WrapperItemKeyedDataSource.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.
*/
package androidx.paging
import androidx.arch.core.util.Function
import java.util.IdentityHashMap
@Suppress("DEPRECATION")
internal class WrapperItemKeyedDataSource<K : Any, A : Any, B : Any>(
private val source: ItemKeyedDataSource<K, A>,
private val listFunction: Function<List<A>, List<B>>
) : ItemKeyedDataSource<K, B>() {
private val keyMap = IdentityHashMap<B, K>()
override fun addInvalidatedCallback(onInvalidatedCallback: InvalidatedCallback) {
source.addInvalidatedCallback(onInvalidatedCallback)
}
override fun removeInvalidatedCallback(onInvalidatedCallback: InvalidatedCallback) {
source.removeInvalidatedCallback(onInvalidatedCallback)
}
override fun invalidate() {
source.invalidate()
}
override val isInvalid
get() = source.isInvalid
fun convertWithStashedKeys(source: List<A>): List<B> {
val dest = convert(listFunction, source)
synchronized(keyMap) {
// synchronize on keyMap, since multiple loads may occur simultaneously.
// Note: manually sync avoids locking per-item (e.g. Collections.synchronizedMap)
for (i in dest.indices) {
keyMap[dest[i]] = this.source.getKey(source[i])
}
}
return dest
}
override fun loadInitial(params: LoadInitialParams<K>, callback: LoadInitialCallback<B>) {
source.loadInitial(params, object : LoadInitialCallback<A>() {
override fun onResult(data: List<A>, position: Int, totalCount: Int) {
callback.onResult(convertWithStashedKeys(data), position, totalCount)
}
override fun onResult(data: List<A>) {
callback.onResult(convertWithStashedKeys(data))
}
})
}
override fun loadAfter(params: LoadParams<K>, callback: LoadCallback<B>) {
source.loadAfter(params, object : LoadCallback<A>() {
override fun onResult(data: List<A>) {
callback.onResult(convertWithStashedKeys(data))
}
})
}
override fun loadBefore(params: LoadParams<K>, callback: LoadCallback<B>) {
source.loadBefore(params, object : LoadCallback<A>() {
override fun onResult(data: List<A>) {
callback.onResult(convertWithStashedKeys(data))
}
})
}
override fun getKey(item: B): K = synchronized(keyMap) {
return keyMap[item]!!
}
}