InvalidatingPagingSourceFactory.kt
/*
* Copyright 2020 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.annotation.VisibleForTesting
/**
* Wrapper class for [PagingSource] factory intended for usage in [Pager] construction.
* Stores reference to the [PagingSource] factory and the [PagingSource]s it produces for
* invalidation when the backing dataset is updated.
*
* Calling [invalidate] on this [InvalidatingPagingSourceFactory] will automatically forward
* invalidate signals to all active [PagingSource]s.
*
* @param pagingSourceFactory The [PagingSource] factory that returns a PagingSource when called
*/
public class InvalidatingPagingSourceFactory<Key : Any, Value : Any>(
private val pagingSourceFactory: () -> PagingSource<Key, Value>
) : () -> PagingSource<Key, Value> {
@VisibleForTesting
internal val pagingSources = mutableListOf<PagingSource<Key, Value>>()
/**
* @return [PagingSource] which will be invalidated when this factory's [invalidate] method
* is called
*/
override fun invoke(): PagingSource<Key, Value> {
return pagingSourceFactory().also { pagingSources.add(it) }
}
/**
* Calls [PagingSource.invalidate] on each [PagingSource] that was produced by this
* [InvalidatingPagingSourceFactory]
*/
public fun invalidate() {
while (pagingSources.isNotEmpty()) {
pagingSources.removeFirst().also {
if (!it.invalid) {
it.invalidate()
}
}
}
}
}