)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");
  }
 });

 //動(dòng)畫(huà)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(huà)的開(kāi)始與結(jié)束以及設(shè)置動(dòng)畫(huà)的監(jiān)聽(tīng)
 //vsync參數(shù)，存在vsync時(shí)會(huì)防止屏幕外動(dòng)畫(huà)（動(dòng)畫(huà)的UI不在當(dāng)前屏幕時(shí)）消耗不必要的資源
 //duration 動(dòng)畫(huà)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(huà)開(kāi)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(huà)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");
  } else if (status == AnimationStatus.dismissed) {
  //動(dòng)畫(huà)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");
  } 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");
  }
 });

 //旋轉(zhuǎn)
 Widget buildRotationTransition() {
 return Center(
  child: RotationTransition(
  //設(shè)置動(dòng)畫(huà)的旋轉(zhuǎn)中心
  alignment: Alignment.center,
  //動(dòng)畫(huà)控制器
  turns: controller,
  //將要執(zhí)行動(dòng)畫(huà)的子view
  child: Container(
   width: 100,
   height: 100,
   color: Colors.grey,
  ),
  ),
 );
 }
}

//動(dòng)畫(huà)開(kāi)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(huà)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");
  //重置起點(diǎn)
  controller.reset();
  //開(kāi)啟
  controller.forward();
  } else if (status == AnimationStatus.dismissed) {
  //動(dòng)畫(huà)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");
  } 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");
  }
 });