LazyList.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.compose.foundation.lazy
import androidx.compose.foundation.gestures.scrollable
import androidx.compose.foundation.layout.PaddingValues
import androidx.compose.foundation.layout.padding
import androidx.compose.runtime.Composable
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.clipToBounds
import androidx.compose.ui.gesture.scrollorientationlocking.Orientation
import androidx.compose.ui.layout.SubcomposeLayout
import androidx.compose.ui.platform.LayoutDirectionAmbient
import androidx.compose.ui.unit.LayoutDirection
@Composable
internal fun LazyList(
itemsCount: Int,
modifier: Modifier = Modifier,
state: LazyListState,
contentPadding: PaddingValues,
horizontalAlignment: Alignment.Horizontal = Alignment.Start,
verticalAlignment: Alignment.Vertical = Alignment.Top,
isVertical: Boolean,
itemContentFactory: LazyItemScope.(Int) -> @Composable () -> Unit
) {
val reverseDirection = LayoutDirectionAmbient.current == LayoutDirection.Rtl && !isVertical
val cachingItemContentFactory = remember { CachingItemContentFactory(itemContentFactory) }
cachingItemContentFactory.itemContentFactory = itemContentFactory
SubcomposeLayout<DataIndex>(
modifier
.scrollable(
orientation = if (isVertical) Orientation.Vertical else Orientation.Horizontal,
reverseDirection = reverseDirection,
controller = state.scrollableController
)
.clipToBounds()
.padding(contentPadding)
.then(state.remeasurementModifier)
) { constraints ->
// this will update the scope object if the constrains have been changed
cachingItemContentFactory.updateItemScope(this, constraints)
state.measure(
this,
constraints,
isVertical,
horizontalAlignment,
verticalAlignment,
itemsCount,
cachingItemContentFactory
)
}
}