ScrollPhysics
简述：用来指定可滚动部件的滚动特性
源码
神奇的ScrollPhysics与Simulation
| ScrollPhysics | 释义 |
|---|---|
| BouncingScrollPhysics | 允许滚动出边界，超过边界时会有回弹效果，会响应滚动事件 |
| ClampingScrollPhysics | 不允许滚动出边界，会响应滚动事件 |
| AlwaysScrollableScrollPhysics | 一直响应滚动事件 |
| NeverScrollableScrollPhysics | 禁止滚动，不响应滚动事件 |
| FixedExtentScrollPhysics | ListWheelScrollView滚轮使用时，item都会停止在中间位置，不会停在分割线 |
| PageScrollPhysics | PageView滚轮使用时，item都会停止在一页，不会停止在分割线位置 |
| RangeMaintainingScrollPhysics | 当内容突然改变尺寸时，试图将滚动位置保持在范围内的滚动物理 |
Scaffold(
appBar: AppBar(
title: Text('AlwaysScrollableScrollPhysicsPage'),
),
body: NotificationListener(
child: Scaffold(
body: ListView.builder(
controller: scrollController,
// physics: const AlwaysScrollableScrollPhysics(),
physics: const BouncingScrollPhysics (),
// physics: const ClampingScrollPhysics (),
// physics: const NeverScrollableScrollPhysics (),
itemCount: 50,
itemBuilder: (context, index) {
return Padding(
padding: const EdgeInsets.only(top: 8.0,left: 16,right: 16),
child: Container(
color: Colors.deepOrange[400],
height: 50,
alignment: Alignment.center,
child: Text('$index',style: TextStyle(color: Colors.white),),
),
);
},
),
),
onNotification: (scrollNotification) {
print('$scrollNotification');
if (scrollNotification is ScrollStartNotification) {
showToast("小部件已开始滚动 ");
}
return true;
},
),
);
BouncingScrollPhysics
只有在滚动控件的高度超过屏幕高度时，才会有效果。
BouncingScrollPhysics.gif
日志：
Performing hot reload...
Syncing files to device Android SDK built for x86...
I/flutter ( 7619): ScrollStartNotification(depth: 0 (local), FixedScrollMetrics(0.0..[511.0]..2389.0), DragStartDetails(Offset(157.0, 393.5)))
I/flutter ( 7619): UserScrollNotification(depth: 0 (local), FixedScrollMetrics(0.0..[511.0]..2389.0), direction: ScrollDirection.reverse)
I/flutter ( 7619): ScrollUpdateNotification(depth: 0 (local), FixedScrollMetrics(1.2..[511.0]..2387.8), scrollDelta: 1.1666666666666667, DragUpdateDetails(Offset(0.0, -4.0)))
I/flutter ( 7619): ScrollUpdateNotification(depth: 0 (local), FixedScrollMetrics(4.7..[511.0]..2384.3), scrollDelta: 3.49609375, DragUpdateDetails(Offset(0.0, -3.5)))
I/flutter ( 7619): ScrollUpdateNotification(depth: 0 (local), FixedScrollMetrics(10.7..[511.0]..2378.3), scrollDelta: 5.996093750000001, DragUpdateDetails(Offset(0.0, -6.0)))
ClampingScrollPhysics
ClampingScrollPhysics.gif
Performing hot reload...
Syncing files to device Android SDK built for x86...
I/flutter ( 7619): ScrollStartNotification(depth: 0 (local), FixedScrollMetrics(0.0..[511.0]..2389.0), DragStartDetails(Offset(204.5, 141.5)))
I/flutter ( 7619): UserScrollNotification(depth: 0 (local), FixedScrollMetrics(0.0..[511.0]..2389.0), direction: ScrollDirection.forward)
I/flutter ( 7619): OverscrollIndicatorNotification(depth: 0 (local), side: leading edge)
I/flutter ( 7619): OverscrollNotification(depth: 0 (local), FixedScrollMetrics(0.0..[511.0]..2389.0), overscroll: -1.0, velocity: 0.0, DragUpdateDetails(Offset(0.0, 1.0)))
I/flutter ( 7619): OverscrollNotification(depth: 0 (local), FixedScrollMetrics(0.0..[511.0]..2389.0), overscroll: -6.0, velocity: 0.0, DragUpdateDetails(Offset(0.0, 6.0)))
AlwaysScrollableScrollPhysics
ClampingScrollPhysics.gif
Performing hot reload...
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Reloaded 0 libraries in 154ms.
I/flutter ( 7619): ScrollStartNotification(depth: 0 (local), FixedScrollMetrics(0.0..[511.0]..2389.0), DragStartDetails(Offset(192.5, 169.0)))
I/flutter ( 7619): UserScrollNotification(depth: 0 (local), FixedScrollMetrics(0.0..[511.0]..2389.0), direction: ScrollDirection.forward)
I/flutter ( 7619): OverscrollIndicatorNotification(depth: 0 (local), side: leading edge)
I/flutter ( 7619): OverscrollNotification(depth: 0 (local), FixedScrollMetrics(0.0..[511.0]..2389.0), overscroll: -3.5, velocity: 0.0, DragUpdateDetails(Offset(0.0, 3.5)))
I/flutter ( 7619): OverscrollNotification(depth: 0 (local), FixedScrollMetrics(0.0..[511.0]..2389.0), overscroll: -1.0, velocity: 0.0, DragUpdateDetails(Offset(0.0, 1.0)))
NeverScrollableScrollPhysics
不会有滚动日志
NeverScrollableScrollPhysics.gif
Performing hot reload...
Syncing files to device Android SDK built for x86...
Reloaded 2 of 565 libraries in 750ms.
FixedExtentScrollPhysics
ListWheelScrollView使用时，每次滚动，都会停留在item处于正中央的位置，不会停留在分割线上。
Center(
child: Stack(
alignment: Alignment.center,
children: [
//ListWheelScrollView中间的分割线
Container(
width: double.infinity,
height: 60,
decoration: BoxDecoration(
border: Border(
top: BorderSide(width: 2,color: Colors.black),
bottom: BorderSide(width: 2,color: Colors.black)
)
),
),
//滚轮view
Container(
margin: EdgeInsets.only(left: 16, right: 16),
height: 200,
child: ListWheelScrollView(
controller: _fixedExtentScrollController,
physics: FixedExtentScrollPhysics(),
children: List.generate(20, (index) {
return Container(
width: double.infinity,
color: Colors.deepOrange[400],
alignment: Alignment.center,
child: Text(
"$index",
style: TextStyle(fontSize: 18.0,color: Colors.white),
),
);
}),
itemExtent: 60.0,
),
),
],
),
);
FixedExtentScrollPhysics.gif
PageScrollPhysics
PageView的pageSnapping属性默认是true,类似吸附效果一样，一页页滚动，每次只滚动一页，不会停止在分割线位置。
如果pageSnapping设置成false,效果会如下
scroPhysics.gif
PageScrollPhysics也可以做到pageSnapping为true的效果:
PageView(
//能达到跟页面捕捉一样的效果
physics: PageScrollPhysics(),
//关闭页面捕捉
pageSnapping: false,
scrollDirection:Axis.horizontal, //设置滚动方向，默认是水平方向
children: [
Container(
color: Colors.orange,
child: Center(
child: Text('PageView-1'),
),
),
Container(
color: Colors.yellow,
child: Center(
child: Text('PageView-2'),
),
),
Container(
color: Colors.pinkAccent,
child: Center(
child: Text('PageView-3'),
),
),
],
);
scroPhysics_6.gif