1. 问题描述
我的目标是构建一个Flutter应用,使用这个workmanager插件和这个location插件获取定期的位置更新。但是当我的Workmanager回调触发时,我无法正确加载Location插件。我收到以下错误信息:
MissingPluginException(No implementation found for method getLocation on channel lyokone/location)
基本上,问题在于当Workmanager插件尝试运行dart代码时,它没有加载Location插件。
2. 其他我研究过的资源
我发现其他人也面临同样的问题,这里, 这里, 和 这里。
据我所知,这些问题提供的解决方案归结为:创建一个名为CustomApplication.java的文件,它扩展了FlutterApplication,并注册您的插件。然后在AndoidManifest.xml文件中注册CustomApplication.java文件。
3. 我迄今为止的代码
我尝试制作一个最基本的应用程序,实现我需要的功能:
1. 实现Workmanager插件(工作正常) 2. 实现Location插件(工作正常) 3. 尝试组合这些特性(不起作用)
要查看我在每个步骤中所做的确切内容,请看这里:https://gitlab.com/tomoerlemans/workmanager_with_location/-/commits/master。(此存储库还可用于快速复制该问题)。
相关的代码文件如下:
main.dart
import 'package:flutter/material.dart';
import 'package:workmanager/workmanager.dart';
import 'package:location/location.dart';
void main() {
WidgetsFlutterBinding.ensureInitialized();
Workmanager.initialize(callbackDispatcher, isInDebugMode: true);
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
RaisedButton(
onPressed: () {
Workmanager.registerPeriodicTask(
"1", "simpleTask");
},
child: Text("Start workmanager"),
),
RaisedButton(
onPressed: () {
getLocation();
},
child: Text("Get current location"),
),
],
),
),
);
}
}
void callbackDispatcher() {
Workmanager.executeTask((task, inputData) {
print("Native called background task at ${DateTime.now().toString()}");
getLocation();
return Future.value(true);
});
}
void getLocation() async {
LocationData currentLocation;
var location = new Location();
try {
currentLocation = await location.getLocation();
} on Exception catch (e) {
print("Error obtaining location: $e");
currentLocation = null;
}
print("Location altitude: ${currentLocation.altitude}");
print("Location longitude: ${currentLocation.longitude}");
}
pubspec.yaml
name: background_location
description: A new Flutter project.
version: 1.0.0+1
environment:
sdk: ">=2.1.0 <3.0.0"
dependencies:
flutter:
sdk: flutter
cupertino_icons: ^0.1.2
workmanager: ^0.2.0
location: ^2.3.5
dev_dependencies:
flutter_test:
sdk: flutter
flutter:
uses-material-design: true
CustomApplication.java
package io.flutter.plugins;
import io.flutter.app.FlutterApplication;
import io.flutter.plugin.common.PluginRegistry;
import io.flutter.plugin.common.PluginRegistry.PluginRegistrantCallback;
import io.flutter.plugins.GeneratedPluginRegistrant;
import be.tramckrijte.workmanager.WorkmanagerPlugin;
import com.lyokone.location.LocationPlugin;
public class CustomApplication extends FlutterApplication implements PluginRegistry.PluginRegistrantCallback {
@Override
public void onCreate() {
super.onCreate();
WorkmanagerPlugin.setPluginRegistrantCallback(this);
}
@Override
public void registerWith(PluginRegistry registry) {
WorkmanagerPlugin.registerWith(registry.registrarFor("be.tramckrijte.workmanager.WorkmanagerPlugin"));
LocationPlugin.registerWith(registry.registrarFor("com.lyokone.location.LocationPlugin"));
}
}
AndroidManifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.background_location">
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<application
android:name="io.flutter.plugins.CustomApplication"
android:label="background_location"
android:icon="@mipmap/ic_launcher">
<activity
android:name=".MainActivity"
android:launchMode="singleTop"
android:theme="@style/LaunchTheme"
android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
android:hardwareAccelerated="true"
android:windowSoftInputMode="adjustResize">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
<meta-data
android:name="flutterEmbedding"
android:value="2" />
</application>
</manifest>
最后,我正在运行以下版本的Dart/Flutter等:
Flutter 1.12.13+hotfix.5 • channel stable • https://github.com/flutter/flutter.git
Framework • revision 27321ebbad (10 weeks ago) • 2019-12-10 18:15:01 -0800
Engine • revision 2994f7e1e6
Tools • Dart 2.7.0