無法啓動活動ComponentInfo：java.lang.NullPointerException at android.app.ActivityThread.performLaunchActivity

Question

我在我的android應用中使用Google map v2。當我嘗試查看此活動時，出現此錯誤。

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 

這是我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 

    } 

    } 

請幫助我。更正代碼對我來說是最好的。

Answer 1

嘗試使用此，一旦評論的GPS時，GPS不會工作在室內...

布爾enabledWiFi =的LocationManager .isProviderEnabled（LocationManager.NETWORK_PROVIDER）;

Answer 2

您的SupportMapFragment的getMap()方法返回NULL。