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私はアンドロイドで道路の方向を描きたいと思います。私は何度も試してみましたが、私はいつもあなたの助けGoogleマップヌルオブジェクトリファレンスでインタフェースメソッド 'int java.util.List.size（）'を呼び出そうとしています
行き方パーサ
public class DirectionsJSONParser {
public List<List<HashMap<String, String>>> parse(JSONObject jObject) {
List<List<HashMap<String, String>>> routes = new ArrayList<List<HashMap<String, String>>>();
JSONArray jRoutes = null;
JSONArray jLegs = null;
JSONArray jSteps = null;
try {
jRoutes = jObject.getJSONArray("routes");
for (int i=0 ; i<jRoutes.length(); i++)
{
jLegs = ((JSONObject)jRoutes.get(i)).getJSONArray("legs");
List path = new ArrayList<HashMap<String, String>>();
for (int j=0; j<jLegs.length(); j++)
{
jSteps = ((JSONObject)jLegs.get(j)).getJSONArray("steps");
for (int k=0; k<jSteps.length(); k++)
{
String polyline = "";
polyline = (String)((JSONObject)((JSONObject)jSteps.get(k)).get("polyline")).get("points");
List<LatLng> list = decodePoly(polyline);
for(int l=0; l<list.size(); l++)
{
HashMap<String, String> hm = new HashMap<String, String>();
hm.put("lat", Double.toString(((LatLng)list.get(l)).latitude));
hm.put("lng", Double.toString(((LatLng)list.get(l)).longitude));
path.add(hm);
}
}
routes.add(path);
}
}
} catch (JSONException e) {
e.printStackTrace();
}catch (Exception e)
{
}
return routes;
}
private List<LatLng> decodePoly(String encoded)
{
List<LatLng> poly = new ArrayList<LatLng>();
int index = 0, len = encoded.length();
int lat = 0, lng = 0;
while (index < len) {
int b, shift = 0, result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lat += dlat;
shift = 0;
result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lng += dlng;
LatLng p = new LatLng((((double) lat/1E5)),
(((double) lng/1E5)));
poly.add(p);
}
return poly;
}
}
DirectionActivityに同じerror.Thankあなたを得る
public class DirectionActivity extends FragmentActivity {
GoogleMap map;
ArrayList<LatLng> markerPoints;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.deneme_activity);
markerPoints = new ArrayList<LatLng>();
map = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.haritafragment)).getMap();
if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
map.setMyLocationEnabled(true);
map.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
@Override
public void onMapClick(LatLng point) {
if(markerPoints.size()>1)
{
markerPoints.clear();
map.clear();
}
markerPoints.add(point);
MarkerOptions options = new MarkerOptions();
options.position(point);
if(markerPoints.size() == 1)
{
options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN));
}else if(markerPoints.size() == 2)
{
options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED));
}
map.addMarker(options);
if(markerPoints.size() >= 2)
{
LatLng origin = markerPoints.get(0);
LatLng dest = markerPoints.get(1);
String url = getDirectionsUrl(origin, dest);
DownloadTask downloadTask = new DownloadTask();
downloadTask.execute();
}
}
});
}
private String getDirectionsUrl(LatLng origin,LatLng dest){
// Origin of route
String str_origin = "origin="+origin.latitude+","+origin.longitude;
// Destination of route
String str_dest = "destination="+dest.latitude+","+dest.longitude;
// Sensor enabled
String sensor = "sensor=false";
// Building the parameters to the web service
String parameters = str_origin+"&"+str_dest+"&"+sensor;
// Output format
String output = "json";
String url = "https://maps.googleapis.com/maps/api/directions/"+output+"?"+parameters;
return url;
}
private String downloadUrl(String strUrl) throws IOException, IOException {
String data = "";
InputStream iStream = null;
HttpURLConnection urlConnection = null;
try{
URL url = new URL(strUrl);
urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while((line = br.readLine()) != null){
sb.append(line);
}
data = sb.toString();
br.close();
}catch(Exception e){
Log.d("Exception while downloading url", e.toString());
}finally{
iStream.close();
urlConnection.disconnect();
}
return data;
}
// Fetches data from url passed
private class DownloadTask extends AsyncTask<String, Void, String> {
// Downloading data in non-ui thread
@Override
protected String doInBackground(String... url) {
// For storing data from web service
String data = "";
try{
// Fetching the data from web service
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
// Executes in UI thread, after the execution of
// doInBackground()
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
ParserTask parserTask = new ParserTask();
// Invokes the thread for parsing the JSON data
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]);
DirectionsJSONParser parser = new DirectionsJSONParser();
// Starts parsing data
routes = parser.parse(jObject);
}catch(Exception e){
e.printStackTrace();
}
return routes;
}
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> result) {
ArrayList<LatLng> points = null;
PolylineOptions lineOptions = null;
MarkerOptions markerOptions = new MarkerOptions();
// Traversing through all the routes
for(int i=0;i<result.size();i++){
points = new ArrayList<LatLng>();
lineOptions = new PolylineOptions();
// Fetching i-th route
List<HashMap<String, String>> path = result.get(i);
// Fetching all the points in i-th route
for(int j=0;j<path.size();j++){
HashMap<String,String> point = path.get(j);
double lat = Double.parseDouble(point.get("lat"));
double lng = Double.parseDouble(point.get("lng"));
LatLng position = new LatLng(lat, lng);
points.add(position);
}
// Adding all the points in the route to LineOptions
lineOptions.addAll(points);
lineOptions.width(2);
lineOptions.color(Color.RED);
}
// Drawing polyline in the Google Map for the i-th route
map.addPolyline(lineOptions);
}
}
}
とERROR
04-07 05：59：35.517 19387から19387/E/AndroidRuntime com.example.mapdemo：致命的な例外：メイン プロセス：com.example.mapdemo、PID：19387 java.lang.NullPointerException：ヌルオブジェクトリファレンスでインタフェースメソッド 'int java.util.List.size（）'を呼び出そうとしました com.example.mapdemo.DirectionActivity $ ParserTask.onPostExecute（DirectionActivity.java:215） at com.example.mapdemo.DirectionActivity $ ParserTask.onPostExecute（DirectionActivity.java:189） android.os.AsyncTask.finish（ AsyncTask.java:636） android.os.AsyncTask.access $ 500（AsyncTask.java:177） at android.os.AsyncTask $ InternalHandler.handleMessage（AsyncTask.java:653） android.os.Handler.dispatchMessage （Handler.java:102） android.os.Looper.loop（Looper.java:135） android.app.ActivityThread.main（ActivityThread.java:5254） at java.lang.reflect.Method.invoke （ネイティブメソッド） at java.lang.reflect.Mava.zip（0120） internal.os.ZygoteInit.main（ZygoteInit.ja VA：698）
