Flutter后台定位插件background_locator的使用

插件简介

background_locator 是一个Flutter插件，允许在应用程序被杀死的情况下仍能接收位置更新。该插件可以满足开发者对于应用在后台或完全关闭后继续获取用户地理位置的需求，例如用于记录运动轨迹、地理围栏等功能。

更多详情请参考 Wiki页面，其中包括但不限于：

• 安装
• 设置
• 如何使用
• 回调中使用其他插件
• 应用程序终止时停止
• LocationSettings选项
• 设备重启时重启服务(Android only)

License

本项目采用MIT许可证，详细内容见LICENSE文件。

Contributor

感谢所有为此插件做出贡献的人，包括但不限于：

• Gerardo Ibarra
• RomanJos
• Marcelo Henrique Neppel

示例代码

下面是一个完整的示例demo，演示了如何使用background_locator插件来实现后台定位功能。

import 'dart:async';
import 'dart:isolate';
import 'dart:ui';

import 'package:background_locator/background_locator.dart';
import 'package:background_locator/location_dto.dart';
import 'package:background_locator/settings/android_settings.dart';
import 'package:background_locator/settings/ios_settings.dart';
import 'package:background_locator/settings/locator_settings.dart';
import 'package:flutter/material.dart';
import 'package:location_permissions/location_permissions.dart';

import 'file_manager.dart';
import 'location_callback_handler.dart';
import 'location_service_repository.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  ReceivePort port = ReceivePort();

  String logStr = '';
  bool isRunning;
  LocationDto lastLocation;

  @override
  void initState() {
    super.initState();

    if (IsolateNameServer.lookupPortByName(LocationServiceRepository.isolateName) != null) {
      IsolateNameServer.removePortNameMapping(LocationServiceRepository.isolateName);
    }

    IsolateNameServer.registerPortWithName(port.sendPort, LocationServiceRepository.isolateName);

    port.listen(
      (dynamic data) async {
        await updateUI(data);
      },
    );
    initPlatformState();
  }

  @override
  void dispose() {
    super.dispose();
  }

  Future<void> updateUI(LocationDto data) async {
    final log = await FileManager.readLogFile();

    await _updateNotificationText(data);

    setState(() {
      if (data != null) {
        lastLocation = data;
      }
      logStr = log;
    });
  }

  Future<void> _updateNotificationText(LocationDto data) async {
    if (data == null) {
      return;
    }

    await BackgroundLocator.updateNotificationText(
        title: "new location received",
        msg: "${DateTime.now()}",
        bigMsg: "${data.latitude}, ${data.longitude}");
  }

  Future<void> initPlatformState() async {
    print('Initializing...');
    await BackgroundLocator.initialize();
    logStr = await FileManager.readLogFile();
    print('Initialization done');
    final _isRunning = await BackgroundLocator.isServiceRunning();
    setState(() {
      isRunning = _isRunning;
    });
    print('Running ${isRunning.toString()}');
  }

  @override
  Widget build(BuildContext context) {
    final start = SizedBox(
      width: double.maxFinite,
      child: ElevatedButton(
        child: Text('Start'),
        onPressed: () {
          _onStart();
        },
      ),
    );
    final stop = SizedBox(
      width: double.maxFinite,
      child: ElevatedButton(
        child: Text('Stop'),
        onPressed: () {
          onStop();
        },
      ),
    );
    final clear = SizedBox(
      width: double.maxFinite,
      child: ElevatedButton(
        child: Text('Clear Log'),
        onPressed: () {
          FileManager.clearLogFile();
          setState(() {
            logStr = '';
          });
        },
      ),
    );
    String msgStatus = "-";
    if (isRunning != null) {
      if (isRunning) {
        msgStatus = 'Is running';
      } else {
        msgStatus = 'Is not running';
      }
    }
    final status = Text("Status: $msgStatus");

    final log = Text(
      logStr,
    );

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Flutter background Locator'),
        ),
        body: Container(
          width: double.maxFinite,
          padding: const EdgeInsets.all(22),
          child: SingleChildScrollView(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.center,
              children: <Widget>[start, stop, clear, status, log],
            ),
          ),
        ),
      ),
    );
  }

  void onStop() async {
    await BackgroundLocator.unRegisterLocationUpdate();
    final _isRunning = await BackgroundLocator.isServiceRunning();
    setState(() {
      isRunning = _isRunning;
    });
  }

  void _onStart() async {
    if (await _checkLocationPermission()) {
      await _startLocator();
      final _isRunning = await BackgroundLocator.isServiceRunning();

      setState(() {
        isRunning = _isRunning;
        lastLocation = null;
      });
    } else {
      // show error
    }
  }

  Future<bool> _checkLocationPermission() async {
    final access = await LocationPermissions().checkPermissionStatus();
    switch (access) {
      case PermissionStatus.unknown:
      case PermissionStatus.denied:
      case PermissionStatus.restricted:
        final permission = await LocationPermissions().requestPermissions(
          permissionLevel: LocationPermissionLevel.locationAlways,
        );
        if (permission == PermissionStatus.granted) {
          return true;
        } else {
          return false;
        }
        break;
      case PermissionStatus.granted:
        return true;
        break;
      default:
        return false;
        break;
    }
  }

  Future<void> _startLocator() async{
    Map<String, dynamic> data = {'countInit': 1};
    return await BackgroundLocator.registerLocationUpdate(LocationCallbackHandler.callback,
        initCallback: LocationCallbackHandler.initCallback,
        initDataCallback: data,
        disposeCallback: LocationCallbackHandler.disposeCallback,
        iosSettings: IOSSettings(
            accuracy: LocationAccuracy.NAVIGATION, distanceFilter: 0),
        autoStop: false,
        androidSettings: AndroidSettings(
            accuracy: LocationAccuracy.NAVIGATION,
            interval: 5,
            distanceFilter: 0,
            client: LocationClient.google,
            androidNotificationSettings: AndroidNotificationSettings(
                notificationChannelName: 'Location tracking',
                notificationTitle: 'Start Location Tracking',
                notificationMsg: 'Track location in background',
                notificationBigMsg:
                    'Background location is on to keep the app up-tp-date with your location. This is required for main features to work properly when the app is not running.',
                notificationIconColor: Colors.grey,
                notificationTapCallback:
                    LocationCallbackHandler.notificationCallback)));
  }
}

代码说明

• ReceivePort 和 IsolateNameServer 用于处理与后台服务之间的通信。
• updateUI 方法负责更新UI以反映最新的位置信息。
• _updateNotificationText 方法用于更新通知文本。
• initPlatformState 方法初始化平台状态并检查服务是否正在运行。
• _onStart 和 onStop 方法分别用于启动和停止位置更新服务。
• _checkLocationPermission 方法确保应用具有必要的权限来访问位置数据。
• _startLocator 方法配置并注册位置更新服务，包括iOS和Android的具体设置。

以上就是关于background_locator插件的详细介绍及使用示例。希望对您有所帮助！如果有任何问题或者需要进一步的帮助，请随时提问。