如何在未来的特定时间创建通知？(Android)

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    CharSequence channelName = "My Channel";
    String channelId = "my_channel_id";
    int importance = NotificationManager.IMPORTANCE_DEFAULT;
    NotificationChannel channel = new NotificationChannel(channelId, channelName, importance);
    channel.setDescription("My Channel Description");
    
    NotificationManager notificationManager = getSystemService(NotificationManager.class);
    notificationManager.createNotificationChannel(channel);
}

AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);

Intent intent = new Intent(this, MyReceiver.class);
intent.setAction("com.example.MY_ALARM_ACTION");

PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0);

// 设置闹钟在特定时间触发
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.HOUR_OF_DAY, 8);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);

alarmManager.setExact(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent);

public class MyReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        // 创建通知
        NotificationCompat.Builder builder = new NotificationCompat.Builder(context, "my_channel_id")
                .setSmallIcon(R.drawable.notification_icon)
                .setContentTitle("My Notification")
                .setContentText("This is a notification.");

        // 显示通知
        NotificationManagerCompat notificationManager = NotificationManagerCompat.from(context);
        notificationManager.notify(1, builder.build());
    }
}

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