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Simplify and reduce overhead of lazy view binding in Fragments #4269

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merged 2 commits into from
Feb 23, 2024
Merged

Simplify and reduce overhead of lazy view binding in Fragments #4269

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74509ed
simplify and reduce overhead of lazy viewBinding in Fragments
cbeyls Feb 23, 2024
1799052
add URL to the article explaining the refactoring rationale
cbeyls Feb 23, 2024
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73 changes: 24 additions & 49 deletions app/src/main/java/com/keylesspalace/tusky/util/ViewBindingExtensions.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -4,16 +4,14 @@ 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
* Original code: https://medium.com/@Zhuinden/simple-one-liner-viewbinding-in-fragments-and-activities-with-kotlin-961430c6c07c
* Refactor: https://bladecoder.medium.com/viewlifecyclelazy-and-other-ways-to-avoid-view-memory-leaks-in-android-fragments-4aa982e6e579
*/

inline fun <T : ViewBinding> AppCompatActivity.viewBinding(
Expand All @@ -22,55 +20,32 @@ inline fun <T : ViewBinding> AppCompatActivity.viewBinding(
bindingInflater(layoutInflater)
}

class FragmentViewBindingDelegate<T : ViewBinding>(
val fragment: Fragment,
val viewBindingFactory: (View) -> T
) : ReadOnlyProperty<Fragment, T> {
private var binding: T? = null

init {
fragment.lifecycle.addObserver(object : DefaultLifecycleObserver {
val viewLifecycleOwnerLiveDataObserver =
Observer<LifecycleOwner?> {
val viewLifecycleOwner = it ?: return@Observer

viewLifecycleOwner.lifecycle.addObserver(object : DefaultLifecycleObserver {
override fun onDestroy(owner: LifecycleOwner) {
binding = null
}
})
}

override fun onCreate(owner: LifecycleOwner) {
fragment.viewLifecycleOwnerLiveData.observeForever(
viewLifecycleOwnerLiveDataObserver
)
private class ViewLifecycleLazy<out T : Any>(
private val fragment: Fragment,
private val initializer: (View) -> T
) : Lazy<T>, LifecycleEventObserver {
private var cached: T? = null

override val value: T
get() {
return cached ?: run {
val newValue = initializer(fragment.requireView())
cached = newValue
fragment.viewLifecycleOwner.lifecycle.addObserver(this)
newValue
}
}

override fun onDestroy(owner: LifecycleOwner) {
fragment.viewLifecycleOwnerLiveData.removeObserver(
viewLifecycleOwnerLiveDataObserver
)
}
})
}
override fun isInitialized() = cached != null

override fun getValue(thisRef: Fragment, property: KProperty<*>): T {
val binding = binding
if (binding != null) {
return binding
}
override fun toString() = cached.toString()

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."
)
override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
if (event == Lifecycle.Event.ON_DESTROY) {
cached = null
}

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)
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