如何在时间间隔后删除通知栏

Question

这是我的代码，工作正常。如果通知从通知栏中删除，它会每20秒显示一次通知栏，但我想每隔18秒从通知栏中删除通知，并且每20秒再次显示我该怎么办？如何删除通知表单通知栏??

 public class NotificationActivity extends Activity {

AlarmManager am;

 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_notification);
  am = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
  setRepeatingAlarm();
 }

  public void setRepeatingAlarm() {
  Intent intent = new Intent(this, TimeAlarm.class);
  PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0,
    intent, PendingIntent.FLAG_CANCEL_CURRENT);
  am.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(),
    (20 * 1000), pendingIntent);
  System.out.println("Calling Alaram...");
 }
  }



           public class TimeAlarm extends BroadcastReceiver {

NotificationManager nm;

@Override
public void onReceive(Context context, Intent intent) {
 nm = (NotificationManager) context
   .getSystemService(Context.NOTIFICATION_SERVICE);
 CharSequence from = "Lokesh";
 CharSequence message = "Notification Test...";
 PendingIntent contentIntent = PendingIntent.getActivity(context, 0,
   new Intent(), 0);
 Notification notif = new Notification(R.drawable.cherry_icon,
   "Notification Test...", System.currentTimeMillis());
 notif.setLatestEventInfo(context, from, message, contentIntent);
 nm.notify(1, notif);
}
}