private void sendNotify() {
 NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
 NotificationCompat.Builder builder = new NotificationCompat.Builder(MainActivity.this,"default");
 Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("https://www.baidu.com"));  // 此处根据需要改为打开应用
 PendingIntent pi = PendingIntent.getActivity(MainActivity.this, 0, intent, 0);
 Notification notify = builder.setSmallIcon(R.mipmap.ic_launcher_round)
 .setPriority(Notification.PRIORITY_DEFAULT) //通知的优先级
 .setCategory(Notification.CATEGORY_MESSAGE) //通知的类型
 .setContentTitle("Order Notify")
 .setAutoCancel(true)
 .setContentIntent(pi)
 .setContentText("a new order message")
 .setFullScreenIntent(pi, true) //不设置此项不会悬挂,false 不会出现悬挂
 .build(); 
  manager.notify(1,notify);
}

android 桌面通知notify