onPostExecute未正确启动活动

Question

我正在使用AsyncTask在mySQL在线数据库中运行信息。然后我使用JSON解析将数据库中的信息添加为MapBox地图上的标记。目前，当用户上传新标记（代码中的washroom）时，它会将信息上载到数据库，然后运行onPostExecute方法并返回到MapsActivity.java。 MapsActivity.java应重新加载地图并显示新添加的标记，但它不会;它只显示在添加新标记之前添加的标记。如果您关闭并打开应用程序，则会更新标记，并显示包括新标记在内的所有标记！任何帮助，将不胜感激！ MapsActivity.java的

部分

public class MapsActivity extends FragmentActivity { 


private MapView mapView; 
private MapboxMap map; 
private ImageButton locationToggle; 
private LocationServices locationServices; 
private String json_string; 
private JSONObject jsonObject; 
private JSONArray jsonArray; 

public static String WASHROOMINFO; 

public static String CURRENT_LOCATION; 

private static final int PERMISSIONS_LOCATION = 0; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    MapboxAccountManager.start(this, getString(R.string.accessToken)); 
    setContentView(R.layout.activity_maps); 


    //getting location services 
    locationServices = com.mapbox.mapboxsdk.location.LocationServices.getLocationServices(MapsActivity.this); 

    //onClick to go to add washroom activity 
    findViewById(R.id.addWashroom).setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 

      if (CURRENT_LOCATION != null) { 

       Intent intent = new Intent(getBaseContext(), AddWashroom.class); 
       startActivity(intent); 

      } else { 

       Toast.makeText(getBaseContext(),"You Must Turn on User Location Before Adding a Washroom!",Toast.LENGTH_LONG).show(); 

      } 

     } 
    }); 

    //washrooms have not been loaded in yet 
    if (!BackgroundTask.WASHROOMS_LOADED) { 
     //getting database info 
     String method = "getWashroom"; 
     BackgroundTask backgroundTask = new BackgroundTask(getBaseContext()); 
     backgroundTask.execute(method); 
     finish(); 

    } 

    mapView = (MapView) findViewById(R.id.mapview); 
    mapView.onCreate(savedInstanceState); 
    mapView.getMapAsync(new OnMapReadyCallback() { 
     @Override 
     public void onMapReady(MapboxMap mapboxMap) { 
      //when map is ready assign mapboxMap variable 
      map = mapboxMap; 

      //Washroom loading has been requested and JSON data is ready 
      if (BackgroundTask.WASHROOMS_LOADED) { 

       //Getting JSON data from intent 
       json_string = getIntent().getExtras().getString("json_data"); 
       try { 
        //new JSON object from JSON data 
       jsonObject = new JSONObject(json_string); 
        //gets JSON array from JSON object 
        jsonArray = jsonObject.getJSONArray("server_response"); 

        //Marker list for buffering markers 
        List<Marker> markers = new ArrayList<Marker>(); 

        //do this for all markers! 
        for (int i = 0; i < jsonArray.length(); i++) { 
         //Single JSON object of single marker 
         JSONObject JO = jsonArray.getJSONObject(i); 

         //Dividing location field into lat & lng 
         String latlng = JO.getString("location"); 
         String[] latlngSplit = latlng.split(" , ",2); 
         double lat = Double.valueOf(latlngSplit[0]); 
         double lng = Double.valueOf(latlngSplit[1]); 


         //adding marker 
         Marker marker = map.addMarker(new MarkerOptions() 
         .title(JO.getString("name")) 
           .setSnippet(JO.getString("price")) 
           .position(new LatLng(lat,lng)) 
         ); 

         //add marker to markers list. 
         markers.add(marker); 

        } 

        BackgroundTask.WASHROOMS_LOADED = false; 

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

      } 

     } 
    }); 

    locationToggle = (ImageButton) findViewById(R.id.location_toggle); 
    locationToggle.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      if (map != null) { 
       //toggle GPS when clicking show location button 
       toggleGps(!map.isMyLocationEnabled()); 
      } 
     } 
    }); 

} 

BackgroundTask（的AsyncTask）

class BackgroundTask extends AsyncTask<String, Void, String> { 
Context ctx; 
public static boolean WASHROOMS_LOADED; 
private String JSON_STRING; 
private String json_string; 

BackgroundTask(Context ctx) { 
    this.ctx = ctx.getApplicationContext(); 


} 

@Override 
protected void onPreExecute() { 
    super.onPreExecute(); 
} 
String add_url = "http://appart-software.com/add_washroom.php"; 
String get_url = "http://appart-software.com/get_washroom.php"; 
@Override 
protected String doInBackground(String... params) { 
    String method = params[0]; 
    if (method.equals("addWashroom")) { 

     String location = params[1]; 
     String name = params[2]; 
     String price = params[3]; 

     try { 
      URL url = new URL(add_url); 
      HttpURLConnection httpUrlConnection = (HttpURLConnection) url.openConnection(); 
      httpUrlConnection.setRequestMethod("POST"); 
      httpUrlConnection.setDoOutput(true); 
      OutputStream outputStream = httpUrlConnection.getOutputStream(); 
      BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream,"UTF-8")); 
      String data_string = URLEncoder.encode("WClocation","UTF-8")+"="+URLEncoder.encode(location,"UTF-8")+"&"+ 
        URLEncoder.encode("WCname","UTF-8")+"="+URLEncoder.encode(name,"UTF-8")+"&"+ 
        URLEncoder.encode("WCprice","UTF-8")+"="+URLEncoder.encode(price,"UTF-8"); 
      bufferedWriter.write(data_string); 
      bufferedWriter.flush(); 
      bufferedWriter.close(); 
      outputStream.close(); 
      InputStream inputStream = httpUrlConnection.getInputStream(); 
      inputStream.close(); 
      httpUrlConnection.disconnect(); 
      return "Washroom Added!"; 

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


     //You want to get washroom info 
    } else if (method.equals("getWashroom")){ 

     try { 

      URL url = new URL(get_url); 
      HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection(); 
      InputStream inputStream = httpURLConnection.getInputStream(); 
      BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,"iso-8859-1")); 
      StringBuilder stringBuilder = new StringBuilder(); 
      while ((JSON_STRING = bufferedReader.readLine())!=null) { 

       stringBuilder.append(JSON_STRING+"\n"); 
      } 

      bufferedReader.close(); 
      inputStream.close(); 
      httpURLConnection.disconnect(); 
      //Return JSON formatted info 
      return stringBuilder.toString().trim(); 


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


    } 

    return null; 
} 

@Override 
protected void onProgressUpdate(Void... values) { 
    super.onProgressUpdate(values); 
} 

@Override 
protected void onPostExecute(String result) { 

    if (result.equals("Washroom Added!")) { 

     Toast.makeText(ctx,result,Toast.LENGTH_LONG).show(); 

     WASHROOMS_LOADED = false; 


    } else { 

     //setting result as a movable string 
     json_string = result; 

     //intent and sending JSON data 
     Intent intent = new Intent(ctx,MapsActivity.class); 
     intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 
     intent.putExtra("json_data",json_string); 
     ctx.startActivity(intent); 

     WASHROOMS_LOADED = true; 


    } 
} 
} 

如果你不再需要我的代码，我会很乐意展示更多一些。

Answer 1

您在重新打开应用程序时得到新标记，因为您正在获取仅在活动开始时触发的onCreate()方法中的数据库信息。尝试获取数据库信息时，位置更改或尝试覆盖onNewIntent方法。首先将onNewIntent覆盖您的活动的launchmode至清单中的singleTop。