dhmitchell

dhmitchell

Kotlin Coroutine Confidence: TimerApplication: won't app finish before timer?

In the example “timers/v7/src/main/kotlin/com/example/timers/TimerApplication.kt”
Why doesn’t the program just exit after queuing the timer.schedule rather than waiting for them to callback?

Marked As Solved

sam-cooper

sam-cooper

Author of Kotlin Coroutine Confidence

Great question! As I very briefly mention a couple of pages earlier, the java.util.Timer() class has its own thread, which it uses to run all its callbacks. It’s the existence of this thread which keeps the program running. When we reach the callback, we call timer.cancel(), which shuts down the timer’s thread and allows the program to exit.

I’ll see if I can update the text to make it a little clearer why the program behaves this way.

The fact that active threads keep the program alive is pretty useful for our Timer code examples, but it doesn’t have to apply to all threads. You can also configure a thread as a daemon to allow the program to exit without waiting for the thread to finish. You’ll spot that we have to do this for the Retrofit HTTP client we use later on in the same chapter. Setting up all the code examples so that they exit correctly when all our coroutines and callbacks have finished—but not before—was actually a really interesting challenge!

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
GilWright
Working through the steps (checking that the Info,plist matches exactly), run the demo game and what appears is grey but does not fill th...
New
mikecargal
Title: Hands-On Rust (Chapter 11: prefab) Just played a couple of amulet-less games. With a bit of debugging, I believe that your can_p...
New
joepstender
The generated iex result below should list products instead of product for the metadata. (page 67) iex> product = %Product{} %Pento....
New
Chrichton
Dear Sophie. I tried to do the “Authorization” exercise and have two questions: When trying to plug in an email-service, I found the ...
New
adamwoolhether
When trying to generate the protobuf .go file, I receive this error: Unknown flag: --go_opt libprotoc 3.12.3 MacOS 11.3.1 Googling ...
New
brunogirin
When I run the coverage example to report on missing lines, I get: pytest --cov=cards --report=term-missing ch7 ERROR: usage: pytest [op...
New
taguniversalmachine
It seems the second code snippet is missing the code to set the current_user: current_user: Accounts.get_user_by_session_token(session["...
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
dachristenson
@mfazio23 Android Studio will not accept anything I do when trying to use the Transformations class, as described on pp. 140-141. Googl...
New

Other popular topics Top

AstonJ
What chair do you have while working… and why? Is there a ‘best’ type of chair or working position for developers?
New
New
AstonJ
Thanks to @foxtrottwist’s and @Tomas’s posts in this thread: Poll: Which code editor do you use? I bought Onivim! :nerd_face: https://on...
New
PragmaticBookshelf
“Finding the Boundaries” Hero’s Journey with Noel Rappin @noelrappin Even when you’re ultimately right about what the future ho...
New
Rainer
Not sure if following fits exactly this thread, or if we should have a hobby thread… For many years I’m designing and building model air...
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
First poster: bot
The overengineered Solution to my Pigeon Problem. TL;DR: I built a wifi-equipped water gun to shoot the pigeons on my balcony, controlle...
New
PragmaticBookshelf
Author Spotlight: Peter Ullrich @PJUllrich Data is at the core of every business, but it is useless if nobody can access and analyze ...
New
AnfaengerAlex
Hello, I’m a beginner in Android development and I’m facing an issue with my project setup. In my build.gradle.kts file, I have the foll...
New
New

Sub Categories: