I wanted to create a selfcontained “show version” ...

# compose

[Mikael Alfredsson]

I wanted to create a selfcontained “show version” component, simplest case would be like this

@Composable
    fun versionText(){
        val versionName = packageManager.getPackageInfo(packageName, 0).versionName
        Text(text = versionName)
    }

either this is the completely wrong way to do something like this, or I need some way to know if this composable is currently running in a preview, since the preview engine will not really show anything here (I think it even crashes silently somewhere)

[steelahhh]

The preview probably doesn’t work because it knows nothing about android context, since it’s not running on a device

Try extracting access to packageManager outside of the component, passing only the string (in the snippet case) as an argument

Otherwise there’s nothing wrong with this code

[Mikael Alfredsson]

in the old view system, we could look for isInEditMode() to create a ‘preview’ version of the output. Would be nice to have something similar for code executed under @preview

[steelahhh]

Here comes the beauty of compose – you can easily compose

This should come at basically no cost; might be wrong tho, but all the compose material components do this, so it should be quite cheap

If you do something like this:

@Preview
@Composable
fun VersionTextPreview() {
  VersionTextImpl("1.2.3")
}

@Composable
fun VersionText() {
  val context = ContextAmbient.current.applicationContext
  val packageName = context.packageName
  val versionName = context.packageManager.getPackageInfo(packageName, 0).versionName

  VersionTextImpl(versionName = versionName)
}

@Composable
private fun VersionTextImpl(
  versionName: String
) {
  Text(versionName)
}

That way you both get your preview working, and your public API stays the same

[Mikael Alfredsson]

feels like it could easy be bloated when/if you have many components that does this. a simple flag in the composable context sound for me easier, but I guess that is missing and i thank you for the example.