ViewTreeLifecycleOwner.kt
/*
* Copyright 2019 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
@file:JvmName("ViewTreeLifecycleOwner")
package androidx.lifecycle
import android.view.View
import androidx.lifecycle.runtime.R
/**
* Set the [LifecycleOwner] responsible for managing the given [View].
* Calls to [get] from this view or descendants will return `lifecycleOwner`.
*
* This should only be called by constructs such as activities or fragments that manage
* a view tree and reflect their own lifecycle through a [LifecycleOwner]. Callers
* should only set a [LifecycleOwner] that will be *stable.* The associated
* lifecycle should report that it is destroyed if the view tree is removed and is not
* guaranteed to later become reattached to a window.
*
* @param lifecycleOwner LifecycleOwner representing the manager of the given view
*/
@JvmName("set")
fun View.setViewTreeLifecycleOwner(lifecycleOwner: LifecycleOwner?) {
setTag(R.id.view_tree_lifecycle_owner, lifecycleOwner)
}
/**
* Retrieve the [LifecycleOwner] responsible for managing the given [View].
* This may be used to scope work or heavyweight resources associated with the view
* that may span cycles of the view becoming detached and reattached from a window.
*
* @return The [LifecycleOwner] responsible for managing this view and/or some subset
* of its ancestors
*/
@JvmName("get")
fun View.findViewTreeLifecycleOwner(): LifecycleOwner? {
return generateSequence(this) { currentView ->
currentView.parent as? View
}.mapNotNull { viewParent ->
viewParent.getTag(R.id.view_tree_lifecycle_owner) as? LifecycleOwner
}.firstOrNull()
}