Flutter 音樂波形圖動畫效果

音樂波形圖動畫效果是Loading動畫系列中的一個，github地址：https://github.com/LaoMengFlutter/flutter-do

Loading動畫效果如下

其中音樂波形圖動畫效果如下

下面我們看看音樂波形圖動畫效果是如何實現(xiàn)的？動畫效果實現(xiàn)的思路是繪制一個靜止的效果，其中可變的效果使用參數(shù)控制，效果如下：

一個柱形條代碼如下：

class?Bar?extends?StatelessWidget?{
??final?double?width;
??final?double?height;
??final?Color?color;
??final?BorderRadiusGeometry?borderRadius;

??const?Bar({
????Key??key,
????required?this.width,
????required?this.height,
????this.color?=?Colors.white,
????required?this.borderRadius,
??})?:?super(key:?key);

??@override
??Widget?build(BuildContext?context)?{
????return?SizedBox(
????????width:?width,
????????height:?height,
????????child:?DecoratedBox(
??????????decoration:?BoxDecoration(
????????????shape:?BoxShape.rectangle,
????????????color:?color,
????????????borderRadius:?borderRadius,
??????????),
????????));
??}
}

4個柱形條代碼如下：

Row(
????????????crossAxisAlignment:?CrossAxisAlignment.end,
????????????mainAxisAlignment:?MainAxisAlignment.spaceBetween,
????????????children:?[
??????????????Bar(
????????????????color:?widget.color,
????????????????width:?widget.width,
????????????????borderRadius:?widget.borderRadius,
????????????????height:?.5?*?widget.height,
??????????????),
??????????????Bar(
????????????????color:?widget.color,
????????????????width:?widget.width,
????????????????borderRadius:?widget.borderRadius,
????????????????height:?.5?*?widget.height,
??????????????),
??????????????Bar(
????????????????color:?widget.color,
????????????????width:?widget.width,
????????????????borderRadius:?widget.borderRadius,
????????????????height:?.5?*?widget.height,
??????????????),
??????????????Bar(
????????????????color:?widget.color,
????????????????width:?widget.width,
????????????????borderRadius:?widget.borderRadius,
????????????????height:?.5?*?widget.height,
??????????????),
????????????],
??????????)

下面讓4個柱形條動起來，改變其高度，代碼如下：

class?BarMusicLoading?extends?StatefulWidget?{
??final?double?width;
??final?double?height;
??final?Color?color;
??final?BorderRadiusGeometry?borderRadius;
??final?Duration?duration;
??final?Curve?curve;

??const?BarMusicLoading(
??????{Key??key,
????????this.width?=?3.0,
????????this.height?=?40.0,
????????this.color?=?Colors.blue,
????????this.borderRadius?=?const?BorderRadius.only(
????????????topLeft:?Radius.circular(3),?topRight:?Radius.circular(3)),
????????this.duration?=?const?Duration(milliseconds:?3000),
????????this.curve?=?Curves.easeInOut})
??????:?super(key:?key);

??@override
??_BarMusicLoadingState?createState()?=>?_BarMusicLoadingState();
}

class?_BarMusicLoadingState?extends?State<BarMusicLoading>
????with?SingleTickerProviderStateMixin?{
??late?AnimationController?_controller;

??late?Animation?_animation,?_animation1,?_animation2,?_animation3;
??List?values?=?[
????[0.0,?0.7,?0.4,?0.05,?0.95,?0.3,?0.9,?0.4,?0.15,?0.18,?0.75,?0.01],
????[0.05,?0.95,?0.3,?0.9,?0.4,?0.15,?0.18,?0.75,?0.01,?0.0,?0.7,?0.4],
????[0.9,?0.4,?0.15,?0.18,?0.75,?0.01,?0.0,?0.7,?0.4,?0.05,?0.95,?0.3],
????[0.18,?0.75,?0.01,?0.0,?0.7,?0.4,?0.05,?0.95,?0.3,?0.9,?0.4,?0.15],
??];

??@override
??void?initState()?{
????_controller?=?AnimationController(vsync:?this,?duration:?widget.duration)
??????..repeat();

????_animation?=?TweenSequence([
??????...List.generate(11,?(index)?{
????????return?TweenSequenceItem(
????????????tween:?Tween(begin:?values[0][index],?end:?values[0][index?+?1]),
????????????weight:?100.0?/?values.length);
??????}).toList()
????]).animate(CurvedAnimation(parent:?_controller,?curve:?widget.curve));

????_animation1?=?TweenSequence([
??????...List.generate(11,?(index)?{
????????return?TweenSequenceItem(
????????????tween:?Tween(begin:?values[1][index],?end:?values[1][index?+?1]),
????????????weight:?100.0?/?values.length);
??????}).toList()
????]).animate(CurvedAnimation(parent:?_controller,?curve:?widget.curve));

????_animation2?=?TweenSequence([
??????...List.generate(11,?(index)?{
????????return?TweenSequenceItem(
????????????tween:?Tween(begin:?values[2][index],?end:?values[2][index?+?1]),
????????????weight:?100.0?/?values.length);
??????}).toList()
????]).animate(CurvedAnimation(parent:?_controller,?curve:?widget.curve));

????_animation3?=?TweenSequence([
??????...List.generate(11,?(index)?{
????????return?TweenSequenceItem(
????????????tween:?Tween(begin:?values[3][index],?end:?values[3][index?+?1]),
????????????weight:?100.0?/?values.length);
??????}).toList()
????]).animate(CurvedAnimation(parent:?_controller,?curve:?widget.curve));

????super.initState();
??}

??@override
??void?dispose()?{
????_controller.dispose();
????super.dispose();
??}

??@override
??Widget?build(BuildContext?context)?{
????return?AnimatedBuilder(
????????animation:?_controller,
????????builder:?(context,?child)?{
??????????return?Row(
????????????crossAxisAlignment:?CrossAxisAlignment.end,
????????????mainAxisAlignment:?MainAxisAlignment.spaceBetween,
????????????children:?[
??????????????Bar(
????????????????color:?widget.color,
????????????????width:?widget.width,
????????????????borderRadius:?widget.borderRadius,
????????????????height:?_animation.value?*?widget.height,
??????????????),
??????????????Bar(
????????????????color:?widget.color,
????????????????width:?widget.width,
????????????????borderRadius:?widget.borderRadius,
????????????????height:?_animation1.value?*?widget.height,
??????????????),
??????????????Bar(
????????????????color:?widget.color,
????????????????width:?widget.width,
????????????????borderRadius:?widget.borderRadius,
????????????????height:?_animation2.value?*?widget.height,
??????????????),
??????????????Bar(
????????????????color:?widget.color,
????????????????width:?widget.width,
????????????????borderRadius:?widget.borderRadius,
????????????????height:?_animation3.value?*?widget.height,
??????????????),
????????????],
??????????);
????????});
??}
}

最終的效果如下：