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

iPaul
page 37 ANTLRInputStream input = new ANTLRInputStream(is); as of ANTLR 4 .8 should be: CharStream stream = CharStreams.fromStream(i...
New
johnp
Running the examples in chapter 5 c under pytest 5.4.1 causes an AttributeError: ‘module’ object has no attribute ‘config’. In particula...
New
herminiotorres
Hi @Margaret , On page VII the book tells us the example and snippets will be all using Elixir version 1.11 But on page 3 almost the en...
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
New
leonW
I ran this command after installing the sample application: $ cards add do something --owner Brian And got a file not found error: Fil...
New
oaklandgit
Hi, I completed chapter 6 but am getting the following error when running: thread 'main' panicked at 'Failed to load texture: IoError(O...
New
s2k
Hi all, currently I wonder how the Tailwind colours work (or don’t work). For example, in app/views/layouts/application.html.erb I have...
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

Devtalk
Hello Devtalk World! Please let us know a little about who you are and where you’re from :nerd_face:
New
PragmaticBookshelf
Machine learning can be intimidating, with its reliance on math and algorithms that most programmers don't encounter in their regular wor...
New
PragmaticBookshelf
Design and develop sophisticated 2D games that are as much fun to make as they are to play. From particle effects and pathfinding to soci...
New
AstonJ
poll poll Be sure to check out @Dusty’s article posted here: An Introduction to Alternative Keyboard Layouts It’s one of the best write-...
New
AstonJ
Do the test and post your score :nerd_face: :keyboard: If possible, please add info such as the keyboard you’re using, the layout (Qw...
New
dimitarvp
Small essay with thoughts on macOS vs. Linux: I know @Exadra37 is just waiting around the corner to scream at me “I TOLD YOU SO!!!” but I...
New
AstonJ
Continuing the discussion from Thinking about learning Crystal, let’s discuss - I was wondering which languages don’t GC - maybe we can c...
New
Margaret
Hello everyone! This thread is to tell you about what authors from The Pragmatic Bookshelf are writing on Medium.
1147 29994 760
New
First poster: AstonJ
Jan | Rethink the Computer. Jan turns your computer into an AI machine by running LLMs locally on your computer. It’s a privacy-focus, l...
New
NewsBot
Node.js v22.14.0 has been released. Link: Release 2025-02-11, Version 22.14.0 'Jod' (LTS), @aduh95 · nodejs/node · GitHub
New

Sub Categories: