How can I shorten this code in Android using view binding by Kotlin?

Issue

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        select(viewBinding.btnPearKind1)
        select(viewBinding.btnPearKind2)
        select(viewBinding.btnPearKind3)
        select(viewBinding.btnPearKind4)
        select(viewBinding.btnPearKind5)
        select(viewBinding.btnPearKind6)
    }

Clicking one button changes the other 5 buttons.

I use these functions.

fun select(btn: Button){
        btn.setOnClickListener {      
            val kind = listOf("1","2","3","4","5","6")
            for(i in kind) {
                    if (i != btn.tag){
                        viewBinding.kindGrid.findViewWithTag<View>(i).backgroundTintList =
                            ContextCompat.getColorStateList(it.context, R.color.btn_color_off)
                    }else{
                        viewBinding.kindGrid.findViewWithTag<View>(i).backgroundTintList =
                            ContextCompat.getColorStateList(it.context, R.color.btn_color)
                    }
            }
        }
    }

When I wrote it with view combination, the duplicate code came out like this. How can I reduce it?

Solution

Your select function is already hardcoded to find all the buttons in the view hierarchy by the looks of it? Personally I'd just repurpose that code to create a button lookup, and then you can use that for easy click listener setting and UI changes:

lateinit val buttons: List<Button>

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    val tags = listOf("1","2","3","4","5","6")
    // look up all your buttons, creating a list of Button views
    buttons = tags.map { tag ->
        viewBinding.kindGrid.findViewWithTag<Button>(tag)
    }
    // now you can just apply a click listener to each of them
    buttons.forEach {
        setOnClickListener { view -> select(view as Button) }
    }
}

fun select(selected: Button){
    buttons.forEach { button ->
        // you could check the tags, but since we have a list of all the actual
        // buttons, we can just check which of them has been passed in
        val colour = if (button == selected) R.color.btn_color else R.color.btn_color_off
        button.backgroundTintList = ContextCompat.getColorStateList(it.context, colour)
    }
}

You could also do tags.associateWith instead of map to build up a tag -> Button Map, if you needed to directly look up a button by tag instead of iterating over them

Answered By - cactustictacs