堆栈中定位颤动的微件导致异常 [英] Flutter - Positioned Widget in Stack causing Exception
本文介绍了堆栈中定位颤动的微件导致异常的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
当我试图用定位的小部件封装PandemicCard时,我得到以下异常。如果我呈现卡片单独/未定位的小部件,它将正常工作。
I/flutter ( 7331): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter ( 7331): The following assertion was thrown during performLayout():
I/flutter ( 7331): RenderStack object was given an infinite size during layout.
I/flutter ( 7331): This probably means that it is a render object that tries to be as big as possible, but it was put
I/flutter ( 7331): inside another render object that allows its children to pick their own size.
I/flutter ( 7331): The nearest ancestor providing an unbounded height constraint is:
I/flutter ( 7331): RenderFlex#2b18c relayoutBoundary=up2 NEEDS-LAYOUT NEEDS-PAINT OVERFLOWING
I/flutter ( 7331): creator: Column ← Center ← MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ←
用于此代码。有人能帮我找出我做错了什么吗?
class PandemicCard extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
height: 120.0,
width: 76.0,
decoration: BoxDecoration(
color: Colors.blue,
boxShadow: [
BoxShadow(
blurRadius: 5.0,
color: Colors.grey)
]),
child: Text('Hi'),
);
}
}
class PandemicCardStackState extends State<PandemicCardStack> {
// final _cards = <PandemicCard>[ PandemicCard(), PandemicCard()];
final _cards = <PandemicCard>[ PandemicCard()];
@override
Widget build( BuildContext context) {
return Stack(
// This Bombs!
children: <Widget>[ Positioned( left: 0.0, top: 0.0, child: _cards[0])]
// This works!
// children: <Widget>[ _cards[0]]
);
}
}
class PandemicCardStack extends StatefulWidget {
@override
PandemicCardStackState createState() => PandemicCardStackState();
}
感谢您抽出时间!
推荐答案
添加一个空的Container
作为堆栈的child
:
@override
Widget build( BuildContext context) {
return Stack(
children: <Widget>[
Container(),
Positioned( left: 0.0, top: 0.0, child: _cards[0]),
]
);
}
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