java.lang.IllegalMonitorStateException：在notify（）之前没有被线程锁定的对象

Question

//我从sq-lite数据库中获取数据处理程序类的数据。

public class ReminderReciever extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
DateFormat df = new SimpleDateFormat("dd-MM-yyyy HH:mm");
List<Reminder> reminderList;
Date dateobj = new Date();

//调用方法从sqlite获取列表

new DataBaseHandler(context).getAllReminderList();
reminderList = Util.reminderList;
for (int i = 0; i < reminderList.size(); i++) {
Reminder reminder = reminderList.get(i);
if (df.format(dateobj).equalsIgnoreCase(reminder.getDatetime())) {
try {
     new DataBaseHandler(context).deleteReminder(reminder.getTaskid());
     Intent intent1 = new Intent(context, TaskDetail.class);
     intent1.putExtra("id", reminder.getTaskid());
    PendingIntent pendingIntent = PendingIntent.getActivity(context, 1,                                  intent1, 0);
   String taskName = reminder.getTaskname();

//显示通知

   NotificationManager notificationManager = (NotificationManager)                                                   context.getSystemService(Context.NOTIFICATION_SERVICE);
  Uri alert = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM);
  if (alert == null) {
       alert = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_RINGTONE);
                }
   Notification.Builder builder = new Notification.Builder(context);
   NotificationManager manager = (NotificationManager)                    context.getSystemService(context.NOTIFICATION_SERVICE);
 Notification myNotication;
 builder.setSmallIcon(R.drawable.st);
 builder.setContentTitle("SharedTasklist Notification");
builder.setTicker("SharedTasklist Reminder");
builder .setContentText("It's time to do " + taskName);
builder .setAutoCancel(true);
builder .setOngoing(true);
builder .setContentIntent(pendingIntent);
builder .setSound(alert); //This sets the sound to play
builder.build();
builder.getNotification().flags |= Notification.FLAG_AUTO_CANCEL;
myNotication = builder.getNotification();
Random random = new Random();
int m = random.nextInt(9999 - 1000) + 1000;
manager.notify(m, myNotication);

//我检查所有其他课程，它没问题。这里显示了在通知之前对象未锁定线程的错误..

   alert.notify();
                 }

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