我正在创建一个流构建器，列出要拉出的用户列表。我正在使用ListView.builder()和Cards放在其中。但是，我遇到了很多错误，尤其是与NEEDS-LAYOUT NEEDS-PAINT
这是代码：
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:mobile_hiking_app/Constants.dart';
import 'Database.dart';
import 'HikerPage.dart';
class Hikers extends StatefulWidget {
@override
_Hikers createState() => new _Hikers();
}
Database temp = new Database();
Card profileCard(String name, var miles, String profPic) {
if (name != globalUserName) {
if (miles == null) {
miles = 0;
}
if (profPic == "") {
profPic =
"https://amp.businessinsider.com/images/5899ffcf6e09a897008b5c04-750-750.jpg";
}
return new Card(
child: new Column(mainAxisSize: MainAxisSize.min, children: <Widget>[
ListTile(
leading: CircleAvatar(backgroundImage: NetworkImage(profPic)),
title: Text(name),
subtitle: new Text("Miles Hiked: " + miles.toString()),
),
]));
}
else {return null;}
}
class _Hikers extends State<Hikers> {
@override
void initState() {
super.initState();
}
Widget build(BuildContext context) {
Color lightDark = Color(0xff243447);
return new Scaffold(
appBar: new AppBar(
backgroundColor: lightDark,
title: new Text("Hikers"),
actions: <Widget>[],
),
body: new Column(children: <Widget>[
new Flexible(
child: StreamBuilder(
stream: Firestore.instance.collection("USERS").snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) {
return Container(child: Center(child: Text("No data")));
}
return ListView.builder(
padding: EdgeInsets.all(8.0),
reverse: false,
itemCount: snapshot.data.documents.length-1,
itemBuilder: (BuildContext context, int index) {
String user = snapshot.data.documents[index]["Name"];
var miles =
snapshot.data.documents[index]["MilesHiked"];
String profPic =
snapshot.data.documents[index]["profilePic"];
return new GestureDetector(
onTap: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => HikerPage(
name: user,
profPic: profPic,
miles: miles.toString(),
)),
);
},
child: profileCard(user, miles, profPic),
);
});
})),
]));
}
}
这是错误：
flutter: ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
flutter: The following assertion was thrown during performLayout():
flutter: RenderPointerListener object was given an infinite size during layout.
flutter: This probably means that it is a render object that tries to be as big as possible, but it was put
flutter: inside another render object that allows its children to pick their own size.
flutter: The nearest ancestor providing an unbounded height constraint is:
flutter: RenderIndexedSemantics#fec43 relayoutBoundary=up3 NEEDS-LAYOUT NEEDS-PAINT
flutter: creator: IndexedSemantics ← NotificationListener<KeepAliveNotification> ← KeepAlive ←
flutter: AutomaticKeepAlive ← SliverList ← SliverPadding ← Viewport ← IgnorePointer-[GlobalKey#35708] ←
flutter: Semantics ← Listener ← _GestureSemantics ←
flutter: RawGestureDetector-[LabeledGlobalKey<RawGestureDetectorState>#2dfed] ← ⋯
flutter: parentData: index=0; layoutOffset=0.0 (can use size)
flutter: constraints: BoxConstraints(w=398.0, 0.0<=h<=Infinity)
flutter: semantic boundary
flutter: size: Size(398.0, Infinity)
flutter: index: 0
flutter: The constraints that applied to the RenderPointerListener were:
flutter: BoxConstraints(w=398.0, 0.0<=h<=Infinity)
flutter: The exact size it was given was:
flutter: Size(398.0, Infinity)
flutter: See https://flutter.dev/layout/ for more information.
flutter:
flutter: When the exception was thrown, this was the stack:
flutter: #0 RenderBox.debugAssertDoesMeetConstraints.<anonymous closure>
package:flutter/…/rendering/box.dart:1749
flutter: #1 RenderBox.debugAssertDoesMeetConstraints
package:flutter/…/rendering/box.dart:1823
flutter: #2 RenderBox.size=.<anonymous closure>
package:flutter/…/rendering/box.dart:1543
flutter: #3 RenderBox.size=
package:flutter/…/rendering/box.dart:1543
flutter: #4 RenderPointerListener.performResize
package:flutter/…/rendering/proxy_box.dart:2613
flutter: #5 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:108
flutter: #6 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #7 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #8 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #9 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #10 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #11 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #12 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #13 RenderSliverList.performLayout
package:flutter/…/rendering/sliver_list.dart:165
flutter: #14 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #15 RenderSliverPadding.performLayout
package:flutter/…/rendering/sliver_padding.dart:182
flutter: #16 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #17 RenderViewportBase.layoutChildSequence
package:flutter/…/rendering/viewport.dart:407
flutter: #18 RenderViewport._attemptLayout
package:flutter/…/rendering/viewport.dart:1322
flutter: #19 RenderViewport.performLayout
package:flutter/…/rendering/viewport.dart:1240
flutter: #20 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #21 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #22 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #23 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #24 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #25 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #26 RenderObject.layout
flutter: #27 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #28 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #29 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #30 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #31 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #32 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #33 RenderFlex.performLayout
package:flutter/…/rendering/flex.dart:799
flutter: #34 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #35 MultiChildLayoutDelegate.layoutChild
package:flutter/…/rendering/custom_layout.dart:142
flutter: #36 _ScaffoldLayout.performLayout
package:flutter/…/material/scaffold.dart:431
flutter: #37 MultiChildLayoutDelegate._callPerformLayout
package:flutter/…/rendering/custom_layout.dart:212
flutter: #38 RenderCustomMultiChildLayoutBox.performLayout
package:flutter/…/rendering/custom_layout.dart:356
flutter: #39 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #40 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #41 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #42 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #43 _RenderCustomClip.performLayout
package:flutter/…/rendering/proxy_box.dart:1206
flutter: #44 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #45 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #46 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #47 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #48 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #49 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #50 RenderObject.layout
flutter: #51 RenderStack.performLayout
package:flutter/…/rendering/stack.dart:510
flutter: #52 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #53 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #54 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #55 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #56 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #57 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #58 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #59 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #60 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #61 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #62 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #63 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #64 RenderOffstage.performLayout
package:flutter/…/rendering/proxy_box.dart:3015
flutter: #65 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #66 RenderStack.performLayout
package:flutter/…/rendering/stack.dart:510
flutter: #67 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #68 __RenderTheatre&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #69 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #70 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #71 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #72 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #73 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #74 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #75 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #76 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout
package:flutter/…/rendering/proxy_box.dart:105
flutter: #77 RenderObject.layout
package:flutter/…/rendering/object.dart:1644
flutter: #78 RenderView.performLayout
package:flutter/…/rendering/view.dart:151
flutter: #79 RenderObject._layoutWithoutResize
package:flutter/…/rendering/object.dart:1519
flutter: #80 PipelineOwner.flushLayout
package:flutter/…/rendering/object.dart:766
flutter: #81 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding.drawFrame
package:flutter/…/rendering/binding.dart:347
flutter: #82 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame
package:flutter/…/widgets/binding.dart:701
flutter: #83 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback
package:flutter/…/rendering/binding.dart:286
flutter: #84 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback
package:flutter/…/scheduler/binding.dart:1012
flutter: #85 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame
package:flutter/…/scheduler/binding.dart:952
flutter: #86 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.scheduleWarmUpFrame.<anonymous closure>
package:flutter/…/scheduler/binding.dart:773
flutter: #88 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:382:19)
flutter: #89 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:416:5)
flutter: #90 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:171:12)
flutter: (elided one frame from package dart:async-patch)
flutter:
flutter: The following RenderObject was being processed when the exception was fired:
flutter: RenderPointerListener#9a81c relayoutBoundary=up6 NEEDS-LAYOUT NEEDS-PAINT
flutter: creator: Listener ← _GestureSemantics ← RawGestureDetector ← GestureDetector ←
flutter: RepaintBoundary-[<0>] ← IndexedSemantics ← NotificationListener<KeepAliveNotification> ← KeepAlive
flutter: ← AutomaticKeepAlive ← SliverList ← SliverPadding ← Viewport ← ⋯
flutter: parentData: <none> (can use size)
flutter: constraints: BoxConstraints(w=398.0, 0.0<=h<=Infinity)
flutter: size: Size(398.0, Infinity)
flutter: behavior: translucent
flutter: listeners: down
flutter: This RenderObject has no descendants.
flutter: ════════════════════════════════════════════════════════════════════════════════════════════════════
flutter: Another exception was thrown: RenderSemanticsGestureHandler object was given an infinite size during layout.
flutter: Another exception was thrown: RenderRepaintBoundary object was given an infinite size during layout.
flutter: Another exception was thrown: RenderIndexedSemantics object was given an infinite size during layout.
Reloaded 8 of 580 libraries in 813ms.
flutter: Another exception was thrown: RenderIndexedSemantics object was given an infinite size during layout.
flutter: Another exception was thrown: 'package:flutter/src/rendering/sliver_multi_box_adaptor.dart': Failed assertion: line 470 pos 12: 'child.hasSize': is not true.