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

jon
Some minor things in the paper edition that says “3 2020” on the title page verso, not mentioned in the book’s errata online: p. 186 But...
New
ianwillie
Hello Brian, I have some problems with running the code in your book. I like the style of the book very much and I have learnt a lot as...
New
lirux
Hi Jamis, I think there’s an issue with a test on chapter 6. I own the ebook, version P1.0 Feb. 2019. This test doesn’t pass for me: ...
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
joepstender
The generated iex result below should list products instead of product for the metadata. (page 67) iex> product = %Product{} %Pento....
New
jskubick
I’m running Android Studio “Arctic Fox” 2020.3.1 Patch 2, and I’m embarrassed to admit that I only made it to page 8 before running into ...
New
Charles
In general, the book isn’t yet updated for Phoenix version 1.6. On page 18 of the book, the authors indicate that an auto generated of ro...
New
New
rainforest
Hi, I’ve got a question about the implementation of PubSub when using a Phoenix.Socket.Transport behaviour rather than channels. Before ...
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

Other popular topics Top

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
Learn from the award-winning programming series that inspired the Elixir language, and go on a step-by-step journey through the most impo...
New
PragmaticBookshelf
Write Elixir tests that you can be proud of. Dive into Elixir’s test philosophy and gain mastery over the terminology and concepts that u...
New
Exadra37
Please tell us what is your preferred monitor setup for programming(not gaming) and why you have chosen it. Does your monitor have eye p...
New
New
DevotionGeo
The V Programming Language Simple language for building maintainable programs V is already mentioned couple of times in the forum, but I...
New
New
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
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

Sub Categories: