Question

我得到了一个nullpointerexception。我检查库和所有但无法解决它。也许可能是背景？ ontext。或者是我在代码中遗漏的东西。

任何帮助都会被贬低。调试只是说.... nullpointerex ... 这是我的java类：

package bla;




import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.List;

import org.json.JSONObject;

import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.Fragment;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.MapFragment;

import android.support.v4.app.FragmentManager;

import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

import android.app.Activity;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import android.app.Activity;
import android.content.Context;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import android.os.Bundle;
import android.view.InflateException;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;

import android.os.AsyncTask;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.util.Log;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.List;

import org.json.JSONObject;

import android.app.Dialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

public class RiverFragment extends Fragment implements LocationListener {


protected LocationManager locationManager;
// GoogleMap googleMap;

LatLng myPosition;
private SupportMapFragment map;
private GoogleMap mMapView;
int fragVal2;
static Context ontext;
private static View view;


//lo que se ocupa para construir los sitios

String[] mPlaceType=null;
String[] mPlaceTypeName=null;

double mLatitude=0;
double mLongitude=0;


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        // Array of place types
                mPlaceType = getResources().getStringArray(R.array.rivers);

                // Array of place type names
                mPlaceTypeName = getResources().getStringArray(R.array.rivers2);

        if (view != null) {
            ViewGroup parent = (ViewGroup) view.getParent();
            if (parent != null)
                parent.removeView(view);
        }
        try {
            view = inflater.inflate(R.layout.fragment_layout, container,
                    false);

            android.support.v4.app.FragmentManager fm = getFragmentManager();
            map = (SupportMapFragment) fm.findFragmentById(R.id.map);
            if (map == null) {
                map = SupportMapFragment.newInstance();
                fm.beginTransaction().replace(R.id.map, map).commit();
            }

            //  mMapView = fm.getMap();
            mMapView = map.getMap();
                // Enabling MyLocation Layer of Google Map
            mMapView.setMyLocationEnabled(true);

            // Getting LocationManager object from System Service LOCATION_SERVICE
            LocationManager locationManager = (LocationManager) ontext.getSystemService(Context.LOCATION_SERVICE);

            // Creating a criteria object to retrieve provider
            Criteria criteria = new Criteria();

            // Getting the name of the best provider
            String provider = locationManager.getBestProvider(criteria, true);

            // Getting Current Location From GPS
            Location location = locationManager.getLastKnownLocation(provider);

            if(location!=null){
                onLocationChanged(location);
        }

        locationManager.requestLocationUpdates(provider, 20000, 0, this);

        // Getting reference to the TextView of the Fragment
        //TextView tv = (TextView) view.findViewById(R.id.tv_content);

         // Retrieving the currently selected item number
            int position = getArguments().getInt("position");

            // List of rivers
            String[] rivers = getResources().getStringArray(R.array.rivers);

        // Setting currently selected river name in the TextView
            String type = mPlaceType[position];     

            StringBuilder sb = new StringBuilder("https://maps.googleapis.com/maps/api/place/nearbysearch/json?");
            sb.append("location="+mLatitude+","+mLongitude);
            sb.append("&radius=5000");
            sb.append("&types="+type);
            sb.append("&sensor=true");
            sb.append("&key=yeah");


            // Creating a new non-ui thread task to download Google place json data 
            PlacesTask placesTask = new PlacesTask();                                   

            // Invokes the "doInBackground()" method of the class PlaceTask
            placesTask.execute(sb.toString());



        // Updating the action bar title
//      getActivity().getActionBar().setTitle(rivers[position]);

        //return layoutView;


         // Retrieving the currently selected item number
            //  int position = getArguments().getInt("position");

                // List of rivers
            //  String[] rivers = getResources().getStringArray(R.array.rivers);

                // Creating view correspoding to the fragment

        } catch (InflateException e) {
            /* map is already there, just return view as it is */
        }
        return view;
        }



    /** 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;
    }         


    /** A class, to download Google Places */
    private class PlacesTask extends AsyncTask<String, Integer, String>{

        String data = null;

        // Invoked by execute() method of this object
        @Override
        protected String doInBackground(String... url) {
            try{
                data = downloadUrl(url[0]);
            }catch(Exception e){
                 Log.d("Background Task",e.toString());
            }
            return data;
        }

        // Executed after the complete execution of doInBackground() method
        @Override
        protected void onPostExecute(String result){            
            ParserTask parserTask = new ParserTask();

            // Start parsing the Google places in JSON format
            // Invokes the "doInBackground()" method of the class ParseTask
            parserTask.execute(result);
        }

    }

    /** A class to parse the Google Places in JSON format */
    private class ParserTask extends AsyncTask<String, Integer, List<HashMap<String,String>>>{

        JSONObject jObject;

        // Invoked by execute() method of this object
        @Override
        protected List<HashMap<String,String>> doInBackground(String... jsonData) {

            List<HashMap<String, String>> places = null;            
            PlaceJSONParser placeJsonParser = new PlaceJSONParser();

            try{
                jObject = new JSONObject(jsonData[0]);

                /** Getting the parsed data as a List construct */
                places = placeJsonParser.parse(jObject);

            }catch(Exception e){
                    Log.d("Exception",e.toString());
            }
            return places;
        }

        // Executed after the complete execution of doInBackground() method
        @Override
        protected void onPostExecute(List<HashMap<String,String>> list){            

            // Clears all the existing markers 
            mMapView.clear();

            for(int i=0;i<list.size();i++){

                // Creating a marker
                MarkerOptions markerOptions = new MarkerOptions();

                // Getting a place from the places list
                HashMap<String, String> hmPlace = list.get(i);

                // Getting latitude of the place
                double lat = Double.parseDouble(hmPlace.get("lat"));                

                // Getting longitude of the place
                double lng = Double.parseDouble(hmPlace.get("lng"));

                // Getting name
                String name = hmPlace.get("place_name");

                // Getting vicinity
                String vicinity = hmPlace.get("vicinity");

                LatLng latLng = new LatLng(lat, lng);

                // Setting the position for the marker
                markerOptions.position(latLng);

                // Setting the title for the marker. 
                //This will be displayed on taping the marker
                markerOptions.title(name + " : " + vicinity);               

                // Placing a marker on the touched position
                mMapView.addMarker(markerOptions);            

            }       

        }

    }



/*  @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }   */

    @Override
    public void onLocationChanged(Location location) {
        mLatitude = location.getLatitude();
        mLongitude = location.getLongitude();
        LatLng latLng = new LatLng(mLatitude, mLongitude);

        mMapView.moveCamera(CameraUpdateFactory.newLatLng(latLng));
        mMapView.animateCamera(CameraUpdateFactory.zoomTo(12));

    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub

    }
     /*
     @Override
    public void onDestroyView() {
        super.onDestroyView();
        MapFragment f = (MapFragment) getFragmentManager().findFragmentById(R.id.map);
if (f != null) 
getFragmentManager().beginTransaction().remove(f).commit();
    }   */  
}

错误在于此部分：

// Getting LocationManager object from System Service LOCATION_SERVICE
            LocationManager locationManager = (LocationManager) ontext.getSystemService(Context.LOCATION_SERVICE);

日志说

06-10 19:58:53.423: E/AndroidRuntime(30871): FATAL EXCEPTION: main
06-10 19:58:53.423: E/AndroidRuntime(30871): java.lang.NullPointerException
06-10 19:58:53.423: E/AndroidRuntime(30871):    at in.wptrafficanalyzer.navigationdrawerdemo.RiverFragment.onCreateView(RiverFragment.java:163)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at android.support.v4.app.Fragment.performCreateView(Fragment.java:1460)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:911)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1444)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:429)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at android.os.Handler.handleCallback(Handler.java:615)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at android.os.Handler.dispatchMessage(Handler.java:92)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at android.os.Looper.loop(Looper.java:153)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at android.app.ActivityThread.main(ActivityThread.java:4987)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at java.lang.reflect.Method.invokeNative(Native Method)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at java.lang.reflect.Method.invoke(Method.java:511)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:821)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
06-10 19:58:53.423: E/AndroidRuntime(30871):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

您的变量ontext（上下文）在引用时为空我没看到你在哪里初始化它。在使用之前初始化它。或者你可以使用

LocationManager locationManager = (LocationManager) getActivity().getSystemService(Context.LOCATION_SERVICE);

GPS位置服务中的Nullpointerexception

1 个答案: