java - 为什么我无法检索当前位置的名称？

Question

我正在制作一个应用程序，我必须在其中显示当前位置的名称。我正在获取纬度和经度，但无法获取该位置的名称。

我试图这样做的代码是：

context = getApplicationContext();
Location location;
LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
double lon, lat;
try
{
    location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
    lon = location.getLongitude();
    lat = location.getLatitude();

    Toast.makeText(context, "Lat: "+lat+"\nLon: "+lon, Toast.LENGTH_LONG).show();

    List<Address> mAddresses = null;

    Geocoder gcd = new Geocoder(getApplicationContext(), Locale.getDefault());

    try 
    {
        mAddresses = gcd.getFromLocation(location.getLatitude(),
                location.getLongitude(), 1);
        }  

    catch (IOException e) 
        {
        e.printStackTrace();
    }

    @SuppressWarnings("unchecked")
    String cityName = (mAddresses != null) ? ((List<Address>) mAddresses).get(0)
        .getLocality() : TimeZone.getDefault().getID();
    @SuppressWarnings("unchecked")
    String countryName = (mAddresses != null) ? ((List<Address>) mAddresses).get(0)
        .getCountryName() : Locale.getDefault().getDisplayCountry()
        .toString();

    try
    {
        lm.clearTestProviderLocation(LocationManager.GPS_PROVIDER);
        }
    catch(Exception e)
    {}

    Toast.makeText(context, "Using GPS Provider", Toast.LENGTH_SHORT).show();       }

  catch(Exception exp1){

    try
    {
        location = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
            lon= location.getLongitude();
            lat = location.getLatitude();
            Toast.makeText(context, "Lat: "+lat+"\nLon: "+lon, Toast.LENGTH_LONG).show();

            List<Address> mAddresses = null;

        Geocoder gcd = new Geocoder(getApplicationContext(), Locale.getDefault());

        try 
        {
            mAddresses = gcd.getFromLocation(location.getLatitude(), location.getLongitude(), 1);
        } 

        catch (IOException e) 
        {
            e.printStackTrace();
        }

        @SuppressWarnings("unchecked")
        String cityName = (mAddresses != null) ? ((List<Address>) mAddresses).get(0).getLocality() : TimeZone.getDefault().getID();

            @SuppressWarnings("unchecked")
        String countryName = (mAddresses != null) ? ((List<Address>) mAddresses).get(0).getCountryName() : Locale.getDefault().getDisplayCountry().toString();

            try
            {   
                    lm.clearTestProviderLocation(LocationManager.NETWORK_PROVIDER);
            }
            catch(Exception e)
            {}

            Toast.makeText(context, "Using Network Provider", Toast.LENGTH_SHORT).show();

    }

Answer 1

最好在异步任务中执行，例如

private class LocationTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... parms) {

            LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
            String provider = locationManager.getBestProvider(new Criteria(),
                    true);

            Location locations = locationManager.getLastKnownLocation(provider);
            List<String> providerList = locationManager.getAllProviders();
            if (null != locations && null != providerList
                    && providerList.size() > 0) {
                double longitude = locations.getLongitude();
                double latitude = locations.getLatitude();
                Geocoder geocoder = new Geocoder(getApplicationContext(),
                        Locale.getDefault());
                try {
                    List<Address> listAddresses = geocoder.getFromLocation(
                            latitude, longitude, 1);
                    if (null != listAddresses && listAddresses.size() > 0) {
                        String _Location = listAddresses.get(0).getAddressLine(
                                1);

                        // 1000).show();
                        return _Location;

                    }
                } catch (IOException e) {

                                            e.printStackTrace();

                }

            }
            return " ";
        }

        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();

        }

        @Override
        protected void onPostExecute(String locOutcome) {

            //Use locOutcome here
        }
    }

不要忘记添加权限

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />