Regarding the NotificationCompat.Builder(this) error, it does not work, and the solution is no longer used.

Reason:
After the Android.o version, this method of instantiating notifications is no longer supported, but an additional channelid parameter is added:

 Notification notification = new NotificationCompat.Builder(this,"one");

So how to get this parameter?

Call the following method, the parameters are chanelid, channelname, and notification priority.

createNotificationChanneler("one","notiChannelName",3);

//建立通知部分格式 NotificationChannel, 参数Channelid, Channel名， 优先级
    public void createNotificationChanneler(String c_channelid,String c_channelname,int c_importance){
    
    
        //检测 Channel是否已经被创建了，避免重复创建
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    
    //检测Android版本

            if (getNotificationManager().getNotificationChannel(c_channelid)!=null){
    
    
                return; }//要是没被创建那么
            NotificationChannel notificationChannel = new NotificationChannel(c_channelid,c_channelname,c_importance);
            notificationChannel.enableLights(true);//开启提示灯
            notificationChannel.enableVibration(true);//开启震动
            notificationChannel.setSound(Uri.fromFile(new File("/system/media/audio/ringtones/Luna.ogg")),null);
            notificationChannel.setBypassDnd(true);//可绕过免打扰模式
            notificationChannel.setImportance(c_importance);//设置优先级
            notificationChannel.setLightColor(Color.RED);//设置提示灯颜色
            notificationChannel.setLockscreenVisibility(Notification.VISIBILITY_PUBLIC);//设置锁屏界面图标可见
            notificationChannel.setShowBadge(true);//有图标
            notificationChannel.setVibrationPattern(new long[]{
    
    0,1000,1000,1000});
            getNotificationManager().createNotificationChannel(notificationChannel);
        }else {
    
    
            return;
        }
    }
 //获取通知管理、
    private NotificationManager getNotificationManager(){
    
    
        return (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
    }

Call createNotificationChanneler(,,)
before creating the notification and then you can create the notification

Intent intent  = new Intent(this, ServerActivity.class);
        PendingIntent pi = PendingIntent.getActivity(this,0, intent,0);
        //由于Android7.0以后，通知的builder创建时，要多加一个参数，channelid,String类型
        //以下函数可以获得这个channelid,需要三个参数，id，name,和优先级。
        createNotificationChanneler("one","notiChannelName",3);
        Notification notification = new NotificationCompat.Builder(this,"one")
                .setContentTitle("通知标题")
                .setContentText("通知内容，通知内容")
                .setSmallIcon(R.mipmap.ic_launcher)
                .setLargeIcon(BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher_round))
                .setContentIntent(pi)
                .build();
getNotificationManager.notify(1,notification);

Regarding priority parameters:

public static final int IMPORTANCE_DEFAULT = 3;
public static final int IMPORTANCE_HIGH = 4;
public static final int IMPORTANCE_LOW = 2;
public static final int IMPORTANCE_MAX = 5;
public static final int IMPORTANCE_MIN = 1;
public static final int IMPORTANCE_NONE = 0;
public static final int IMPORTANCE_UNSPECIFIED = -1000;