Is getting references to views in an Activity like this considered a bad practice ?

val button : Button by lazy {
    findViewById(R.id.button)
}

Well if you put that code inside an Activity directly, then yes, it’s very bad.

I've had issues with this in the past with navigating back to fragments, at least. Remember that the fragment/activity might be destroyed while the actual object might still exist.

@ribesg why do you think so? @sindrenm what do you mean with "the actual object?" the fragment/activity? or the view? or the lazy?

Well inside a

Fragment

it’s wrong, but inside an

Activity

it may be ok

@ribesg what's the reason

Look at the Fragment lifecycle

maybe just easier to use synthetics and not bother with onCreateView or only use onCreateView to inflate your fragment and use synthetics in onViewCreated

I use synthetic imports myself and haven't had problems with them. Although I tend to also keep references to them in the activity/fragment as well, but through “virtual” properties with a getter:

private val button: Button
  get() = the_button_in_the_layout // synthetically imported

@ribesg Makes sense, thanks 👍

Or just don’t use XML views 😛

I'm not doing any of these things. But I needed to understand the reason behind why it's not a good idea

You can safely do that

val button : Button
    get() = findViewById(R.id.button)

But in this case you may end up calling

button

multiple times in the same function like it’s nothing. Well, it’s not huge, but it’s better to have a local var and call

findViewById

only once if you can

KotterKnife (https://github.com/JakeWharton/kotterknife/blob/master/src/main/kotlin/kotterknife/ButterKnife.kt) appears to be implemented like the first case though

That’s not what I’m understanding from the link you give

🤔 How do you understand the implementation then?

@ribesg: Note that I was using a getter together with synthetic imports, which does in fact cache the views for you. Just so there's no misunderstanding. 😒imple_smile:

@sindrenm Yes, it would be best but if you have synthetic imports you just use them directly usually

Yeah, but some people use snake_case in IDs and some people use prefixes (e.g.

signInEmailAddressEditText

), so I prefer to keep track of them in property getters. 😒imple_smile:

@gsala oh, I see. Nothing tells you to bind your views as property though. The given example is inside a ViewGroup

True. I'm now reading through the conversation that spawned this reply : https://kotlinlang.slack.com/archives/C0B8M7BUY/p1532693549000239

In ButterKnife, you should call

ButterKnife.bind(this);

after the view has been created to replace the instances by the ones for the newly created view, which dereferences old views in the process

Indeed, but that thread is so 2018. 😏

For me the best way is not to have XML anyway

Yeah, Anko was great for that and Splitties probably is, but I'm just so incredibly used to the preview thingymabob that I've grown quite dependent on it. Although I don't seem to need it when writing Flutter apps (a whole discussion all in its own, I guess), but then again that has proper hot reloading. 😛

Both Anko and Splitties support preview in IDE

Yah, they do support it, but you'll have to build the code first, which is not the case for XML layouts. And while I usually know what I want, it's a whole lot easier to be able to preview my constraint layouts while writing it. And no, I don't build my layouts graphically, I prefer having full control over the resulting XML. Although, to be fair, the WYSIWYG editor does usually build decent XML.

It’s not like writing views with code is long, compared to XML

Oh, I know it's not long. I really like the idea behind it. And I did use Anko UI for a while. But complex views are a bit … complex.

class MainView(override val ctx: Context) : Ui {

    val myTextView =
        textView {
            textResource = R.string.my_string
        }

    override val root = constraintLayout {

        add(myTextView, lParams {
            centerInParent()
        })

    }

}

Splitties is better than Anko, it works differently and fixes some general issues. And for complex views, you can very easily split them in multiple files. It’s also a lot better to just have your views there, like

myTextView

in my example. It’s just there. In my Activity/Fragment I just have

view.myTextView

. Also parsing XML is something not-trivial in terms of resources 😛

As I said, I really like the concept, no need to convince me. Like, I love having stuff like

centerInParent()

, for instance. But the preview is not as good as it is with XML layouts. Also, the XML files aren't shipped as XML, it's binary. 😒imple_smile:

Was talking about the preview 😛

Oh, right. Yeah, that's definitely not for free. 😛

If you can, you should most likely disable thread safety over this, it's not like you need double-check lock synchronization to get a view from your view's... views. Lately it is easier to just use Kotlin synthetics

I'm also a big fan of Kotlin synthetics

Bigger fan of databinding 😔

Came back to this 3 months later, looks like kotlin synthetics are not very performance friendly! Need to learn databinding asap. Also just found kotterknife, wondering how that will be

Better off learning databinding