LazyLayoutPrefetchPolicy.kt
/*
* Copyright 2021 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.compose.foundation.lazy.layout
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.runtime.Composable
import androidx.compose.runtime.Stable
import androidx.compose.runtime.remember
import androidx.compose.ui.unit.Constraints
/** Creates a [LazyLayoutPrefetchPolicy]. */
@ExperimentalFoundationApi
@Composable
internal fun rememberLazyLayoutPrefetchPolicy(): LazyLayoutPrefetchPolicy = remember {
LazyLayoutPrefetchPolicy()
}
/**
* Controller for lazy items prefetching, used by lazy layouts to instruct the prefetcher.
*/
@ExperimentalFoundationApi
@Stable
internal class LazyLayoutPrefetchPolicy {
internal var prefetcher: Subscriber? = null
/** Schedules new items to prefetch, specified by [indices]. */
fun scheduleForPrefetch(indices: List<Pair<Int, Constraints>>) =
prefetcher?.scheduleForPrefetch(indices)
/** Notifies the prefetcher that previously scheduled items are no longer likely to be needed. */
fun cancelScheduledPrefetch() = prefetcher?.cancelScheduledPrefetch()
interface Subscriber {
fun scheduleForPrefetch(indices: List<Pair<Int, Constraints>>)
fun cancelScheduledPrefetch()
}
}