Flutter iOS调用location包获取位置时应用立即崩溃

问题描述 #

在Flutter v3.0.5中使用location ^4.4.0包获取设备位置时，调用该包的任意方法都会导致应用崩溃。已在Info.plist中添加相关权限配置：

<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>...</string>
<key>NSLocationAlwaysUsageDescription</key>
<string>...</string>
<key>NSLocationWhenInUseUsageDescription</key>
<string>...</string>
<key>UIBackgroundModes</key>
<string>location</string>

实现代码直接取自包示例，但在location.serviceEnabled()处崩溃：

user_location.dart代码 #

import 'package:location/location.dart';

class UserLocation {
  Location location = Location();

  late bool _serviceIsEnabled;
  late PermissionStatus _permissionGranted;
  late LocationData _locationData;

  Future<LocationData?> getLocation() async {
    print("Getting location");
   
    _serviceIsEnabled = await location.serviceEnabled(); // 在此处崩溃 <-

    if (!_serviceIsEnabled) {
      _serviceIsEnabled = await location.requestService();
      if (!_serviceIsEnabled) return null;
    }

    _permissionGranted = await location.hasPermission();

    if (_permissionGranted == PermissionStatus.denied) {
      _permissionGranted = await location.requestPermission();
      if (_permissionGranted != PermissionStatus.granted) {
        return null;
      }
    }

    _locationData = await location.getLocation();
    return _locationData;
  }
}

main.dart相关代码 #

Future main() async {
  await dotenv.load();
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  LocationData? _userLocation;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) {
      setState(() async {
        final location = await UserLocation().getLocation();
        _userLocation = location;
      });
    });
  }
}

解决方案 #

• 配置iOS端初始化代码
  location包在iOS上需要额外的初始化配置，否则会因插件注册问题崩溃。修改ios/Runner/AppDelegate.swift（Swift项目）：

  import UIKit
  import Flutter
  import location
  
  @UIApplicationMain
  @objc class AppDelegate: FlutterAppDelegate {
    override func application(
      _ application: UIApplication,
      didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
      GeneratedPluginRegistrant.register(with: self)
      // 添加location插件注册回调
      LocationPlugin.setPluginRegistrantCallback { registry in
        GeneratedPluginRegistrant.register(with: registry)
      }
      return super.application(application, didFinishLaunchingWithOptions: launchOptions)
    }
  }
  

  若为Objective-C项目，修改ios/Runner/AppDelegate.m：

  #import "AppDelegate.h"
  #import "GeneratedPluginRegistrant.h"
  #import <location/LocationPlugin.h>
  
  @implementation AppDelegate
  
  - (BOOL)application:(UIApplication *)application
      didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    [GeneratedPluginRegistrant registerWithRegistry:self];
    // 添加location插件注册回调
    [LocationPlugin setPluginRegistrantCallback:^(NSObject<FlutterPluginRegistry>* registry) {
      [GeneratedPluginRegistrant registerWithRegistry:registry];
    }];
    return [super application:application didFinishLaunchingWithOptions:launchOptions];
  }
  
  @end
  

• 修复异步调用的错误写法
  setState的回调不能是异步函数，这会导致状态更新逻辑异常。修改_MyHomePageState的initState方法：

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) async {
      final location = await UserLocation().getLocation();
      setState(() {
        _userLocation = location;
      });
    });
  }
  

  将async移至addPostFrameCallback的回调函数上，确保异步操作完成后再调用setState更新状态。

• 清理项目缓存并重新构建
  执行以下命令清理旧的构建缓存，避免残留文件导致的问题：

  flutter clean
  flutter pub get
  cd ios && pod install && cd ..
  flutter run
  

• 确保权限描述不为空
  Info.plist中的权限说明字符串不能是占位符...，需要替换为实际的用途说明，比如：

  <key>NSLocationWhenInUseUsageDescription</key>
  <string>需要获取您的位置信息以提供定位服务</string>
  

内容的提问来源于stack exchange，提问作者Ryan Roberts