I am trying to show data from api and while loading data , there should be shown a circularprogressindicator,

but when I start app..it directly showing data instead of circularprogressindicator

class _HomeScreenState extends State<HomeScreen> {
  bool isloading = false;
  var maplist ;
  Future<void> fetchdata() async {

   setState(() {
     isloading=true;
   });
    var resp =
        await http.get(Uri.parse("https://jsonplaceholder.typicode.com/posts"));
    maplist = json.decode(resp.body);
   setState(() {
      isloading = false;
       });
  }
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    fetchdata();
  }

  @override
  Widget build(BuildContext context) {
    return SafeArea(
        child: Scaffold(
      body: MyBody(),
    ));
  }

  MyBody() {
    return isloading==true ? Center(child: CircularProgressIndicator()) : ListView.builder(
        itemCount: maplist.length,
        itemBuilder: (context,index){
          return Container(
            padding: EdgeInsets.all(8.0),
              
              child: Text(maplist[index]['title']));
        });
  }
}

CodePudding user response：

It's actually working perfectly fine, it shows too fast because it is receiving data quickly( could be cache case).

If you like to have more delay you can add, future.delay which is unnecessary

  Future<void> fetchdata() async {
    setState(() {
      isloading = true;
    });
    var resp =
        await http.get(Uri.parse("https://jsonplaceholder.typicode.com/posts"));
    maplist = json.decode(resp.body);
    // get more delay
    await Future.delayed(Duration(seconds: 2));
    setState(() {
      isloading = false;
    });
  }

A better of way of handling future method with FutureBuilder

CodePudding user response：

You need to use FutureBuilder, it is not good to use async function in initState, try this:

FutureBuilder<List<Map>>(
        future: fetchdata(),
        builder: (context, snapshot) {
          switch (snapshot.connectionState) {
            case ConnectionState.waiting:
              return Center(child: CircularProgressIndicator());
            default:
              if (snapshot.hasError) {
                return Text('Error: ${snapshot.error}');
              } else {
                List<Map> data = snapshot.data ?? [];

                return ListView.builder(
                    itemCount: data.length,
                    itemBuilder: (context, index) {
                      return Container(
                          padding: EdgeInsets.all(8.0),
                          child: Text(data[index]['title']));
                    });
              }
          }
        },
      ),

also you need to change your fetchdata to this:

Future<List<Map>> fetchdata() async {
    var resp =
        await http.get(Uri.parse("https://jsonplaceholder.typicode.com/posts"));
    return json.decode(resp.body);
  }

CodePudding user response：

Try the following code:

class _HomeScreenState extends State<HomeScreen> {
  var maplist;
  Future<void> fetchdata() async {
    var resp =
        await http.get(Uri.parse("https://jsonplaceholder.typicode.com/posts"));
    setState(() {
      maplist = json.decode(resp.body);
    }
  }

  @override
  Widget build(BuildContext context) {
    return SafeArea(
        child: Scaffold(
      body: MyBody(),
    ));
  }

  MyBody() {
    return FutureBuilder(
      future: fetchdata(),
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const CircularProgressIndicator();
        }

        return ListView.builder(
        itemCount: maplist.length,
        itemBuilder: (context,index){
          return Container(
            padding: EdgeInsets.all(8.0),
              
              child: Text(maplist[index]['title']));
        });
      }
  }
}

CodePudding user response：

Try this one,set isloading default true

class _HomeScreenState extends State<HomeScreen> {
  bool isloading = true;
  var maplist ;
  Future<void> fetchdata() async {

    var resp =
        await http.get(Uri.parse("https://jsonplaceholder.typicode.com/posts"));
    maplist = json.decode(resp.body);
   setState(() {
      isloading = false;
       });
  }
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    fetchdata();
  }

  @override
  Widget build(BuildContext context) {
    return SafeArea(
        child: Scaffold(
      body: MyBody(),
    ));
  }

  MyBody() {
    return isloading ? Center(child: CircularProgressIndicator()) : ListView.builder(
        itemCount: maplist.length,
        itemBuilder: (context,index){
          return Container(
            padding: EdgeInsets.all(8.0),
              
              child: Text(maplist[index]['title']));
        });
  }
}

CodePudding user response：

You can use like that

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

class HomeScreen extends StatefulWidget {
  const HomeScreen({super.key});

  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  bool isloading = false;
  var maplist;
  Future<void> fetchdata() async {
    setState(() {
      isloading = true;
    });
    var resp = await http.get(Uri.parse("https://jsonplaceholder.typicode.com/posts"));
    maplist = json.decode(resp.body);

    setState(() {
      isloading = false;
    });
  }

  @override
  void initState() {
    super.initState();
    fetchdata();
  }

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: isloading ? const CircularProgressIndicator() : const MyBody(),
    );
  }
}

class MyBody extends StatelessWidget {
  const MyBody({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      //Write your code here
    );
  }
}