google 如何在 android 设备离线的情况下获取地图地址

Question

我刚刚创建了一个带有一些标记的地图 activity，同时单击标记标题获取标记位置的地址用于教育目的，一切正常。

即使设备未连接到互联网，它也会获取地址。我没有在清单中授予互联网许可。 ACCESS_FINE_LOCATION 是授予应用程序的唯一权限。

我的问题是：即使设备处于离线模式，应用程序如何能够获取地址？它背后的想法或技术是什么！！？

Nb: 我从未在我的代码中使用过 getLastKnownLocation 方法。 Wifi 和 gps 都关闭并且没有插入 sim 卡。

这是我的代码：

    public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {

    private GoogleMap mMap;
    TextView mapPosition;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        mapPosition = (TextView) findViewById(R.id.textplace);

        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }


    /**
     * Manipulates the map once available.
     * This callback is triggered when the map is ready to be used.
     * This is where we can add markers or lines, add listeners or move the camera. In this case,
     * we just add a marker near Sydney, Australia.
     * If Google Play services is not installed on the device, the user will be prompted to install
     * it inside the SupportMapFragment. This method will only be triggered once the user has
     * installed Google Play services and returned to the app.
     */
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
       // double lat = Double.valueOf(8.524139);
        // Add a marker in Sydney and move the camera
        LatLng sydney = new LatLng(-34, 151); LatLng ind = new LatLng(8.524139, 76.936638);
        mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
        mMap.addMarker(new MarkerOptions().position(ind).title("Marker in Trivandrum"));
        mMap.moveCamera(CameraUpdateFactory.newLatLng(ind));

        mMap.setOnMarkerClickListener(new GoogleMap.OnMarkerClickListener() {
            @Override
            public boolean onMarkerClick(Marker marker) {






                return false;
            }
        });

    mMap.setOnInfoWindowClickListener(new GoogleMap.OnInfoWindowClickListener() {
        @Override
        public void onInfoWindowClick(Marker marker) {
            Geocoder geocoder;
            List<Address> addresses;
            geocoder = new Geocoder(MapsActivity.this, Locale.getDefault());

            try {
                addresses = geocoder.getFromLocation(marker.getPosition().latitude, marker.getPosition().longitude, 1);

                // Here 1 represent max location result to returned, by documents it recommended 1 to 5

                String address = addresses.get(0).getAddressLine(0);
                // If any additional address line present than only, check with max available address lines by getMaxAddressLineIndex()
                String city = addresses.get(0).getLocality();
                String state = addresses.get(0).getAdminArea();
                String country = addresses.get(0).getCountryName();
                String postalCode = addresses.get(0).getPostalCode();
                String knownName = addresses.get(0).getFeatureName();
                String countrycode = addresses.get(0).getCountryCode();

                mapPosition.setText(""+ address);

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

    }
}

Answer 1

您可以通过网络、gps 或 location.getLastKnownLocation(LocationManager.NETWORK_PROVIDER)（没有网络）获取经纬度。

看到这个。或许能帮到你。

然后从纬度和经度，您可以使用地理编码器 class 获得完整地址：

    Geocoder geocoder;
List<Address> addresses;
geocoder = new Geocoder(this, Locale.getDefault());

addresses = geocoder.getFromLocation(latitude, longitude, 1); // Here 1 represent max location result to returned, by documents it recommended 1 to 5

String address = addresses.get(0).getAddressLine(0); // If any additional address line present than only, check with max available address lines by getMaxAddressLineIndex()
String city = addresses.get(0).getLocality();
String state = addresses.get(0).getAdminArea();
String country = addresses.get(0).getCountryName();
String postalCode = addresses.get(0).getPostalCode();
String knownName = addresses.get(0).getFeatureName();

Answer 2

答案似乎是缓存内存。我第一次检查互联网，所以应用程序存储它缓存这就是为什么我仍然在设备离线时加载地图并获取相同纬度和经度的地址。

问题中提到的代码工作正常。感谢@pskink。

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