Flutter：RenderBox未被布置

83

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，这是一个正在进行的工作，并且此错误使我无法继续执行自己的工作。

dart  flutter  flutter-layout 
— 亚历山德罗·贝尔托齐（Alessandro Bertozzi）
source

Answers:

146

问题是您将ListView内部放置在列/行中。异常中的文字很好地说明了错误。

为了避免错误，您需要在ListView内部提供一个尺寸。

我建议您使用此代码Expanded来告知水平尺寸（最大可用空间）和SizedBox（可能是容器）height:

    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,
    )

，

— 化学am
source
1
我使用“列”而不是“行”作为根。将其更改为“行”后，修复了该错误。谢谢您的帮助。
— ABHIMANGAL MS
77

您可以添加一些这样的代码 

ListView.builder{
   shrinkWrap: true,
}
— 穆阿沙林·阿尔凡
source
谁能指导我如何在模板中使用它？
— 卡文达（Kavinda Jayakody）
1
rinkWrap对我不起作用，我使用了适合我的@chemamolins解决方案。
— Kamlesh
对于长列表来说，这是一个不好的解决方案。来自文档：“收缩包装滚动视图的内容比扩展到最大允许大小要昂贵得多，因为在滚动过程中内容可以扩展和收缩，这意味着每当滚动位置更改时，都需要重新计算滚动视图的大小。 ”。
— boldnik
25

错误原因：

Column尝试在垂直轴上扩展，也会这样做ListView，因此您需要限制的高度ListView。

解决方案

  1. 使用Expanded或Flexible如果您想允许ListView占用的整个左侧空间，请使用Column。

    Column(
  children: <Widget>[
    Expanded(
      child: ListView(...),
    )
  ],
)

  1. 使用SizedBox，如果你想的大小限制ListView到一定的高度。

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

  1. 使用shrinkWrap，如果你ListView是不是太大。

    Column(
  children: <Widget>[
    ListView(
      shrinkWrap: true, // use it
    )
  ],
)
— 公路警察
source
谢谢！这是迄今为止最好，最简洁的答案！我不知道为什么在我的情况下，如果使用相同的Column包装方式，ListView我会收到一个错误Expanded，但使用SizedBox🤔可以正常工作
— boldnik
@boldnik您中还有哪些其他小部件Column，您实际上可以将其作为问题提问，也可以直接与我开始聊天，以防您认为可以在评论部分中进行处理。
— CopsOnRoad
收缩包装：正确，//这解决了我的问题
— 大卫·B。
2

一世

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];
            },
          ),
        ],
      ),
    );
— 穆罕默德·拜尔文德
source
2

将列表视图放在“灵活”窗口小部件中也可能会有所帮助，

Flexible( fit: FlexFit.tight, child: _buildYourListWidget(..),)
— 我的钥匙
source
1

将您的ListView包裹在扩展小部件中

 Expanded(child:MyListView())
— MobileMon
source
2
如果不能Expanded是Column
— 尼克
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