[英]FutureBuilder not working as intended in flutter
I am fetching json from here: https://api.myjson.com/bins/1g3xpe , in my flutter app. 我正在从我的flutter应用程序中从这里获取json: https ://api.myjson.com/bins/1g3xpe。
Here is the code (I have removed unrelated part).The issue is, FutureBuilder's builder part is never getting called. 这是代码(我删除了不相关的部分)。问题是,FutureBuilder的生成器部分永远不会被调用。 This line
debugPrint(snapshot.hasData.toString());
这行
debugPrint(snapshot.hasData.toString());
is never getting called. 永远不会被打电话。
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:nirmithi/objects/project.dart';
import 'dart:convert';
class Projects extends StatefulWidget {
@override
ProjectsState createState() => new ProjectsState();
}
class ProjectsState extends State<Projects> {
@override
Widget build(BuildContext context) {
return Scaffold(
primary: true,
appBar: EmptyAppBar(),
body: Column(
children: <Widget>[
headerWidget(),
Container(
child: futureBuilder(),
)
],
),
);
}
@override
void setState(fn) {
super.setState(fn);
}
}
Future<List<Project>> getData() async {
String getProjects = "https://api.myjson.com/bins/1g3xpe";
final response = await http.get(getProjects);
if (response.statusCode == 200) {
List responseJson = json.decode(response.body);
return responseJson.map((m) => Project.fromJson(m)).toList();
} else
throw Exception(response.toString());
}
Widget futureBuilder() {
FutureBuilder<List<Project>>(
future: getData(),
builder: (context, snapshot) {
debugPrint(snapshot.hasData.toString());
},
);
return Center(
child: CircularProgressIndicator(),
);
}
Widget listWidget(List<Project> data) {
return ListView.builder(
itemCount: data.length,
itemBuilder: (BuildContext context, int index) {
listItem(data.elementAt(index));
},
);
}
Widget listItem(Project project) {
return Card(
elevation: 6.0,
child: Column(
children: <Widget>[Text(project.projectId), Text(project.projectName)],
),
);
}
class EmptyAppBar extends StatelessWidget implements PreferredSizeWidget {
@override
Widget build(BuildContext context) {
return Container();
}
@override
Size get preferredSize => Size(0.0, 0.0);
}
UPDATE: This is the code in builder part which I removed to debug. 更新:这是构建器部分中的代码,我已删除其进行调试。
switch (snapshot.connectionState) {
case ConnectionState.none:
case ConnectionState.waiting:
return new Text('loading...');
default:
if (snapshot.hasError)
return new Text('Error: ${snapshot.error}');
else
return listWidget(snapshot.data);
}
You need to return your FutureBuilder
so its part of the widget tree: 您需要返回
FutureBuilder
,使其成为小部件树的一部分:
Widget futureBuilder() {
return FutureBuilder<List<Project>>(
future: getData(),
builder: (context, snapshot) {
// ...
},
);
}
Simply creating an instance of it wouldn't resolve the future. 简单地创建它的实例并不能解决未来。
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