警报在KitKat中无效

Question

我的活动中有这个：

        AlarmManager alarmMgr;
        PendingIntent alarmIntent;

        Calendar calendar = Calendar.getInstance();
        calendar.setTimeInMillis(System.currentTimeMillis());
        calendar.set(Calendar.HOUR_OF_DAY, 12);
        calendar.set(Calendar.MINUTE, 20);
        calendar.set(Calendar.SECOND, 00);

        Intent intent = new Intent(this, AlarmBroadcastReceiver.class);
        alarmIntent = PendingIntent.getBroadcast(
                this.getApplicationContext(), 123456, intent, 0);

        alarmMgr = (AlarmManager) this
                .getSystemService(Context.ALARM_SERVICE);

        alarmMgr.setInexactRepeating(AlarmManager.RTC_WAKEUP,
                calendar.getTimeInMillis(), AlarmManager.INTERVAL_DAY,
                alarmIntent);

        Toast.makeText(this, "Alarm added", Toast.LENGTH_SHORT).show();

这是我的广播接收器类：

    @Override
public void onReceive(Context context, Intent intent) {

    Intent mIntent = new Intent(context, AlarmMessageActivity.class); 
    mIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    context.startActivity(mIntent);

    Toast.makeText(context, "Alarm", Toast.LENGTH_SHORT).show();

    Vibrator vibrator = (Vibrator) context
            .getSystemService(Context.VIBRATOR_SERVICE);
    vibrator.vibrate(2000);     
}

我还将这些添加到清单文件

    <activity
        android:name=".AlarmMessageActivity"
        android:label="@string/title_activity_alarm_message" >
    </activity>

    <receiver android:name=".AlarmBroadcastReceiver" >
    </receiver>

AlarmMessageActivity类只是一个显示文本的简单页面。

以上代码适用于sdk 8.但是对于Kitkat它不起作用，我在设置闹钟或广播接收器执行时也没有出现任何错误。我希望所有版本的闹钟都能正常工作，我的min sdk是8。

有谁能告诉我哪里可能错了。我是android的新手。