getLastKnownLocation 返回 null

Question

我已经阅读了一些关于此的问题，但我并没有找到我需要的答案。

所以，情况是我设置了我的地图，我想获取我当前的 gps 位置。 我检查了我的变量不是 NULL，但我的结果来自：

getLastKnownLocation(provider, false);

虽然给我 null，所以这是我需要帮助的地方。 我添加了 COARSE + FINE 位置的权限。但是我通常会为我的手机禁用各种网络数据，因为我对手机账单中不可预测的数据流费用不太满意。所以我只为这个测试启用并连接了 WiFi。

我还需要启用什么才能使这成为可能吗？我认为 WiFi 应该足够了？

Answer 1

使用此方法获取最后一个已知位置：

LocationManager mLocationManager;
Location myLocation = getLastKnownLocation();

private Location getLastKnownLocation() {
    mLocationManager = (LocationManager)getApplicationContext().getSystemService(LOCATION_SERVICE);
    List<String> providers = mLocationManager.getProviders(true);
    Location bestLocation = null;
    for (String provider : providers) {
        Location l = mLocationManager.getLastKnownLocation(provider);
        if (l == null) {
            continue;
        }
        if (bestLocation == null || l.getAccuracy() < bestLocation.getAccuracy()) {
            // Found best last known location: %s", l);
            bestLocation = l;
        }
    }
    return bestLocation;
}

Answer 2

您不应该将新旧位置 API 混合在一起。

要获取最后一个已知位置，您只需拨打电话

compile "com.google.android.gms:play-services-location:11.0.1"
mLocationClient.getLastLocation();

一旦连接了定位服务。

了解如何使用新的位置 API

http://developer.android.com/training/location/retrieve-current.html#GetLocation

 private void getLastLocationNewMethod(){
    FusedLocationProviderClient mFusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
    mFusedLocationClient.getLastLocation()
            .addOnSuccessListener(new OnSuccessListener<Location>() {
                @Override
                public void onSuccess(Location location) {
                    // GPS location can be null if GPS is switched off
                    if (location != null) {
                        getAddress(location);
                    }
                }
            })
            .addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    Log.d("MapDemoActivity", "Error trying to get last GPS location");
                    e.printStackTrace();
                }
            });
}

Answer 3

您正在尝试从网络提供商处获取缓存位置。您必须等待几分钟才能获得有效的修复。由于网络提供商的缓存是空的，你显然在那里得到了一个空值..

Answer 4

添加此代码

if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
     return;
}

之前函数：

locationManagerObject.requestLocationUpdates(LocationManager.GPS_PROVIDER, MINIMUM_TIME_BETWEEN_UPDATES, MINIMUM_DISTANCE_CHANGE_FOR_UPDATES, new LocationListener()) 以及函数：locationManagerObject.getLastKnownLocation(LocationManager.GPS_PROVIDER)

Answer 5

试试这个，它对我很有用：-

LocationManager mLocationManager;
Location myLocation = getLastKnownLocation();

        private Location getLastKnownLocation() {
            Location oldLoc;
            while (true){
                oldLoc = mLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                if (oldLoc == null){
                    continue;
                }
                else {
                    break;
                }
            }
            return oldLoc;
        }

您可以使用 NETWORK_PROVIDER 代替 GPS_PROVIDER 以获得更快的结果..

Answer 6

我在 Xamarin.Android 中遇到了这个问题。

Location location = locationManager.GetLastKnownLocation(provider); 返回空值。我检查了我的代码并知道我刚刚请求了 ACCESS_COARSE_LOCATION 的权限。我添加了代码来请求 ACCESS_FINE_LOCATION 的权限，现在它没有返回 null。这是我的代码：

void AskPermissions()
{
    if (CheckSelfPermission(Manifest.Permission.AccessCoarseLocation) != (int)Permission.Granted ||
            CheckSelfPermission(Manifest.Permission.AccessFineLocation) != (int)Permission.Granted)
        RequestPermissions(new string[] { Manifest.Permission.AccessCoarseLocation, Manifest.Permission.AccessFineLocation }, 0);
    else
        GetLocation();
}

public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
{
    if (CheckSelfPermission(Manifest.Permission.AccessCoarseLocation) == (int)Permission.Granted &&
            CheckSelfPermission(Manifest.Permission.AccessFineLocation) == (int)Permission.Granted)
        GetLocation();
    else
        Log.Info(tag, "Permission not Granted: Please enter desired Location manually.");
}

void GetLocation()
{
    locationManager = (LocationManager)GetSystemService(LocationService);
    provider = locationManager.GetBestProvider(new Criteria(), false);
    Location location = locationManager.GetLastKnownLocation(provider);
    if (location != null)
        Log.Info(tag, "Location Lat: " + location.Latitude + " Lon: " + location.Longitude);
    else
        Log.Info(tag, "Location is null");
}

万一来自 Xamarin.Android (C#) 的人会发现它很有用。对于 Java 或 Android Studio，代码将与一些小的语法更改类似，例如 GetLastKnownLocation() 将是 getLastKnownLocation()，因为 Java 中的方法名称以小写字母开头，而 C# 中的方法名称以大写字母开头。

Answer 7

我喜欢这个更新位置的解决方案：

Update location

在简历中，添加条件：

Location myLocation = getLastKnownLocation();
if (myLocation == null) {
      locationManager.requestLocationUpdates(
      LocationManager.PASSIVE_PROVIDER,
      MIN_TIME_BW_UPDATES,
      MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
      Log.d("GPS", "GPS Enabled");
 }

也许是一些基本的，但请检查 GPS 是否开启。

Answer 8

private void getLastLocation()
{
    LocationManager locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);


    LocationListener locationListener = new LocationListener() {
        public void onLocationChanged(Location location) {
            Log.e("location",location.getLatitude()+"");

        }

        public void onStatusChanged(String provider, int status, Bundle extras) {}

        public void onProviderEnabled(String provider) {}

        public void onProviderDisabled(String provider) {}
    };

    locationManager.requestSingleUpdate(LocationManager.NETWORK_PROVIDER,locationListener,null);

}

// 这将帮助您在 gps 启用后获取位置

locationManager.requestSingleUpdate(LocationManager.NETWORK_PROVIDER,locationListener,null);

Answer 9

用

替换你的行

Location location = LocationServices.FusedLocationApi.getLastLocation(googleApiClient);