我在我的Android应用中使用谷歌地图v2。当我尝试查看此活动时，我收到此错误。
01-22 08:46:26.271: E/AndroidRuntime(1349): FATAL EXCEPTION: main
01-22 08:46:26.271: E/AndroidRuntime(1349): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mad.restaurantfinderrm/com.mad.restaurantfinderrm.MapActivity}: java.lang.NullPointerException
01-22 08:46:26.271: E/AndroidRuntime(1349): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
01-22 08:46:26.271: E/AndroidRuntime(1349): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
01-22 08:46:26.271: E/AndroidRuntime(1349): at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-22 08:46:26.271: E/AndroidRuntime(1349): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
01-22 08:46:26.271: E/AndroidRuntime(1349): at android.os.Handler.dispatchMessage(Handler.java:99)
01-22 08:46:26.271: E/AndroidRuntime(1349): at android.os.Looper.loop(Looper.java:137)
01-22 08:46:26.271: E/AndroidRuntime(1349): at android.app.ActivityThread.main(ActivityThread.java:5103)
01-22 08:46:26.271: E/AndroidRuntime(1349): at java.lang.reflect.Method.invokeNative(Native Method)
01-22 08:46:26.271: E/AndroidRuntime(1349): at java.lang.reflect.Method.invoke(Method.java:525)
01-22 08:46:26.271: E/AndroidRuntime(1349): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
01-22 08:46:26.271: E/AndroidRuntime(1349): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-22 08:46:26.271: E/AndroidRuntime(1349): at dalvik.system.NativeStart.main(Native Method)
01-22 08:46:26.271: E/AndroidRuntime(1349): Caused by: java.lang.NullPointerException
01-22 08:46:26.271: E/AndroidRuntime(1349): at com.mad.restaurantfinderrm.MapActivity.onCreate(MapActivity.java:74)
01-22 08:46:26.271: E/AndroidRuntime(1349): at android.app.Activity.performCreate(Activity.java:5133)
01-22 08:46:26.271: E/AndroidRuntime(1349): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
01-22 08:46:26.271: E/AndroidRuntime(1349): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
01-22 08:46:26.271: E/AndroidRuntime(1349): ... 11 more
这是我的MapActivity.java文件
public class MapActivity extends FragmentActivity implements LocationListener {
GoogleMap map;
ArrayList<LatLng> markerPoints;
ArrayList<LatLng> positions;
String address;
String restName;
LatLng contactLocation = null;
LatLng myLocationLL = null;
Address a;
Location myLocation = null;
Marker myMarker;
Marker contactMarker;
private LocationManager locationManager;
private String provider;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_map);
positions = new ArrayList<LatLng>();
// Getting reference to SupportMapFragment of the activity_main
SupportMapFragment fm = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
// Getting Map for the SupportMapFragment
map = fm.getMap();
// Enable MyLocation Button in the Map
map.setMyLocationEnabled(true);
// get my current location
locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
boolean enabledGPS = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
//boolean enabledWiFi = locationManager
// .isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!enabledGPS) {
Toast.makeText(this, "GPS signal not found", Toast.LENGTH_LONG)
.show();
// TODO
// Intent intent = new
// Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
// startActivity(intent);
}
Criteria criteria = new Criteria();
provider = locationManager.getBestProvider(criteria, false);
myLocation = locationManager.getLastKnownLocation(provider);
// Initialize the location fields
if (myLocation != null) {
Toast.makeText(this, "Selected Provider " + provider,
Toast.LENGTH_SHORT).show();
onLocationChanged(myLocation);
myLocationLL = new LatLng(myLocation.getLatitude(),
myLocation.getLongitude());
positions.add(myLocationLL);
} else {
positions.add(null);
}
// get contacts address location
Intent intent = getIntent();
address = intent.getExtras().getString("address");
Log.v("ADDRESS", address);
restName = intent.getExtras().getString("restName");
Log.v("ADDRESS", restName);
String fulladdress = restName + ", " + address;
Geocoder geocoder = new Geocoder(getApplicationContext(),
Locale.getDefault());
List<Address> fromLocationName = null;
try {
fromLocationName = geocoder.getFromLocationName(fulladdress, 1);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (fromLocationName != null && fromLocationName.size() > 0) {
a = fromLocationName.get(0);
contactLocation = new LatLng(a.getLatitude(), a.getLongitude());
contactMarker = map.addMarker(new MarkerOptions().position(
contactLocation).title(restName));
contactMarker.showInfoWindow();
positions.add(contactLocation);
// move the camera instantly to the festival with a zoom of X.
map.moveCamera(CameraUpdateFactory.newLatLng(contactLocation));
map.animateCamera(CameraUpdateFactory.zoomTo(16), 2000, null);
} else {
positions.add(null);
}
// Initializing
markerPoints = new ArrayList<LatLng>();
if (positions.size() == 2) {
for (LatLng position : positions) {
// Adding new item to the ArrayList
markerPoints.add(position);
// Creating MarkerOptions
MarkerOptions options = new MarkerOptions();
// Setting the position of the marker
options.position(position);
/**
* For the start location, the color of marker is GREEN and for
* the end location, the color of marker is RED.
*/
if (markerPoints.size() == 1) {
options.icon(BitmapDescriptorFactory
.defaultMarker(BitmapDescriptorFactory.HUE_GREEN));
} else if (markerPoints.size() == 2) {
options.icon(BitmapDescriptorFactory
.defaultMarker(BitmapDescriptorFactory.HUE_RED));
}
// Add new marker to the Google Map Android API V2
map.addMarker(options);
// Checks, whether start and end locations are captured
if (markerPoints.size() >= 2) {
LatLng origin = markerPoints.get(0);
LatLng dest = markerPoints.get(1);
// Getting URL to the Google Directions API
String url = getDirectionsUrl(origin, dest);
DownloadTask downloadTask = new DownloadTask();
// Start downloading json data from Google Directions API
downloadTask.execute(url);
}
}
}
}
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";
// 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);
ParserTask parserTask = new ParserTask();
// Invokes the thread for parsing the JSON data
parserTask.execute(result);
}
}
/** 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) {
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);
}
}
@Override
public void onLocationChanged(Location location) {
LatLng coordinate = new LatLng(location.getLatitude(),
location.getLongitude());
// Toast.makeText(this, "Location " +
// coordinate.latitude+","+coordinate.longitude,
// Toast.LENGTH_LONG).show();
if (myMarker != null) {
// Toast.makeText(this, "!=null", Toast.LENGTH_LONG).show();
myMarker.remove();
}
myMarker = map.addMarker(new MarkerOptions().position(coordinate)
.title("Here I am!"));
myMarker.showInfoWindow();
// move the camera instantly to the festival with a zoom of X.
map.moveCamera(CameraUpdateFactory.newLatLng(coordinate));
map.animateCamera(CameraUpdateFactory.zoomTo(16), 2000, null);
}
@Override
public void onProviderDisabled(String arg0) {
// TODO Auto-generated method stub
}
@Override
public void onProviderEnabled(String arg0) {
// TODO Auto-generated method stub
}
@Override
public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
// TODO Auto-generated method stub
}
}
请帮帮我。更正代码对我来说是最好的。
答案 0 :(得分：0)
尝试使用此功能并对gps进行一次评论，gps不会在室内使用...
boolean enabledWiFi = locationManager .isProviderEnabled（LocationManager.NETWORK_PROVIDER）;
答案 1 :(得分：0)
getMap()的{{1}}方法正在返回SupportMapFragment。