| /* |
| * 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.compose.foundation.lazy |
| |
| import androidx.compose.Applier |
| import androidx.compose.Composable |
| import androidx.compose.ExperimentalComposeApi |
| import androidx.compose.compositionReference |
| import androidx.compose.currentComposer |
| import androidx.compose.emit |
| import androidx.compose.onDispose |
| import androidx.compose.remember |
| import androidx.ui.core.ExperimentalLayoutNodeApi |
| import androidx.ui.core.LayoutNode |
| import androidx.ui.core.Modifier |
| import androidx.ui.core.Ref |
| import androidx.ui.core.clipToBounds |
| import androidx.ui.core.gesture.scrollorientationlocking.Orientation |
| import androidx.ui.core.materialize |
| import androidx.compose.foundation.gestures.rememberScrollableController |
| import androidx.compose.foundation.gestures.scrollable |
| import androidx.compose.foundation.layout.InnerPadding |
| import androidx.compose.foundation.layout.Spacer |
| import androidx.compose.foundation.layout.padding |
| import androidx.ui.core.Alignment |
| import androidx.ui.unit.dp |
| |
| /** |
| * A vertically scrolling list that only composes and lays out the currently visible items. |
| * |
| * @param items the backing list of data to display |
| * @param modifier the modifier to apply to this layout |
| * @param contentPadding convenience param to specify a padding around the whole content. This will |
| * add padding for the content after it has been clipped, which is not possible via [modifier] |
| * param. Note that it is *not* a padding applied for each item's content |
| * @param horizontalGravity the horizontal gravity applied to the items |
| * @param itemContent emits the UI for an item from [items] list. May emit any number of components, |
| * which will be stacked vertically. Note that [LazyColumnItems] can start scrolling incorrectly |
| * if you emit nothing and then lazily recompose with the real content, so even if you load the |
| * content asynchronously please reserve some space for the item, for example using [Spacer]. |
| */ |
| @Composable |
| fun <T> LazyColumnItems( |
| items: List<T>, |
| modifier: Modifier = Modifier, |
| contentPadding: InnerPadding = InnerPadding(0.dp), |
| horizontalGravity: Alignment.Horizontal = Alignment.Start, |
| itemContent: @Composable (T) -> Unit |
| ) { |
| LazyItems( |
| items = items, |
| modifier = modifier, |
| contentPadding = contentPadding, |
| horizontalGravity = horizontalGravity, |
| itemContent = itemContent, |
| isVertical = true |
| ) |
| } |
| |
| /** |
| * A horizontally scrolling list that only composes and lays out the currently visible items. |
| * |
| * @param items the backing list of data to display |
| * @param modifier the modifier to apply to this layout |
| * @param contentPadding convenience param to specify a padding around the whole content. This will |
| * add padding for the content after it has been clipped, which is not possible via [modifier] |
| * param. Note that it is *not* a padding applied for each item's content |
| * @param verticalGravity the vertical gravity applied to the items |
| * @param itemContent emits the UI for an item from [items] list. May emit any number of components, |
| * which will be stacked horizontally. Note that [LazyRowItems] can start scrolling incorrectly |
| * if you emit nothing and then lazily recompose with the real content, so even if you load the |
| * content asynchronously please reserve some space for the item, for example using [Spacer]. |
| */ |
| @Composable |
| fun <T> LazyRowItems( |
| items: List<T>, |
| modifier: Modifier = Modifier, |
| contentPadding: InnerPadding = InnerPadding(0.dp), |
| verticalGravity: Alignment.Vertical = Alignment.Top, |
| itemContent: @Composable (T) -> Unit |
| ) { |
| LazyItems( |
| items = items, |
| modifier = modifier, |
| contentPadding = contentPadding, |
| itemContent = itemContent, |
| verticalGravity = verticalGravity, |
| isVertical = false |
| ) |
| } |
| |
| @Composable |
| @OptIn(ExperimentalLayoutNodeApi::class) |
| private fun <T> LazyItems( |
| items: List<T>, |
| modifier: Modifier = Modifier, |
| contentPadding: InnerPadding, |
| itemContent: @Composable (T) -> Unit, |
| horizontalGravity: Alignment.Horizontal = Alignment.Start, |
| verticalGravity: Alignment.Vertical = Alignment.Top, |
| isVertical: Boolean |
| ) { |
| val state = remember { LazyItemsState<T>(isVertical = isVertical) } |
| @OptIn(ExperimentalComposeApi::class) |
| state.recomposer = currentComposer.recomposer |
| state.itemContent = itemContent |
| state.items = items |
| state.compositionRef = compositionReference() |
| state.forceRecompose = true |
| state.horizontalAlignment = horizontalGravity |
| state.verticalAlignment = verticalGravity |
| |
| val materialized = currentComposer.materialize( |
| modifier |
| .scrollable( |
| orientation = if (isVertical) Orientation.Vertical else Orientation.Horizontal, |
| controller = rememberScrollableController(consumeScrollDelta = state.onScrollDelta) |
| ) |
| .clipToBounds() |
| .padding(contentPadding) |
| .plus(state.remeasurementModifier) |
| ) |
| @OptIn(ExperimentalComposeApi::class) |
| emit<LayoutNode, Applier<Any>>( |
| ctor = LayoutEmitHelper.constructor, |
| update = { |
| set(materialized, LayoutEmitHelper.setModifier) |
| set(state.rootNodeRef, LayoutEmitHelper.setRef) |
| set(state.measureBlocks, LayoutEmitHelper.setMeasureBlocks) |
| } |
| ) |
| state.recomposeIfAttached() |
| onDispose { |
| state.disposeAllChildren() |
| } |
| } |
| |
| /** |
| * Object of pre-allocated lambdas used to make emits to LayoutNodes allocation-less. |
| */ |
| @OptIn(ExperimentalLayoutNodeApi::class) |
| private object LayoutEmitHelper { |
| val constructor: () -> LayoutNode = { LayoutNode() } |
| val setModifier: LayoutNode.(Modifier) -> Unit = { this.modifier = it } |
| val setMeasureBlocks: LayoutNode.(LayoutNode.MeasureBlocks) -> Unit = |
| { this.measureBlocks = it } |
| val setRef: LayoutNode.(Ref<LayoutNode>) -> Unit = { it.value = this } |
| } |