Flutter 中列内的扩展列表视图
[英]Expanded Listview inside a Column in Flutter
问题描述
I'm new to Flutter and I've been stuck here for a while now.
我是 Flutter 的新手，我已经被困在这里一段时间了。 I am trying to make a main screen in Flutter for web, but I keep getting this error every time I try to apply the expanded property to the listview widget.我正在尝试在 Flutter 中为 web 制作一个主屏幕，但每次尝试将扩展属性应用于列表视图小部件时，我都会收到此错误。
This is the code, the error, and what I'm trying to get:这是代码，错误，以及我想要得到的：
[我正在尝试做什么]：
Launching lib\main.dart on Chrome in debug mode...
Syncing files to device Chrome...
Debug service listening on ws://127.0.0.1:62280/NmOsZXmtIqE=
Debug service listening on ws://127.0.0.1:62280/NmOsZXmtIqE=
══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
The following assertion was thrown during performLayout():
RenderFlex children have non-zero flex but incoming height constraints are unbounded.
When a column is in a parent that does not provide a finite height constraint, for example if it is
in a vertical scrollable, it will try to shrink-wrap its children along the vertical axis. Setting a
flex on a child (e.g. using Expanded) indicates that the child is to expand to fill the remaining
space in the vertical direction.
These two directives are mutually exclusive. If a parent is to shrink-wrap its child, the child
cannot simultaneously expand to fit its parent.
Consider setting mainAxisSize to MainAxisSize.min and using FlexFit.loose fits for the flexible
children (using Flexible rather than Expanded). This will allow the flexible children to size
themselves to less than the infinite remaining space they would otherwise be forced to take, and
then will cause the RenderFlex to shrink-wrap the children rather than expanding to fit the maximum
constraints provided by the parent.
If this message did not help you determine the problem, consider using debugDumpRenderTree():
https://flutter.dev/debugging/#rendering-layer
http://api.flutter.dev/flutter/rendering/debugDumpRenderTree.html
The affected RenderFlex is:
RenderFlex#f5e21 relayoutBoundary=up2 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE(creator: Column ← Column ← Align ← ConstrainedBox ← Container ← Center ← MainScreen ← _BodyBuilder ← MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ← AnimatedBuilder ← ⋯, parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size), constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=Infinity), size: MISSING, direction: vertical, mainAxisAlignment: start, mainAxisSize: max, crossAxisAlignment: center, verticalDirection: down)
The creator information is set to:
Column ← Column ← Align ← ConstrainedBox ← Container ← Center ← MainScreen ← _BodyBuilder ←
MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ← AnimatedBuilder ← ⋯
The nearest ancestor providing an unbounded width constraint is: RenderFlex#62f2b relayoutBoundary=up1 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE:
creator: Column ← Align ← ConstrainedBox ← Container ← Center ← MainScreen ← _BodyBuilder ←
MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ← AnimatedBuilder ←
DefaultTextStyle ← ⋯
parentData: offset=Offset(0.0, 0.0) (can use size)
constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=876.0)
size: MISSING
direction: vertical
mainAxisAlignment: start
mainAxisSize: max
crossAxisAlignment: center
verticalDirection: down
See also: https://flutter.dev/layout/
If none of the above helps enough to fix this problem, please don't hesitate to file a bug:
https://github.com/flutter/flutter/issues/new?template=BUG.md
The relevant error-causing widget was:
Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:46:13
When the exception was thrown, this was the stack:
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 196:49 throw_
package:flutter/src/rendering/flex.dart 693:11 <fn>
package:flutter/src/rendering/flex.dart 717:15 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/flex.dart 746:14 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/shifted_box.dart 394:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 265:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/shifted_box.dart 394:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/custom_layout.dart 171:10 layoutChild
package:flutter/src/material/scaffold.dart 484:7 performLayout
package:flutter/src/rendering/custom_layout.dart 240:7 [_callPerformLayout]
package:flutter/src/rendering/custom_layout.dart 399:14 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/proxy_box.dart 1247:11 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/proxy_box.dart 3224:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/widgets/overlay.dart 700:14 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/proxy_box.dart 110:13 performLayout
package:flutter/src/rendering/object.dart 1767:7 layout
package:flutter/src/rendering/view.dart 167:48 performLayout
package:flutter/src/rendering/object.dart 1630:7 [_layoutWithoutResize]
package:flutter/src/rendering/object.dart 887:17 flushLayout
package:flutter/src/rendering/binding.dart 401:19 drawFrame
package:flutter/src/widgets/binding.dart 884:13 drawFrame
package:flutter/src/rendering/binding.dart 283:5 [_handlePersistentFrameCallback]
package:flutter/src/scheduler/binding.dart 1108:15 [_invokeFrameCallback]
package:flutter/src/scheduler/binding.dart 1047:9 handleDrawFrame
package:flutter/src/scheduler/binding.dart 856:7 <fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/isolate_helper.dart 50:19 internalCallback
The following RenderObject was being processed when the exception was fired: RenderFlex#f5e21 relayoutBoundary=up2 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE:
creator: Column ← Column ← Align ← ConstrainedBox ← Container ← Center ← MainScreen ← _BodyBuilder ←
MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ← AnimatedBuilder ← ⋯
parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size)
constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=Infinity)
size: MISSING
direction: vertical
mainAxisAlignment: start
mainAxisSize: max
crossAxisAlignment: center
verticalDirection: down
This RenderObject had the following descendants (showing up to depth 5):
child 1: RenderFlex#9da6e NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
child 1: RenderRepaintBoundary#b779b NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
child: RenderCustomPaint#67333 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
child: RenderRepaintBoundary#89099 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
child: _RenderScrollSemantics#0b273 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
child 2: RenderFlex#fb6ad NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
child 1: _RenderColoredBox#0acb4 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
child: RenderParagraph#61e06 NEEDS-LAYOUT NEEDS-PAINT
text: TextSpan
════════════════════════════════════════════════════════════════════════════════════════════════════
Another exception was thrown: Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/box.dart:1694:12
Another exception was thrown: Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/shifted_box.dart:322:12
Another exception was thrown: NoSuchMethodError: '<Unexpected Null Value>'
════════ Exception caught by rendering library ═════════════════════════════════════════════════════
The following NoSuchMethodError was thrown during paint():
'<Unexpected Null Value>'
method not found
Receiver: null
Arguments: []
The relevant error-causing widget was:
Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16
When the exception was thrown, this was the stack:
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 196:49 throw_
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 37:3 throwNullValueError
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 450:39 _notNull
package:flutter/src/rendering/flex.dart 475:38 get [_hasOverflow]
package:flutter/src/rendering/flex.dart 949:10 paint
...
The following RenderObject was being processed when the exception was fired: RenderFlex#62f2b relayoutBoundary=up1
... needs compositing
... parentData: offset=Offset(0.0, 0.0) (can use size)
... constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=876.0)
... size: MISSING
... direction: vertical
... mainAxisAlignment: start
... mainAxisSize: max
... crossAxisAlignment: center
... verticalDirection: down
RenderObject: RenderFlex#62f2b relayoutBoundary=up1
needs compositing
parentData: offset=Offset(0.0, 0.0) (can use size)
constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=876.0)
size: MISSING
direction: vertical
mainAxisAlignment: start
mainAxisSize: max
crossAxisAlignment: center
verticalDirection: down
... child 1: RenderFlex#6be7a NEEDS-LAYOUT NEEDS-PAINT
... needs compositing
... parentData: offset=Offset(0.0, 0.0); flex=1; fit=FlexFit.tight
... constraints: MISSING
... size: MISSING
... direction: vertical
... mainAxisAlignment: start
... mainAxisSize: max
... crossAxisAlignment: center
... verticalDirection: down
... child 1: RenderRepaintBoundary#15c70 NEEDS-LAYOUT NEEDS-PAINT
... needs compositing
... parentData: offset=Offset(0.0, 0.0); flex=null; fit=null
... constraints: MISSING
... size: MISSING
... usefulness ratio: no metrics collected yet (never painted)
... child: RenderCustomPaint#79694 NEEDS-LAYOUT NEEDS-PAINT
... needs compositing
... parentData: <none>
... constraints: MISSING
... size: MISSING
... child: RenderRepaintBoundary#81e95 NEEDS-LAYOUT NEEDS-PAINT
... needs compositing
... parentData: <none>
... constraints: MISSING
... size: MISSING
... usefulness ratio: no metrics collected yet (never painted)
... child 2: RenderFlex#f5e21 relayoutBoundary=up2 NEEDS-PAINT
... needs compositing
... parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size)
... constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=Infinity)
... size: MISSING
... direction: vertical
... mainAxisAlignment: start
... mainAxisSize: max
... crossAxisAlignment: center
... verticalDirection: down
... child 1: RenderFlex#9da6e NEEDS-LAYOUT NEEDS-PAINT
... needs compositing
... parentData: offset=Offset(0.0, 0.0); flex=1; fit=FlexFit.tight
... constraints: MISSING
... size: MISSING
... direction: horizontal
... mainAxisAlignment: spaceEvenly
... mainAxisSize: max
... crossAxisAlignment: center
... textDirection: ltr
... verticalDirection: down
... child 1: RenderRepaintBoundary#b779b NEEDS-LAYOUT NEEDS-PAINT
... needs compositing
... parentData: offset=Offset(0.0, 0.0); flex=null; fit=null
... constraints: MISSING
... size: MISSING
... usefulness ratio: no metrics collected yet (never painted)
... child: RenderCustomPaint#67333 NEEDS-LAYOUT NEEDS-PAINT
... needs compositing
... parentData: <none>
... constraints: MISSING
... size: MISSING
... child 2: RenderFlex#fb6ad NEEDS-LAYOUT NEEDS-PAINT
... parentData: offset=Offset(0.0, 0.0); flex=1; fit=FlexFit.tight
... constraints: MISSING
... size: MISSING
... direction: horizontal
... mainAxisAlignment: spaceEvenly
... mainAxisSize: max
... crossAxisAlignment: center
... textDirection: ltr
... verticalDirection: down
... child 1: _RenderColoredBox#0acb4 NEEDS-LAYOUT NEEDS-PAINT
... parentData: offset=Offset(0.0, 0.0); flex=null; fit=null
... constraints: MISSING
... size: MISSING
... behavior: opaque
... child: RenderParagraph#61e06 NEEDS-LAYOUT NEEDS-PAINT
... parentData: <none>
... constraints: MISSING
... size: MISSING
... textAlign: start
... textDirection: ltr
... softWrap: wrapping at box width
... overflow: clip
... locale: en_US
... maxLines: unlimited
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ (2) Exception caught by rendering library ═════════════════════════════════════════════════
RenderFlex children have non-zero flex but incoming height constraints are unbounded.
The relevant error-causing widget was:
Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:46:13
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ (3) Exception caught by rendering library ═════════════════════════════════════════════════
Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/box.dart:1694:12
hasSize
"RenderBox was not laid out: RenderFlex#f5e21 relayoutBoundary=up2 NEEDS-PAINT"
The relevant error-causing widget was:
Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ (4) Exception caught by rendering library ═════════════════════════════════════════════════
Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/shifted_box.dart:322:12
child.hasSize
is not true
The relevant error-causing widget was:
Container file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:21:14
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ (5) Exception caught by rendering library ═════════════════════════════════════════════════
'<Unexpected Null Value>'
method not found
Receiver: null
Arguments: []
The relevant error-causing widget was:
Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ (6) Exception caught by rendering library ═════════════════════════════════════════════════
Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/box.dart:1694:12
hasSize
"RenderBox was not laid out: RenderFlex#f5e21 relayoutBoundary=up2 NEEDS-PAINT"
The relevant error-causing widget was:
Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ (7) Exception caught by rendering library ═════════════════════════════════════════════════
Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/shifted_box.dart:322:12
child.hasSize
is not true
The relevant error-causing widget was:
Container file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:21:14
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ (8) Exception caught by rendering library ═════════════════════════════════════════════════
'<Unexpected Null Value>'
method not found
Receiver: null
Arguments: []
The relevant error-causing widget was:
Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ (9) Exception caught by rendering library ═════════════════════════════════════════════════
'<Unexpected Null Value>'
method not found
Receiver: null
Arguments: []
The relevant error-causing widget was:
Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16
════════════════════════════════════════════════════════════════════════════════════════════════════
════════ (10) Exception caught by rendering library ════════════════════════════════════════════════
'<Unexpected Null Value>'
method not found
Receiver: null
Arguments: []
The relevant error-causing widget was:
Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16
════════════════════════════════════════════════════════════════════════════════════════════════════
Application finished.
The error log:错误日志：
Launching lib\\main.dart on Chrome in debug mode... Syncing files to device Chrome... Debug service listening on ws://127.0.0.1:62280/NmOsZXmtIqE= Debug service listening on ws://127.0.0.1:62280/NmOsZXmtIqE= ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════ The following assertion was thrown during performLayout(): RenderFlex children have non-zero flex but incoming height constraints are unbounded. When a column is in a parent that does not provide a finite height constraint, for example if it is in a vertical scrollable, it will try to shrink-wrap its children along the vertical axis. Setting a flex on a child (eg using Expanded) indicates that the child is to expand to fill the remaining space in the vertical direction. These two directives are mutually exclusive. If a parent is to shrink-wrap its child, the child cannot simultaneously expand to fit its parent. Consider setting mainAxisSize to MainAxisSize.min and using FlexFit.loose fits for the flexible children (using Flexible rather than Expanded). This will allow the flexible children to size themselves to less than the infinite remaining space they would otherwise be forced to take, and then will cause the RenderFlex to shrink-wrap the children rather than expanding to fit the maximum constraints provided by the parent. If this message did not help you determine the problem, consider using debugDumpRenderTree(): https://flutter.dev/debugging/#rendering-layer http://api.flutter.dev/flutter/rendering/debugDumpRenderTree.html The affected RenderFlex is: RenderFlex#f5e21 relayoutBoundary=up2 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE(creator: Column ← Column ← Align ← ConstrainedBox ← Container ← Center ← MainScreen ← _BodyBuilder ← MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ← AnimatedBuilder ← ⋯, parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size), constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=Infinity), size: MISSING, direction: vertical, mainAxisAlignment: start, mainAxisSize: max, crossAxisAlignment: center, verticalDirection: down) The creator information is set to: Column ← Column ← Align ← ConstrainedBox ← Container ← Center ← MainScreen ← _BodyBuilder ← MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ← AnimatedBuilder ← ⋯ The nearest ancestor providing an unbounded width constraint is: RenderFlex#62f2b relayoutBoundary=up1 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE: creator: Column ← Align ← ConstrainedBox ← Container ← Center ← MainScreen ← _BodyBuilder ← MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ← AnimatedBuilder ← DefaultTextStyle ← ⋯ parentData: offset=Offset(0.0, 0.0) (can use size) constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=876.0) size: MISSING direction: vertical mainAxisAlignment: start mainAxisSize: max crossAxisAlignment: center verticalDirection: down See also: https://flutter.dev/layout/ If none of the above helps enough to fix this problem, please don't hesitate to file a bug: https://github.com/flutter/flutter/issues/new?template=BUG.md The relevant error-causing widget was: Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:46:13 When the exception was thrown, this was the stack: C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 196:49 throw_ package:flutter/src/rendering/flex.dart 693:11 <fn> package:flutter/src/rendering/flex.dart 717:15 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/flex.dart 746:14 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/shifted_box.dart 394:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 265:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/shifted_box.dart 394:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/custom_layout.dart 171:10 layoutChild package:flutter/src/material/scaffold.dart 484:7 performLayout package:flutter/src/rendering/custom_layout.dart 240:7 [_callPerformLayout] package:flutter/src/rendering/custom_layout.dart 399:14 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/proxy_box.dart 1247:11 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/proxy_box.dart 3224:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/widgets/overlay.dart 700:14 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/proxy_box.dart 110:13 performLayout package:flutter/src/rendering/object.dart 1767:7 layout package:flutter/src/rendering/view.dart 167:48 performLayout package:flutter/src/rendering/object.dart 1630:7 [_layoutWithoutResize] package:flutter/src/rendering/object.dart 887:17 flushLayout package:flutter/src/rendering/binding.dart 401:19 drawFrame package:flutter/src/widgets/binding.dart 884:13 drawFrame package:flutter/src/rendering/binding.dart 283:5 [_handlePersistentFrameCallback] package:flutter/src/scheduler/binding.dart 1108:15 [_invokeFrameCallback] package:flutter/src/scheduler/binding.dart 1047:9 handleDrawFrame package:flutter/src/scheduler/binding.dart 856:7 <fn> C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/isolate_helper.dart 50:19 internalCallback The following RenderObject was being processed when the exception was fired: RenderFlex#f5e21 relayoutBoundary=up2 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE: creator: Column ← Column ← Align ← ConstrainedBox ← Container ← Center ← MainScreen ← _BodyBuilder ← MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ← AnimatedBuilder ← ⋯ parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size) constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=Infinity) size: MISSING direction: vertical mainAxisAlignment: start mainAxisSize: max crossAxisAlignment: center verticalDirection: down This RenderObject had the following descendants (showing up to depth 5): child 1: RenderFlex#9da6e NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE child 1: RenderRepaintBoundary#b779b NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE child: RenderCustomPaint#67333 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE child: RenderRepaintBoundary#89099 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE child: _RenderScrollSemantics#0b273 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE child 2: RenderFlex#fb6ad NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE child 1: _RenderColoredBox#0acb4 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE child: RenderParagraph#61e06 NEEDS-LAYOUT NEEDS-PAINT text: TextSpan ════════════════════════════════════════════════════════════════════════════════════════════════════ Another exception was thrown: Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/box.dart:1694:12 Another exception was thrown: Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/shifted_box.dart:322:12 Another exception was thrown: NoSuchMethodError: '<Unexpected Null Value>' ════════ Exception caught by rendering library ═════════════════════════════════════════════════════ The following NoSuchMethodError was thrown during paint(): '<Unexpected Null Value>' method not found Receiver: null Arguments: [] The relevant error-causing widget was: Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16 When the exception was thrown, this was the stack: C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 196:49 throw_ C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 37:3 throwNullValueError C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 450:39 _notNull package:flutter/src/rendering/flex.dart 475:38 get [_hasOverflow] package:flutter/src/rendering/flex.dart 949:10 paint ... The following RenderObject was being processed when the exception was fired: RenderFlex#62f2b relayoutBoundary=up1 ... needs compositing ... parentData: offset=Offset(0.0, 0.0) (can use size) ... constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=876.0) ... size: MISSING ... direction: vertical ... mainAxisAlignment: start ... mainAxisSize: max ... crossAxisAlignment: center ... verticalDirection: down RenderObject: RenderFlex#62f2b relayoutBoundary=up1 needs compositing parentData: offset=Offset(0.0, 0.0) (can use size) constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=876.0) size: MISSING direction: vertical mainAxisAlignment: start mainAxisSize: max crossAxisAlignment: center verticalDirection: down ... child 1: RenderFlex#6be7a NEEDS-LAYOUT NEEDS-PAINT ... needs compositing ... parentData: offset=Offset(0.0, 0.0); flex=1; fit=FlexFit.tight ... constraints: MISSING ... size: MISSING ... direction: vertical ... mainAxisAlignment: start ... mainAxisSize: max ... crossAxisAlignment: center ... verticalDirection: down ... child 1: RenderRepaintBoundary#15c70 NEEDS-LAYOUT NEEDS-PAINT ... needs compositing ... parentData: offset=Offset(0.0, 0.0); flex=null; fit=null ... constraints: MISSING ... size: MISSING ... usefulness ratio: no metrics collected yet (never painted) ... child: RenderCustomPaint#79694 NEEDS-LAYOUT NEEDS-PAINT ... needs compositing ... parentData: <none> ... constraints: MISSING ... size: MISSING ... child: RenderRepaintBoundary#81e95 NEEDS-LAYOUT NEEDS-PAINT ... needs compositing ... parentData: <none> ... constraints: MISSING ... size: MISSING ... usefulness ratio: no metrics collected yet (never painted) ... child 2: RenderFlex#f5e21 relayoutBoundary=up2 NEEDS-PAINT ... needs compositing ... parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size) ... constraints: BoxConstraints(0.0<=w<=929.0, 0.0<=h<=Infinity) ... size: MISSING ... direction: vertical ... mainAxisAlignment: start ... mainAxisSize: max ... crossAxisAlignment: center ... verticalDirection: down ... child 1: RenderFlex#9da6e NEEDS-LAYOUT NEEDS-PAINT ... needs compositing ... parentData: offset=Offset(0.0, 0.0); flex=1; fit=FlexFit.tight ... constraints: MISSING ... size: MISSING ... direction: horizontal ... mainAxisAlignment: spaceEvenly ... mainAxisSize: max ... crossAxisAlignment: center ... textDirection: ltr ... verticalDirection: down ... child 1: RenderRepaintBoundary#b779b NEEDS-LAYOUT NEEDS-PAINT ... needs compositing ... parentData: offset=Offset(0.0, 0.0); flex=null; fit=null ... constraints: MISSING ... size: MISSING ... usefulness ratio: no metrics collected yet (never painted) ... child: RenderCustomPaint#67333 NEEDS-LAYOUT NEEDS-PAINT ... needs compositing ... parentData: <none> ... constraints: MISSING ... size: MISSING ... child 2: RenderFlex#fb6ad NEEDS-LAYOUT NEEDS-PAINT ... parentData: offset=Offset(0.0, 0.0); flex=1; fit=FlexFit.tight ... constraints: MISSING ... size: MISSING ... direction: horizontal ... mainAxisAlignment: spaceEvenly ... mainAxisSize: max ... crossAxisAlignment: center ... textDirection: ltr ... verticalDirection: down ... child 1: _RenderColoredBox#0acb4 NEEDS-LAYOUT NEEDS-PAINT ... parentData: offset=Offset(0.0, 0.0); flex=null; fit=null ... constraints: MISSING ... size: MISSING ... behavior: opaque ... child: RenderParagraph#61e06 NEEDS-LAYOUT NEEDS-PAINT ... parentData: <none> ... constraints: MISSING ... size: MISSING ... textAlign: start ... textDirection: ltr ... softWrap: wrapping at box width ... overflow: clip ... locale: en_US ... maxLines: unlimited ════════════════════════════════════════════════════════════════════════════════════════════════════ ════════ (2) Exception caught by rendering library ═════════════════════════════════════════════════ RenderFlex children have non-zero flex but incoming height constraints are unbounded. The relevant error-causing widget was: Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:46:13 ════════════════════════════════════════════════════════════════════════════════════════════════════ ════════ (3) Exception caught by rendering library ═════════════════════════════════════════════════ Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/box.dart:1694:12 hasSize "RenderBox was not laid out: RenderFlex#f5e21 relayoutBoundary=up2 NEEDS-PAINT" The relevant error-causing widget was: Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16 ════════════════════════════════════════════════════════════════════════════════════════════════════ ════════ (4) Exception caught by rendering library ═════════════════════════════════════════════════ Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/shifted_box.dart:322:12 child.hasSize is not true The relevant error-causing widget was: Container file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:21:14 ════════════════════════════════════════════════════════════════════════════════════════════════════ ════════ (5) Exception caught by rendering library ═════════════════════════════════════════════════ '<Unexpected Null Value>' method not found Receiver: null Arguments: [] The relevant error-causing widget was: Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16 ════════════════════════════════════════════════════════════════════════════════════════════════════ ════════ (6) Exception caught by rendering library ═════════════════════════════════════════════════ Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/box.dart:1694:12 hasSize "RenderBox was not laid out: RenderFlex#f5e21 relayoutBoundary=up2 NEEDS-PAINT" The relevant error-causing widget was: Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16 ════════════════════════════════════════════════════════════════════════════════════════════════════ ════════ (7) Exception caught by rendering library ═════════════════════════════════════════════════ Assertion failed: file:///C:/flutter/packages/flutter/lib/src/rendering/shifted_box.dart:322:12 child.hasSize is not true The relevant error-causing widget was: Container file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:21:14 ════════════════════════════════════════════════════════════════════════════════════════════════════ ════════ (8) Exception caught by rendering library ═════════════════════════════════════════════════ '<Unexpected Null Value>' method not found Receiver: null Arguments: [] The relevant error-causing widget was: Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16 ════════════════════════════════════════════════════════════════════════════════════════════════════ ════════ (9) Exception caught by rendering library ═════════════════════════════════════════════════ '<Unexpected Null Value>' method not found Receiver: null Arguments: [] The relevant error-causing widget was: Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16 ════════════════════════════════════════════════════════════════════════════════════════════════════ ════════ (10) Exception caught by rendering library ════════════════════════════════════════════════ '<Unexpected Null Value>' method not found Receiver: null Arguments: [] The relevant error-causing widget was: Column file:///C:/Users/Jorge%20Antelo/Desktop/Flutter/hotelmanager/lib/mainContainer.dart:25:16 ════════════════════════════════════════════════════════════════════════════════════════════════════ Application finished.
1 个解决方案
解决方案1
0 已采纳 2020-03-26 03:25:36
The error occurs because you are trying to expand without constrains.发生该错误是因为您试图无限制地扩展。 Expanded Widget is used with a parent with dimension constrains. Expanded Widget与具有维度约束的父级一起使用。 Since you are using it directly as one of the children in a column it can't infer which dismission to take.由于您直接将它用作列中的子项之一，因此无法推断要采取哪种解雇。
By default Expanded expand to fill dimension of the parent so you have to provide a parent like a container or padding or sizeBoxed默认情况下Expanded展开以填充父级的尺寸，因此您必须提供父级，例如容器或填充或 sizeBoxed
Edit:编辑：
You will also need some flex widgets ( Flexible ) to achieve the layout.您还需要一些 flex 小部件（ Flexible ）来实现布局。 follow this link to see a sample I made in dartpad.按照此 链接查看我在 dartpad 中制作的示例。
return Column(
children: <Widget>[
Flexible(
flex: 1,
child: Row(children: <Widget>[
Expanded(
child: Container(
height: 150,
color: Colors.black,
child: RaisedButton(onPressed: null)))
])),
Flexible(
flex: 6,
child: Row(
children: <Widget>[
Flexible(
flex: 1,
child: Column(children: <Widget>[
Expanded(
child: Container(
width: 200,
color: Colors.white,
child: RaisedButton(onPressed: null)))
])),
Flexible(
flex: 3,
child: Column(
children: <Widget>[
Flexible(
flex: 1,
child: Row(children: <Widget>[
Expanded(
child: Container(
height: height,
color: Colors.red,
child: RaisedButton(onPressed: null)))
])),
Flexible(
flex: 10,
child: Row(children: <Widget>[
Expanded(
child: Container(
height: height,
color: Colors.green,
child: RaisedButton(
onPressed: null,
)))
])),
],
),
),
],
),
),
],
);
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