广播接收器意图附加内容始终为NULL

Question

我目前正在创建一个简单的计划管理器，它使用警报管理器在出现问题或启动时触发广播接收器。我可以成功地将广播接收器设置为onReceive但是附加到intent的所有附加内容都将为null。触发器类只需获取接下来的内容并为其设置警报。我已经把头撞到墙上两天了，现在我觉得我现在对这个问题太熟悉了。

public class Trigger {

private Context mConext;
private Schedule schedule;

private StringTime stringTime;

public Trigger(Schedule schedule, Context activity){
    this.schedule = schedule;
    this.mConext = activity;
    this.stringTime = new StringTime();
}

public void setNext(){
    //returns a time in string format ie "11:00"
    String nextScan = schedule.getNextScanTime();
    String triggerType = "Scan";
    if (nextScan == null){
        nextScan = "00:00";
        triggerType = "Schedule";
    }
    Log.d("Intended trigger", nextScan);
    Log.d("Trigger type", triggerType);

    Intent alarmIntent = new Intent(mConext, TriggerReceiver.class);
    alarmIntent.putExtra("Trigger", triggerType);
    alarmIntent.putExtra("Lecture", schedule.getTodaysLectures().get(0));
    PendingIntent pendingIntent = PendingIntent.getBroadcast(mConext, 0, alarmIntent, PendingIntent.FLAG_UPDATE_CURRENT);

    setAlarm(getTriggerTimeAsCalendar(nextScan), pendingIntent);
}

//returns a calendar set with the nextScan time
private Calendar getTriggerTimeAsCalendar(String nextScan){
    // get a Calendar object with current time
    Calendar cal = Calendar.getInstance();
    Log.d("Current Time", cal.getTime().toString());

    int nextScanHour = stringTime.getHourFromString(nextScan);
    int nextScanMinute = stringTime.getMinuteFromString(nextScan);

    cal.set(Calendar.HOUR_OF_DAY, nextScanHour);
    cal.set(Calendar.MINUTE, nextScanMinute);
    cal.set(Calendar.SECOND, 0);

    if (nextScan.equals("00:00")){
        cal.add(Calendar.DAY_OF_MONTH, 1);
    }
    return cal;
}

private void setAlarm(Calendar cal, PendingIntent pendingIntent){
    AlarmManager manager = (AlarmManager) mConext.getSystemService(Context.ALARM_SERVICE);//get instance of alarm manager
    manager.setExact(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(), pendingIntent);//set alarm manager with entered timer by converting into milliseconds
    Log.d("Next Trigger", cal.getTime().toString());
}





public class TriggerReceiver extends BroadcastReceiver {

@Override
public void onReceive(Context context, Intent intent) {
    Calendar cal = Calendar.getInstance();
    Log.d("Triggered", cal.getTime().toString());

    Bundle extras = intent.getExtras();
    String message = extras.getString("Trigger");
    //Always Null?
    System.out.println(message);
}