SwiftUI Previews in Xcode cause Skip to re-launch Android build

[arshmeets]

Hi,

I read the documentation regarding previews in Xcode and here is what I got:

Dual-Platform Apps
Assuming you followed the app creation instructions using skip init, each successful build of your Skip app will automatically attempt to launch it on the running Android emulator or device. Exactly one emulator or device must be running in order for the Skip project’s Launch APK script phase to install and run the app successfully.
If you are having trouble with Skip’s Xcode plugin, check the Troubleshooting section for help.
Xcode Previews will not work in Skip apps until you have performed one full build. After an initial successful build, you can iterate using Previews.

But I am still having trouble with running the previews. I made a full build as the documentation says, but the preview will never load and the android app will keep reloading.

[davidakoontz]

Yes, I'm seeing similar Canvas/Preview makes the Android device reload the App. I don't understand the tie in ... I know Xcode does a build for the preview and the simulator device when one opens the Canvas. Don't know why the Gradle/Android build would get involved.

[marcprux]

What version of Xcode are you running?

[arshmeets]

Xcode Version 16.0 (16A242d)

[davidakoontz]

Xcode 16 as well. David Koontz     Email: ***@***.***     (360) 259-8380     http://about.me/davidakoontzOn Oct 17, 2024, at 9:13 AM, marcprux ***@***.***> wrote: What version of Xcode are you running? —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you commented.Message ID: ***@***.***>

[marcprux]

Can you take a look at your app's target's "Build Phases" tab and examine the "Run skip gradle" phase to ensure that it looks like this:

This is something that is created when the app is first initialized, and so if you created it a while ago (before this check was added), then it might not have been added.

FTR, the complete "Run skip gradle" script should look like:

if [ "${SKIP_ZERO}" != "" ]; then
	echo "note: skipping skip due to SKIP_ZERO"
	exit 0
elif [ "${ENABLE_PREVIEWS}" == "YES" ]; then
	echo "note: skipping skip due to ENABLE_PREVIEWS"
	exit 0
elif [ "${ACTION}" == "install" ]; then
	echo "note: skipping skip due to archive install"
	exit 0
else
	SKIP_ACTION="${SKIP_ACTION:-launch}"
fi
PATH=${BUILD_ROOT}/Debug:${BUILD_ROOT}/../../SourcePackages/artifacts/skip/skip/skip.artifactbundle/macos:${PATH}:${HOMEBREW_PREFIX:-/opt/homebrew}/bin
echo "note: running gradle build with: $(which skip) gradle -p ${PWD}/../Android ${SKIP_ACTION:-launch}${CONFIGURATION:-Debug}"
skip gradle -p ../Android ${SKIP_ACTION:-launch}${CONFIGURATION:-Debug}

FWIW, previews work for me in Xcode 16 with the default "Hello Skip" app (created with skip init --open-xcode --appid=com.xyz.HelloSkip hello-skip HelloSkip and then adding the #Preview block).

[arshmeets]

Didn't want to do this, but I just cleaned everything by deleting the project and recloning my GitHub repo.

@davidakoontz might be of help.

[marcprux]

Does the Preview work for you now? Did you try my suggestion?

[arshmeets]

Appreciate your suggestion. Tried the android Run skip gradle code which I hadn't changed since the start of making my project so didn't make a difference there and the #Preview suggestion also didn't work. Still had the issue of the android app restarting so I decided to clean and repull repo from Github

[davidakoontz]

Marc - here’s my Build Phase code:  First part looks similar/same - but (above) also… 

…

On Oct 17, 2024, at 10:47 AM, marcprux ***@***.***> wrote: Can you take a look at your app's target's "Build Phases" tab and examine the "Run skip gradle" phase to ensure that it looks like this: Screenshot.2024-10-17.at.12.41.59.png (view on web) <https://github.com/user-attachments/assets/9478fef1-d7c9-4181-bf79-5aa6166bdfc3> This is something that is created when the app is first initialized, and so if you created it a while ago (before this check was added), then it might not have been added. FTR, the complete "Run skip gradle" script should look like: if [ "${SKIP_ZERO}" != "" ]; then echo "note: skipping skip due to SKIP_ZERO" exit 0 elif [ "${ENABLE_PREVIEWS}" == "YES" ]; then echo "note: skipping skip due to ENABLE_PREVIEWS" exit 0 elif [ "${ACTION}" == "install" ]; then echo "note: skipping skip due to archive install" exit 0 else SKIP_ACTION="${SKIP_ACTION:-launch}" fi PATH=${BUILD_ROOT}/Debug:${BUILD_ROOT}/../../SourcePackages/artifacts/skip/skip/skip.artifactbundle/macos:${PATH}:${HOMEBREW_PREFIX:-/opt/homebrew}/bin echo "note: running gradle build with: $(which skip) gradle -p ${PWD}/../Android ${SKIP_ACTION:-launch}${CONFIGURATION:-Debug}" skip gradle -p ../Android ${SKIP_ACTION:-launch}${CONFIGURATION:-Debug} FWIW, previews work for me in Xcode 16 with the default "Hello Skip" app (created with skip init --open-xcode --appid=com.xyz.HelloSkip hello-skip HelloSkip and then adding the #Preview block). Screenshot.2024-10-17.at.12.41.03.png (view on web) <https://github.com/user-attachments/assets/d360796d-0b33-42b4-acf1-2c6972b84b92> — Reply to this email directly, view it on GitHub <#263 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA3SNU4XCQBVWIKR5JSHYS3Z37S3DAVCNFSM6AAAAABQBJ355WVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTAOJXGQYTKNA>. You are receiving this because you commented.

[davidakoontz]

weird the images didn't transmit... it's going to be one of THOSE days...

Trying again... WITH FEELING...

[davidakoontz]

Not sure what you suggestion was - tell me again. @marcprux

[arshmeet-s]

The suggestion was to check the build code as you've done. Have you tried my solution of cleaning everything and pulling your github repo? First make sure that you have a github repo btw.

[davidakoontz]

Yeah I’ve got a REPO - my count is up to 15 times I’ve started fresh… it’s an estimate. I’d like to solve the actual issue - given that it has happened TWICE. I make lots of stupid mistakes… but this one has proven to exist outside of my influence!

…

On Oct 17, 2024, at 1:11 PM, arshmeet-s ***@***.***> wrote: The suggestion was to check the build code as you've done. Have you tried my solution of cleaning everything and pulling your github repo? First make sure that you have a github repo btw. — Reply to this email directly, view it on GitHub <#263 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA3SNU2ZEKXYNNK3FFQSRMTZ4ADWFAVCNFSM6AAAAABQBJ355WVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTAOJXGU2DKNY>. You are receiving this because you were mentioned.

[marcprux]

The problem is discussed at https://developer.apple.com/forums/thread/761439: Xcode no longer sets the ENABLE_PREVIEWS environment variable for SwiftUI previews, which is the only way we have to prevent running the skip gradle Xcode build phase command that handles the compile/launch on Android. Toggling the "Editor > Canvas > Use Legacy Previews Execution" menu item should work around the issue for now, but note that that setting will be reset every time Xcode upgrades, so you will need to re-enable it every time there is an update.

The other solution is to just comment-out the "skip gradle" command in the "Run skip gradle" build script when you are developing with SwiftUI previews, and then just remember to re-enable it the next time you need to launch on Android.

Important

We encourage anyone encountering this issue to chime in on the thread mentioned above to try to elicit a less unsatisfactory long-term solution, as well as to file a Feedback Assistant issue referencing FB16424982.

[davidakoontz]

Thank you for the explaination ( the apple link ). Had to search for the - suggested workaround: "Use legacy preview execution"

Look in Xcode > Editor > Canvas (2nd entry) then bottom of that 2nd Canvas menu > Use legacy...

[davidakoontz]

Love having my Previews back!! Thanks Marc!

I must have missed the memo from Apple...

[timkoss]

I am on Xcode 16.2 and I don't have the 2nd Canvas item. I can't fine the Legacy Previews anywhere. Any ideas?

[timkoss]

Just reading more and I found this:

In Xcode 16.2, Apple removed the Legacy Previews Execution option as it continues to refine SwiftUI previews. If you're having trouble with SwiftUI previews or need a similar behavior to the old Legacy mode, here are some options to troubleshoot and adjust your development environment:

Any other solutions to this problem?

[JeffFlowerday]

Xcode 26.2 has Legacy Previews Execution back. Or maybe it returned in an earlier 26.x release.

[davidakoontz]

Well that is a surprise - I assumed the legacy workaround would remain forever… I’m wrong again - happens more and more… I’ve got noting - it took me weeks to find out about the legacy menu item… I’m currently not working with Skip code… I’d revert back to 16.1 - thanks for the warning!

…

On Jan 10, 2025, at 4:41 PM, timkoss ***@***.***> wrote: Just reading more and I found this: In Xcode 16.2, Apple removed the Legacy Previews Execution option as it continues to refine SwiftUI previews. If you're having trouble with SwiftUI previews or need a similar behavior to the old Legacy mode, here are some options to troubleshoot and adjust your development environment: Any other solutions to this problem? — Reply to this email directly, view it on GitHub <#263 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA3SNU5ZB7MH4QRRULC2SKL2KBLDRAVCNFSM6AAAAABQBJ355WVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTCOBQGM2TSNI>. You are receiving this because you were mentioned.

[timkoss]

Thanks. I did roll back to 16.1 and that solves the problem. Hopefully there will be a long term solution

[marcprux]

I opened a TSI with Apple last week to see if they have a solution. As it stands right now, it is unfortunately impossible to use SwiftUI #Previews along with the default build script that Skip uses to launch the app in 6.2 due to their removal of the "Legacy Previews Execution" option.

[marcprux]

Note that "Legacy Previews Execution" does sometimes work in 16.2, but other times it is disabled. We're not yet sure the conditions under which the option is available.

[AbdulelahHajjar]

Not sure if it is still an issue, but I got it to work on Xcode 26 by wrapping the Preview macro with:

#if !SKIP_BRIDGE
#Preview {
    TestView()
}
#endif

I also kept SKIP_ACTION = build as I want it to display compiler errors if I use an unsupported SwiftUI view or modifiers, which it does correctly.

When using Supported Views / Modifiers

When using Unsupported Views / Modifiers (fails as expected)