当我尝试通知某些事件时发生空错误

Question

嗨，大家好我是Android的开始，我试图从与我的主要活动不同的类发出通知。但e.printStackTrace（）声明为“null”，并停在行：“NotificationManager notificationManager =（NotificationManager）getSystemService（NOTIFICATION_SERVICE）;”如果我从mainActivity发出同样的通知一切顺利。你能帮我吗？

if(giorni_di_differenza <= 15) 
{ 

    try{ 
     PendingIntent pi = PendingIntent.getActivity(context, 0, new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS), 0); 
     NotificationCompat.Builder n = new NotificationCompat.Builder(context) 
      .setContentTitle(nome_evento) 
      .setContentText(descrizione_evento) 
      .setContentIntent(pi) 
      .setAutoCancel(true) 
      .setLights(Color.GREEN, 1000, 1000) 
      .setSmallIcon(R.drawable.ic_launcher); 

     NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE); 

     notificationManager.notify(0, n.build()); 

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

如果您需要更多代码，我可以寄给您。

的logcat：http://pastebin.com/W4hKbf6W（暂停GC错误是错误的，由于三星股票ROM）

Answer 1

onCreate()后访问NotificationManager雅，因为它没有找到在类方面：

NotificationManager nm = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE); 

做这样的：

或

//pass different id for different notifications 
private void showNotification(Context con, int notificationID) { 
    if(giorni_di_differenza <= 15) 
    { 

     try{ 
      PendingIntent pi = PendingIntent.getActivity(con, 0, new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS), 0); 
      NotificationCompat.Builder n = new NotificationCompat.Builder(con) 
       .setContentTitle(nome_evento) 
       .setContentText(descrizione_evento) 
       .setContentIntent(pi) 
       .setAutoCancel(true) 
       .setLights(Color.GREEN, 1000, 1000) 
       .setSmallIcon(R.drawable.ic_launcher); 
     NotificationManager notificationManager = (NotificationManager) con.getSystemService(NOTIFICATION_SERVICE); 

     notificationManager.notify(notificationID, n.build()); 

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

Answer 2

需要Context从外面Activity

NotificationManager notificationManager = (NotificationManager) context.getSystemService(NOTIFICATION_SERVICE); 

访问NotificationManager，也是你的logcat中明确表示

java.lang.IllegalStateException：系统服务不可用于 onC之前的活动reate（）

只能的Activity