Android ItemizedOverlay 问题

Question

我必须在特定点的 map 上放置一些叠加层，我从 API 获取点坐标。我在异步任务中进行抓取。我成功地放置了叠加层，当我放大 map 或跨越它时，响应非常慢。这是我的 overlayitem 类和我的异步任务

public class Marker extends ItemizedOverlay<OverlayItem> {
    private Context con;

    private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();


    public Marker(Drawable defaultMarker) {
        super(boundCenterBottom(defaultMarker));
        // TODO Auto-generated constructor stub
    }

    public Marker(Drawable defaultMarker, Context context) {
        super(boundCenterBottom(defaultMarker));
        con=context;
        // TODO Auto-generated constructor stub
    }

    @Override
    protected OverlayItem createItem(int i) {
        // TODO Auto-generated method stub
        return mOverlays.get(i);
    }

    @Override
    public int size() {
        // TODO Auto-generated method stub
        return mOverlays.size();
    }

    public void addOverlay(OverlayItem overlay) {
        mOverlays.add(overlay);
        populate();
    }
}

...

private class TeleportdAPIParser extends AsyncTask<Void, Object, Void> {

        private final HttpTransport http= AndroidHttp.newCompatibleTransport();
        private HttpRequestFactory fact;
        private HttpRequest request; 
        private HttpResponse response; 
        private String urlString;
        private JsonFactory jsonFactory; 
        private JsonParser jp;
        MapView mapView;
        Marker marker;
        List<Overlay> mapOverlays;
        ImageAdapter adapter;



        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            mapView=(MapView) findViewById(R.id.mapView);
            Drawable drawable = getResources().getDrawable(R.drawable.puce);
            marker = new Marker(drawable);
            mapOverlays = mapView.getOverlays();
            adapter=new ImageAdapter();
            GridView gridview=(GridView) findViewById(R.id.gridView);


        }


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

            fact=http.createRequestFactory();
            jsonFactory = new JsonFactory();
            TPortItem tpi= new TPortItem();
            TPortItemList tpl=new TPortItemList();


                urlString="http://v1.api.teleportd.com:8080/search?apikey=1c5a31ccf46c54572e484e103c97239bd&loc=%5B48.87,2.34,5.0,5.0%5D";
                try {
                    //urlString=URLEncoder.encode(urlString,"UTF-8");
                    request = fact.buildGetRequest(new GenericUrl(urlString));
                    HttpHeaders header=new HttpHeaders();
                    header.setAcceptEncoding("gzip");
                    request.setHeaders(header);
                    response = request.execute();
                    jp = jsonFactory.createJsonParser(new BufferedInputStream(response.getContent()));


                    while(jp.nextValue()!=JsonToken.NOT_AVAILABLE){

                        jp.nextValue();
                        while(jp.getCurrentToken()!=JsonToken.END_OBJECT && jp.getCurrentToken()!=null){                            

                                if(jp.getCurrentName().equals("sha")){
                                    tpi.sha=jp.getText();
                                }

                                if(jp.getCurrentName().equals("date")){
                                    tpi.date=jp.getIntValue();          
                                }

                                if(jp.getCurrentName().equals("age")){
                                    tpi.age=jp.getIntValue();
                                }

                                if(jp.getCurrentName().equals("thumb")){
                                    tpi.thumb=jp.getText();
                                    if(adapter.URLS.size()<10)
                                        adapter.URLS.add(tpi.thumb);

                                }

                                if(jp.getCurrentName().equals("rank")){
                                    tpi.rank=jp.getIntValue();
                                }

                                if(jp.getCurrentName().equals("grade")){
                                    tpi.grade=jp.getIntValue();
                                }

                                if(jp.getCurrentName().equals("loc")){
                                    jp.nextValue().toString();
                                    tpi.loc[0]=(int) (jp.getFloatValue()*1E6);
                                    jp.nextValue().toString();
                                    tpi.loc[1]=(int) (jp.getFloatValue()*1E6);
                                    jp.nextValue();
                                    publishProgress(new GeoPoint (tpi.loc[0],tpi.loc[1]));

                                }

                                jp.nextValue(); 
                            }



                        //tpl.i.add(new TPortItem(tpi.sha, tpi.loc,tpi.age, tpi.date,tpi.thumb, tpi.rank, tpi.grade));


                    }   

                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

            return null;
        }

        @Override
        protected void onProgressUpdate(Object... values) {
            super.onProgressUpdate(values);
            marker.addOverlay(new OverlayItem((GeoPoint) values[0], "Hola, Mundo!", "I'm in Mexico City!"));
            mapOverlays.add(marker); // adding the whole overlays (list) on the maps


        }


        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            mapView.invalidate();
            //gridview.setAdapter(adapter);
        }
}

Answer 1

MapView 可以处理的叠加项数量是有限制的。没有关于此限制的官方消息，但一段时间后，您会在缩放/平移期间看到缓慢的行为。

一些解决方案是:

• > LazyLoading of MapView
• 只加载尽可能多的可见标记，根据缩放级别和跨度执行此操作。
• 10 个 99 点叠加层比 1 个 990 点叠加层更快。