Javaru

Javaru

Kotlin Coroutine Confidence: Placeholder message does not appear (pg 41)

Pg 41 states “Run the code, and you’ll see the placeholder message in a small window, just like last time.” for the code astronomy/v4/src/main/kotlin/com/example/astronomy/AstronomyApplication.kt. However when I run this, I get the a blank JFrame. The “Loading your image…” JLabel does not show.

This is in the B3 version of the book with the example code downloaded on 2025-04-19 at 14:42 EDT.

book-kotlin-coroutine-confidence pragprog

Marked As Solved

sam-cooper

sam-cooper

Author of Kotlin Coroutine Confidence

You’re absolutely right, the message is missing here for me too. It must have been working when I originally wrote and tested the code, so I’ll have to go back and see where the problem crept in.

To fix this one, we can add a call to window.revalidate() after adding the JLabel:

class ImageViewer : WindowAdapter() {
  override fun windowOpened(e: WindowEvent) {
    val window = e.window as JFrame
    window.add(JLabel("Loading your image…", JLabel.CENTER))
    window.revalidate()
    // TODO: download and display an image
  }
}

Let me know if this fixes the code for you. I’ll do a little more digging to make sure I understand how I missed the problem. Thank you so much for spotting the issue and letting me know about it!

Where Next?

Popular Pragmatic Bookshelf topics Top

brianokken
Many tasks_proj/tests directories exist in chapters 2, 3, 5 that have tests that use the custom markers smoke and get, which are not decl...
New
simonpeter
When I try the command to create a pair of migration files I get an error. user=> (create-migration "guestbook") Execution error (Ill...
New
JohnS
I can’t setup the Rails source code. This happens in a working directory containing multiple (postgres) Rails apps. With: ruby-3.0.0 s...
New
jeremyhuiskamp
Title: Web Development with Clojure, Third Edition, vB17.0 (p9) The create table guestbook syntax suggested doesn’t seem to be accepted ...
New
swlaschin
The book has the same “Problem space/Solution space” diagram on page 18 as is on page 17. The correct Problem/Solution space diagrams ar...
New
hazardco
On page 78 the following code appears: <%= link_to ‘Destroy’, product, class: ‘hover:underline’, method: :delete, data: { confirm...
New
ggerico
I got this error when executing the plot files on macOS Ventura 13.0.1 with Python 3.10.8 and matplotlib 3.6.1: programming_ML/code/03_...
New
bjnord
Hello @herbert ! Trying to get the very first “Hello, Bracket Terminal!" example to run (p. 53). I develop on an Amazon EC2 instance runn...
New
gorkaio
root_layout: {PentoWeb.LayoutView, :root}, This results in the following following error: no “root” html template defined for PentoWeb...
New
dachristenson
I’ve got to the end of Ch. 11, and the app runs, with all tabs displaying what they should – at first. After switching around between St...
New

Other popular topics Top

Exadra37
I am thinking in building or buy a desktop computer for programing, both professionally and on my free time, and my choice of OS is Linux...
New
DevotionGeo
I know that -t flag is used along with -i flag for getting an interactive shell. But I cannot digest what the man page for docker run com...
New
PragmaticBookshelf
From finance to artificial intelligence, genetic algorithms are a powerful tool with a wide array of applications. But you don't need an ...
New
New
Exadra37
I am asking for any distro that only has the bare-bones to be able to get a shell in the server and then just install the packages as we ...
New
PragmaticBookshelf
Use WebRTC to build web applications that stream media and data in real time directly from one user to another, all in the browser. ...
New
AstonJ
If you get Can't find emacs in your PATH when trying to install Doom Emacs on your Mac you… just… need to install Emacs first! :lol: bre...
New
PragmaticBookshelf
Build modern server-driven web applications using htmx. Whatever programming language you use, you’ll write less (and cleaner) code. ...
New
CommunityNews
A Brief Review of the Minisforum V3 AMD Tablet. Update: I have created an awesome-minisforum-v3 GitHub repository to list information fo...
New
PragmaticBookshelf
Escape callback hell and ship fast, clean code that reads as smoothly as it runs. Squash bugs and stamp out memory leaks with an intuitiv...
New

Sub Categories: