Experiment with backgroundFetch for android

This sadly requires the minSdkVersion to be bumped to 30.

android/app/build.gradle

@@ -42,7 +42,7 @@ if (!keystoreProperties.containsKey('keyAlias')) {
 }
 
 android {
-    compileSdkVersion 29
+    compileSdkVersion rootProject.ext.compileSdkVersion
 
     lintOptions {
         disable 'InvalidPackage'
@@ -51,7 +51,7 @@ android {
     defaultConfig {
         applicationId "io.gitjournal.gitjournal"
         minSdkVersion 21
-        targetSdkVersion 29
+        targetSdkVersion rootProject.ext.targetSdkVersion
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

android/app/src/main/AndroidManifest.xml

@@ -5,6 +5,7 @@ SPDX-License-Identifier: Apache-2.0
 -->
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
     package="io.gitjournal.gitjournal">
 
     <uses-permission android:name="android.permission.INTERNET"/>
@@ -17,6 +18,7 @@ SPDX-License-Identifier: Apache-2.0
     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
 
     <application
+        tools:replace="android:label"
         android:label="@string/app_name"
         android:icon="@mipmap/launcher_icon"
         android:requestLegacyExternalStorage="true">

android/build.gradle

@@ -3,6 +3,12 @@
 // SPDX-License-Identifier: Apache-2.0
 
 buildscript {
+    ext.kotlin_version = '1.3.72'
+    ext {
+        compileSdkVersion   = 30
+        targetSdkVersion    = 30
+        appCompatVersion    = "1.1.0"
+    }
     repositories {
         google()
         jcenter()
@@ -19,7 +25,8 @@ allprojects {
         jcenter()
 
         maven {
-            url 'https://maven.google.com/'
+            // [required] background_fetch
+            url "${project(':background_fetch').projectDir}/libs"
         }
     }
 }

lib/experiments/main_background.dart

@@ -0,0 +1,156 @@
+import 'dart:async';
+import 'package:flutter/material.dart';
+
+import 'package:background_fetch/background_fetch.dart';
+
+// [Android-only] This "Headless Task" is run when the Android app
+// is terminated with enableHeadless: true
+void backgroundFetchHeadlessTask(HeadlessTask task) async {
+  String taskId = task.taskId;
+  bool isTimeout = task.timeout;
+  if (isTimeout) {
+    // This task has exceeded its allowed running-time.
+    // You must stop what you're doing and immediately .finish(taskId)
+    print("[BackgroundFetch] Headless task timed-out: $taskId");
+    BackgroundFetch.finish(taskId);
+    return;
+  }
+  print('[BackgroundFetch] Headless event received.');
+  // Do your work here...
+  BackgroundFetch.finish(taskId);
+}
+
+void main() {
+  // Enable integration testing with the Flutter Driver extension.
+  // See https://flutter.io/testing/ for more info.
+  runApp(MyApp());
+
+  // Register to receive BackgroundFetch events after app is terminated.
+  // Requires {stopOnTerminate: false, enableHeadless: true}
+  BackgroundFetch.registerHeadlessTask(backgroundFetchHeadlessTask);
+}
+
+class MyApp extends StatefulWidget {
+  @override
+  _MyAppState createState() => _MyAppState();
+}
+
+class _MyAppState extends State<MyApp> {
+  bool _enabled = true;
+  int _status = 0;
+  final List<DateTime> _events = [];
+
+  @override
+  void initState() {
+    super.initState();
+    initPlatformState();
+  }
+
+  // Platform messages are asynchronous, so we initialize in an async method.
+  Future<void> initPlatformState() async {
+    // Configure BackgroundFetch.
+    int status = await BackgroundFetch.configure(
+        BackgroundFetchConfig(
+            minimumFetchInterval: 15,
+            stopOnTerminate: false,
+            enableHeadless: true,
+            requiresBatteryNotLow: false,
+            requiresCharging: false,
+            requiresStorageNotLow: false,
+            requiresDeviceIdle: false,
+            requiredNetworkType: NetworkType.NONE), (String taskId) async {
+      // <-- Event handler
+      // This is the fetch-event callback.
+      print("[BackgroundFetch] Event received $taskId");
+      setState(() {
+        _events.insert(0, DateTime.now());
+      });
+      // IMPORTANT:  You must signal completion of your task or the OS can punish your app
+      // for taking too long in the background.
+      BackgroundFetch.finish(taskId);
+    }, (String taskId) async {
+      // <-- Task timeout handler.
+      // This task has exceeded its allowed running-time.  You must stop what you're doing and immediately .finish(taskId)
+      print("[BackgroundFetch] TASK TIMEOUT taskId: $taskId");
+      BackgroundFetch.finish(taskId);
+    });
+    print('[BackgroundFetch] configure success: $status');
+    setState(() {
+      _status = status;
+    });
+
+    // If the widget was removed from the tree while the asynchronous platform
+    // message was in flight, we want to discard the reply rather than calling
+    // setState to update our non-existent appearance.
+    if (!mounted) return;
+  }
+
+  void _onClickEnable(enabled) {
+    setState(() {
+      _enabled = enabled;
+    });
+    if (enabled) {
+      BackgroundFetch.start().then((int status) {
+        print('[BackgroundFetch] start success: $status');
+      }).catchError((e) {
+        print('[BackgroundFetch] start FAILURE: $e');
+      });
+    } else {
+      BackgroundFetch.stop().then((int status) {
+        print('[BackgroundFetch] stop success: $status');
+      });
+    }
+  }
+
+  void _onClickStatus() async {
+    int status = await BackgroundFetch.status;
+    print('[BackgroundFetch] status: $status');
+    setState(() {
+      _status = status;
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      home: Scaffold(
+        appBar: AppBar(
+            title: const Text('BackgroundFetch Example',
+                style: TextStyle(color: Colors.black)),
+            backgroundColor: Colors.amberAccent,
+            actions: <Widget>[
+              Switch(value: _enabled, onChanged: _onClickEnable),
+            ]),
+        body: Container(
+          color: Colors.black,
+          child: ListView.builder(
+              itemCount: _events.length,
+              itemBuilder: (BuildContext context, int index) {
+                DateTime timestamp = _events[index];
+                return InputDecorator(
+                    decoration: const InputDecoration(
+                        contentPadding:
+                            EdgeInsets.only(left: 10.0, top: 10.0, bottom: 0.0),
+                        labelStyle: TextStyle(
+                            color: Colors.amberAccent, fontSize: 20.0),
+                        labelText: "[background fetch event]"),
+                    child: Text(timestamp.toString(),
+                        style: const TextStyle(
+                            color: Colors.white, fontSize: 16.0)));
+              }),
+        ),
+        bottomNavigationBar: BottomAppBar(
+            child: Row(children: <Widget>[
+          ElevatedButton(
+              onPressed: _onClickStatus, child: const Text('Status')),
+          Container(
+              child: Text("$_status"),
+              margin: const EdgeInsets.only(left: 20.0))
+        ])),
+      ),
+    );
+  }
+}
+
+// Stuff to be saved -
+// (gitRepo, remoteName, lastSyncedWhen, lastError)

pubspec.lock

@@ -78,6 +78,15 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "3.0.0-nullsafety.0"
+  background_fetch:
+    dependency: "direct main"
+    description:
+      path: "."
+      ref: HEAD
+      resolved-ref: "724a13feeead45dcc491a9d52f867bf6f9c86d50"
+      url: "https://github.com/Fishbowler/flutter_background_fetch.git"
+    source: git
+    version: "1.0.1"
   badges:
     dependency: "direct main"
     description:

pubspec.yaml

@@ -96,6 +96,8 @@ dependencies:
       url: https://github.com/NearHuscarl/flutter_login.git
       ref: develop
   android_external_storage: ^0.1.0
+  background_fetch:
+    git: https://github.com/Fishbowler/flutter_background_fetch.git
 
 dev_dependencies:
   #flutter_driver: