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

jamis
The following is cross-posted from the original Ray Tracer Challenge forum, from a post by garfieldnate. I’m cross-posting it so that the...
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
raul
Page 28: It implements io.ReaderAt on the store type. Sorry if it’s a dumb question but was the io.ReaderAt supposed to be io.ReadAt? ...
New
cro
I am working on the “Your Turn” for chapter one and building out the restart button talked about on page 27. It recommends looking into ...
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
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
dsmith42
Hey there, I’m enjoying this book and have learned a few things alredayd. However, in Chapter 4 I believe we are meant to see the “>...
New
creminology
Skimming ahead, much of the following is explained in Chapter 3, but new readers (like me!) will hit a roadblock in Chapter 2 with their ...
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
rainforest
Hi, I’ve got a question about the implementation of PubSub when using a Phoenix.Socket.Transport behaviour rather than channels. Before ...
New

Other popular topics Top

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
PragmaticBookshelf
Rust is an exciting new programming language combining the power of C with memory safety, fearless concurrency, and productivity boosters...
New
New
AstonJ
I ended up cancelling my Moonlander order as I think it’s just going to be a bit too bulky for me. I think the Planck and the Preonic (o...
New
AstonJ
This looks like a stunning keycap set :orange_heart: A LEGENDARY KEYBOARD LIVES ON When you bought an Apple Macintosh computer in the e...
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
Help
I am trying to crate a game for the Nintendo switch, I wanted to use Java as I am comfortable with that programming language. Can you use...
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
Margaret
Ask Me Anything with Mark Volkmann @mvolkmann On February 24 and 25, we are giving you a chance to ask questions of PragProg author M...
New

Sub Categories: