Android 试图通过cell tower获取位置，但仍返回null

我试图做的是从用户那里获取位置。首先，它尝试通过GPS获取位置，并检查位置是否可用。若并没有，那个么它会试图通过网络塔。当GPS打开时，它工作正常。但当我关闭GPS时，它无法使用网络提供商获取位置

 manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    provider = manager.getBestProvider(new Criteria(), false);

    Log.i("ITEMSET best", provider);


    manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        // TODO: Consider calling
        //    ActivityCompat#requestPermissions
        // here to request the missing permissions, and then overriding
        //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
        //                                          int[] grantResults)
        // to handle the case where the user grants the permission. See the documentation
        // for ActivityCompat#requestPermissions for more details.
        return;
    }

    Log.i("ITEMSET provider", provider);

    location = manager.getLastKnownLocation(provider);
    Log.i("ITEMSET netLoc", location + "");
    if(location==null) {
        provider = LocationManager.NETWORK_PROVIDER;
        location = manager.getLastKnownLocation(provider);
        Log.i("ITEMSET netLoc", location + "qqq");
    }



    Log.i("ITEMSET current", provider);
    Log.i("ITEMSET location", location  + "");

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位置最初为空，因为GPS未打开。但随后将提供商更改为网络提供商。但位置仍然为空

检查网络是否已启用

 isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);

然后：

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您应该使用

GoogleAppClient

获取您的位置。请访问

您是否已授予精细定位权限？是的，我已授予精细定位和粗略定位权限。可能您尚未请求位置更新，这就是为什么它会发出isNetworkEnabled{locationManager.requestLocationUpdates（locationManager.NETWORK_PROVIDER，5000100，this）；Log.d(“网络”、“网络”）；if（locationManager！=null）{location=locationManager.getLastKnownLocation（locationManager.Network_提供程序）；if（location！=null）{latitude=location.getLatitude（）；longitude=location.getLongitude（）}我在onresume块中请求了locationupdate就是这样。似乎提供程序未启用

     if (isNetworkEnabled) {
   locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 5000,10, this);
                Log.d("Network", "Network");
                if (locationManager != null) {
                    location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                    if (location != null) {

                        latitude = location.getLatitude();
                        longitude = location.getLongitude();


                    }
                }