How to do http requests periodically correctly? - flutter

Question

I want to make requests in the background every 30 seconds and foreground every 5 seconds, how to use Stream in this case?
here is my code:
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> with WidgetsBindingObserver {
#override
void didChangeAppLifecycleState(AppLifecycleState state) {
super.didChangeAppLifecycleState(state);
if (state == AppLifecycleState.resumed) {
// background proccess off
setPost(30);
} else {
// background proccess on
setPost(5);
}
}
Stream<int> setPost(int seconds) async* {
yield* Stream.periodic(Duration(seconds: seconds), (int i) {
post();
return i;
});
}
void post() async {
try {
var header = {
"Content-Type": "application/json",
};
var response = await http.post(url, headers: header);
if (response.statusCode == 200) {
print(response.body);
} else {
print(response.body);
}
} on SocketException catch (_) {
print('not connected');
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Container(),
);
}
}

Answer 1

Just use Timer.pediodic:
class _MyHomePageState extends State<MyHomePage> with WidgetsBindingObserver {
Timer timer;
bool waitingForResponse = false;
#override
void initState() {
super.initState();
WidgetsBinding.instance.addObserver(this); // Adding an observer
setTimer(false); // Setting a timer on init
}
#override
void dispose() {
timer?.cancel(); // Cancelling a timer on dispose
WidgetsBinding.instance.removeObserver(this); // Removing an observer
super.dispose();
}
#override
void didChangeAppLifecycleState(AppLifecycleState state) {
super.didChangeAppLifecycleState(state);
setTimer(state != AppLifecycleState.resumed);
}
void setTimer(bool isBackground) {
int delaySeconds = isBackground ? 5 : 3;
// Cancelling previous timer, if there was one, and creating a new one
timer?.cancel();
timer = Timer.periodic(Duration(seconds: delaySeconds), (t) async {
// Not sending a request, if waiting for response
if (!waitingForResponse) {
waitingForResponse = true;
await post();
waitingForResponse = false;
}
});
}
// Async method returns Future<> object
Future<void> post() async {
...
}
...