如何通过处理程序更新地图？

Question

我正在用Asynctask更新地图。现在我想用Handler做同样的事情。我环顾四周，但无法理解我应该做什么。 AsyncTask有点慢，我希望它有点快。

下面是我在做什么在的AsyncTask：

class DrawRouteTask extends AsyncTask<GeoPoint, Void, Polyline> { 

    private Exception exception; 
    private Polyline roadOverLay; 

    @Override 
    protected void onPostExecute(Polyline polyline) { 
     super.onPostExecute(polyline); 
     Log.i("AsyncTAsk ", " in post execute " + roadOverLay); 
     roadOverlay = roadOverLay; 


     // mOsmv.invalidate(); 

     mOsmv.getOverlays().add(roadOverLay); 
     mOsmv.invalidate(); 
    } 

    @Override 
    protected Polyline doInBackground(GeoPoint... geoPoints) { 
     try { 
      Log.i("AsyncTask", "Start Point >> " + geoPoints[0]); 
      Log.i("AsyncTask", "End Point >> " + geoPoints[1]); 

      RoadManager roadManager = new OSRMRoadManager(getContext()); 

      ArrayList<GeoPoint> waypoints = new ArrayList<>(); 
      waypoints.add(geoPoints[0]); 
      waypoints.add(geoPoints[1]); 


      Marker marker = new Marker(mOsmv); 
      marker.setPosition(geoPoints[0]); 
      marker.setPosition(geoPoints[1]); 

      marker.setTitle("Your Location "); 
      Log.i("AsyncTask ", "Drawable >> "+ ContextCompat.getDrawable(getContext(), R.drawable.pin)); 
      marker.setIcon(ContextCompat.getDrawable(getContext(), R.drawable.pin)); 


      mOsmv.getOverlays().add(marker); 

      road = roadManager.getRoad(waypoints); 

      roadOverLay = RoadManager.buildRoadOverlay(road); 
      roadOverLay.setColor(Color.RED); 


      return roadOverLay; 


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

     return null; 

    } 
} 

任何帮助，将不胜感激。

Answer 1

你的意思是由一个线程和处理程序？

做任何在你的doInBackground（）函数内的线程，并通过处理程序发送到主线程。

你的代码应该看起来大致像这样。

new Thread(new Runnable(){ 
      public void run(){ 
       // your doInBackground() codes.. 
       Message msg = handler.obtainMessage(what);//what refers to a field what inside Message; 
       msg.obj = anything you want to put; 
       msg.sendToTarget(); //dispatches msg to the certain handler. 
      } 

    }).start(); 

private Handler handler = new Handler(){ 
    public void handleMessage(Message msg){ 
    //handles message dispatched from the above code. 
    int what = msg.what; //You can use the 'what' as a switch-case case. 
    SomeObject data = (SomeObject) msg.obj; // 
    } 

} 

注意，线程的run（）或的AsyncTask的doInBackground不是UI线程，这意味着，改变这些方法中的UI会造成死机。但是，handlerMessage（）或onPostExecute（）方法在主线程内执行，您可以使用它来更新视图。