MainFragment.kt

package io.github.hkusu.sample.ui

import android.os.Bundle
import android.view.View
import androidx.fragment.app.Fragment
import io.github.hkusu.sample.databinding.MainFragmentBinding

class MainFragment : Fragment(R.layout.main_fragment) {

    private val binding: MainFragmentBinding by viewBinding()

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

        binding.message.text = "テストテスト"
    }

    override fun onDestroy() {
        super.onDestroy()

        // この時点でFragment#getView()は死んでいる

        safeViewBinding {
            binding.message.text = "安全！"
        }
    }
}

ViewDetaBindingExt.kt

package io.github.hkusu.sample.ext

import android.util.Log
import android.view.ViewGroup
import androidx.appcompat.app.AppCompatActivity
import androidx.core.view.get
import androidx.databinding.DataBindingUtil
import androidx.databinding.ViewDataBinding
import androidx.fragment.app.Fragment
import kotlin.properties.ReadOnlyProperty
import kotlin.reflect.KProperty

// ref: https://satoshun.github.io/2020/01/fragment-view-memory-leak/
//      https://satoshun.github.io/2019/04/jetpack-coroutine-support/

fun <T : ViewDataBinding> AppCompatActivity.viewBinding(): ReadOnlyProperty<AppCompatActivity, T> {
    return object : ReadOnlyProperty<AppCompatActivity, T> {
        override fun getValue(thisRef: AppCompatActivity, property: KProperty<*>): T {
            val view = thisRef.findViewById<ViewGroup>(android.R.id.content)[0]
            val binding = DataBindingUtil.bind<T>(view)!!
            binding.lifecycleOwner = thisRef
            return binding
        }
    }
}

fun <T : ViewDataBinding> Fragment.viewBinding(): ReadOnlyProperty<Fragment, T> {
    return object : ReadOnlyProperty<Fragment, T> {
        override fun getValue(thisRef: Fragment, property: KProperty<*>): T {
            val view = thisRef.view ?: throw FragmentViewNotFoundException()
            val binding = DataBindingUtil.bind<T>(view)!!
            binding.lifecycleOwner = thisRef.viewLifecycleOwner
            return binding
        }
    }
}

// Fragment.viewBinding() 用
class FragmentViewNotFoundException : Exception("Fragment#getView() returned null.")

// Fragment.viewBinding() 用。コールバックや遅延実行等でonDestroyView()後にBindingを触る可能性がある場合に利用する
inline fun Fragment.safeViewBinding(block: () -> Unit) {
    try {
        block.invoke()
    } catch (e: FragmentViewNotFoundException) {
        Log.w(this::class.java.simpleName, e.message!!)
    }
}

// そもそも binding を Nullable にして安全に扱いたい場合は Fragment.viewBinding() の代わりにこちらを利用する
fun <T : ViewDataBinding> Fragment.safeViewBinding(): ReadOnlyProperty<Fragment, T?> {
    return object : ReadOnlyProperty<Fragment, T?> {
        override fun getValue(thisRef: Fragment, property: KProperty<*>): T? {
            val view = thisRef.view ?: return null
            val binding = DataBindingUtil.bind<T>(view)!!
            binding.lifecycleOwner = thisRef.viewLifecycleOwner
            return binding
        }
    }
}