我试图将一个geojson层显示在Google地图上。代码如下。geojson文件存储在我的raw文件夹中。该文件有286个特征(约15MB)。因此,读取并显示它需要消耗更多的时间。最初,我遇到了内存不足的错误,通过在清单文件中设置大堆为true来解决了这个问题。如何快速加载此文件(当前需要一分钟或更长时间)?我想知道是否有其他有效的方法来做到这一点。之后,我还要执行其他任务,如获取功能并显示一些属性。
@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文件的一个非常小的部分如下:
{
"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,并并行地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(AsyncTask):
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();
}
}
这个建议可行吗?这么做可以比之前缩短时间,但考虑到用户体验因素,速度仍然不够快。