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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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Nik Clayton 2024-03-19 16:42:08 +01:00 committed by GitHub
parent c2fc3d1f08
commit 4f9b283432
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1 changed files with 24 additions and 47 deletions
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71
core/common/src/main/kotlin/app/pachli/core/common/extensions/ViewBindingExtensions.kt
View File

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