android - 在 android 谷歌地图中显示大的 geojson 文件

Question

我正在尝试向 Google map 显示一个 geojson 图层。代码如下。 geojson 文件本地存储在我的原始文件夹中。该文件有 286 个特征(大约 15MB)。因此，读取此文件并显示它会消耗更多时间。最初，我遇到了内存不足错误，通过在 list 文件中将 large heap 设置为 true 来消除该错误。我怎样才能快速加载这个文件(目前，它需要一分钟或更长时间)？我想知道是否有其他有效的方法可以做到这一点。在此之后，我还将有其他任务，如获取功能和显示一些属性。

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

@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(myanmar, 5.25f));
    new MyAsyncTask().execute();
}

public class MyAsyncTask extends AsyncTask <Void, Void, Void> {

    ProgressDialog pd;
    GeoJsonLayer layer;

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pd = new ProgressDialog(MapsActivity.this);
        pd.setMessage("Loading Data");
        pd.show();
    }

    @Override
    protected Void doInBackground(Void... voids) {
        try {
            layer = new GeoJsonLayer(mMap, R.raw.myanmar, getApplicationContext());
        } catch (Exception e) {
            Log.d("Error is : ", e.toString());
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);
        pd.cancel();
        layer.addLayerToMap();
     }
}

我的geojson文件的一小部分如下:

{
 "type": "FeatureCollection",
 "crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } },
 "features": [
{ "type": "Feature", "properties": { "ID_3": 193, "NAME_3": "Chaung-U" }, "geometry": { "type": "MultiPolygon", "coordinates": [ [ [ [ 95.348327636718807, 21.878610610961914 ], [ 95.297210693359432, 21.860000610351676 ], [ 95.286926269531307, 21.853612899780387 ], [ 95.276092529296989, 21.850000381469727 ], [ 95.265823364257926, 21.84832954406744 ], [ 95.257217407226676, 21.846940994262695 ] ] ] ] } },
{ "type": "Feature", "properties": { "ID_3": 199, "NAME_3": "Myaung" }, "geometry": { "type": "MultiPolygon", "coordinates": [ [ [ [ 95.376281738281193, 21.708541870117301 ], [ 95.375259399414119, 21.703050613403434 ], [ 95.370529174804801, 21.681390762329102 ], [ 95.367752075195313, 21.664720535278434 ], [ 95.366699218750114, 21.658369064331055 ], [ 95.362762451171875, 21.649999618530273 ] ] ] ] } }
]}

我尝试将文件分成多个小文件单元并并行运行单独的异步任务，每个任务处理一个单独的文件:

for (int i = 1; i < 3; i++) {
        new MyAsyncTask().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,i);
}

异步任务:

public class MyAsyncTask extends AsyncTask <Integer, Void, GeoJsonLayer> {

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

    @Override
    protected GeoJsonLayer doInBackground(Integer... integers) {
        int i = integers[0];
        try {
            GeoJsonLayer layer = null;
            switch (i) {
                case 1:
                    layer = new GeoJsonLayer(mMap, R.raw.small_1,
                            getApplicationContext());
                    break;
                case 2:
                    layer = new GeoJsonLayer(mMap, R.raw.small_2,
                            getApplicationContext());
                    break;
                //other cases
            }
            for (GeoJsonFeature feature : layer.getFeatures()) {
                geoJsonFeatures.put(Integer.parseInt(feature.getProperty("ID_3")), feature);
            }
            return layer;
        } catch (Exception e) {
            return null;
        }
    }

    @Override
    protected void onPostExecute(GeoJsonLayer layer) {
        super.onPostExecute(layer);
        layer.addLayerToMap();
    }
}

这是推荐的吗？这样一来，时间比之前有所减少，但考虑到用户体验因素，还是不够快。

Answer 1

最后，通过减小 geojson 文件的大小解决了这个问题。二手http://mapshaper.org/ ，一种在线工具，可为您提供缩小尺寸但保持形状的选项。用它来获取简化文件(近300KB)和bang，加载在几秒钟内完成。希望这对面临同样问题的人有所帮助。