init

lib/polling.dart

@@ -0,0 +1,64 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+
+const pollInterval = Duration(seconds: 5);
+
+/// Calls [onPoll] every five seconds while the app is resumed.
+class ForegroundPoll extends StatefulWidget {
+  const ForegroundPoll({super.key, required this.onPoll, required this.child});
+
+  final Future<void> Function() onPoll;
+  final Widget child;
+
+  @override
+  State<ForegroundPoll> createState() => _ForegroundPollState();
+}
+
+class _ForegroundPollState extends State<ForegroundPoll>
+    with WidgetsBindingObserver {
+  Timer? _timer;
+
+  @override
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance.addObserver(this);
+    _start();
+  }
+
+  @override
+  void dispose() {
+    _stop();
+    WidgetsBinding.instance.removeObserver(this);
+    super.dispose();
+  }
+
+  @override
+  void didChangeAppLifecycleState(AppLifecycleState state) {
+    switch (state) {
+      case AppLifecycleState.resumed:
+        _start();
+        unawaited(widget.onPoll());
+      case AppLifecycleState.paused:
+      case AppLifecycleState.hidden:
+      case AppLifecycleState.detached:
+        _stop();
+      case AppLifecycleState.inactive:
+        break;
+    }
+  }
+
+  void _start() {
+    _timer ??= Timer.periodic(pollInterval, (_) {
+      unawaited(widget.onPoll());
+    });
+  }
+
+  void _stop() {
+    _timer?.cancel();
+    _timer = null;
+  }
+
+  @override
+  Widget build(BuildContext context) => widget.child;
+}