Question

我正在尝试创建ListView，但是当我导入list_form.dart类时，出现此错误。也许我在布局上犯了一些错误，因为如果尝试在主文件中运行它，我不会得到此错误。

这是错误：

    I/flutter (12956): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (12956): The following assertion was thrown during performResize():
I/flutter (12956): Vertical viewport was given unbounded height.
I/flutter (12956): Viewports expand in the scrolling direction to fill their container.In this case, a vertical
I/flutter (12956): viewport was given an unlimited amount of vertical space in which to expand. This situation
I/flutter (12956): typically happens when a scrollable widget is nested inside another scrollable widget.
I/flutter (12956): If this widget is always nested in a scrollable widget there is no need to use a viewport because
I/flutter (12956): there will always be enough vertical space for the children. In this case, consider using a Column
I/flutter (12956): instead. Otherwise, consider using the "shrinkWrap" property (or a ShrinkWrappingViewport) to size
I/flutter (12956): the height of the viewport to the sum of the heights of its children.
I/flutter (12956):
I/flutter (12956): When the exception was thrown, this was the stack:
I/flutter (12956): #0      RenderViewport.performResize.<anonymous closure> (package:flutter/src/rendering/viewport.dart:1133:15)
I/flutter (12956): #1      RenderViewport.performResize (package:flutter/src/rendering/viewport.dart:1186:6)
I/flutter (12956): #2      RenderObject.layout (package:flutter/src/rendering/object.dart:1616:9)
I/flutter (12956): #3      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #4      RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #5      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #6      RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #7      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #8      RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #9      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #10     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #11     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #12     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #13     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #14     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #15     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #16     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #17     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #18     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #19     RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:738:15)
I/flutter (12956): #20     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #21     RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:738:15)
I/flutter (12956): #22     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #23     RenderPositionedBox.performLayout (package:flutter/src/rendering/shifted_box.dart:381:13)
I/flutter (12956): #24     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #25     MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:141:11)
I/flutter (12956): #26     _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:339:7)
I/flutter (12956): #27     MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:211:7)
I/flutter (12956): #28     RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:355:14)
I/flutter (12956): #29     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #30     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #31     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #32     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #33     _RenderCustomClip.performLayout (package:flutter/src/rendering/proxy_box.dart:1192:11)
I/flutter (12956): #34     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #35     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #36     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #37     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #38     _RenderCustomClip.performLayout (package:flutter/src/rendering/proxy_box.dart:1192:11)
I/flutter (12956): #39     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #40     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #41     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #42     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #43     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #44     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #45     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #46     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #47     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #48     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #49     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #50     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #51     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #52     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #53     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #54     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #55     RenderOffstage.performLayout (package:flutter/src/rendering/proxy_box.dart:2884:13)
I/flutter (12956): #56     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #57     RenderStack.performLayout (package:flutter/src/rendering/stack.dart:520:15)
I/flutter (12956): #58     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #59     __RenderTheatre&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #60     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #61     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #62     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #63     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #64     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #65     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #66     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #67     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #68     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #69     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:108:13)
I/flutter (12956): #70     RenderObject.layout (package:flutter/src/rendering/object.dart:1631:7)
I/flutter (12956): #71     RenderView.performLayout (package:flutter/src/rendering/view.dart:147:13)
I/flutter (12956): #72     RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1506:7)
I/flutter (12956): #73     PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:765:18)
I/flutter (12956): #74     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:270:19)
I/flutter (12956): #75     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:674:13)
I/flutter (12956): #76     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:208:5)
I/flutter (12956): #77     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter (12956): #78     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter (12956): #79     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:751:7)
I/flutter (12956): #81     _Timer._runTimers (dart:isolate/runtime/libtimer_impl.dart:382:19)
I/flutter (12956): #82     _Timer._handleMessage (dart:isolate/runtime/libtimer_impl.dart:416:5)
I/flutter (12956): #83     _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:171:12)
I/flutter (12956): (elided one frame from package dart:async)
I/flutter (12956):
I/flutter (12956): The following RenderObject was being processed when the exception was fired:
I/flutter (12956):   RenderViewport#925a8 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (12956):   creator: Viewport ← _ScrollableScope ← IgnorePointer-[GlobalKey#8e8f7] ← Semantics ← Listener ←
I/flutter (12956):   _GestureSemantics ← RawGestureDetector-[LabeledGlobalKey<RawGestureDetectorState>#67ae5] ←
I/flutter (12956):   _ScrollSemantics-[GlobalKey#17eb8] ← RepaintBoundary ← CustomPaint ← RepaintBoundary ←
I/flutter (12956):   NotificationListener<ScrollNotification> ← ⋯
I/flutter (12956):   parentData: <none> (can use size)
I/flutter (12956):   constraints: BoxConstraints(unconstrained)
I/flutter (12956):   size: MISSING
I/flutter (12956):   axisDirection: down
I/flutter (12956):   crossAxisDirection: right
I/flutter (12956):   offset: ScrollPositionWithSingleContext#c4917(offset: 0.0, range: null..null, viewport: null,
I/flutter (12956):   ScrollableState, AlwaysScrollableScrollPhysics -> ClampingScrollPhysics, IdleScrollActivity#2fecf,
I/flutter (12956):   ScrollDirection.idle)
I/flutter (12956):   anchor: 0.0
I/flutter (12956): This RenderObject had the following descendants (showing up to depth 5):
I/flutter (12956):   RenderSliverPadding#74d62 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (12956):     RenderSliverList#5c56d NEEDS-LAYOUT NEEDS-PAINT
I/flutter (12956): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderViewport#925a8 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderViewport#925a8 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderIgnorePointer#8bbda relayoutBoundary=up11 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderSemanticsAnnotations#209b4 relayoutBoundary=up10 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderPointerListener#a9641 relayoutBoundary=up9 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderSemanticsGestureHandler#9f5b4 relayoutBoundary=up8 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: _RenderScrollSemantics#47944 relayoutBoundary=up7 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#e17a8 relayoutBoundary=up6 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderCustomPaint#a2328 relayoutBoundary=up5 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#02607 relayoutBoundary=up4 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: RenderBox was not laid out: RenderFlex#79164 relayoutBoundary=up3 NEEDS-PAINT
I/flutter (12956): Another exception was thrown: 'package:flutter/src/rendering/shifted_box.dart': Failed assertion: line 310 pos 12: 'child.hasSize': is not true.
I/flutter (12956): Another exception was thrown: NoSuchMethodError: The method '<=' was called on null.

这是list_form.dart类：

import 'package:flutter/material.dart';

class ListForm extends StatefulWidget {
  @override
  ListFormState createState() => new ListFormState();
}

class ListFormState extends State<ListForm> {
    List<String> products = ["Test1", "Test2", "Test3"];
    @override
    Widget build(BuildContext context) {
      return new Container(
        child: new Center(
          child: new Column(
            children: <Widget>[
              new Row(
                children: <Widget>[
                  new ListView.builder(
                    itemCount: products.length,
                    itemBuilder: (BuildContext ctxt, int index) {
                      return new Text(products[index]);
                    }
                  ),
                  new IconButton(
                    icon: Icon(Icons.remove_circle),
                    onPressed: () { },
                  )
                ],
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
              ),
              new TextField(
                decoration: new InputDecoration(
                  hintText: "Prodotto"
                ),
                onSubmitted: (String str) {
                  setState(() {
                    products.add(str);
                  });
                },
              ),
            ]
          )
        )
      );
    }
}

这是app_base.dart类：

import 'package:flutter/material.dart';
import '../UI/list_form.dart';

class AppBase extends StatefulWidget {
  @override
  State createState() => new AppBaseState();
}

class AppBaseState extends State<AppBase> {
  bool _pressed = true;

  @override
  Widget build(BuildContext context) {
    return new Material(
      color: Colors.greenAccent,
      child: new Scaffold(
        body:
          new ListForm(),
        appBar: AppBar(
          centerTitle: true,
          title: const Text('Skeeper'),
          backgroundColor: Colors.green,
        ),
        floatingActionButton: FloatingActionButton(
          tooltip: 'Test',
          child: new Icon(Icons.add),
          backgroundColor: Colors.green,
          onPressed: () {
              setState(() {
                _pressed = !_pressed;
              });
          },
        ),
      )
    );
  }
}

不用担心是否有一些未使用的代码，这是一个正在进行中的工作，此错误只是阻止了我继续做我的工作。

Answer 1

错误原因：

Column尝试在垂直轴上扩展，ListView也尝试在垂直轴上扩展，因此您需要限制ListView的高度。

解决方案

如果要允许Expanded占用Flexible中的整个左侧空间，请使用ListView或Column。
```
Column(
  children: <Widget>[
    Expanded(
      child: ListView(...),
    )
  ],
)
```

如果要将SizedBox的大小限制为特定高度，请使用ListView。

Column(
  children: <Widget>[
    SizedBox(
      height: 200, // constrain height
      child: ListView(),
    )
  ],
)

如果您的shrinkWrap不太大，请使用ListView。

Column(
  children: <Widget>[
    ListView(
      shrinkWrap: true, // use it
    )
  ],
)

Answer 2

您可以添加一些这样的代码

ListView.builder{
   shrinkWrap: true,
}

Answer 3

问题是您将ListView放在列/行内。异常中的文字很好地说明了错误。

为避免错误，您需要在ListView内提供一个大小。

我为您建议此代码使用Expanded来通知SizedBox的水平尺寸（最大可用空间）和height:（可能是容器）

    new Row(
      children: <Widget>[
        Expanded(
          child: SizedBox(
            height: 200.0,
            child: new ListView.builder(
              scrollDirection: Axis.horizontal,
              itemCount: products.length,
              itemBuilder: (BuildContext ctxt, int index) {
                return new Text(products[index]);
              },
            ),
          ),
        ),
        new IconButton(
          icon: Icon(Icons.remove_circle),
          onPressed: () {},
        ),
      ],
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
    )

，

Answer 4

将列表视图放入“灵活”窗口小部件可能也有帮助，

Flexible( fit: FlexFit.tight, child: _buildYourListWidget(..),)

Answer 5

我使用此代码解决了在水平列表中显示项目的问题。

new Container(
      height: 20,
      child: Row(
        mainAxisAlignment: MainAxisAlignment.end,
        children: <Widget>[
          ListView.builder(
            scrollDirection: Axis.horizontal,
            shrinkWrap: true,
            itemCount: array.length,
            itemBuilder: (context, index){
              return array[index];
            },
          ),
        ],
      ),
    );

Answer 6

我遇到了一个类似的问题，但就我而言，我被排在了Listview的最前面，当然，它占用了所有空间。我只需要使Row脱颖而出，就解决了。我建议检查问题是否是其容器无法容纳的小部件。

Answer 7

我有一个类似的问题，但在我的例子中，我在 ListView 的前面放了一行，当然，它占用了所有空间。我只需要从领先中取出Row，它就解决了。我建议检查问题是否是一个比其容器可以容纳的更大的小部件。

Expanded(child:MyListView())

Answer 8

我的应用程序开始崩溃，出现同样的错误，只是完全出乎意料。

我非常感谢在此页面上提到的其他答案。但没有一个对我有用。我使用的是 Flutter 2.0.0 并升级到 Flutter 2.2.2 解决了该问题，而无需更改现有代码中的任何内容。

Answer 9

当我使用一个大小的盒子时会出现这个错误，但没有给它一个高度和宽度。例如，只给它一个没有宽度的高度就会出现这个错误。

Flutter：RenderBox未被布置

9 个答案: