getLastKnownLocation null - 如何获取数据？

Question

我正在尝试使用 getLastKnownLocation 获取位置信息，但我经常得到 null。

这是我的工作：

1. 在“设置”中关闭定位
2. 运行我的应用程序 - getLastKnownLocation 返回 null - 这是预期的
3. 在“设置”中开启定位功能
4. 再次运行我的应用 - getLastKnownLocation 返回 null ！？
5. 运行 Google 地图
6. 再次运行我的应用 - getLastKnownLocation 返回有效位置！？

我发现了这个问题，其中接受的答案建议首先启动地图以获取位置： FusedLocationApi.getLastLocation always null

问题是：Google 地图如何获取位置？我怎样才能在我的代码中做同样的事情？

谢谢！

Answer 1

感谢大家的帮助！

我的清单中缺少 uses-features 声明 - 感谢@CommonsWare 提供链接：https://developer.android.com/guide/topics/location/strategies.html#java

<!-- Needed only if your app targets Android 5.0 (API level 21) or higher. -->
<uses-feature android:name="android.hardware.location.gps" />
<uses-feature android:name="android.hardware.location.network" />

此外，还需要像这样请求更新：

locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);

在我的情况下，GPS 提供商需要几分钟来连接并开始发送数据 - 网络提供商似乎更快，但并不总是有效 - 所以我将同时使用它们。

更新：几个关键点

1. 这不是很直观，但是为了从 getLastKnownLocation 获取数据，设备上的某些应用程序（无论是 Google 地图还是我们自己的应用程序）需要调用 requestLocationUpdates。
2. 某些提供程序可能未在特定设备上启用 - 因此最好同时使用 GPS_PROVIDER 和 NETWORK_PROVIDER - 或使用所有已启用的提供程序：locationManager.getProviders(true)

这是我最终使用的代码：

for ( String provider : locationManager.getProviders(true) ) {
    setLocation( locationManager.getLastKnownLocation(provider) );
    locationManager.requestLocationUpdates(provider, Tools.MIN_5, 0, locationListener);
}
// call setLocation again in locationListener.onLocationChanged

Answer 2

这是一个可以帮助你的代码块。

  if (!::mFusedLocationProviderClient.isInitialized) {
        mFusedLocationProviderClient = FusedLocationProviderClient(mContext)
        mLocationRequest = LocationRequest()
        mLocationRequest.priority = LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY
        mLocationRequest.interval = 10000
        mLocationRequest.fastestInterval = 5000
        mLocationRequest.smallestDisplacement = 1000 * 100f
    }
    if (ActivityCompat.checkSelfPermission(
            AppName.appContext,
            android.Manifest.permission.ACCESS_FINE_LOCATION
        ) != PackageManager.PERMISSION_GRANTED || ActivityCompat.checkSelfPermission(
            AppName.appContext,
            android.Manifest.permission.ACCESS_COARSE_LOCATION
        ) != PackageManager.PERMISSION_GRANTED
    ) {
        // not enough permission
        return
    }
    mFusedLocationProviderClient.requestLocationUpdates(mLocationRequest, object : LocationCallback() {
        override fun onLocationResult(p0: LocationResult?) {
            super.onLocationResult(p0)
            mFusedLocationProviderClient.removeLocationUpdates(this)
            if (p0 != null) {
             //here is your location
            } else {
              // location is null
            }
        }

        override fun onLocationAvailability(p0: LocationAvailability?) {
            if(p0?.isLocationAvailable!= true){
       //location not available.
            }
        }

    }, Looper.getMainLooper())

Answer 3

确保您授予所有权限，如果您在 6.1 设备以上运行应用程序，则处理权限..

之后使用此代码..

将以下依赖项添加到应用级 gradle 文件中..

//Place API
implementation 'com.google.android.gms:play-services-places:16.0.0'
implementation 'com.google.android.gms:play-services-location:16.0.0'

将其定义为类级别作为全局减速。

private lateinit var fusedLocationClient: FusedLocationProviderClient
private var context: Context? = null
private var locationCallback: LocationCallback? = null
private var locationRequest: LocationRequest? = null
private var googleApiClient: GoogleApiClient? = null

在 onCreate 方法之后..

        fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)

获取位置的方法..

fun getCurrentLocation() {
    // Get Current location and do reverse geocoding
    ProgressUtils.showOldProgressDialog(this)


    locationCallback = object : LocationCallback() {
        override fun onLocationResult(locationResult: LocationResult?) {
            locationResult ?: return
            ProgressUtils.closeOldProgressDialog()
            for (location in locationResult.locations) {
                // here you get current lat ,long,etc value.. 
                        stopLocationUpdates()
                    }
                } catch (e: Exception) {
                    e.message.loggerError()
                    stopLocationUpdates()
                }
            }
        }
    }

    locationRequest = LocationRequest().apply {
        interval = 10000
        fastestInterval = 5000
        priority = LocationRequest.PRIORITY_HIGH_ACCURACY
    }


    startLocationUpdates()


}

进行位置更新..

 fun startLocationUpdates() {

    googleApiClient = GoogleApiClient.Builder(this)
            .addApi(LocationServices.API)
            .build()

    googleApiClient!!.connect()


    val builder = LocationSettingsRequest.Builder().addLocationRequest(locationRequest!!)
    builder.setAlwaysShow(true)

    val result = LocationServices.SettingsApi.checkLocationSettings(googleApiClient, builder.build())
    result.setResultCallback { result ->
        val status = result.status
        when (status.statusCode) {
            LocationSettingsStatusCodes.SUCCESS -> {
                Log.i(TAG, "All location settings are satisfied.")
                fusedLocationClient.requestLocationUpdates(locationRequest, locationCallback, null)
            }
            LocationSettingsStatusCodes.RESOLUTION_REQUIRED -> {
                Log.i(TAG, "Location settings are not satisfied. Show the user a dialog to upgrade location settings ")

                try {
                    // Show the dialog by calling startResolutionForResult(), and check the result
                    // in onActivityResult().
                    status.startResolutionForResult(this, LOCATION_SETTING_REQUEST_CODE)
                } catch (e: IntentSender.SendIntentException) {
                    Log.i(TAG, "PendingIntent unable to execute request.")
                }

            }
            LocationSettingsStatusCodes.SETTINGS_CHANGE_UNAVAILABLE -> Log.i(TAG, "Location settings are inadequate, and cannot be fixed here. Dialog not created.")
        }
    }

}

制作停止位置的方法..

private fun stopLocationUpdates() {

    if (locationCallback != null) {
        fusedLocationClient?.removeLocationUpdates(locationCallback)
    }
}

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

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

如果处理权限比权限被授予，那么回调获取 onActivity Result 方法放下面的代码..

     fusedLocationClient.requestLocationUpdates(locationRequest, locationCallback, null)