License: Apache License 2.0
The Race tracker app simulates the progress of two players in a race. The idea is to demonstrate basic concepts of Kotlin coroutines. A user can start, pause, or reset the race with buttons in the UI.
Repository does not contain SyncWorker class specified in Note section of async()
step 6
then you can wrap your code in a call to measureTimeMillis() which will return the time it in milliseconds that it takes to run the block of code passed in.
should read
then you can wrap your code in a call to measureTimeMillis() which will return the time in milliseconds that it takes to run the block of code passed in.
There is no search form in the panel.
link broken
In this part of the coroutines training, there is a link to SyncWorker that is not available anymore.
Hello,
Hello. I found an error in the 2nd paragraph in the code area.
suspend fun run() {
try {
while (currentProgress < maxProgress) {
delay(progressDelayMillis)
currentProgress += progressIncrement
}
} catch (e: CancellationException) {
Log.e("RaceParticipant", "$name: ${e.message}")
throw e // Always re-throw CancellationException.
}
}
Cannot catch an error
It should be mentioned in Parts 3,4 and 6 that the following import should be added to the classes RaceParticipant.kt, RaceTrackerApp.kt and RaceParticipantTest.kt.
import kotlinx.coroutines.*
delay, launch etc. appear with error otherwise.
In Part 7 focusing on testing, the build.grale.kts that needs to be updated is the one of the module. This could be clarified.
It should also be clarified which imports to do:
import org.junit.Test
import org.junit.Assert.assertEquals
In part 7 focusing on testing, it is written: 6. Run the test to confirm that it passes. It would be good to write how to run the tests and have a screenshot for users new to JUnit.
I think i found a little mistake
when you call the method inside the launch{}, it should be printForecast() and NOT getForecast() when you explain about the
"Get a reference to the job for the coroutine that fetches the forecast, and store it in a variable called job."
From the output, you can observe that `getTemperature()` throws an exception.
this is not true; from the output it is known only that getWeatherReport function threw an exception - only looking at the source code we know that it was getTemperature() as the throwing of the exception is hard coded
Note: As a real-world example of async(), you can check out this part of the Now in Android app. In the SyncWorker class, the call to sync() returns a boolean if the sync to a particular backend was successful. If any of the sync operations failed, then the app needs to perform a retry.
In the above test, the link to SyncWorker is no longer valid
In the section:
Note: As a real-world example of async(), you can check out this part of the [Now in Android app](https://github.com/android/nowinandroid). In the [SyncWorker](https://github.com/android/nowinandroid/blob/main/sync/work/src/main/java/com/google/samples/apps/nowinandroid/sync/workers/SyncWorker.kt#L65) class, the call to sync() returns a boolean if the sync to a particular backend was successful. If any of the sync operations failed, then the app needs to perform a retry.
The link to SyncWorker.kt links through a non existant java folder, should be kotlin
Android Studio reports an error when you don't make the main function suspend if you are using delay
But in the codelab they made it to a normal main function and used delay
Hi,
I have a question about the Cancellation in Kotlin coroutines in the codelab for Android Basics.
In the following link: https://developer.android.com/codelabs/basic-android-kotlin-compose-coroutines-kotlin-playground?continue=https%3A%2F%2Fdeveloper.android.com%2Fcourses%2Fpathways%2Fandroid-basics-compose-unit-5-pathway-1#3
I have seen that in the step 2 of the Cancellation it says that when using the temperature.cancel() it will not show the temperature value because it was cancelled, however I can see that if the ${temperature.await() is not removed I get the following error:
Testing the code here I can see that if I just remove the ${temperature.await() from the code (without adding the temperature.cancel()) I get the same result as in the step 3.
My question is, what is the usability of the cancellation if it doesn't work without completelly removing the return of the function?
Thank you very much in advance for your time!
Can't download the starter code.
NET::ERR_CERT_COMMON_NAME_INVALID
Hi On the page Asynchronous code
The url for the SyncWorker is in correct, the block is:
Note: As a real-world example of async(), you can check out this part of the Now in Android app. In the SyncWorker class, the call to sync() returns a boolean if the sync to a particular backend was successful. If any of the sync operations failed, then the app needs to perform a retry.
The url should be:
SyncWorker
Thanks for the Codelab!
The note about Now in Android app is out of date. The link is broken.
Add print statements to see what thread you are on by calling Thread.currentThread().name.
code is not properly indented
should be
runBlocking {
println("${Thread.currentThread().name} - runBlocking function")
launch {
println("${Thread.currentThread().name} - launch function")
withContext(Dispatchers.Default) {
println("${Thread.currentThread().name} - withContext function")
delay(1000)
println("10 results found.")
}
println("${Thread.currentThread().name} - end of launch function")
}
println("Loading...")
}In the Write unit tests to test coroutines, the second test could have a expectedProgress value as the previous one for readability purposes
There is spelling mistake in Chinese Traditional version.
The word in the sentense "Android 應用程式中的 CororineScope" should be "CoroutineScope", I guess.
The provided github is for the completed code rather than the incomplete code, so I can't follow along
Syncworker link is broken. Correct link is here I think: https://github.com/android/nowinandroid/blob/main/sync/work/src/main/kotlin/com/google/samples/apps/nowinandroid/sync/workers/SyncWorker.kt
Spelling error in second note on the seventh page.
runtTest is probably supposed to be runTest.
Hello
The link to the SyncWorker class in Introduction to Coroutines in Kotlin Playground is broken 💔
Actually Kotlin playground executes with the delay, but just prints everything in the box when it is finished, so I cannot see the effect of the delay properly.
Course: Android Basics with Compose
Module: Connect to the Internet - Get Data
Section: Introduction to Coroutines in Kotlin Playground
In this section, the content briefs about Cancellation in Coroutines. There is an issue with the explanation here. Please refer to the below image
In this example, it is mentioned that "The weather report only consists of the weather forecast Sunny, but not the temperature because that coroutine was cancelled."
But the reason why weather report only consists of weather forecast Sunny but not temperature because we are not returning temperature back.
So cancel and temperature not being in the weather forecast have no relation and the example given does not make sense
In the part 4.Exception and Cancelation at the section Cancelation, when executing this piece of code :
import kotlinx.coroutines.*
import kotlin.system.*
suspend fun getForecast(): String {
delay(1000)
return "Sunny"
}
suspend fun getTemperature(): String {
delay(1000)
return "30\u00b0C"
}
suspend fun getWeatherReport() = coroutineScope {
val forecast = async { getForecast() }
val temperature = async { getTemperature() }
delay(200)
temperature.cancel()
"${forecast.await()} ${temperature.await()}"
}
fun main() {
val time = measureTimeMillis {
runBlocking {
println("Weather forecast")
println(getWeatherReport())
println("Have a good day!")
}
}
println("Execution time ${time / 1000.0} seconds")
}
I have the following issue:
Weather forecast
Exception in thread "main" kotlinx.coroutines.JobCancellationException: DeferredCoroutine was cancelled
at kotlinx.coroutines.JobSupport.cancel (JobSupport.kt:1558)
at kotlinx.coroutines.Job$DefaultImpls.cancel$default (Job.kt:199)
at FileKt$getWeatherReport$2.invokeSuspend (File.kt:19)
Caused by: kotlinx.coroutines.JobCancellationException: DeferredCoroutine was cancelled
at kotlinx.coroutines.JobSupport .cancel(JobSupport.kt:1558)
at kotlinx.coroutines.Job$DefaultImpls .cancel$default(Job.kt:199)
at FileKt$getWeatherReport$2 .invokeSuspend(File.kt:19)
I am supposed to have the following message :
Weather forecast
Sunny
Have a good day!
Imports libraries are missing from example code for kotlin coroutine items like launch and coroutineScope.
Log file output at the bottom of step 6 is incorrect.
the link mentioned in the "Note" block of https://github.com/android/nowinandroid/blob/main/sync/work/src/main/java/com/google/samples/apps/nowinandroid/sync/workers/SyncWorker.kt#L65 is 404!!!
Formatting issue. This was intended to be an output but is formatted as code.
Weather forecast
Caught exception java.lang.AssertionError: Temperature is invalid
Sunny { No temperature found }
Have a good day!
Good day. I may have misunderstood something, but in this section you contradict yourself. You first say that the launch() function Dispatchers.Default as a default dispatcher (Fig. 1), but then you give an example where in launch() you output the stream name and "main" is output, that means that Dispatchers.Main is used by default for some reason (Fig. 2). So, what is used in launch() by default: Dispatchers.Main or Dispatchers.Default
Task 4 (Start the race):
Step 1 should read:
"Open the RaceTrackerApp.kt file located in the com.example.racetracker.ui package." instead of
"Open to the RaceTrackerApp.kt file located in the com.example.racetracker.ui package."
SyncWorker class link is not working.
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