Delegates for easier view init in Activities and Fragments

ViewDelegates.kt

import android.app.Activity
import androidx.annotation.IdRes
import androidx.fragment.app.Fragment
import android.view.View
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleEventObserver
import kotlin.properties.ReadOnlyProperty
import kotlin.reflect.KProperty

fun <V : View> Activity.view(@IdRes viewId: Int) = lazy<V>(LazyThreadSafetyMode.NONE) { findViewById(viewId) }

fun <V : View> Fragment.view(@IdRes viewId: Int) = object : ReadOnlyProperty<Fragment, V> {
    private var cached: V? = null
    private val lifecycleListener = LifecycleEventObserver { _, event ->
        if (event == Lifecycle.Event.ON_DESTROY) {
            cached = null
        }
    }

    init {
        viewLifecycleOwner.lifecycle.addObserver(lifecycleListener)
    }

    override fun getValue(thisRef: Fragment, property: KProperty<*>): V =
        cached ?: requireView().findViewById<V>(viewId).also { cached = it }
}