Android MVVM with Custom State Widget

attrs.xml

<declare-styleable name="ElementStatus">
        <attr name="state_on" format="boolean" />
        <attr name="state_loading" format="boolean" />
</declare-styleable>

background_element_status.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto">

    <item android:drawable="@drawable/round_rectangle_status_on" app:state_loading="true" />
    <item android:drawable="@drawable/round_rectangle_status_on" app:state_on="true" />
    <item android:drawable="@drawable/round_rectangle_status_off" />

</selector>

ElementViewModel.kt

abstract class ElementViewModel<T : Element> : RxViewModel() {

    lateinit var element: T

    protected fun initialize(element: T) {
        this.element = element
        isOn.set(element.isOn())
        onStatusUpdate()
    }

    val isEnabled: ObservableField<Boolean> = ObservableField()
    val isLoading: ObservableField<Boolean> = ObservableField(false)
    val isOn: ObservableField<Boolean> = ObservableField()

    open fun onStatusToggle(button: View) {

        val currentStatus = element.status

        if (element.isOn()) {
            element.off()
        } else {
            element.on()
        }

        addDisposables(
                apiRepository.modifyElementStatus(element, element.status!!)
                        .compose(UiModel.apiRequestTransformer)
                        .subscribe({
                            if (it is UiModel.Loading) {
                                isLoading.set(true)
                                button.isEnabled = false
                            } else {
                                if (it is UiModel.Failure) {
                                    ToastUtils.show(R.string.formatter_element_status_control_failed, element.getDisplayName())
                                    element.status = currentStatus
                                }
                                isLoading.set(false)
                                isOn.set(element.isOn())
                                button.isEnabled = true
                                onStatusUpdate()
                            }
                        })
        )

    }

    open fun onStatusUpdate() {
    }

}

item_single_light.xml

<?xml version="1.0" encoding="utf-8"?>
<layout>

    <data>

        <variable
            name="vm"
            type="com.acciio.homeapp.ui.main.home.viewmodel.LightViewModel" />
    </data>

    <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="112dp">


        <TextView
            android:id="@+id/textView8"
            style="@style/Text.Caption2.CardDesc"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginEnd="8dp"
            android:layout_marginStart="8dp"
            android:layout_marginTop="16dp"
            android:text="@{vm.statusText}"
            app:layout_constraintEnd_toStartOf="@+id/guideline6"
            app:layout_constraintStart_toStartOf="@+id/guideline"
            app:layout_constraintTop_toTopOf="parent" />

        <android.support.constraint.Guideline
            android:id="@+id/guideline"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_begin="16dp" />

        <android.support.constraint.Guideline
            android:id="@+id/guideline6"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_end="16dp" />

        <com.acciio.homeapp.custom.view.state.StateImageButton
            android:id="@+id/imageButton"
            android:layout_width="0dp"
            android:layout_height="60dp"
            android:layout_marginEnd="8dp"
            android:layout_marginStart="8dp"
            android:layout_marginTop="4dp"
            android:background="@drawable/background_element_status"
            android:onClick="@{(v) -> vm.onStatusToggle(v)}"
            android:scaleType="center"
            android:src="@drawable/icon_light_status"
            app:layout_constraintEnd_toStartOf="@+id/guideline6"
            app:layout_constraintStart_toStartOf="@+id/guideline"
            app:layout_constraintTop_toBottomOf="@+id/textView8"
            app:state_loading="@{safeUnbox(vm.isLoading)}"
            app:state_on="@{safeUnbox(vm.isOn)}" />
    </android.support.constraint.ConstraintLayout>
</layout>

StateImageButton.kt

class StateImageButton @JvmOverloads constructor(
        context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : AppCompatImageButton(context, attrs, defStyleAttr) {


    var isOn = false
        set(value) {
            field = value
            refreshDrawableState()
        }
    var isLoading = false
        set(value) {
            field = value
            refreshDrawableState()
        }

    override fun onCreateDrawableState(extraSpace: Int): IntArray {
        val drawableState = super.onCreateDrawableState(extraSpace + EXTRA_STATES.size)

        if (isLoading) {
            AppCompatButton.mergeDrawableStates(drawableState, intArrayOf(EXTRA_STATES[0]))
        }

        if (isOn) {
            AppCompatButton.mergeDrawableStates(drawableState, intArrayOf(EXTRA_STATES[1]))
        }

        return drawableState
    }

    override fun drawableStateChanged() {
        super.drawableStateChanged()
    }

    companion object {
        private val EXTRA_STATES = intArrayOf(R.attr.state_loading, R.attr.state_on)
    }
}

ViewBindingAdapter.kt

object ViewBindingAdapter {

    @JvmStatic
    @BindingAdapter("app:state_loading")
    fun setLoading(view: StateImageButton, isLoading: Boolean) {
        view.isLoading = isLoading
    }

    @JvmStatic
    @BindingAdapter("app:state_on")
    fun setStatus(view: StateImageButton, isOn: Boolean) {
        view.isOn = isOn
    }

    @JvmStatic
    @BindingAdapter("app:state_loading")
    fun setLoading(view: StateButton, isLoading: Boolean) {
        view.isLoading = isLoading
    }

    @JvmStatic
    @BindingAdapter("app:state_on")
    fun setStatus(view: StateButton, isOn: Boolean) {
        view.isOn = isOn
    }

    @JvmStatic
    @BindingAdapter("app:error")
    fun setError(view: TextInputLayout, error: String) {
        view.error = error
    }
}