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| package com.marcellogalhardo.AutoClearedValue | |
| import androidx.fragment.app.Fragment | |
| import androidx.lifecycle.DefaultLifecycleObserver | |
| import androidx.lifecycle.LifecycleOwner | |
| import androidx.lifecycle.observe | |
| import kotlin.properties.ReadOnlyProperty | |
| import kotlin.properties.ReadWriteProperty | |
| import kotlin.reflect.KProperty | |
| /** | |
| * Creates a new instance of the [AutoClearedDelegate] associated with this | |
| * fragment. | |
| */ | |
| fun <T : Any> Fragment.autoCleared(): ReadWriteProperty<Fragment, T> = AutoClearedDelegate(this) | |
| /** | |
| * Creates a new instance of the [AutoClearedDelegate] associated with this | |
| * fragment that uses the specified initialization function [initializer]. | |
| */ | |
| fun <T : Any> Fragment.autoCleared( | |
| initializer: (() -> T) | |
| ): ReadOnlyProperty<Fragment, T> = AutoClearedDelegate(this, initializer) | |
| /** | |
| * A lazy property that gets cleaned up when the fragment's view is destroyed. | |
| * | |
| * Accessing this variable while the fragment's view is destroyed will throw [IllegalStateException]. | |
| */ | |
| private class AutoClearedDelegate<T : Any>( | |
| private val fragment: Fragment, | |
| private val initializer: (() -> T)? = null | |
| ) : ReadWriteProperty<Fragment, T>, ReadOnlyProperty<Fragment, T> { | |
| private var _value: T? = null | |
| private val fragmentLifecycleObserver = object : DefaultLifecycleObserver { | |
| override fun onCreate(owner: LifecycleOwner) { | |
| fragment.viewLifecycleOwnerLiveData.observe(fragment) { viewLifecycleOwner -> | |
| viewLifecycleOwner?.lifecycle?.addObserver(viewLifecycleObserver) | |
| } | |
| } | |
| } | |
| private val viewLifecycleObserver = object : DefaultLifecycleObserver { | |
| override fun onDestroy(owner: LifecycleOwner) { | |
| _value = null | |
| } | |
| } | |
| init { | |
| fragment.lifecycle.addObserver(fragmentLifecycleObserver) | |
| } | |
| override fun getValue(thisRef: Fragment, property: KProperty<*>): T { | |
| checkNotNull(thisRef.view) { | |
| "Property '${property.name}' of fragment '${thisRef.javaClass.name}': view should be created before get." | |
| } | |
| if (_value == null && initializer != null) { | |
| _value = initializer.invoke() | |
| } | |
| return checkNotNull(_value) { | |
| "Property '${property.name}' of fragment '${thisRef.javaClass.name}': should be initialized before get." | |
| } | |
| } | |
| override fun setValue(thisRef: Fragment, property: KProperty<*>, value: T) { | |
| _value = value | |
| } | |
| } |
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