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# SliverLayoutBuilder
根据组件的约束条件提供子组件,比如当用户向下划动时,盒子显示红色,向上滑动时显示蓝色:
CustomScrollView(
slivers: <Widget>[
SliverLayoutBuilder(
builder: (BuildContext context, SliverConstraints constraints) {
print('${constraints.userScrollDirection}');
var color = Colors.red;
if (constraints.userScrollDirection == ScrollDirection.forward) {
color = Colors.blue;
}
return SliverToBoxAdapter(
child: Container(
height: 100,
color: color,
));
},
),
],
)
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