LazyLayoutPrefetchState

import androidx.compose.foundation.background import androidx.compose.foundation.layout.Box import androidx.compose.foundation.layout.Column import androidx.compose.foundation.layout.height import androidx.compose.foundation.layout.size import androidx.compose.foundation.layout.width import androidx.compose.foundation.lazy.layout.LazyLayout import androidx.compose.foundation.lazy.layout.LazyLayoutItemProvider import androidx.compose.foundation.lazy.layout.LazyLayoutPrefetchState import androidx.compose.material.Button import androidx.compose.material.Text import androidx.compose.runtime.Composable import androidx.compose.runtime.remember import androidx.compose.ui.Modifier import androidx.compose.ui.graphics.Color import androidx.compose.ui.layout.Placeable import androidx.compose.ui.unit.Constraints import androidx.compose.ui.unit.dp val items = remember { (0..100).toList().map { it.toString() } } var currentHandle = remember<LazyLayoutPrefetchState.PrefetchHandle?> { null } val prefetchState = remember { LazyLayoutPrefetchState() } // Create an item provider val itemProvider = remember {  {  object : LazyLayoutItemProvider {  override val itemCount: Int  get() = 100  @Composable  override fun Item(index: Int, key: Any) {  Box(  modifier =  Modifier.width(100.dp)  .height(100.dp)  .background(color = if (index % 2 == 0) Color.Red else Color.Green)  ) {  Text(text = items[index])  }  }  }  } } Column {  Button(onClick = { currentHandle = prefetchState.schedulePrecomposition(10) }) {  Text(text = "Prefetch Item 10")  }  Button(onClick = { currentHandle?.cancel() }) { Text(text = "Cancel Prefetch") }  LazyLayout(modifier = Modifier.size(500.dp), itemProvider = itemProvider) { constraints ->  // plug the measure policy, this is how we create and layout items.  val placeablesCache = mutableListOf<Pair<Placeable, Int>>()  fun Placeable.mainAxisSize() = width  fun Placeable.crossAxisSize() = height  val childConstraints =  Constraints(maxWidth = Constraints.Infinity, maxHeight = constraints.maxHeight)  var currentItemIndex = 0  var crossAxisSize = 0  var mainAxisSize = 0  // measure items until we either fill in the space or run out of items.  while (mainAxisSize < constraints.maxWidth && currentItemIndex < items.size) {  val itemPlaceables = compose(currentItemIndex).map { it.measure(childConstraints) }  for (item in itemPlaceables) {  // save placeable to be placed later.  placeablesCache.add(item to mainAxisSize)  mainAxisSize += item.mainAxisSize() // item size contributes to main axis size  // cross axis size will the size of tallest/widest item  crossAxisSize = maxOf(crossAxisSize, item.crossAxisSize())  }  currentItemIndex++  }  val layoutWidth = minOf(mainAxisSize, constraints.maxHeight)  val layoutHeight = crossAxisSize  layout(layoutWidth, layoutHeight) {  // since this is a linear list all items are placed on the same cross-axis position  for ((placeable, position) in placeablesCache) {  placeable.place(position, 0)  }  }  } }