我想通过从 json 获取经度和纬度在谷歌地图上显示标记

Posted 2023-04-19

【中文标题】我想通过从 json 获取经度和纬度在谷歌地图上显示标记

【英文标题】：i want to show marker on google map by getting longitude and latitude from json

【发布时间】：2016-12-15 06:13:40

【问题描述】：

我想通过从 json 获取经度和纬度来在谷歌地图上显示标记。如果我在 AsyncTask 中使用标记，它不会在给定的纬度显示标记... 到目前为止我在这里......提前谢谢......

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback 

private GoogleMap mMap;
String city = "New Delhi";
String location = null;
double lat;
double lng ;


@Override
protected void onCreate(Bundle savedInstanceState) 
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);
    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
            .findFragmentById(R.id.map);
    mapFragment.getMapAsync(this);


    new JSONTask().execute("http://www.xxxxxxx.com/bar/mob.php");


@Override
public void onMapReady(GoogleMap googleMap) 
    mMap = googleMap;

    // Add a marker in Sydney and move the camera
    LatLng latLng = new LatLng(-30, 140);
    mMap.addMarker(new MarkerOptions().position(latLng).title("Marker"));
    mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));

    // i want use that lat and lng here which i am getting in AsyncTask
    LatLng latLng1 = new LatLng(lat, lng);
    mMap.addMarker(new MarkerOptions().position(latLng1).title("Marker"));
    mMap.setMyLocationEnabled(true);


private class JSONTask extends AsyncTask<String, String, List<Bardata>> 

    @Override
    protected List<Bardata> doInBackground(String... params) 

        HttpURLConnection connection = null;
        BufferedReader reader = null;


        try 
            URL url = new URL(params[0]);
            connection = (HttpURLConnection) url.openConnection();
            connection.setReadTimeout(10000);
            connection.setConnectTimeout(15000);
            connection.setRequestMethod("POST");
            connection.setDoInput(true);
            connection.setDoOutput(true);

            Uri.Builder builder = new Uri.Builder()
                    .appendQueryParameter("location", location)
                    .appendQueryParameter("city", city);
            String query = builder.build().getEncodedQuery();


            OutputStream os = connection.getOutputStream();
            BufferedWriter writer = new BufferedWriter(
                    new OutputStreamWriter(os, "UTF-8"));
            writer.write(query);
            writer.flush();
            writer.close();
            os.close();
            connection.connect();
            InputStream stream = connection.getInputStream();

            reader = new BufferedReader(new InputStreamReader(stream));

            StringBuffer buffer = new StringBuffer();

            String line = "";
            while ((line = reader.readLine()) != null) 
                buffer.append(line);
            
            String finalJson = buffer.toString();
            System.out.println("Returned value " + finalJson.toString());

            JSONObject parentObject = new JSONObject(finalJson);
            JSONArray parentArray = parentObject.getJSONArray("home");

            List<Bardata> bardataList = new ArrayList<>();
            Gson gson = new Gson();
            for (int i = 0; i < parentArray.length(); i++) 


                JSONObject finalObject = parentArray.getJSONObject(i);
                Bardata barData = gson.fromJson(finalObject.toString(), Bardata.class);
                bardataList.add(barData);


                lat = barData.getLatitude();
                lng = barData.getLongitude();

               /* LatLng latLng1 = new LatLng(lat, lng);
                mMap.addMarker(new MarkerOptions().position(latLng1).title("Marker"));
                mMap.setMyLocationEnabled(true);*/



            
            return bardataList;


         catch (MalformedURLException e) 
            e.printStackTrace();
         catch (IOException e) 
            e.printStackTrace();
         catch (JSONException e) 
            e.printStackTrace();
        


        return null;
    

    @Override
    protected void onPreExecute() 
        super.onPreExecute();

    

    @Override
    protected void onPostExecute(final List<Bardata> result) 
        super.onPostExecute(result);
        if (result != null) 

         else 
            Toast.makeText(getApplicationContext(), "Currently,we are not present in your city", Toast.LENGTH_SHORT).show();
        

    

bardata.java

public class Bardata 


private String barname;
private double longitude;
private double latitude;

public double getLongitude() 
    return longitude;


public void setLongitude(double longitude) 
    this.longitude = longitude;


public double getLatitude() 
    return latitude;


public void setLatitude(double latitude) 
    this.latitude = latitude;



public String getBarname() 
    return barname;


public void setBarname(String barname) 
    this.barname = barname;

【参考方案1】：

对于这个问题，github 上给出了示例代码 试试this

【参考方案2】：

您需要在 UI 线程上添加标记，因此您需要调用方法从 runOnUiThread 中添加标记

for (int i = 0; i < parentArray.length(); i++) 


 JSONObject finalObject = parentArray.getJSONObject(i);
 Bardata barData = gson.fromJson(finalObject.toString(), Bardata.class);
 bardataList.add(barData);


 lat = barData.getLatitude();
 lng = barData.getLongitude();
 LatLng latLng1 = new LatLng(lat, lng);

 runOnUiThread(new Runnable() 
  public void run() 
   try 

    mMap.addMarker(new MarkerOptions().position(latLng1).title("Marker"));
    mMap.setMyLocationEnabled(true);

    catch (JSONException e) 
    Log.e(LOG_TAG, "Error adding marker", e);
   
  
 );

【讨论】：

logcat 没有错误或警告，但标记未显示。

添加的标记是否与地图初始化的位置相同？在 onMapReady 方法中，您将地图移动到悉尼。