better support for background tasks that fire state changes anytime, even when flutter in the process of building a frame

Author: devxpy

example/lib/main.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:shared_value/shared_value.dart';
 
@@ -8,12 +10,19 @@ final SharedValue<int> counter = SharedValue(
   autosave: true, // autosave to shared prefs when value changes
 );
 
+final SharedValue<Duration> randomValue = SharedValue();
+
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
 
   // load previous value from shared prefs
   counter.load();
 
+  DateTime startedAt = DateTime.now();
+  Timer.periodic(Duration(milliseconds: 50), (timer) {
+    randomValue.$ = DateTime.now().difference(startedAt);
+  });
+
   runApp(
     // don't forget this!
     SharedValue.wrapApp(
@@ -44,6 +53,10 @@ class MyApp extends StatelessWidget {
                 'You have pushed the button this many times:',
               ),
               CounterText(),
+              Padding(
+                padding: const EdgeInsets.all(32),
+                child: RandomText(),
+              ),
             ],
           ),
         ),
@@ -56,11 +69,11 @@ class MyApp extends StatelessWidget {
 class CounterText extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
-    print("CounterText.build()");
-
     // The .of(context) bit makes this widget rebuild automatically
     int counterValue = counter.of(context);
 
+    print("CounterText.build() - $counterValue");
+
     return Text(
       '$counterValue',
       style: Theme.of(context).textTheme.headline4,
@@ -85,3 +98,10 @@ class CounterButton extends StatelessWidget {
     counter.$ += 1;
   }
 }
+
+class RandomText extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return Text("Your time here: ${randomValue.of(context)}");
+  }
+}

example/pubspec.lock

@@ -127,7 +127,7 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "0.3.0"
+    version: "0.3.1"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -190,5 +190,5 @@ packages:
     source: hosted
     version: "2.1.0-nullsafety.3"
 sdks:
-  dart: ">=2.10.0-110 <2.11.0"
+  dart: ">=2.10.0 <2.11.0"
   flutter: ">=1.12.13+hotfix.4 <2.0.0"

example/pubspec.yaml

@@ -14,7 +14,7 @@ description: A new Flutter project.
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.1.0 <3.0.0"
+  sdk: ">=2.10.0 <3.0.0"
 
 dependencies:
   flutter:

lib/manager_widget.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart';
 
 import 'inherited_model.dart';
@@ -8,12 +9,11 @@ class StateManagerWidget extends StatefulWidget {
   final StateManagerWidgetState state;
   final Map<SharedValue, double> stateNonceMap;
 
-  const StateManagerWidget(
-    this.child,
-    this.state,
-    this.stateNonceMap, {
-    Key key,
-  }) : super(key: key);
+  const StateManagerWidget(this.child,
+      this.state,
+      this.stateNonceMap, {
+        Key key,
+      }) : super(key: key);
 
   @override
   StateManagerWidgetState createState() {
@@ -22,10 +22,9 @@ class StateManagerWidget extends StatefulWidget {
 }
 
 class StateManagerWidgetState extends State<StateManagerWidget> {
-  void rebuild() {
-    WidgetsBinding.instance.addPostFrameCallback((_) {
-      if (mounted) setState(() {});
-    });
+  Future<void> rebuild() async {
+    await SchedulerBinding.instance.endOfFrame;
+    if (mounted) setState(() {});
   }
 
   @override