android - RenderCustomMultiChildLayoutBox 对象在布局期间被赋予了无限大小。 flutter 错误

Question

我是 Flutter 的新手，正在尝试在 Flutter 中实现自定义 ListView 。 在布局错误期间，它的给定 RenderCustomMultiChildLayoutBox 对象被赋予了无限大小

1. 我无法获取哪个小部件的抛出错误

2 另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小部件信息

请在下面找到相同的代码:

      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);
            }
        ),
    );
  }
}

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确切的问题。

当您编译并运行该应用程序时，您可能会注意到您的违规小部件应该是一个无限长的黑色区域。

错误的第二行写着

was given an infinite size during layout

这意味着需要限制小部件的大小。

我的解决方案是将 PhotoView 包装在 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"),
...

在此示例中，我使用了固定的宽度和高度，但您始终可以根据属于其中的任何内容动态调整小部件的大小。

关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，但确实有效。