在 kotlin 中使用 MapView 检索片段中的当前位置？

Question

我想检索当前位置并在用户移动时更新他的位置。我在创建地图时有一个 mapView。现在我的问题是如何获取用户当前位置，如果他移动位置是否更新？由于 ApiLevel，我使用 googleApliclient 并使用 Mapview。我可以检索权限，但遗憾的是我不知道如何检索用户位置并更新它。也欢迎对代码进行改进。

class MapFragment : Fragment(), OnMapReadyCallback, GoogleApiClient.ConnectionCallbacks,
    GoogleApiClient.OnConnectionFailedListener {
    private var mapView: MapView? = null
    private var gMap: GoogleMap? = null
    private val LOCATION_PERMISSION_REQUEST_CODE = 1234


    private lateinit var mapViewModel: MapViewModel

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

        mapViewModel =
            ViewModelProvider(this).get(MapViewModel::class.java)
        val root = inflater.inflate(R.layout.fragment_map, container, false)
        mapView = root.findViewById(R.id.mapView) as MapView
        if (mapView != null) {
            mapView!!.onCreate(null);
            mapView!!.onResume();
            mapView!!.getMapAsync(this);
            checkLocationPermission();
        }
        checkLocationPermission();
        return root
    }


    override fun onResume() {
        super.onResume()
        mapView?.onResume()
    }

    override fun onPause() {
        super.onPause()
        mapView?.onPause()
    }

    override fun onStart() {
        super.onStart()
        mapView?.onStart()
    }

    override fun onStop() {
        super.onStop()
        mapView?.onStop()
    }

    override fun onDestroy() {
        super.onDestroy()
        mapView?.onDestroy()
    }

    override fun onLowMemory() {
        super.onLowMemory()
        mapView?.onLowMemory()
    }


    override fun onMapReady(googleMap: GoogleMap) {
        MapsInitializer.initialize(context)
        gMap = googleMap
        val coffeys = LatLng(52.075890, 4.309170)
        gMap!!.addMarker(MarkerOptions().position(coffeys).title("coffeys"))
        gMap!!.moveCamera(CameraUpdateFactory.newLatLngZoom(coffeys, 12f))

    }

    fun checkLocationPermission(): Boolean {
        return if (ContextCompat.checkSelfPermission(
                requireActivity(),
                Manifest.permission.ACCESS_FINE_LOCATION
            )
            != PackageManager.PERMISSION_GRANTED
        ) {


            // Asking user if explanation is needed
            if (ActivityCompat.shouldShowRequestPermissionRationale(
                    requireActivity(),
                    Manifest.permission.ACCESS_FINE_LOCATION
                )
            ) {
                //Prompt the user once explanation has been shown
                requestPermissions(
                    arrayOf(Manifest.permission.ACCESS_FINE_LOCATION),
                    LOCATION_PERMISSION_REQUEST_CODE
                )
            } else {
                // No explanation needed, we can request the permission.
                requestPermissions(
                    arrayOf(Manifest.permission.ACCESS_FINE_LOCATION),
                    LOCATION_PERMISSION_REQUEST_CODE
                )
            }
            false
        } else {
            true
        }
    }

    override fun onConnected(p0: Bundle?) {

    }

    override fun onConnectionSuspended(p0: Int) {
        TODO("Not yet implemented")
    }

    override fun onConnectionFailed(p0: ConnectionResult) {
        TODO("Not yet implemented")
    }


}

Answer 1

使用融合位置提供程序检索设备的最后已知位置。

private lateinit var fusedLocationClient: FusedLocationProviderClient

override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

    // ...

    fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
}

请求最后已知位置并处理响应：

fusedLocationClient.lastLocation
        .addOnSuccessListener { location : Location? ->
            // Got last known location. In some rare situations this can be null.
        }

此 returns 任务可用于获取具有地理位置经纬度坐标的 Location 对象。

更多详情： https://developer.android.com/training/location/request-updates

更新：完成实施

@SuppressLint("MissingPermission")
    private fun getDeviceLocation() {
        /*
         * Get the best and most recent location of the device, which may be null in rare
         * cases when a location is not available.
         */
        try {
            if (locationPermissionGranted) {
                val locationResult = fusedLocationProviderClient.lastLocation
                locationResult.addOnCompleteListener(requireActivity()) { task ->

                    if (task.isSuccessful) {

                        // Set the map's camera position to the current location of the device.
                        lastKnownLocation = task.result
                        if (lastKnownLocation != null) {
                            Timber.d("last  known location $lastKnownLocation")

                            map.moveCamera(
                                CameraUpdateFactory.newLatLngZoom(
                                    LatLng(
                                        lastKnownLocation!!.latitude,
                                        lastKnownLocation!!.longitude
                                    ), DEFAULT_ZOOM.toFloat()
                                )
                            )
                        } else {
                            Timber.e( "Exception: %s", task.exception)
                            map.moveCamera(
                                CameraUpdateFactory
                                    .newLatLngZoom(defaultLocation, DEFAULT_ZOOM.toFloat())
                            )
                            map.uiSettings?.isMyLocationButtonEnabled = false
                        }
                    }
                }
            }
        } catch (e: SecurityException) {
            Timber.e("Exception: %s", e.message)
        }
    }

更新 2：位置更新

此代码来自官方文档，为 activity 实现。应该也适用于片段。注意：我没有测试过这个。

调用 requestLocationUpdates()，将您的 locationRequest 对象实例和 locationCallback 传递给它。定义一个 startLocationUpdates() 方法，如以下代码示例所示：

override fun onResume() {
    super.onResume()
    if (requestingLocationUpdates) startLocationUpdates()
}

private fun startLocationUpdates() {
    fusedLocationClient.requestLocationUpdates(locationRequest,
            locationCallback,
            Looper.getMainLooper())
}

融合位置提供程序调用 LocationCallback.onLocationResult() 回调方法。传入参数包含一个列表 Location 对象，其中包含位置的纬度和经度。以下代码片段展示了如何实现 LocationCallback 接口并定义方法，然后获取位置更新的时间戳并在应用程序的用户界面上显示纬度、经度和时间戳：

private lateinit var locationCallback: LocationCallback

// ...

override fun onCreate(savedInstanceState: Bundle?) {
    // ...

    locationCallback = object : LocationCallback() {
        override fun onLocationResult(locationResult: LocationResult?) {
            locationResult ?: return
            for (location in locationResult.locations){
                // Update UI with location data
                // ...
            }
        }
    }
}

要停止位置更新，请调用 removeLocationUpdates()，将其传递给 locationCallback，如以下代码示例所示：

override fun onPause() {
    super.onPause()
    stopLocationUpdates()
}

private fun stopLocationUpdates() {
    fusedLocationClient.removeLocationUpdates(locationCallback)
}

设备配置的更改，例如屏幕方向或语言的更改，可能会导致当前 activity 被破坏。因此，您的应用必须存储重新创建 activity 所需的任何信息。一种方法是通过存储在 Bundle 对象中的实例状态。

以下代码示例显示了如何使用 activity 的 onSaveInstanceState() 回调来保存实例状态：

override fun onSaveInstanceState(outState: Bundle?) {
    outState?.putBoolean(REQUESTING_LOCATION_UPDATES_KEY, requestingLocationUpdates)
    super.onSaveInstanceState(outState)
}

定义一个 updateValuesFromBundle() 方法来从 activity 的先前实例中恢复保存的值（如果它们可用）。从 activity 的 onCreate() 方法调用方法，如以下代码示例所示：

override fun onCreate(savedInstanceState: Bundle?) {
    // ...
    updateValuesFromBundle(savedInstanceState)
}

private fun updateValuesFromBundle(savedInstanceState: Bundle?) {
    savedInstanceState ?: return

    // Update the value of requestingLocationUpdates from the Bundle.
    if (savedInstanceState.keySet().contains(REQUESTING_LOCATION_UPDATES_KEY)) {
        requestingLocationUpdates = savedInstanceState.getBoolean(
                REQUESTING_LOCATION_UPDATES_KEY)
    }

    // ...

    // Update UI to match restored state
    updateUI()
}

为了更持久的存储，您可以将用户的首选项存储在您应用的 SharedPreferences 中。在 activity 的 onPause() 方法中设置共享首选项，并在 onResume()

中检索首选项

在 kotlin 中使用 MapView 检索片段中的当前位置？

Retrieve the current Location in fragment with MapView in kotlin?

android

fragment

google-api-client

kotlin

android-mapview