RenderCustomMultiChildLayoutBox对象在布局过程中被赋予了无限大的大小.颤振误差

Question

我是flutter的新手，正在尝试在flutter中实现自定义列表视图。其给定为RenderCustomMultiChildLayoutBox对象在布局错误期间被给定了无限大小

1. 我无法获取哪个小部件的抛出错误

2此外，请建议如何调试这些布局错误，因为错误跟踪没有引发错误的特定窗口小部件信息

请找到以下相同的代码：

class ChatItemSreen extends StatelessWidget {
var leftSection;
var middleSection;
var rightSection;
ChatModel _chartObj;
ChatItemSreen(ChatModel _chartObj) {
this._chartObj = _chartObj;
//.........the left section ...........................
CircleAvatar image = new CircleAvatar(
backgroundColor: Colors.lightGreen,
backgroundImage: new NetworkImage(this._chartObj.geturl()),
radius: 24.0,
);
leftSection = new Container(child: image);
//.........the middle section ...........................
middleSection = new Expanded(
child: new Container(
padding: new EdgeInsets.only(left: 8.0),
child: new Column(
crossAxisAlignment: CrossAxisAlignment.start,
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
new Text(this._chartObj.getuserName(),
style: new TextStyle(
color: Colors.black,
fontWeight: FontWeight.w300,
fontSize: 16.0)),
new Text(this._chartObj.getmessage(),
style: new TextStyle(color: Colors.grey))
],
),
));
//.........the right section ...........................
rightSection = new Container(
child: new Column(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
new Text(this._chartObj.gettimeStamp()),
new CircleAvatar(
backgroundColor: Colors.lightGreen,
radius: 12.0,
child: new Text(
this._chartObj.getunreadMsgNo(),
style: new TextStyle(color: Colors.white, fontSize: 12.0),
))
],
),
);
}
@override
Widget build(BuildContext context) {
return new Scaffold(
body: new Container(
margin: new EdgeInsets.all(2.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[leftSection, middleSection, rightSection],
)),
);
}
}
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(title: "Shashank List", home: RandomWords());
}
}
class RowItemState extends State<RandomWords>
{
final List<ChatModel> items = new List();
@override
void initState()
{
super.initState();
setState(()
{
items.add(new ChatModel("http://img2.thejournal.ie/inline/2470754/original?width=428&version=2470754", "9:35", "2", "Shashank", "Missed vedio call!!"));
items.add(new ChatModel("http://img2.thejournal.ie/inline/2470754/original?width=428&version=2470754", "10:35", "3", "Kakroo", "Missed vedio call!!"));
items.add(new ChatModel("http://img2.thejournal.ie/inline/2470754/original?width=428&version=2470754", "02:45", "4", "Alpha 1", "Missed vedio call!!"));
items.add(new ChatModel("http://img2.thejournal.ie/inline/2470754/original?width=428&version=2470754", "12:30", "6", "Beta 2", "Missed vedio call!!"));
});
}
@override
Widget build(BuildContext context)
{
return MaterialApp(
home: ListView.builder(
itemCount: items.length,
itemBuilder: (context,position)
{
ChatModel obj = items.elementAt(position);
return new ChatItemSreen(obj);
}
),
);
}
}

正在给我以下错误：

XCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (15078): The following assertion was thrown during performLayout():
I/flutter (15078): RenderCustomMultiChildLayoutBox object was given an infinite size during layout.
I/flutter (15078): This probably means that it is a render object that tries to be as big as possible, but it was put
I/flutter (15078): inside another render object that allows its children to pick their own size.
I/flutter (15078): The nearest ancestor providing an unbounded height constraint is:
I/flutter (15078):   RenderIndexedSemantics#a9825 relayoutBoundary=up3 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (15078):   creator: IndexedSemantics ← NotificationListener<KeepAliveNotification> ← KeepAlive ←
I/flutter (15078):   AutomaticKeepAlive ← SliverList ← MediaQuery ← SliverPadding ← Viewport ← _ScrollableScope ←
I/flutter (15078):   IgnorePointer-[GlobalKey#e8d9b] ← Semantics ← Listener ← ⋯
I/flutter (15078):   parentData: index=0; layoutOffset=0.0 (can use size)
I/flutter (15078):   constraints: BoxConstraints(w=411.4, 0.0<=h<=Infinity)
I/flutter (15078):   semantic boundary
I/flutter (15078):   size: MISSING
I/flutter (15078):   index: 0
I/flutter (15078): The constraints that applied to the RenderCustomMultiChildLayoutBox were:
I/flutter (15078):   BoxConstraints(w=411.4, 0.0<=h<=Infinity)
I/flutter (15078): The exact size it was given was:
I/flutter (15078):   Size(411.4, Infinity)
I/flutter (15078): See https://flutter.io/layout/ for more information.

Answer 1

我在尝试在单独的文本段落中包含一个可缩放的PhotoView小部件时遇到了这个问题。

当你编译并运行该应用程序时，你可能会注意到，你的小部件应该在一个无限长的黑色区域。

错误的第二行读取

在布局时被赋予了无限大小

这意味着需要限制小部件的大小。

我的解决方案是将PhotoView封装在SizedBox小部件中。

...
Text("Here's some text.nAnd then there's this image:n"),
SizedBox(
width: 200.0,
height: 300.0,
child: PhotoView(
imageProvider: NetworkImage("http://image/url/here.jpg"),
heroTag: "Lauren Mayberry",
),
),
Text("And now more text"),
...

在这个示例中，我使用了固定的宽度和高度，但您可以始终根据小部件中的内容动态调整其大小。

至于如何更好地调试布局错误：我唯一的建议是一次删除一个小部件，直到错误消失。这当然不太理想，但它有效。

Answer 2

只需用SizedBox包装小部件，并在MediaQuery的帮助下给出屏幕的大小。

Size size = MediaQuery.of(context).size;
SizedBox(
height: size.height,
width: size.height,
child: // Your Widget
);

Answer 3

这个问题很久以前就解决了。但除了这些解决方案之外，我还想添加一些不同的内容。

这些天，我在我的项目中防止我的代码成为意大利面条代码：(为此，我打开并编辑了其他文件。当时我遇到了这个错误。我的解决方案是添加expanded。我在主页栏的代码中添加了扩展。