user interface – Java Programming II Course GUI doesn’t work

I’m doing the Java Programming II MOOC course, and I’m having some problems with the section on GUIs. Whenever I copy and paste the code for the GUI into netbeans, it just results in a bunch of errors, and I have no idea how to fix them. The errors are like “package javafx.application does not exist,” and I don’t know how to make it exist. Do I need to install or import something to make it work?

Here’s a screenshot of what my code looks like right now. It’s just copy and pasted from the website, but you can see where the errors are:
GUI code in Netbeans

networking – Network interface dropping in ubuntu 18.04

I have a robot with the follow setup and the ethernet interface (enp4s0) of (Computer A) drops randomly.

The interface does not drop when the computers are not doing much. However when (Computer B) starts streaming a compressed Image stream to (My Computer) via (Computer A), the ethernet interface drops.

Hence it seems like it is a configuration problem where I am possibly flooding the network unintentionally and I would like to get some advice regarding this matter.

Output from dmesg wasn’t really helpful

(Mon Apr 12 13:43:33 2021) igb 0000:04:00.0 enp4s0: igb: enp4s0 NIC Link is Down
(Mon Apr 12 13:43:33 2021) br0: port 1(enp4s0) entered disabled state
(Mon Apr 12 13:43:35 2021) igb 0000:04:00.0 enp4s0: igb: enp4s0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX
(Mon Apr 12 13:43:35 2021) br0: port 1(enp4s0) entered blocking state
(Mon Apr 12 13:43:35 2021) br0: port 1(enp4s0) entered listening state
(Mon Apr 12 13:43:39 2021) br0: port 1(enp4s0) entered learning state
(Mon Apr 12 13:43:44 2021) br0: port 1(enp4s0) entered forwarding state
(Mon Apr 12 13:43:44 2021) br0: topology change detected, propagating
(Mon Apr 12 14:05:50 2021) igb 0000:04:00.0 enp4s0: igb: enp4s0 NIC Link is Down
(Mon Apr 12 14:05:50 2021) br0: port 1(enp4s0) entered disabled state
(Mon Apr 12 14:05:52 2021) igb 0000:04:00.0 enp4s0: igb: enp4s0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX 

Things I have already done:

  1. Checked and replaced all the ethernet cables with new ones.
  2. Swap out the all the computers and sensors with spares
  3. Enable STP on the network bridge with forward delay of 4

Unfortunately I am unable to connect everything to the switch due to the size constrain within the robot.

Any help is greatly appreciated thanks!

Setup

Sorry I do not have sufficient reputation to post an image =(

View post on imgur.com

All the computers are running ubuntu 18.04 and ROS melodic.

I have setup a network bridge using netplan as shown below

# Netplan on Computer A
# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager
  ethernets:
    #Computer B
    enp1s0:
      dhcp4: no
    #Sensor 
    enp2s0:
      dhcp4: no
    #SBC to switch
    enp4s0:
      dhcp4: no
      

  #Setup a bridge and link eno1 to it
  bridges:
    br0:
      interfaces: (enp1s0, enp2s0, enp4s0)
      addresses: (192.168.1.1/24)
      gateway4: 192.168.1.253
      nameservers:
        addresses: (8.8.8.8)
      dhcp4: no

Other things I have tried

Enable Port forwarding & add a route from (Computer B) to (Computer A) & setting up the nics on different subnet

/etc/sysctl.conf

net.ipv4.ip_forward = 1

Computer B

route add -net 192.168.2.0 netmask 255.255.255.0 gw 192.168.1.1


# Netplan on Computer A
# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager
  ethernets:
    #Computer B
    enp1s0:
      addresses:
        - 192.168.2.1/24
      dhcp4: no
    #Sensor 
    enp2s0:
      addresses:
        - 192.168.3.1/24
      dhcp4: no
    #SBC to switch
    enp4s0:
      addresses:
        - 192.168.1.1/24
      dhcp4: no
      gateway4: 192.168.1.253      
      nameservers:
        addresses: (8.8.8.8, 8.8.4.4)

nvidia – Installing 20.04 from CD to remove Ubuntu 20.10 installation – CD Graphical interface never appears

My Ubuntu 20.10 installation damage my nvidia driver setup. I cannot change the display resolution – no matter what.

SO, I tried to move back to Ubuntu 20.04. Created the CD on the MAC, burn the iso and reboot the Linux computer.

It starts but never goes anywhere. The graphical interface never starts.

Any help would be welcomed.

8 – How to create an archive containing files with the Drupal interface?

When you reserve a domain name with a host, it offers a free space of 10 MB to publish a web page (this type of offer does not support PHP).

I created a small 8MB website with HTML, CSS and JS (it’s also a PWA). It is really very simple. Here it is :

https://github.com/S1BIOSE/E-business-Card

I want to create in Drupal 8, a small website generator for my clients. The little website I created should serve as a model.

I want to take the files from my small website and modify them on the fly using a form.

Here’s the idea :
A user completes a form with his information (name of the company, description of the company, postal address, pages on social networks, …), he clicks on a button “Generate the website”. Drupal replaces the information in the files and generates an archive.

That’s all.

This generator must be built with a Bootstrap 4 formula. It must not save anything in the database and generate the files on the fly.

Is it possible to create such a program with Drupal 8 ?

Thank you

interface – Which ergonomic criteria would justify the behavior of redirecting the user to a 404 redirect page?

Without having to reference the criteria (because I think it is not necessary to answer the question), you are probably struggle with the question because of a couple of reasons.

Firstly, it is possible for there to be more than one way of classifying something, and if the criteria doesn’t allow for this (or isn’t flexible enough to adapt) then you should consider customizing it so as to be more fit for your purpose.

Guidance and error management can both fall under the bigger perspective of messaging and notification to the user, which allows the user to feel in control of their actions (in their interaction with the system). So I don’t see this as a problem that you can’t fit it neatly into just one category.

The other thing is that there are ways to implement a 404 page that leads to a more positive user experience, and ways that can make the user more confused and frustrated. So it is not so much redirecting the user to a 404 page that is the problem, because at some point your system will probably generate an error that you can’t necessarily address immediately (e.g. the server is down).

But as with all good error handling and management best practices, if you can:

  • identify the source of the error (i.e. is it caused by the user or
    the system)
  • provide some idea the nature of the error (e.g. is it an expected error caused by things like validation or something unexpected and outside of the system) and then
  • give some ideas of how to resolve the issue or perhaps next steps

Then your users will thank you instead of clogging up your support system/mechanisms.

kotlin – What is the best design pattern to use multiple implementation of one interface for a single class, optional to use all or most of them

Consider an interface:

interface Auth { 
  fun doAuth()
}

this can be implemented for multiple APIs:

class GoogleAuth : Auth {
  override fun doAuth(){
    throw NoGoogleAuthImpl();
  }
}
class TwitterAuth : Auth {
  override fun doAuth(){
    throw NoTwitterAuthImpl();
  }
}

Now, a class can use one of Auths or both of them (or another that would definitely come soon). What is the best design pattern for this?

Strategy can use one:

class AuthHost : Auth by GoogleAuth() {
  fun onGoogleClick(){
    //This uses GoogleAuth#doAuth
    doAuth()  ​
  ​}

  fun onTwitterClick(){
    // can not do this right now
  }
}

user expectation – How to design schedule service interface

I suppose is a big question.

I am trying to create understandable and clear UX design for schedule designer web app. May be, In a fact i’m looking for some well-known practice or production-ready interface, which fits our goals too.

So I think I have to describe our web app entities. To make it easier to understand my question I change names some of them to more usial.

So, imagine we have categories of followers and marketing emails to send. Also we have a schedule: each day we are going to send some pool of emails of some category.

Here is data model:
enter image description here

Also, I have to notice, that sometimes, we need to move some email of some category to another day of schedule, so
emails of day ≠ emails of followers category, even that looks like it.

What I decide to design right now:
enter image description here

The main key of this screen is Generate schedule button. We suggest that user needs to arrange categories to days and generate schedule from this screen. If user needs to move some email to another day so user could do it on another screen, when viewing generated content, and this idea looks bad.

I feel like I’m trying to reinvent the wheel. What is the most right pattern in this case? What already existed decision could fit my goals? Where to find right inspiration to get this done?
Any ideas or questions are welcome…

UPD.
The most problem is that user need to pre-generate schedule, and move some emails to another day if needed. But what if user wants to change schedule and generate one again? All corrections of previous version going to be lost. I look for decision where user could create “ready to use” schedule on fly.

debian – Nftables “Error: Interface does not exist” after reboot

at using nftables on a new virtual machine (Debian 10) I installed and configured nftables as automatic service (systemd). I use also LXC and use an additional interface (lxcbr0).

I recognized the problem that the nftables service does not start successfully after reboot. The error: /etc/nftables.conf:56:32-39: Error: Interface does not exist

It seems that the interface get only up after the nftables service startup:
Startup date of nftables (log output):

Apr 05 11:41:23 WEB01 systemd(1): Starting nftables...

Startup date of the interface:

Apr 05 11:41:25 WEB01 ifup(397): Waiting for lxcbr0 to get ready

–> 2 second delay between the startups

Is there a general solution for this or a common work around? On the wiki of nftables I did not find something like that.

Thanks in advance

interface – Best practice on Web Chat “not working right now” messaging

We are currently integrating a web chat functionality on a utilities website, where customers can query their bill, or changing plans etc. with their cellular bills.

The web chat will sit top right on all paged, and when clicked, will initiate a web chat sessions. In the event of one of our chat integrations failing or not working, we need to design an error screen. I cannot find any best practice information our there, so my thought was to provide the following while the user waits:

An apology message saying that the chat is having technical issues, and recommending that the user email us instead. Any hats thrown into the ring on this one are much appreciated!

Here’s something I put together below as a first pass:

There’s a technical issue with chat right now, and we’re looking into
it. You can also email us, and we’ll get back to you within 30
minutes. Thanks for your patience.