Androidアプリケーションサービスが呼び出されたときに強制終了する

Question

私はバックグラウンドで実行し、アプリケーションの残りの部分と通信する必要があるAndroidサービスを作成しました。コードは以下の通りです。問題は、サービスが呼び出されると、アプリケーションの強制が終了することです。

<service android:enabled="true" android:name=".DownloadSnifferActivity"> 
     </service> 

：そして、どうやらそれは私ものAndroidManifest.xmlに以下のエントリを作成した

package com.org.EasyUpload; 

import java.util.Timer; 
import java.util.TimerTask; 

import android.app.Activity; 
import android.app.Application; 
import android.app.DownloadManager; 
import android.app.NotificationManager; 
import android.app.Service; 
import android.app.DownloadManager.Query; 
import android.app.DownloadManager.Request; 
import android.content.BroadcastReceiver; 
import android.content.Context; 
import android.content.Intent; 
import android.content.IntentFilter; 
import android.content.SharedPreferences; 
import android.database.Cursor; 
import android.net.Uri; 
import android.os.Binder; 
import android.os.Bundle; 
import android.os.IBinder; 
import android.preference.PreferenceManager; 
import android.util.Log; 

public class DownloadSnifferActivity extends Service { 

    public static DownloadManager MAIN_ACTIVITY; 
    private Timer timer = new Timer(); 
    private static long SNIFF_INTERVAL = 1000; 
    private static long DELAY_INTERVAL = 1000; 

    SharedPreferences preferenceManager = PreferenceManager.getDefaultSharedPreferences(this); 
    DownloadManager downloadManager; 

    public int onStartCommand(Intent intent, int flags, int startId) { 
     Log.d("service","Control is in the onStartCommand"); 
//  /_startService(); 
     return START_STICKY; 
    } 


    public IBinder onBind(Intent intent) { 
     //return mBinder; 
     return null; 
    } 

    public void onCreate() { 
     super.onCreate(); 
     Log.d("onCreate", "Inside onCreate"); 
     _startService(); 
    } 

    public void onDestroy(){ 
     super.onDestroy(); 
     _shutdownService(); 
    } 

    public void onDownloadStart(String url, String userAgent, String contentDisposition, 
      String mimeType, long size) { 

     Log.d("URL",url); 
    } 

    public void _startService(){ 
     Log.d("DownloadSniffer", "Inside the thread"); 
     timer.scheduleAtFixedRate(new TimerTask() { 
      @Override 
      public void run() { 
       // TODO Auto-generated method stub 
       try { 
        readDownloadManager(); 
        Log.d("Thread", "The download sniffer service is running"); 
        Thread.sleep(SNIFF_INTERVAL); 
       }catch(InterruptedException ex) { 
        Log.d("Exception",ex.toString()); 
        ex.printStackTrace(); 
       } 
      } 
     }, DELAY_INTERVAL, SNIFF_INTERVAL); 
    } 

    public void _shutdownService() { 

    } 


    public void readDownloadManager() { 
     DownloadManager.Query query = null; 
     DownloadManager downloadManager = null; 
     Cursor c = null; 
     int statusColumnIndex = 0 ; 
     int urlColumnIndex = 0; 
     long downloadProcessIdColumnNo ; 
     try { 
      query = new DownloadManager.Query(); 
      downloadManager = (DownloadManager)getSystemService(DOWNLOAD_SERVICE); 

      //Just for testing I initiated my own download from this url. When an http 
      // reuest for this url is made, since download is taking place, it gets saved in 
      // the download manager. 
      Request request = new Request(Uri.parse("http://ocw.mit.edu/courses" + 
        "/aeronautics-and-astronautics/16-100-aerodynamics-fall-2005" + 
        "/lecture-notes/16100lectre1_kvm.pdf")); 
      if(downloadManager!=null){ 
       downloadManager.enqueue(request); 
      } else { 
       return; 
      } 
      if(query!=null) { 
       query.setFilterByStatus(DownloadManager.STATUS_PENDING); 
      } else { 
       return; 
      } 
      c = downloadManager.query(query); 
      Log.d("Inside", "Atleast Inside"); 
      Log.d("Query",c.toString()); 
      if(true){ 
       statusColumnIndex = c.getColumnIndex(DownloadManager.COLUMN_STATUS); 
       urlColumnIndex = c.getColumnIndex(DownloadManager.COLUMN_URI); 
       downloadProcessIdColumnNo = c.getColumnIndex(DownloadManager.COLUMN_ID); 
       Log.d("Column Count", ((Integer)c.getCount()).toString()); 
       c.moveToFirst(); 
       if(c.getCount() > 0){ 
        String url=""; 
        if(!c.isAfterLast()){ 
         url = c.getString(urlColumnIndex); 
         downloadManager.remove(downloadProcessIdColumnNo); 
         Log.d("Count after remove", ((Integer)c.getCount()).toString()); 
         c.moveToNext(); 
        } 
        Log.d("After", "Stopped Working"); 
        Log.d("url:", url); 
        //Here I am sending the url to another activity, where I can work with it. 
        Intent intent = new Intent(DownloadSnifferActivity.this, EasyUploadActivity.class); 
        Bundle b = new Bundle(); 
        b.putString("url", url); 
        intent.putExtras(b); 
        startActivity(intent); 
       } else { 
        return; 
       } 
      } 

     } catch (NullPointerException ex) { 
      ex.printStackTrace(); 
     } catch (IllegalStateException ex) { 
      ex.printStackTrace(); 
     } 
    } 
} 

を印刷されている私は、などのonCreate、ONSTARTに書かれているログコマンドのどれもサービス自体に達しイマイチ

そして、これは私がサービスへの呼び出しは、それを開始するために作る方法です：LogCatにログイン

startService(new Intent(EasyUploadMainMenu.this, DownloadSnifferActivity.class)); 

例外：

07-28 05:25:06.447: ERROR/AndroidRuntime(348): FATAL EXCEPTION: main 
07-28 05:25:06.447: ERROR/AndroidRuntime(348): java.lang.RuntimeException: Unable to instantiate service com.org.EasyUpload.DownloadSnifferActivity: java.lang.NullPointerException 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at android.app.ActivityThread.handleCreateService(ActivityThread.java:1904) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at android.app.ActivityThread.access$2500(ActivityThread.java:117) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:982) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at android.os.Handler.dispatchMessage(Handler.java:99) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at android.os.Looper.loop(Looper.java:123) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at android.app.ActivityThread.main(ActivityThread.java:3647) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at java.lang.reflect.Method.invoke(Method.java:507) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at dalvik.system.NativeStart.main(Native Method) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348): Caused by: java.lang.NullPointerException 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at android.content.ContextWrapper.getPackageName(ContextWrapper.java:120) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at android.preference.PreferenceManager.getDefaultSharedPreferencesName(PreferenceManager.java:353) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:348) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at com.org.EasyUpload.DownloadSnifferActivity.<init>(DownloadSnifferActivity.java:33) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at java.lang.Class.newInstanceImpl(Native Method) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at java.lang.Class.newInstance(Class.java:1409) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  at android.app.ActivityThread.handleCreateService(ActivityThread.java:1901) 
07-28 05:25:06.447: ERROR/AndroidRuntime(348):  ... 10 more 

Answer 1

この行にはキーワードthisの意味はありますか？

SharedPreferences preferenceManager = PreferenceManager.getDefaultSharedPreferences(this); 

コンテキストが正しくありません。この行は、サービスが初期化される前に書き込むことはできません。クラスにはSharedPreferences preferenceManager;、preferenceManager = PreferenceManager.getDefaultSharedPreferences(this);はonCreate()と宣言してください。