我正在为汽车预订做一个应用程序，在这里我需要在地图上添加行，当汽车从驾驶员位置移动到用户位置时。当我试图使用递归调用方向API时首先它在地图上添加行并将更新近6次并突然崩溃说空指针异常，但为什么？
TheLibabry.executeScript(scriptCode, apiObjects, timeout);
//这里我正在调用另一种在地图上添加行的方法，该方法工作正常但是当我这样做时，它会在6-7调用后崩溃。为什么？或者是他们以任何其他方式动态添加线条，因为汽车在用户i android附近移动
enter code here
public void set_path_onmap( ) {
LatLng driver_location = new LatLng(global_location.getLatitude(), global_location.getLongitude());
Log.i("loc_drive", String.valueOf(driver_location));
Log.i("loc_user", String.valueOf(user_location));
String url = getDirectionsUrl(user_location, driver_location);
DownloadTask downloadTask = new DownloadTask();
downloadTask.execute(url);
}
public void timecalling() {
new CountDownTimer(5000, 1000) {
public void onTick(long millisUntilFinished) {
}
public void onFinish() {
set_path_onmap();
timecalling();
}
}.start();
}
//这是我在地图上添加行的调用 //方向api开始********************************************* ************************************************** ************
enter code here
//在Google Map中为第i条路线绘制折线 mMap.addPolyline（lineOptions）;
private class DownloadTask extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... url) {
String data = "";
try {
data = downloadUrl(url[0]);
} catch (Exception e) {
Log.d("Background Task", e.toString());
}
return data;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
ParserTask parserTask = new ParserTask();
parserTask.execute(result);
}
}
private class ParserTask extends AsyncTask<String, Integer, List<List<HashMap<String, String>>>> {
@Override
protected List<List<HashMap<String, String>>> doInBackground(String... jsonData) {
JSONObject jObject;
List<List<HashMap<String, String>>> routes = null;
try {
jObject = new JSONObject(jsonData[0]);
ParserTask.DirectionsJSONParser parser = new ParserTask.DirectionsJSONParser();
routes = parser.parse(jObject);
} catch (Exception e) {
e.printStackTrace();
}
return routes;
}
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> result) {
/* List<LatLng> points = polyline.getPoints();
points.add(newPoint);
polyline.setPoints(points); */
points = null;
lineOptions = null;
MarkerOptions markerOptions = new MarkerOptions();
for (int i = 0; i < result.size(); i++) {
points = new ArrayList();
lineOptions = new PolylineOptions();
List<HashMap<String, String>> path = result.get(i);
for (int j = 0; j < path.size(); j++) {
HashMap point = path.get(j);
double lat = Double.parseDouble((String) point.get("lat"));
double lng = Double.parseDouble((String) point.get("lng"));
LatLng position = new LatLng(lat, lng);
points.add(position);
Log.i("pointsloop", String.valueOf(points));
}
lineOptions.addAll(points);
lineOptions.width(8);
lineOptions.color(Color.BLACK);
lineOptions.geodesic(true);
}
Log.i("pointsoutside", String.valueOf(points));
Log.i("mapline", String.valueOf(lineOptions));