为什么后台定位在展会应用程序中不起作用？

Question

我正在尝试做后台位置跟踪的测试示例，它适用于 Android，但我无法测试 IOS。几年前我在一些帖子上看到iOS中的expo go应用程序不允许后台位置跟踪，但我不知道是否仍然如此。 我使用的代码：

import React, { useEffect, useState } from "react"
import { StyleSheet, Text, View, Button } from "react-native"

import * as TaskManager from "expo-task-manager"
import * as Location from "expo-location"


const LOCATION_TASK_NAME = "LOCATION_TASK_NAME"
let foregroundSubscription = null

// Define the background task for location tracking
TaskManager.defineTask(LOCATION_TASK_NAME, async ({ data, error }) => {
  if (error) {
    console.error(error)
    return
  }
  if (data) {
    // Extract location coordinates from data
    const { locations } = data
    const location = locations[0]
    if (location) {
      console.log("Location in background", location.coords)
    }
  }
})

export default function App() {
  // Define position state: {latitude: number, longitude: number}
  const [position, setPosition] = useState(null)

  // Request permissions right after starting the app
  useEffect(() => {
    const requestPermissions = async () => {
      const foreground = await Location.requestForegroundPermissionsAsync()
      if (foreground.granted) await Location.requestBackgroundPermissionsAsync()
    }
    requestPermissions()
  }, [])

  // Start location tracking in foreground
  const startForegroundUpdate = async () => {
    // Check if foreground permission is granted
    const { granted } = await Location.getForegroundPermissionsAsync()
    if (!granted) {
      console.log("location tracking denied")
      return
    }

    // Make sure that foreground location tracking is not running
    foregroundSubscription?.remove()

    // Start watching position in real-time
    foregroundSubscription = await Location.watchPositionAsync(
      {
        // For better logs, we set the accuracy to the most sensitive option
        accuracy: Location.Accuracy.BestForNavigation,
      },
      location => {
        setPosition(location.coords)
      }
    )
  }

  // Stop location tracking in foreground
  const stopForegroundUpdate = () => {
    foregroundSubscription?.remove()
    setPosition(null)
  }

  // Start location tracking in background
  const startBackgroundUpdate = async () => {
    // Don't track position if permission is not granted
    const { granted } = await Location.getBackgroundPermissionsAsync()
    if (!granted) {
      console.log("location tracking denied")
      return
    }

    // Make sure the task is defined otherwise do not start tracking
    const isTaskDefined = await TaskManager.isTaskDefined(LOCATION_TASK_NAME)
    if (!isTaskDefined) {
      console.log("Task is not defined")
      return
    }

    // Don't track if it is already running in background
    const hasStarted = await Location.hasStartedLocationUpdatesAsync(
      LOCATION_TASK_NAME
    )
    if (hasStarted) {
      console.log("Already started")
      return
    }

    await Location.startLocationUpdatesAsync(LOCATION_TASK_NAME, {
      // For better logs, we set the accuracy to the most sensitive option
      accuracy: Location.Accuracy.BestForNavigation,
      // Make sure to enable this notification if you want to consistently track in the background
      showsBackgroundLocationIndicator: true,
      foregroundService: {
        notificationTitle: "Location",
        notificationBody: "Location tracking in background",
        notificationColor: "#fff",
      },
    })
  }

  // Stop location tracking in background
  const stopBackgroundUpdate = async () => {
    const hasStarted = await Location.hasStartedLocationUpdatesAsync(
      LOCATION_TASK_NAME
    )
    if (hasStarted) {
      await Location.stopLocationUpdatesAsync(LOCATION_TASK_NAME)
      console.log("Location tacking stopped")
    }
  }

  return (
    <View style={styles.container}>
      <Text>Longitude: {position?.longitude}</Text>
      <Text>Latitude: {position?.latitude}</Text>
      <View style={styles.separator} />
      <Button
        onPress={startForegroundUpdate}
        title="Start in foreground"
        color="green"
      />
      <View style={styles.separator} />
      <Button
        onPress={stopForegroundUpdate}
        title="Stop in foreground"
        color="red"
      />
      <View style={styles.separator} />
      <Button
        onPress={startBackgroundUpdate}
        title="Start in background"
        color="green"
      />
      <View style={styles.separator} />
      <Button
        onPress={stopBackgroundUpdate}
        title="Stop in foreground"
        color="red"
      />
    </View>
  )
}

在 app.json 文件中我有以下配置：

"ios": {
  "supportsTablet": true,
  "infoPlist":{
    "NSLocationUsageDescription":"App requires location even when the App is backgrounded.",
    "NSLocationWhenInUseUsageDescription":"App requires location even when the App is backgrounded.",
    "NSLocationAlwaysUsageDescription":"App requires location even when the App is backgrounded.",
    "NSLocationAlwaysAndWhenInUseUsageDescription":"App requires location even when the App is backgrounded.",
    "UIBackgroundModes": [
      "location",
      "fetch"
    ]
  }
},
"android": {
  "adaptiveIcon": {
    "foregroundImage": "./assets/adaptive-icon.png",
    "backgroundColor": "#ffffff"
  },
  "permissions":    "ACCESS_BACKGROUND_LOCATION"    

Answer 1

我使用相同的代码和配置。但后台位置在我的设备上不起作用。您在哪台设备上进行测试？您是否找到了也适用于 ios 的解决方案？