flutter 动画
2024-10-19 23:40:06
AnimatedCrossFade
AnimatedCrossFade让俩个子widget 交替淡入淡出。
class AnimatedCrossFade1 extends StatefulWidget {
@override
State<StatefulWidget> createState() {
// TODO: implement createState
return new AnimatedCrossFade2();
}
}
class AnimatedCrossFade2 extends State<AnimatedCrossFade1> {
var _first = false;
@override
Widget build(BuildContext context) {
new Timer(new Duration(seconds: 3), () {
setState(() {
_first = !_first;
});
});
return AnimatedCrossFade(
duration: const Duration(seconds: 3),
firstChild:
const FlutterLogo(style: FlutterLogoStyle.horizontal, size: 100.0),
secondChild:
const FlutterLogo(style: FlutterLogoStyle.stacked, size: 100.0),
crossFadeState:
_first ? CrossFadeState.showFirst : CrossFadeState.showSecond,
);
}
}
AnimatedBuilder
AnimatedBuilder构建动画最常用的控件。AnimatedBuilder 由 animation,child,builder 三个参数。
class AnimatedBuilder1 extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return new AnimatedBuilder2();
}
}
class AnimatedBuilder2 extends State<AnimatedBuilder1>
with SingleTickerProviderStateMixin {
@override
Widget build(BuildContext context) {
var controller =
AnimationController(duration: Duration(seconds: 3), vsync: this)
..forward();
return new AnimatedBuilder(
animation: controller,
child: Container(width: 200.0, height: 200.0, color: Colors.green),
builder: (BuildContext context, Widget child) {
print(controller.value);
return Transform.scale(
scale: controller.value,
child: child,
);
});
}
}
当创建一个AnimationController时，需要传递一个vsync参数，存在vsync时会防止屏幕外动画（译者语：动画的UI不在当前屏幕时）消耗不必要的资源。 通过将SingleTickerProviderStateMixin添加到类定义中，可以将stateful对象作为vsync的值。你可以在GitHub的animate1中看到这个例子 。
2.3 DecoratedBoxTransition
DecoratedBoxTransition 装饰widget边界的动画。核心是Animation<Decoration>对象和Child。Animation<Decoration>通过DecorationTween.animate(controller) 得到。
属性：position 代表绘制边框是在widget前还是后。
demo如下：
class DecoratedBoxTransition1 extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return new DecoratedBoxTransition2();
}
}
class DecoratedBoxTransition2 extends State<DecoratedBoxTransition1>
with SingleTickerProviderStateMixin {
@override
Widget build(BuildContext context) {
DecorationTween decorationTween = DecorationTween(
begin: BoxDecoration(
color: Colors.blue,//子widget背景颜色
border: Border.all(
color: Colors.blue,//边界颜色
style: BorderStyle.solid,
width: 1.0,
),
borderRadius: BorderRadius.all(Radius.circular(20)),
shape: BoxShape.rectangle,
boxShadow: const <BoxShadow>[
BoxShadow(
color: Colors.amberAccent,
blurRadius: 5.0,
spreadRadius: 5.0,
)
],
),
end: BoxDecoration(
color: Colors.green,
border: Border.all(
color: Colors.green,
style: BorderStyle.solid,
width: 1.0,
),
shape: BoxShape.rectangle,
boxShadow: const <BoxShadow>[
BoxShadow(
color: Colors.blueGrey,
blurRadius: 5.0,
spreadRadius: 5.0,
)
],
borderRadius: BorderRadius.all(Radius.circular(30)),
),
);
var controller =
AnimationController(duration: Duration(seconds: 3), vsync: this)
..forward();
Animation<Decoration> d = decorationTween.animate(controller);
return new DecoratedBoxTransition(
decoration: d,
position: DecorationPosition.background,
child: new Container(
width: 200,
height: 200,
));
}
}
ps: DecoratedBoxTransition 的child 背景色最好是无色的。不然会影响效果
2.3 FadeTransition 淡入淡出动画
FadeTransition 淡入淡出动画。opacity 属性需要指定一个Animation<double>，child属性指定widget。
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: new FadeTransition(
opacity: new AnimationController(
duration: Duration(seconds: 3),
vsync: this,
)..repeat(),
child: FlutterLogo(style: FlutterLogoStyle.horizontal, size: 100.0),
alwaysIncludeSemantics: true,
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
2.4 PositionedTransition 定位动画
PositionedTransition动画很麻烦，主要由俩个重要的属性：
- rect
规定子widget 离 Stack边距的值。由RelativeRectTween.animate(AnimationController)获得。 - child
顾名思义将被施加动画的widget
ps：PositionedTransition 必须作为Stack 控件的子View，否则就会报错。
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin{
@override
Widget build(BuildContext context) {
Animatable animatable= RelativeRectTween(begin: new RelativeRect.fromLTRB(75.0, 75, 75, 75.0),
end: new RelativeRect.fromLTRB(100.0, 100.0, 100.0, 100.0),
);
Animation frontRelativeRect = animatable.animate(new AnimationController(
duration: Duration(seconds: 3),
vsync: this,
)..repeat());
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Stack(
alignment: Alignment.center,
fit: StackFit.loose,
children: <Widget>[
Container(
width: 200,
height: 200,
color: Colors.blue),
Container(
width: 100,
height: 100,
color: Colors.red,
),
PositionedTransition(
rect: frontRelativeRect,
child: Container(
width: 50,
height: 50,
color: Colors.orange,
) ,
)
],
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}
Stack 控件
Stack层叠控件。其childWidget 可以层叠到一起，层叠顺序：Widget越后创建，层级越靠上
可以控制没有定位的childWidget的布局策略。
可以控制没有定位的childWidget的布局策略
Stack({
this.alignment = AlignmentDirectional.topStart,
this.textDirection,
this.fit = StackFit.loose,
this.overflow = Overflow.clip,
List<Widget> children = const <Widget>[],
})
alignment
决定如何去对齐没有定位（没有使用Positioned）或部分定位的子widget。所谓部分定位，在这里特指没有在某一个轴上定位：left、right为横轴，top、bottom为纵轴，只要包含某个轴上的一个定位属性就算在该轴上有定位textDirection
和Row、Wrap的textDirection功能一样，都用于决定alignment对齐的参考系即：textDirection的值为TextDirection.ltr，则alignment的start代表左，end代表右；textDirection的值为TextDirection.rtl，则alignment的start代表右，end代表左。fit
此参数用于决定没有定位的子widget如何去适应Stack的大小。StackFit.loose表示使用子widget的大小，StackFit.expand表示扩伸到Stack的大小。overflow
此属性决定如何显示超出Stack显示空间的子widget，值为Overflow.clip时，超出部分会被剪裁（隐藏），值为Overflow.visible 时则不会。
2.5 RotationTransition 旋转动画
旋转动画RotationTransition。核心属性child和turns。
class RotationTransitionState extends State<RotationTransition1> with SingleTickerProviderStateMixin {
@override
Widget build(BuildContext context) {
return new RotationTransition(
child: Container(
width: 100,
height: 100,
color: Colors.orange,
),
turns: AnimationController(
duration: Duration(seconds: 1),
vsync: this,
lowerBound: 0,
upperBound: 0.1,
)..forward(),
);
}
}
2.6 ScaleTransition缩放动画
ScaleTransition 核心属性child 和scale。scale类型是Animation<double>。Animation<double>可以根据Tween.animate 生成。
demo：是由1缩小到0
class ScaleTransitionState extends State<ScaleTransition1>
with SingleTickerProviderStateMixin {
@override
Widget build(BuildContext context) {
Animation<double> t =
Tween(begin: 1.0, end: 0.0).animate(AnimationController(
duration: Duration(seconds: 3),
vsync: this,
)..forward()); return new ScaleTransition(
child: Container(
width: 100,
height: 100,
color: Colors.orange,
),
scale: t,
);
}
}
2.6 SlideTransition移动动画
SlideTransition 动画最重要的属性是position和child。position是Animation<Offset>。可以通过Tween.animate 生成。
class SlideTransition1State extends State<SlideTransition1>
with SingleTickerProviderStateMixin {
@override
Widget build(BuildContext context) {
var t = Tween<Offset>(
begin: const Offset(0.0, 2.0),
end: const Offset(0.0, 1.0),
).animate(AnimationController(
duration: Duration(seconds: 3),
vsync: this,
)..forward()); return new SlideTransition(
child: Container(
width: 100,
height: 100,
color: Colors.orange,
),
position: t,
);
}
}
begin: const Offset(0.0, 2.0)表示的意思是：动画刚开始child的x轴的起点不变，y轴起点是(1+2)* y。ps:y是child的高度值
end: const Offset(0.0, 1.0) 表示的意思是:动画结束后，x轴坐标不变，y轴坐标是(1+1)* y
end: const Offset(0.0, 1.0) 表示的意思是:动画结束后，x轴坐标不变，y轴坐标是(1+1)* y
最新文章
- Node.js之路【第三篇】NodeJS异步实现
- Android开发7：简单的数据存储（使用SharedPreferences）和文件操作
- Socket之TCP连接_TcpNoDelay
- python3 密码生成器
- JavaScript中with语句的理解
- SQL创建链接服务器
- Bzoj 2749: [HAOI2012]外星人 欧拉函数,数论,线性筛
- absolute vs fixed
- javascript----bug
- 求绝对值,hdu-2003
- django email用法
- MySQL性能建议者mysqltuner.pl和pt-variable-advisor
- BZOJ 1316: 树上的询问 （点分治+set）
- php短信接口代码
- Java集合之TreeSet
- ecstore中怎样使用ajax提交数据
- Java基础8：深入理解内部类
- 网站项目所有js css无法引用问题解决方案
- Multiresolution Analysis（多分辨率分析）
- BZOJ.4571.[SCOI2016]美味(主席树 贪心)