refactor: Simplify and optimize viewBinding delegate (#544)
Based on Christophe Beyl's technique described in https://bladecoder.medium.com/viewlifecyclelazy-and-other-ways-to-avoid-view-memory-leaks-in-android-fragments-4aa982e6e579
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@ -21,16 +21,14 @@ import android.view.LayoutInflater
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import android.view.View
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import androidx.appcompat.app.AppCompatActivity
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import androidx.fragment.app.Fragment
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import androidx.lifecycle.DefaultLifecycleObserver
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import androidx.lifecycle.Lifecycle
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import androidx.lifecycle.LifecycleEventObserver
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import androidx.lifecycle.LifecycleOwner
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import androidx.lifecycle.Observer
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import androidx.viewbinding.ViewBinding
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import kotlin.properties.ReadOnlyProperty
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import kotlin.reflect.KProperty
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/**
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* https://medium.com/@Zhuinden/simple-one-liner-viewbinding-in-fragments-and-activities-with-kotlin-961430c6c07c
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* https://bladecoder.medium.com/viewlifecyclelazy-and-other-ways-to-avoid-view-memory-leaks-in-android-fragments-4aa982e6e579
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* by Christophe Beyls
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*/
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inline fun <T : ViewBinding> AppCompatActivity.viewBinding(
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@ -39,53 +37,32 @@ inline fun <T : ViewBinding> AppCompatActivity.viewBinding(
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bindingInflater(layoutInflater)
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}
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class FragmentViewBindingDelegate<T : ViewBinding>(
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val fragment: Fragment,
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val viewBindingFactory: (View) -> T,
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) : ReadOnlyProperty<Fragment, T> {
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private class ViewLifecycleLazy<out T : Any>(
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private val fragment: Fragment,
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private val viewBindingFactory: (View) -> T,
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) : Lazy<T>, LifecycleEventObserver {
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private var binding: T? = null
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init {
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fragment.lifecycle.addObserver(
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object : DefaultLifecycleObserver {
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val viewLifecycleOwnerLiveDataObserver =
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Observer<LifecycleOwner?> {
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val viewLifecycleOwner = it ?: return@Observer
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viewLifecycleOwner.lifecycle.addObserver(
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object : DefaultLifecycleObserver {
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override fun onDestroy(owner: LifecycleOwner) {
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binding = null
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}
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},
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)
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}
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override fun onCreate(owner: LifecycleOwner) {
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fragment.viewLifecycleOwnerLiveData.observeForever(viewLifecycleOwnerLiveDataObserver)
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}
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override fun onDestroy(owner: LifecycleOwner) {
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fragment.viewLifecycleOwnerLiveData.removeObserver(viewLifecycleOwnerLiveDataObserver)
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}
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},
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)
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}
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override fun getValue(thisRef: Fragment, property: KProperty<*>): T {
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val binding = binding
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if (binding != null) {
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return binding
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override val value: T
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get() {
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return binding ?: run {
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val newValue = viewBindingFactory(fragment.requireView())
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binding = newValue
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fragment.viewLifecycleOwner.lifecycle.addObserver(this)
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newValue
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}
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}
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val lifecycle = fragment.viewLifecycleOwner.lifecycle
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if (!lifecycle.currentState.isAtLeast(Lifecycle.State.INITIALIZED)) {
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throw IllegalStateException("Should not attempt to get bindings when Fragment views are destroyed.")
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}
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override fun isInitialized() = binding != null
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return viewBindingFactory(thisRef.requireView()).also { this.binding = it }
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override fun toString() = binding.toString()
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override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
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if (event == Lifecycle.Event.ON_DESTROY) {
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binding = null
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}
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}
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}
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fun <T : ViewBinding> Fragment.viewBinding(viewBindingFactory: (View) -> T) =
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FragmentViewBindingDelegate(this, viewBindingFactory)
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fun <T : ViewBinding> Fragment.viewBinding(viewBindingFactory: (View) -> T): Lazy<T> =
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ViewLifecycleLazy(this, viewBindingFactory)
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