How to bind method on RadioGroup on checkChanged event with data-binding

Question

I was searching over the internet for how to perform the new cool android data-binding over the RadioGroup and I didn\'t find a single blog post about it.

Answer 1

In my current project, I did it like this. I have three currency in the project and I choose one of them via RadioGroup.

It's enum with currencies:

enum class Currency(val value: Byte) {
    USD(0),
    EUR(1),
    RUB(2);

    companion object Create {
        fun from(sourceValue: Byte): Currency = values().first { it.value == sourceValue }
        fun from(sourceValue: String): Currency = values().first { it.toString() == sourceValue }
    }
}

A piece of my ViewModel:

    class BaseCurrencyViewModel : ViewModelBase() {
        /**
         * Selected currency
         */
        val currency: MutableLiveData = MutableLiveData()

        /**
         *
         */
        init {
            currency.value = Currency.USD   // Init value
        }
  }

Part of my layout (pay attention to binding in RadioGroup and tags of RadioButton):

And the final part - binding adapter.

@BindingAdapter("selectedCurrency")
fun setSelectedCurrency(view: View, value: MutableLiveData?) {
    view.getParentActivity()?.let { parentActivity ->
        value?.observe(parentActivity, Observer { value ->
            view.findViewWithTag(value.toString())
                ?.also {
                    if(!it.isChecked) {
                        it.isChecked = true
                    }
                }
            }
        )

        (view as RadioGroup).setOnCheckedChangeListener { radioGroup, checkedId ->
            val currency = Currency.from(radioGroup.findViewById(checkedId).tag as String)
            if(value != null && value.value != currency) {
                value.value = currency
            }
        }
    }
}

In this way, I got two-way binding between RadioGroup and a property in my ViewModel.