Java 服务类中的geocoder声明空指针异常

当我将反向地理编码器函数放入服务类并尝试在活动中调用时，我得到了空指针异常。。 这是我的课

import java.io.IOException;
import java.util.List;
import java.util.Locale;

import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.util.Log;
import android.widget.Toast;

public class GPSTracker extends Service implements LocationListener {

    private final Context mContext;

    // flag for GPS status
    boolean isGPSEnabled = false;

    // flag for network status
    boolean isNetworkEnabled = false;

    // flag for GPS status
    boolean canGetLocation = false;

    Location location; // location
    double latitude; // latitude
    double longitude; // longitude
    String tempAddress;
    // The minimum distance to change Updates in meters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters

    // The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute

    // Declaring a Location Manager
    protected LocationManager locationManager;

    public GPSTracker(Context context) {
        this.mContext = context;
        getLocation();
    }

    public Location getLocation() {
        try {
            locationManager = (LocationManager) mContext
                    .getSystemService(LOCATION_SERVICE);

            // getting GPS status
            isGPSEnabled = locationManager
                    .isProviderEnabled(LocationManager.GPS_PROVIDER);

            // getting network status
            isNetworkEnabled = locationManager
                    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

            if (!isGPSEnabled && !isNetworkEnabled) {
                // no network provider is enabled
            } else {
                this.canGetLocation = true;
                if (isNetworkEnabled) {
                    locationManager.requestLocationUpdates(
                            LocationManager.NETWORK_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                    Log.d("Network", "Network");
                    if (locationManager != null) {
                        String locationProvider = LocationManager.NETWORK_PROVIDER;
                        location = locationManager
                                .getLastKnownLocation(locationProvider);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }
                // if GPS Enabled get lat/long using GPS Services
                if (isGPSEnabled) {
                    if (location == null) {
                        locationManager.requestLocationUpdates(
                                LocationManager.GPS_PROVIDER,
                                MIN_TIME_BW_UPDATES,
                                MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                        Log.d("GPS Enabled", "GPS Enabled");
                        if (locationManager != null) {
                            String locationgps=LocationManager.GPS_PROVIDER;
                            location = locationManager
                                    .getLastKnownLocation(locationgps);
                            if (location != null) {
                                latitude = location.getLatitude();
                                longitude = location.getLongitude();
                            }
                        }
                    }
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

        return location;
    }

    /**
     * Stop using GPS listener
     * Calling this function will stop using GPS in your app
     * */
    public void stopUsingGPS(){
        if(locationManager != null){
            locationManager.removeUpdates(GPSTracker.this);
        }       
    }

    /**
     * Function to get latitude
     * */
    public double getLatitude(){
        if(location != null){
            latitude = location.getLatitude();
        }

        // return latitude
        return latitude;
    }

    /**
     * Function to get longitude
     * */
    public double getLongitude(){
        if(location != null){
            longitude = location.getLongitude();
        }

        // return longitude
        return longitude;
    }

    /**
     * Function to check GPS/wifi enabled
     * @return boolean
     * */
    public boolean canGetLocation() {
        return this.canGetLocation;
    }

    /**
     * Function to show settings alert dialog
     * On pressing Settings button will lauch Settings Options
     * */
    public void showSettingsAlert(){
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

        // Setting Dialog Title
        alertDialog.setTitle("GPS is settings");

        // Setting Dialog Message
        alertDialog.setMessage("GPS/Data roaming is not enabled. Do you want to go to settings menu?");

        // On pressing Settings button
        alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog,int which) {
                Intent intent = new Intent(Settings.ACTION_DATA_ROAMING_SETTINGS);
                mContext.startActivity(intent);
            }
        });


        // on pressing cancel button
        alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
            }
        });

        // Showing Alert Message
        alertDialog.show();
    }

    @Override
    public void onLocationChanged(Location location) {
    }


    @Override
    public void onProviderDisabled(String provider) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }
public  String getMyLocationAddress() {

        Geocoder geocoder= new Geocoder(this, Locale.ENGLISH);

        try {

              double latitude=getLatitude();
              double longitude=getLongitude();
              //Place your latitude and longitude
              List<Address> addresses = geocoder.getFromLocation(latitude,longitude, 1);

              if(addresses != null) {

                  Address fetchedAddress = addresses.get(0);
                  StringBuilder strAddress = new StringBuilder();

                  for(int i=0; i<fetchedAddress.getMaxAddressLineIndex(); i++) {
                        strAddress.append(fetchedAddress.getAddressLine(i)).append("\n");
                  }
                  Toast.makeText(getApplicationContext(),"I am at: "+strAddress.toString(),Toast.LENGTH_LONG).show();
                 // myAddress.setText("I am at: " +strAddress.toString());
                  tempAddress=strAddress.toString();

                 return tempAddress; 
                  //Intent intent = new Intent("MyCustomIntent");
                           // add data to the Intent
                          // intent.putExtra("strAddress",strAddress.toString());
                          // intent.setAction("android.provider.Telephony.SMS_RECEIVED");
                         //  sendBroadcast(intent);




                //  Intent intent = new Intent (Menu.this,IncomingSms.class);
                 // intent.putExtra("strAddress",strAddress.toString());
                //  sendBroadcast(intent);

              }

              else
                  Toast.makeText(getApplicationContext(), "No Location found", Toast.LENGTH_LONG).show();
                  //myAddress.setText("No location found..!");

        } 
        catch (IOException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
                 Toast.makeText(getApplicationContext(),"Tidak bisa Menerima Alamat ,, harap cek jaringan dan gps hp anda!", Toast.LENGTH_LONG).show();
                 showSettingsAlert();}
                 tempAddress="Could not Retrive Address!";
                         return tempAddress;
        }

}

这是我的日志：

05-28 14:47:14.187: E/Trace(5031): error opening trace file: No such file or directory (2)
05-28 14:47:14.688: E/AndroidRuntime(5031): FATAL EXCEPTION: main
05-28 14:47:14.688: E/AndroidRuntime(5031): java.lang.RuntimeException: Unable to start activity ComponentInfo{info.MonitoringObjek/mo.database.Menu}: java.lang.NullPointerException
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2070)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2095)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread.access$600(ActivityThread.java:137)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.os.Looper.loop(Looper.java:213)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread.main(ActivityThread.java:4786)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at java.lang.reflect.Method.invokeNative(Native Method)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at java.lang.reflect.Method.invoke(Method.java:511)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at dalvik.system.NativeStart.main(Native Method)
05-28 14:47:14.688: E/AndroidRuntime(5031): Caused by: java.lang.NullPointerException
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.content.ContextWrapper.getPackageName(ContextWrapper.java:127)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.location.GeocoderParams.<init>(GeocoderParams.java:50)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.location.Geocoder.<init>(Geocoder.java:83)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at mo.locationtracking.GPSTracker.getMyLocationAddress(GPSTracker.java:213)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at mo.database.Menu.onCreate(Menu.java:54)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.Activity.performCreate(Activity.java:5008)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2034)
05-28 14:47:14.688: E/AndroidRuntime(5031):     ... 11 more

05-28 14:47:14.187:E/Trace（5031）：打开跟踪文件时出错：没有这样的文件或目录（2）
05-28 14:47:14.688:E/AndroidRuntime（5031）：致命异常：主
05-28 14:47:14.688:E/AndroidRuntime（5031）：java.lang.RuntimeException:无法启动活动组件信息{info.MonitoringObjek/mo.database.Menu}:java.lang.NullPointerException
05-28 14:47:14.688:E/AndroidRuntime（5031）：在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2070）
05-28 14:47:14.688:E/AndroidRuntime（5031）：位于android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2095）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在android.app.ActivityThread.access$600（ActivityThread.java:137）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在android.app.ActivityThread$H.handleMessage（ActivityThread.java:1206）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在android.os.Handler.dispatchMessage（Handler.java:99）上
05-28 14:47:14.688:E/AndroidRuntime（5031）：在android.os.Looper.loop（Looper.java:213）
05-28 14:47:14.688:E/AndroidRuntime（5031）：位于android.app.ActivityThread.main（ActivityThread.java:4786）
05-28 14:47:14.688:E/AndroidRuntime（5031）：位于java.lang.reflect.Method.Invokenactive（本机方法）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在java.lang.reflect.Method.invoke（Method.java:511）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:789）
05-28 14:47:14.688:E/AndroidRuntime（5031）：位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:556）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在dalvik.system.NativeStart.main（本机方法）
05-28 14:47:14.688:E/AndroidRuntime（5031）：由以下原因引起：java.lang.NullPointerException
05-28 14:47:14.688:E/AndroidRuntime（5031）：位于android.content.ContextWrapper.getPackageName（ContextWrapper.java:127）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在android.location.GeocoderParams。（GeocoderParams.java:50）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在android.location.Geocoder.（Geocoder.java:83）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在mo.locationtracking.GPSTracker.getMyLocationAddress（GPSTracker.java:213）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在mo.database.Menu.onCreate（Menu.java:54）中
05-28 14:47:14.688:E/AndroidRuntime（5031）：在android.app.Activity.performCreate（Activity.java:5008）上
05-28 14:47:14.688:E/AndroidRuntime（5031）：在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1079）
05-28 14:47:14.688:E/AndroidRuntime（5031）：在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2034）
05-2814:47:14.688:E/AndroidRuntime（5031）：。。。还有11个

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我从中看到，说地理编码者必须在CreateIn活动中声明。。这不可能在服务类中声明吗？即使我的应用程序关闭了，我也需要geocoder仍然进行更新。

android应用程序的位置不太准确。您可以使用get方法调用google api webservice并解析json结果，您可以获得Area Block city street等

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它比默认值更准确

您能突出显示菜单中的行吗？onCreate（Menu.java:54）这是菜单中的行54 onCreate sir String tempAddress=gps.getMyLocationAddress（）；myAddress.setText（“我在：”+tempAddress）；

05-28 14:47:14.187: E/Trace(5031): error opening trace file: No such file or directory (2)
05-28 14:47:14.688: E/AndroidRuntime(5031): FATAL EXCEPTION: main
05-28 14:47:14.688: E/AndroidRuntime(5031): java.lang.RuntimeException: Unable to start activity ComponentInfo{info.MonitoringObjek/mo.database.Menu}: java.lang.NullPointerException
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2070)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2095)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread.access$600(ActivityThread.java:137)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.os.Looper.loop(Looper.java:213)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread.main(ActivityThread.java:4786)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at java.lang.reflect.Method.invokeNative(Native Method)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at java.lang.reflect.Method.invoke(Method.java:511)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at dalvik.system.NativeStart.main(Native Method)
05-28 14:47:14.688: E/AndroidRuntime(5031): Caused by: java.lang.NullPointerException
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.content.ContextWrapper.getPackageName(ContextWrapper.java:127)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.location.GeocoderParams.<init>(GeocoderParams.java:50)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.location.Geocoder.<init>(Geocoder.java:83)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at mo.locationtracking.GPSTracker.getMyLocationAddress(GPSTracker.java:213)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at mo.database.Menu.onCreate(Menu.java:54)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.Activity.performCreate(Activity.java:5008)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
05-28 14:47:14.688: E/AndroidRuntime(5031):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2034)
05-28 14:47:14.688: E/AndroidRuntime(5031):     ... 11 more