Android: I am attaching the same `textChangedListe...

# getting-started

[Mathias Brandt]

Android: I am attaching the same textChangedListener to multiple input fields. Currently I have this:

withdraw_input.textChangedListener {
    afterTextChanged {
        validateInput()
    }
}

reg_number.textChangedListener {
    afterTextChanged {
        validateInput()
    }
}

I cannot figure out how to extract the listener to a variable and then re-use it, instead of defining the same listener multiple times.
I guess it’s just a syntax issue 🤔 Any hints? 🙂

[karelpeeters]

Do you happen to use some Kotlin-library for this? EditTest.textChangedListener doesn't exist for me.

[karelpeeters]

Maybe it's even a builder, because that afterTextChanged doesn't look like function override syntax to me.

[Mathias Brandt]

Don’t think so … I’m not too good at the super short Kotlin syntax yet, so I’m actually not even sure what I’m doing.

[karelpeeters]

Can you ctrl+B (go to definition) on that function?

[Mathias Brandt]

It’s defined in ListenersWithCoroutines.kt

[karelpeeters]

You're using anko then 🙂

[Mathias Brandt]

Oh, that’s an external library?

[Mathias Brandt]

Didn’t start this project, so I was not aware

[karelpeeters]

Yea it's a util library from jetbrains for android and kotlin.

[Mathias Brandt]

Oh, okay 😄

[karelpeeters]

So yea, there's some DSL trickery going on.

[Mathias Brandt]

Yep. Probably gonna try a solution without anko, then

[Mathias Brandt]

Gotta know what’s going on before using the magic tools

[karelpeeters]

fun textChangedListener(
	context: CoroutineContext = UI,
	init: __TextWatcher.() -> Unit
): android.text.TextWatcher = __TextWatcher(context).apply(init)

[karelpeeters]

If you put that somewhere then you can create a variable listener = textChangedListener { ... } and reuse that.

[Mathias Brandt]

What if I want to do it without the coroutines stuff, something like Shawn is suggesting?

[Mathias Brandt]

so basically an anon inner class

[karelpeeters]

val listener = object : TextWatcher {
        override fun afterTextChanged(s: Editable?) {}
        override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {}
        override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {}
    }

    editText.addTextChangedListener(listener)

[karelpeeters]

That's going to be ugly.

[Mathias Brandt]

Hmm, yes. I liked the solution I made because I only had to override a single function from TextWatcher

[karelpeeters]

Right, that's kinda the point of using anko, makes everything way more elegant.

[karelpeeters]

You can just use the snippet I posted above to do about the same.

[Mathias Brandt]

Yes, I will probably do that, even though I find that code confusing as well

[karelpeeters]

You only need the function once, just hide it somewhere in a Util.kt file 😛

[karelpeeters]

If you want to know what's going on read https://kotlinlang.org/docs/reference/type-safe-builders.html

[Mathias Brandt]

Haha, “never speak of it again”, I like that

[Mathias Brandt]

It says conflicting declarations

[Mathias Brandt]

val listener: TextWatcher and val listener: TextWatcher.() -> Unit

[karelpeeters]

What line gives that error message? Maybe a sceenshot?

[Mathias Brandt]

Oh, never mind, had some other old code that didnt compile

[karelpeeters]

Yea that's what I figured 🙂

[Mathias Brandt]

It’s been a long day - I really appreciate your help 🙂

[karelpeeters]

My pleasure.

[Mathias Brandt]

Okay, so I’ve defined the listener as you said, but cannot figure out how to attach it to the view 🤔

[Mathias Brandt]

Oh, just had to call addTextChangedListener. Right, makes sense

[Mathias Brandt]

Okay, I think I’ve the right solution now, even though I’m still not sure what’s going on. I have an idea, though 😉 Will look at the link you provided.
Thanks again for your help! 🙂

[karelpeeters]

I'd say read trough the entire reference if you find the time, it's really good.

[karelpeeters]

Good luck!

[Mathias Brandt]

Thanks 🙂