/*
* 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.ExperimentalFoundationApi
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.BoxWithConstraints
import androidx.compose.foundation.layout.PaddingValues
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.Spacer
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.dp
/**
* The DSL implementation of a lazy grid layout. It composes only visible rows of the grid.
* This API is not stable, please consider using stable components like [LazyColumn] and [Row]
* to achieve the same result.
*
* @param cells a class describing how cells form columns, see [GridCells] doc for more information
* @param modifier the modifier to apply to this layout
* @param state the state object to be used to control or observe the list's state
* @param contentPadding specify a padding around the whole content
* @param verticalArrangement The vertical arrangement of the layout's children
* @param horizontalArrangement The horizontal arrangement of the layout's children
* @param content the [LazyListScope] which describes the content
*/
@ExperimentalFoundationApi
@Composable
fun LazyVerticalGrid(
cells: GridCells,
modifier: Modifier = Modifier,
state: LazyListState = rememberLazyListState(),
contentPadding: PaddingValues = PaddingValues(0.dp),
verticalArrangement: Arrangement.Vertical = Arrangement.Top,
horizontalArrangement: Arrangement.Horizontal = Arrangement.Start,
content: LazyGridScope.() -> Unit
) {
when (cells) {
is GridCells.Fixed ->
FixedLazyGrid(
nColumns = cells.count,
modifier = modifier,
state = state,
horizontalArrangement = horizontalArrangement,
verticalArrangement = verticalArrangement,
contentPadding = contentPadding,
content = content
)
is GridCells.Adaptive ->
BoxWithConstraints(
modifier = modifier
) {
val nColumns = maxOf((maxWidth / cells.minSize).toInt(), 1)
FixedLazyGrid(
nColumns = nColumns,
state = state,
horizontalArrangement = horizontalArrangement,
verticalArrangement = verticalArrangement,
contentPadding = contentPadding,
content = content
)
}
}
}
/**
* This class describes how cells form columns in vertical grids or rows in horizontal grids.
*/
@ExperimentalFoundationApi
sealed class GridCells {
/**
* Combines cells with fixed number rows or columns.
*
* For example, for the vertical [LazyVerticalGrid] Fixed(3) would mean that there are 3 columns 1/3
* of the parent wide.
*/
@ExperimentalFoundationApi
class Fixed(val count: Int) : GridCells()
/**
* Combines cells with adaptive number of rows or columns. It will try to position as many rows
* or columns as possible on the condition that every cell has at least [minSize] space and
* all extra space distributed evenly.
*
* For example, for the vertical [LazyVerticalGrid] Adaptive(20.dp) would mean that there will be as
* many columns as possible and every column will be at least 20.dp and all the columns will
* have equal width. If the screen is 88.dp wide then there will be 4 columns 22.dp each.
*/
@ExperimentalFoundationApi
class Adaptive(val minSize: Dp) : GridCells()
}
/**
* Receiver scope which is used by [LazyVerticalGrid].
*/
@ExperimentalFoundationApi
interface LazyGridScope {
/**
* Adds a single item to the scope.
*
* @param content the content of the item
*/
fun item(content: @Composable LazyItemScope.() -> Unit)
/**
* Adds a [count] of items.
*
* @param count the items count
* @param itemContent the content displayed by a single item
*/
fun items(count: Int, itemContent: @Composable LazyItemScope.(index: Int) -> Unit)
}
/**
* Adds a list of items.
*
* @param items the data list
* @param itemContent the content displayed by a single item
*/
@ExperimentalFoundationApi
inline fun <T> LazyGridScope.items(
items: List<T>,
crossinline itemContent: @Composable LazyItemScope.(item: T) -> Unit
) = items(items.size) {
itemContent(items[it])
}
/**
* Adds a list of items where the content of an item is aware of its index.
*
* @param items the data list
* @param itemContent the content displayed by a single item
*/
@ExperimentalFoundationApi
inline fun <T> LazyGridScope.itemsIndexed(
items: List<T>,
crossinline itemContent: @Composable LazyItemScope.(index: Int, item: T) -> Unit
) = items(items.size) {
itemContent(it, items[it])
}
/**
* Adds an array of items.
*
* @param items the data array
* @param itemContent the content displayed by a single item
*/
@ExperimentalFoundationApi
inline fun <T> LazyGridScope.items(
items: Array<T>,
crossinline itemContent: @Composable LazyItemScope.(item: T) -> Unit
) = items(items.size) {
itemContent(items[it])
}
/**
* Adds an array of items where the content of an item is aware of its index.
*
* @param items the data array
* @param itemContent the content displayed by a single item
*/
@ExperimentalFoundationApi
inline fun <T> LazyGridScope.itemsIndexed(
items: Array<T>,
crossinline itemContent: @Composable LazyItemScope.(index: Int, item: T) -> Unit
) = items(items.size) {
itemContent(it, items[it])
}
@Composable
@ExperimentalFoundationApi
private fun FixedLazyGrid(
nColumns: Int,
modifier: Modifier = Modifier,
state: LazyListState,
contentPadding: PaddingValues,
verticalArrangement: Arrangement.Vertical,
horizontalArrangement: Arrangement.Horizontal,
content: LazyGridScope.() -> Unit
) {
LazyColumn(
modifier = modifier,
state = state,
verticalArrangement = verticalArrangement,
contentPadding = contentPadding
) {
val scope = LazyGridScopeImpl()
scope.apply(content)
val rows = if (scope.totalSize == 0) 0 else 1 + (scope.totalSize - 1) / nColumns
items(rows) { rowIndex ->
Row(horizontalArrangement = horizontalArrangement) {
for (columnIndex in 0 until nColumns) {
val itemIndex = rowIndex * nColumns + columnIndex
if (itemIndex < scope.totalSize) {
Box(
modifier = Modifier.weight(1f, fill = true),
propagateMinConstraints = true
) {
scope.contentFor(itemIndex, this@items).invoke()
}
} else {
Spacer(Modifier.weight(1f, fill = true))
}
}
}
}
}
}
@ExperimentalFoundationApi
internal class LazyGridScopeImpl : LazyGridScope {
private val intervals = IntervalList<LazyItemScope.(Int) -> (@Composable () -> Unit)>()
val totalSize get() = intervals.totalSize
fun contentFor(index: Int, scope: LazyItemScope): @Composable () -> Unit {
val interval = intervals.intervalForIndex(index)
val localIntervalIndex = index - interval.startIndex
return interval.content(scope, localIntervalIndex)
}
override fun item(content: @Composable LazyItemScope.() -> Unit) {
intervals.add(1) { @Composable { content() } }
}
override fun items(count: Int, itemContent: @Composable LazyItemScope.(index: Int) -> Unit) {
intervals.add(count) {
@Composable { itemContent(it) }
}
}
}