我似乎无法解决这个问题，所以如果有人可以帮助我，我有点被困住了！
import 'dart:async';
import 'dart:convert';
import 'package:http/http.dart' as HTTP;
import 'package:flutter/material.dart';
import 'package:coding/Data.dart';
void main()=>
runApp(new MaterialApp(
home: MyApp(),
debugShowCheckedModeBanner: false,
));
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
@override
Widget build(BuildContext context) {
try {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.transparent,
actions: [new IconButton(icon: Icon(Icons.arrow_back_ios), onPressed: (){}),],
),
body: ListView(
children: <Widget>[
new Container(
height: 500.0,
margin: EdgeInsets.all(7.0),
child: new FutureBuilder(
future: getAllData(),
builder: (BuildContext c,AsyncSnapshot snapshot) {
return ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (BuildContext c,int index) {
return Card(
elevation: 10.0,
child: new Column(
children: <Widget>[
new Image.network(snapshot.data[index].link,
height: 150.0,
width: 150.0,
fit: BoxFit.cover,),
],
),
);
},);
},
),
),
]
),
);
}
catch (e){
}
}
}
Future<List<Data>> getAllData() async{
var api="https://www.awanmart.com/wp-json/wp/v2/categories";
var data=await http.get(api);
var jsonData=json.decode(data.body);
List<Data>listOf=[];
for(var i in jsonData){
Data data=new Data(i["id"],i ["count"], i["description"], i["link"], i["name"], i["slug"],I
["taxonomy"], i["parent"],i ["meta"], i["_links"], i["self"], i["href"], i["collection"],
i["about"], i["post_type"], i["curies"], i["templated"]);
}
return jsonData;
}
（这是我的Debugconsole）
═╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════ The following NoSuchMethodError was thrown building FutureBuilder<List<Data>>(dirty, state:
_FutureBuilderState<List<Data>>#d53db): The getter 'length' was called on null. Receiver: null Tried calling: length
The relevant error-causing widget was:
FutureBuilder<List<Data>> file:///D:/myappp/coding/lib/main.dart:32:28
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
#1 _MyAppState.build.<anonymous closure> (package:coding/main.dart:36:50)
#2 _FutureBuilderState.build (package:flutter/src/widgets/async.dart:740:55)
#3 StatefulElement.build (package:flutter/src/widgets/framework.dart:4663:28)
#4 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4546:15)
#5 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4719:11)
#6 Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
#7 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4525:5)
#8 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4710:11)
#9 ComponentElement.mount (package:flutter/src/widgets/framework.dart:4520:5) ... Normal element mounting (45 frames)
#54 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3490:14)
#55 Element.updateChild (package:flutter/src/widgets/framework.dart:3258:18)
#56 SliverMultiBoxAdaptorElement.updateChild (package:flutter/src/widgets/sliver.dart:1164:36)
#57 SliverMultiBoxAdaptorElement.createChild.<anonymous closure> (package:flutter/src/widgets/sliver.dart:1149:20)
#58 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2620:19)
#59 SliverMultiBoxAdaptorElement.createChild (package:flutter/src/widgets/sliver.dart:1142:11)
#60 RenderSliverMultiBoxAdaptor._createOrObtainChild d.<anonymous closure> (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:356:23)
#61 RenderObject.invokeLayoutCallback.<anonymous closure> (package:flutter/src/rendering/object.dart:1868:58)
#62 PipelineOwner._enableMutationsToDirtySubtrees (package:flutter/src/rendering/object.dart:920:15)
#63 RenderObject.invokeLayoutCallback (package:flutter/src/rendering/object.dart:1868:13)
#64 RenderSliverMultiBoxAdaptor._createOrObtainChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:345:5)
#65 RenderSliverMultiBoxAdaptor.addInitialChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:429:5)
#66 RenderSliverList.performLayout (package:flutter/src/rendering/sliver_list.dart:81:12)
#67 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#68 RenderSliverEdgeInsetsPadding.performLayout (package:flutter/src/rendering/sliver_padding.dart:137:11)
#69 RenderSliverPadding.performLayout (package:flutter/src/rendering/sliver_padding.dart:377:11)
#70 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#71 RenderViewportBase.layoutChildSequence (package:flutter/src/rendering/viewport.dart:471:13)
#72 RenderViewport._attemptLayout (package:flutter/src/rendering/viewport.dart:1465:12)
#73 RenderViewport.performLayout (package:flutter/src/rendering/viewport.dart:1374:20)
#74 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#75 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#76 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#77 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#78 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#79 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#80 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#81 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#82 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#83 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#84 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#85 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#86 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#87 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#88 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#89 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#90 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#91 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#92 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#93 MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:173:11)
#94 _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:495:7)
#95 MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:242:7)
#96 RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:401:14)
#97 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#98 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#99 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#100 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#101 _RenderCustomClip.performLayout (package:flutter/src/rendering/proxy_box.dart:1269:11)
#102 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#103 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#104 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#105 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#106 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#107 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#108 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#109 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#110 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#111 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#112 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#113 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#114 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#115 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#116 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#117 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#118 RenderOffstage.performLayout (package:flutter/src/rendering/proxy_box.dart:3228:13)
#119 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#120 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#121 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#122 _RenderTheatre.performLayout (package:flutter/src/widgets/overlay.dart:702:15)
#123 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#124 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#125 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#126 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#127 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#128 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#129 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#130 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#131 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#132 RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:115:13)
#133 RenderObject.layout (package:flutter/src/rendering/object.dart:1769:7)
#134 RenderView.performLayout (package:flutter/src/rendering/view.dart:170:13)
#135 RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1632:7)
#136 PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:889:18)
#137 RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:404:19)
#138 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:867:13)
#139 RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:286:5)
#140 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1117:15)
#141 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1056:9)
#142 SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:865:7) (elided 11 frames from class _RawReceivePortImpl, class _Timer, dart:async, and dart:async-patch)
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答案 0 :(得分：0)
据我所知，您不会检查# Note: This must be an executable or DLL compiled for .NET
$Path = "D:\calc.exe"
# Get Base64-encoded representation of the bytes that make up the assembly.
$bytes = [System.IO.File]::ReadAllBytes($Path)
$string = [System.Convert]::ToBase64String($bytes)
# ...
# Convert the Base64-encoded string back to a byte array, load
# the byte array as an assembly, and save the object representing the
# loaded assembly for later use.
$bytes = [System.Convert]::FromBase64String($string)
$assembly = [System.Reflection.Assembly]::Load($bytes)
# Get the static method that is the executable's entry point.
# Note: Assumes 'ConsoleApp' as the class name, and a static method named 'Main' as the entry point.
$entryPointMethod = $assembly.
GetType('ConsoleApp', [Reflection.BindingFlags] 'Public, NonPublic').
GetMethod('Main', [Reflection.BindingFlags] 'Static, Public, NonPublic')
# Now you can call the entry point.
# This example passes two arguments, 'foo' and 'bar'
$entryPointMethod.Invoke($null, (, [string[]] ('foo', 'bar')))
是否不是snapshot：
null应该看起来像这样：
builder: (BuildContext c,AsyncSnapshot snapshot) {
return ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (BuildContext c,int index) {
return Card(
elevation: 10.0,