android - 如何将我的数据库的 AsyncTask 与 android 中的谷歌地图结合起来？

Question

我有一张 map ，点击按钮后会显示附近的地点。然后，我使用 google map utils 自定义了我的标记。例如:

icon(BitmapDescriptorFactory.fromBitmap(iconFactory.makeIcon(Here would be the data from database)))

因此，标记将显示其中的数据。问题是在我的项目中实现 AsynTask 之前一切正常，标记将默认显示地点名称，它将是这样的:

.icon(BitmapDescriptorFactory.fromBitmap(iconFactory.makeIcon(place.getName().toString())))

在我的项目中AsynTask之后，它停止工作，甚至在单击按钮后标记也不会显示。完整的代码如下:

public class MainActivity extends ActionBarActivity implements GoogleMap.OnMyLocationChangeListener, View.OnClickListener, GoogleMap.OnInfoWindowClickListener {

private static final String TAG = "MapsActivity";

private GoogleMap mMap; // Might be null if Google Play services APK is not available.
private Button btnFindNearby;
double latitude = 0;
double longitude = 0;
private Location currentLocation;
private static final int DEFAULT_RADIUS = 500;
private Map<Marker, Result> places = new HashMap<>();
//Json url to get the place's name varaible to json
private static final String JSON_URL = "http://192.168.1.2/dataconnection.php";
String myJSON;
private JSONArray users = null;
private static final String JSON_ARRAY ="result";
private static final String name = "name";
private static final String description = "description";
private static final String title = "title";
private String JSName;
private String JSDesc;
private String JSTitle;
private String Jname;
private String Jtitle;
Private String iconTitle;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);
    setTitle(getString(R.string.map));
    initializeViews();
}

private void initializeViews() {
    setUpMapIfNeeded();
    btnFindNearby = (Button) findViewById(R.id.button_findNearby);
    btnFindNearby.setOnClickListener(this);
}

@Override
protected void onResume() {
    super.onResume();
    setUpMapIfNeeded();
}


private void setUpMapIfNeeded() {
    // Do a null check to confirm that we have not already instantiated the map.
    if (mMap == null) {
        // Try to obtain the map from the SupportMapFragment.
        mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                .getMap();
        // Check if we were successful in obtaining the map.
        if (mMap != null) {
            setUpMap();
        }
    }
}

private void setUpMap() {
    mMap.setMyLocationEnabled(true);
    mMap.setOnMyLocationChangeListener(this);
    mMap.setOnInfoWindowClickListener(this);
}

private void addMarker(Result place,String Jname.String Jtitle) {
    com.mkpazon.foodnearby.net.Location location =           place.getGeometry().getLocation();
    IconGenerator iconFactory = new IconGenerator(this);
    double latitude = location.getLat();
    double longitude = location.getLng();
if(Jname.equals(place.getName().toString()))
{
      iconTitle=Jtitle;
}else{
     iconTitle=place.getName().toString();
}
    Marker marker = mMap.addMarker(new MarkerOptions()
            .icon(BitmapDescriptorFactory.fromBitmap(iconFactory.makeIcon(iconTitle)))
            .position(new LatLng(latitude, longitude))
            .title(place.getName())
            .anchor(iconFactory.getAnchorU(), iconFactory.getAnchorV())
            .snippet(place.getVicinity()));
    places.put(marker, place);


}

private void clearMarkers() {
    for (Marker marker : places.keySet()) {
        //Remove marker from map
        marker.remove();
    }
    places.clear();
}

@Override
public void onMyLocationChange(Location location) {
    this.currentLocation = location;
    //zoom  the map automatically
    float zoomLevel = (float) 16.0; //This goes up to 21
   latitude = location.getLatitude();
   longitude = location.getLongitude();
   LatLng latLng = new LatLng(latitude, longitude);
    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng, zoomLevel));

}

@Override
public void onClick(View v) {
    if (v == btnFindNearby) {
        if (currentLocation != null) {
            List<String> types = new ArrayList<>();
            types.add("food");
            types.add("cafe");
            types.add("restaurant");
            getJSON(JSON_URL);
            PlacesUtility.findPlacesWithinRadius(this, types, currentLocation, DEFAULT_RADIUS, new PlacesSearchListener() {
                @Override
                public void onResult(SearchResponse response) {
                    Log.d(TAG, "Clearing all markers");
                    clearMarkers();

                    Log.d(TAG, "Adding result markers");
                    List<Result> results = response.getResults();


                    for (Result result : results) {
                      for(int i=0;i<users.length();i++){
                        try {
                            JSONObject c = users.getJSONObject(i);
                            JSName = c.getString(name);
                            JSDesc = c.getString(description);
                            JSTitle = c.getString(title);
                        }
                        catch(JSONException e)
                        {
                            e.printStackTrace();
                        }

                        com.mkpazon.foodnearby.net.Location location = result.getGeometry().getLocation();
                        double latitude = location.getLat();
                        double longitude = location.getLng();
                        Log.d(TAG, "> " + result.getName() + " " + latitude + "," + longitude);
                        addMarker(result,JSName,JSTitle);

                    }
                }
                     }
            });

        } else {
            Log.d(TAG, "Current location not available");
            final Dialog dialog = InfoDialog.newInstance(this, getString(R.string.error),
                    getString(R.string.current_location_not_available), null);
            dialog.show();
        }
    }
}//end of find button

@Override
public void onInfoWindowClick(Marker marker) {
    Log.d(TAG, "Info window of marker \"" + marker.getTitle() + "\" has been clicked.");
    Result place = places.get(marker);

    Gson gson = new Gson();
    String placeJson = gson.toJson(place);

    Intent intent = new Intent(this, PlaceDetailsActivity.class);
    intent.putExtra(PlaceDetailsActivity.EXTRA_PLACE_JSON, placeJson);
    startActivity(intent);
}

//Async Task to access the web
private void getJSON(String url) {
    class GetJSON extends AsyncTask<String, Void, String> {
        String result = null;
        //ProgressDialog loading;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
           loading = ProgressDialog.show(MainActivity.this, "Please Wait...",null,true,true);
        }

        @Override
        protected String doInBackground(String... params) {

            String uri = params[0];

            BufferedReader bufferedReader = null;
            try {
                URL url = new URL(uri);
                HttpURLConnection con = (HttpURLConnection) url.openConnection();
                StringBuilder sb = new StringBuilder();

                bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));

                String json;
                while((json = bufferedReader.readLine())!= null){
                    sb.append(json+"\n");
                }
                result=sb.toString().trim();
                return sb.toString().trim();

            }catch(Exception e){
                return null;
            }

        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            myJSON=result;
            extractJSON(myJSON);
            //loading.dismiss();
            //textViewJSON.setText(s);

        }
    }
    GetJSON gj = new GetJSON();
    gj.execute(url);
}

//Extrta JSON
public void extractJSON(String myJSONString)
{
    try {
        JSONObject jsonObject = new JSONObject(myJSONString);
        users = jsonObject.getJSONArray(JSON_ARRAY);
    } catch (JSONException e) {
        e.printStackTrace();
    }

  }
  }

请帮我找到解决这个问题的方法。谢谢。

Answer 1

AsyncTask 在另一个线程中运行，因此它是异步的。

您使用 PlacesUtility.findPlacesWithinRadius 的代码应该在 AsyncTask 完成时执行，而不是并行执行。因此，您必须将 PlacesUtility.findPlacesWithinRadius(仅此)从 AsyncTask 移动到 onPostExecute。

移动代码应该可以解决您的问题。