这个异常来自哪里？

Question

我处理以下问题： 我开始一个服务，这一点：

Intent startIntent = new Intent(this, GPSService.class); 
startService(startIntent); 

服务的代码：

package com.example.eapp; 

import android.app.Notification; 
import android.app.NotificationManager; 
import android.app.PendingIntent; 
import android.app.Service; 
import android.content.Context; 
import android.content.Intent; 
import android.location.Criteria; 
import android.location.Location; 
import android.location.LocationListener; 
import android.location.LocationManager; 
import android.os.Bundle; 
import android.os.IBinder; 
import android.support.v4.app.NotificationCompat; 
import android.widget.Toast; 

public class GPSService extends Service implements LocationListener { 

    public final static int NOTIFICATION_ID = 1; 
    private String team = getString(R.string.team); 
    private String server = "http://server.com"; 
    private int updateRate = 0; 
    private int updateDistance = 0; 

    private NotificationManager notifyManager; 
    private LocationManager locationManager; 

    @Override 
    public IBinder onBind(Intent intent) { 
     return null; 
    } 

    @Override 
    public int onStartCommand(Intent intent, int flags, int startId) { 
     super.onStartCommand(intent, flags, startId); 
     final boolean gpsEnabled = getLocationManager().isProviderEnabled(
       LocationManager.GPS_PROVIDER); 
     if (gpsEnabled) { 
      showIcon(); 
      requestLocationUpdates(); 
     } else { 
      Toast.makeText(this, R.string.gpsDisabled, Toast.LENGTH_SHORT) 
        .show(); 
      stopSelf(); 
     } 
     return Service.START_STICKY; 
    } 

    @Override 
    public void onDestroy() { 
     super.onDestroy(); 
     getLocationManager().removeUpdates(this); 
     notifyManager.cancel(NOTIFICATION_ID); 
    } 

    @Override 
    public void onLocationChanged(Location location) { 
     String url = server + "/setUserPosition.php" + "?latitude=" 
       + location.getLatitude() + "&longitude=" 
       + location.getLongitude() + "&dir=" + location.getBearing() 
       + "&speed=" + location.getSpeed() + "&alt=" 
       + location.getAltitude() + "&accuracy=" 
       + location.getAccuracy() + "&user=" + team; 
     new GetTask().execute(url); 
    } 

    @Override 
    public void onProviderDisabled(String provider) { 
     // stopSelf(); 
    } 

    @Override 
    public void onProviderEnabled(String provider) { 
     // requestLocationUpdates(); 
    } 

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

    } 

    private void requestLocationUpdates() { 
     if (locationManager != null) 
      locationManager.removeUpdates(this); 

     // get location service 
     Criteria crit = new Criteria(); 
     crit.setAccuracy(Criteria.ACCURACY_FINE); 
     String bestProvider = getLocationManager().getBestProvider(crit, true); 
     getLocationManager().requestLocationUpdates(bestProvider, 
       updateRate * 1000, updateDistance, this); 

    } 

    private LocationManager getLocationManager() { 
     if (this.locationManager == null) 
      this.locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); 
     return this.locationManager; 
    } 

    private void showIcon() { 
     notifyManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE); 
     Intent notificationIntent = new Intent(this, TrackActivity.class); 
     PendingIntent pIntent = PendingIntent.getActivity(this, 0, 
       notificationIntent, 0); 
     Notification notification = new NotificationCompat.Builder(this) 
       .setContentTitle(getString(R.string.app_name)) 
       .setContentText(getString(R.string.status_bar_message, team)) 
       .setSmallIcon(R.drawable.ic_launcher).setContentIntent(pIntent) 
       .build(); 
     notification.flags |= Notification.FLAG_NO_CLEAR; 
     notifyManager.notify(NOTIFICATION_ID, notification); 
    } 
} 

当我试图开始我是服务得到以下例外：

03-29 21:22:21.688: E/AndroidRuntime(17548): FATAL EXCEPTION: main 
03-29 21:22:21.688: E/AndroidRuntime(17548): java.lang.RuntimeException: Unable to instantiate service com.example.eapp.GPSService: java.lang.NullPointerException 
03-29 21:22:21.688: E/AndroidRuntime(17548): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2538) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at android.app.ActivityThread.access$1600(ActivityThread.java:139) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1325) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at android.os.Handler.dispatchMessage(Handler.java:99) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at android.os.Looper.loop(Looper.java:154) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at android.app.ActivityThread.main(ActivityThread.java:4945) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at java.lang.reflect.Method.invokeNative(Native Method) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at java.lang.reflect.Method.invoke(Method.java:511) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at dalvik.system.NativeStart.main(Native Method) 
03-29 21:22:21.688: E/AndroidRuntime(17548): Caused by: java.lang.NullPointerException 
03-29 21:22:21.688: E/AndroidRuntime(17548): at android.content.ContextWrapper.getResources(ContextWrapper.java:81) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at android.content.Context.getString(Context.java:283) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at com.jhquadrat.rauscher24.GPSService.<init>(GPSService.java:21) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at java.lang.Class.newInstanceImpl(Native Method) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at java.lang.Class.newInstance(Class.java:1319) 
03-29 21:22:21.688: E/AndroidRuntime(17548): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2535) 
03-29 21:22:21.688: E/AndroidRuntime(17548): ... 10 more 

有没有人知道这个异常来自哪里以及我必须做什么 摆脱它 ？

Answer 1

查看堆栈跟踪上一个“由...引发”消息。这是触发整个输出的异常。这一个是通过调用生成getString您的代码的行21 NullPointerException：

private String team = getString(R.string.team); 

的问题是，你不能叫getString()之前onCreate被称为为您服务。该框架尚未建立将服务代码与应用程序资源相关联的结构。只需覆盖onCreate并在那里设置team。

. . . 
private String team; 
. . . 

@Override 
public void onCreate() { 
    team = getString(R.string.team); 
}