Iam在带有标记的两个指定位置之间绘制路径。
如果直接硬编码经度和latitutde值工作正常。
两点之间的路径和标记显示良好。
但从其他意图获取经度和latitutde值然后显示标记点，显示空指针异常。
帮我解决这个问题。（从其他意图中恢复经度和latitutde值，在Toast Messsage中显示）
04-22 15:21:46.268: W/System.err(3561): java.lang.NullPointerException
04-22 15:21:46.323: D/dalvikvm(3561): GC_FOR_ALLOC freed 1088K, 20% free 11180K/13943K, paused 54ms, total 54ms
04-22 15:21:46.341: W/System.err(3561): at com.google.maps.api.android.lib6.d.bh.<init>(Unknown Source)
04-22 15:21:46.342: W/System.err(3561): at com.google.maps.api.android.lib6.d.fk.a(Unknown Source)
04-22 15:21:46.342: W/System.err(3561): at com.google.android.gms.maps.internal.l.onTransact(SourceFile:137)
04-22 15:21:46.342: W/System.err(3561): at android.os.Binder.transact(Binder.java:326)
04-22 15:21:46.342: W/System.err(3561): at com.google.android.gms.maps.internal.IGoogleMapDelegate$a$a.addPolyline(Unknown Source)
04-22 15:21:46.342: W/System.err(3561): at com.google.android.gms.maps.GoogleMap.addPolyline(Unknown Source)
04-22 15:21:46.342: W/System.err(3561): at com.example.locatiowaypath.MainActivity$ParserTask.onPostExecute(MainActivity.java:330)
04-22 15:21:46.342: W/System.err(3561): at com.example.locatiowaypath.MainActivity$ParserTask.onPostExecute(MainActivity.java:1)
04-22 15:21:46.342: W/System.err(3561): at android.os.AsyncTask.finish(AsyncTask.java:631)
04-22 15:21:46.342: W/System.err(3561): at android.os.AsyncTask.access$600(AsyncTask.java:177)
04-22 15:21:46.343: W/System.err(3561): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
04-22 15:21:46.343: W/System.err(3561): at android.os.Handler.dispatchMessage(Handler.java:99)
04-22 15:21:46.343: W/System.err(3561): at android.os.Looper.loop(Looper.java:153)
04-22 15:21:46.344: W/System.err(3561): at android.app.ActivityThread.main(ActivityThread.java:5086)
04-22 15:21:46.344: W/System.err(3561): at java.lang.reflect.Method.invokeNative(Native Method)
04-22 15:21:46.344: W/System.err(3561): at java.lang.reflect.Method.invoke(Method.java:511)
04-22 15:21:46.344: W/System.err(3561): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:821)
04-22 15:21:46.344: W/System.err(3561): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
04-22 15:21:46.348: W/System.err(3561): at dalvik.system.NativeStart.main(Native Method)
DirectionsJSONParser.java
package com.example.locatiowaypath;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import com.google.android.gms.maps.model.LatLng;
public class DirectionsJSONParser {
/** Receives a JSONObject and returns a list of lists containing latitude and longitude */
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");
/** Traversing all routes */
for(int i=0;i<jRoutes.length();i++){
jLegs = ( (JSONObject)jRoutes.get(i)).getJSONArray("legs");
List path = new ArrayList<HashMap<String, String>>();
/** Traversing all legs */
for(int j=0;j<jLegs.length();j++){
jSteps = ( (JSONObject)jLegs.get(j)).getJSONArray("steps");
/** Traversing all 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);
/** Traversing all points */
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;
}
/**
* Method to decode polyline points
* Courtesy : jeffreysambells.com/2010/05/27/decoding-polylines-from-google-maps-direction-api-with-java
* */
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;
}
}
MainActivity.java
public class MainActivity extends FragmentActivity implements OnInfoWindowClickListener{
public double Latitude1_Current_double,Longitutde1_Current_double,Latitude1_Center_double,Longitude1_Center_double;
private int zoomLevel = 11;
LatLng origin1 = new LatLng(Latitude1_Current_double, Longitutde1_Current_double);
LatLng dest1 = new LatLng(Latitude1_Service_double,Longitude1_Service_double);
double lat1=Latitude1_Current_double;
double lang1=Longitutde1_Current_double;
double lat2=Latitude1_Center_double;
double lang2=Longitude1_Center_double;
GoogleMap map;
ArrayList<LatLng> markerPoints;
/*private int zoomLevel1 = 14;
private int zoomLevel2 = 11;*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Latitude1_Current_double = 12.9400834;
Longitutde1_Current_double = 77.6953668;
Latitude1_Center_double = 12.971599;
Longitude1_Center_double = 77.594563;
Toast.makeText(getApplicationContext(), "Get Direction"+Latitude1_Current_double+","+Longitutde1_Current_double+
Latitude1_Center_double+","+Longitude1_Center_double,Toast.LENGTH_SHORT).show();
// Initializing
markerPoints = new ArrayList<LatLng>();
// Getting reference to SupportMapFragment of the activity_main
SupportMapFragment fm = (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);
// Getting reference to Button
// Button btnDraw = (Button)findViewById(R.id.btn_draw);
// Getting Map for the SupportMapFragment
map = fm.getMap();
// Enable MyLocation Button in the Map
map.setMyLocationEnabled(true);
map.addMarker(new MarkerOptions().position(origin1)
.title("User Current Location")
.snippet("LatLng"+"("+lat1+","+lang1+")")
.icon(BitmapDescriptorFactory
.defaultMarker(BitmapDescriptorFactory.HUE_GREEN)));
map.addMarker(new MarkerOptions().position(dest1)
.title("Service Center Destination Location")
.snippet("LatLng"+"("+lat2+","+lang2+")")
.icon(BitmapDescriptorFactory
.defaultMarker(BitmapDescriptorFactory.HUE_RED)));
map.moveCamera(CameraUpdateFactory.newLatLngZoom(origin1, zoomLevel));
map.moveCamera(CameraUpdateFactory.newLatLngZoom(dest1, zoomLevel));
markerPoints.add(origin1);
markerPoints.add(dest1);
// Getting URL to the Google Directions API
String url = getDirectionsUrl(origin1, dest1);
DownloadTask downloadTask = new DownloadTask();
// Start downloading json data from Google Directions API
downloadTask.execute(url);
// The map will be cleared on long click
map.setOnMapLongClickListener(new OnMapLongClickListener() {
@Override
public void onMapLongClick(LatLng point) {
// Removes all the points from Google Map
map.clear();
// Removes all the points in the ArrayList
markerPoints.clear();
}
});
}
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";
// Waypoints
String waypoints = "";
for(int i=2;i<markerPoints.size();i++)
{
LatLng point = (LatLng) markerPoints.get(i);
if(i==2)
waypoints = "waypoints=";
waypoints += point.latitude + "," + point.longitude + "|";
}
// Building the parameters to the web service
String parameters = str_origin+"&"+str_dest+"&"+sensor+"&"+waypoints;
// Output format
String output = "json";
// Building the url to the web service
String url = "https://maps.googleapis.com/maps/api/directions/"+output+"?"+parameters;
return url;
}
/** A method to download json data from url */
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
HttpURLConnection urlConnection = null;
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
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);
try
{
ParserTask parserTask = new ParserTask();
// Invokes the thread for parsing the JSON data
parserTask.execute(result);
}
catch (Exception e)
{
e.printStackTrace();
Log.i("Exceptoin in DownloadTask onPostExecute", "Errroor");
}
}
}
/** A class to parse the Google Places in JSON format */
private class ParserTask extends AsyncTask<String, Integer, List<List<HashMap<String,String>>> >{
// Parsing the data in non-ui thread
@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;
}
// Executes in UI thread, after the parsing process
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> result)
{
try
{
ArrayList<LatLng> points = null;
PolylineOptions lineOptions = null;
// 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(5);
lineOptions.color(Color.BLUE);
}
// Drawing polyline in the Google Map for the i-th route
map.addPolyline(lineOptions);
}
catch (Exception e)
{
e.printStackTrace();
Log.i("Exceptoin in parsing process onPostExecute", "Errroor");
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public void onInfoWindowClick(Marker marker)
{
Intent intent = new Intent(this, NewActivity.class);
intent.putExtra("snippet", marker.getSnippet());
intent.putExtra("title", marker.getTitle());
intent.putExtra("position", marker.getPosition());
startActivity(intent);
}
}
答案 0 :(得分：0)
可能您的地图尚未初始化。您可以使用以下方式保证完成初始化：
map.setOnMapLoadedCallback(new GoogleMap.OnMapLoadedCallback() {
@Override
public void onMapLoaded() {
initMap();
}
});
private void initMap() {
// Add pins and polylines to map here
}