java.lang.RuntimeException：无法实例化服务：java.lang.NullPointerException

Question

我是一个完整的newcome android和java和我正在写android应用程序与android工作室，应显示在地图上的每个5秒点（这只是一个测试）。当我运行模拟器上的应用程序，我得到这个在logcat的：

03-13 13:22:28.373 2964-2964/com.example.francesca.geoapp  

E/AndroidRuntime﹕ FATAL EXCEPTION: main 
Process: com.example.francesca.geoapp, PID: 2964 
java.lang.RuntimeException: Unable to instantiate service com.example.francesca.geoapp.DataService: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference 
     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2716) 
     at android.app.ActivityThread.access$1800(ActivityThread.java:144) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1361) 
     at android.os.Handler.dispatchMessage(Handler.java:102) 
     at android.os.Looper.loop(Looper.java:135) 
     at android.app.ActivityThread.main(ActivityThread.java:5221) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at java.lang.reflect.Method.invoke(Method.java:372) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference 
     at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:105) 
     at android.support.v4.content.LocalBroadcastManager.getInstance(LocalBroadcastManag er.java:102) at com.example.francesca.geoapp.DataService.<init> (DataService.java:56) 
     at java.lang.reflect.Constructor.newInstance(Native Method) 
     at java.lang.Class.newInstance(Class.java:1572) 
     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2713) 
            at android.app.ActivityThread.access$1800(ActivityThread.java:144) 
            at  android.app.ActivityThread$H.handleMessage(ActivityThread.java:1361) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:135) 
            at android.app.ActivityThread.main(ActivityThread.java:5221) 
            at java.lang.reflect.Method.invoke(Native Method) 
            at java.lang.reflect.Method.invoke(Method.java:372) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 

的intentService DataService的代码是

public class DataService extends IntentService { 

private LocalBroadcastManager BroadcastNotifier ; 
private Timer timer = new Timer(); 
private List dataList = new ArrayList<testData>(); 
int i = 0; 

//constructor 
public DataService() { 
    super("DataService"); 

    dataList.add(new testData(new LatLng(52.519804, 13.404988), new LatLng(52.519125, 13.406061), 50, 30)); 
    dataList.add(new testData(new LatLng(52.520692, 13.403722), new LatLng(52.519804, 13.404988), 60, 40)); 
    dataList.add(new testData(new LatLng(52.522023, 13.404730), new LatLng(52.520692, 13.403722), 50, 30)); 
    dataList.add(new testData(new LatLng(52.523388, 13.407143), new LatLng(52.522023, 13.404730), 40, 20)); 
    dataList.add(new testData(new LatLng(52.522911, 13.408807), new LatLng(52.523388, 13.407143), 80, 30)); 
    dataList.add(new testData(new LatLng(52.523982, 13.409623), new LatLng(52.522911, 13.408807), 50, 40)); 
    dataList.add(new testData(new LatLng(52.524713, 13.407434), new LatLng(52.523982, 13.409623), 30, 50)); 

    BroadcastNotifier = LocalBroadcastManager.getInstance(this); 
    timer.scheduleAtFixedRate(task, 0, 5000); 
} 

protected void onHandleIntent(Intent i) { 

} 

//timerTask to send request to the webservice 
TimerTask task = new TimerTask() { 
    @Override 
    public void run() { 
     if(i <7) { 
      testData test = (testData) dataList.get(i); 
      data.setCurrentPosition(test.currentPosition); 
      data.setLatestPosition(test.latestPosition); 
      data.setSpeed(test.speed); 
      data.setMediumSpeed(test.mediumSpeed); 
      i++; 
     } 
    } 
}; 


//method to tell subscribers that a newData has arrived 
private void OnNewDataSeen() { 
    Intent localIntent = new Intent(); 
    localIntent.setAction("com.example.android.threadsample.BROADCAST"); 

    localIntent.addCategory(Intent.CATEGORY_DEFAULT); 

    // Broadcasts the Intent 
    BroadcastNotifier.sendBroadcast(localIntent); 
} 

}

，并应启动intentService的MenuActivity被

​​

}

我做错了什么？

Answer 1

你不能有这个

BroadcastNotifier = LocalBroadcastManager.getInstance(this); 

在你的构造函数

。把它放入onHandleIntent()

this没有完全在你的构造函数初始化和Context无法获得，它为什么它是null，你会得到NPE。

Answer 2

您应该仅给super打电话并使用onCreate生命周期回调方法。