Building a fine app

Getting started with Fyne

The hard truth is that I am lazy. Very lazy. Sometimes that’s good and sometimes it’s rather not. In this case it’s rather not. I want to be able to build mobile apps. Why is that? Well, sometimes I have some brain fart ideas and want to be able to prototype them quickly. Now the issue is, that the js package ecosystem is such a mess that I hate to touch it and therefore React Native is not really something I am keen on using. So what else can we use that’s nicely building cross-platform? Flutter. The issue with the laziness is now that I would really need to learn dart and I couldn’t convince myself so far beyond being able to read it and write some basic stuff.

How can I stay lazy and actually make mobile apps? Why isn’t there something in go. I mean I know go already and I could write app and backend in the same language. How great would that be?! Apparently there is something out there, that promises to make this work: Fyne and I will try this out.

This blog may be a little unstructured because I’ll write this while I’m experimenting with Fyne.

Getting Started

If you’ve been reading this blog a for a bit, you know that my favorite IDE is Goland. Yes it’s paid, but it’s also a big value add for me so that’s fine. Let’s get started with a new empty project, nothing really special to see here.

We create a new main.go and a go mod file and then look at the hello world example that’s provided on the fyne docs.

This example looks something like this:

package main

import (
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/widget"
)

func main() {
	a := app.New()
	w := a.NewWindow("Hello World")

	w.SetContent(widget.NewLabel("Hello World!"))
	w.ShowAndRun()
}

Great stuff, let’s build it and run it (you can use go run main.go as well).

GolandBuildConfig

Now, if we decide to actually run this, we will get a nice window:

HelloWorldBuild

That was really very, very convenient. Next up, since I’m on a Mac, how about we try to build the same thing as iOS app. You need to get the Fyne Cli just like documented using go install fyne.io/fyne/v2/cmd/fyne@latest. Next up, we use that CLI to create our iOS app like so:

$ fyne package -os iossimulator -appID com.example.myapp
Missing application icon at "/Users/a1dbe91/GolandProjects/fyniere/Icon.png"

If you looked at the docs you’ll see that I tried to be lazy (again) and not add an Icon, but apparently Fyne doesn’t like that a lot, so we need to add just some random icon. There’s a generator that I used to get a dummy icon: https://jpmallow.github.io/CopiCon/#/dashboard. Not pretty, but we don’t care about that for now. Add the whole shebang to the images directory and then edit our build command to add the icon and run it again:

$ fyne package -os iossimulator -appID com.example.myapp -icon resources/_gen/images/ios_store_icon.png
failed to look up certificate : exit status 44

Mhkay. A tiny bit of googling later, I found an old issue and got a superfast response from the maintainers: https://github.com/fyne-io/fyne/issues/4460#issuecomment-2117371642. I really didn’t know what “fully set up” means in this context, so I this is a bit of trial and error. Long story: you need to actually start up xcode, go to settings add your appleID and then manage certificates and if you click the little plus, you can add a developer certificate like so:

AppleDeveloperCert

Now we can run the build again and succeed (or at least not get an error). I am in fact a little confused, because what exactly did I just build and where is it? We can probably get to it later. Let’s focus on making our app run for now. To do that, we run xcrun simctl install booted myapp.app like so:

$ fyne package -os iossimulator -appID com.example.myapp -icon resources/_gen/images/ios_store_icon.png && xcrun simctl install booted myapp.app
No devices are booted.

Okay, that makes sense, we need to actually have a running simulator device. We just open the Simulator app and start an iPhone 15 from there. Now we can try again.

$ fyne package -os iossimulator -appID com.example.myapp -icon resources/_gen/images/ios_store_icon.png && xcrun simctl install booted myapp.app
An error was encountered processing the command (domain=NSPOSIXErrorDomain, code=2):
Simulator device failed to install the application.
An application bundle was not found at the provided path.
Provide a valid path to the desired application bundle.
Underlying error (domain=NSPOSIXErrorDomain, code=2):
        Failed to install the requested application
        An application bundle was not found at the provided path.

Well, that’s kinda not working and that is just maybe, because I didn’t adjust the name of the app. In my case that’s fyniere so I need to adjust the command accordingly to xcrun simctl install booted fyniere.app and running that again will at least not error and actually the app is now on the simulator device:

IosFyniereSimulator

The sad part is, that it instantly crashes when I try to click and open it in the sim so how are we going to debug this? Well apparently, we can’t really, or at least I can’t and this conducts the end of the journey for now: https://github.com/fyne-io/fyne/issues/4828#issuecomment-2128069746

I’ll follow up when I can.

golang  Fyne 

See also