我希望在FlowRow中显示一个列表元素，并且我希望FlowRow方向为RTL
我尝试使用CompositionLocalProvider，但它没有改变任何东西：
CompositionLocalProvider(LocalLayoutDirection provides LayoutDirection.Rtl) {
FlowRow(
mainAxisSpacing = 10.dp,
crossAxisSpacing = 10.dp,
modifier = Modifier
.fillMaxWidth()
.padding(4.dp),
mainAxisAlignment = MainAxisAlignment.Center
) {
state.myList.forEach {
MyItem(item = it)
}
}
}
这是一个已知的问题。在Google修复该问题之前，您可以使用以下两个文件(最初由Sven提供(，而不是使用accompanist-flowlayout库。API完全相同。
布局.kt
import androidx.compose.ui.unit.Constraints
internal enum class LayoutOrientation {
Horizontal,
Vertical
}
internal data class OrientationIndependentConstraints(
val mainAxisMin: Int,
val mainAxisMax: Int,
val crossAxisMin: Int,
val crossAxisMax: Int
) {
constructor(c: Constraints, orientation: LayoutOrientation) : this(
if (orientation === LayoutOrientation.Horizontal) c.minWidth else c.minHeight,
if (orientation === LayoutOrientation.Horizontal) c.maxWidth else c.maxHeight,
if (orientation === LayoutOrientation.Horizontal) c.minHeight else c.minWidth,
if (orientation === LayoutOrientation.Horizontal) c.maxHeight else c.maxWidth
)
}
流量.kt
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.runtime.Composable
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.Layout
import androidx.compose.ui.layout.Placeable
import androidx.compose.ui.unit.Constraints
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.IntSize
import androidx.compose.ui.unit.LayoutDirection
import androidx.compose.ui.unit.dp
import kotlin.math.max
/**
* A composable that places its children in a horizontal flow. Unlike [Row], if the
* horizontal space is too small to put all the children in one row, multiple rows may be used.
*
* Note that just like [Row], flex values cannot be used with [FlowRow].
*
* @param modifier The modifier to be applied to the FlowRow.
* @param mainAxisSize The size of the layout in the main axis direction.
* @param mainAxisAlignment The alignment of each row's children in the main axis direction.
* @param mainAxisSpacing The main axis spacing between the children of each row.
* @param crossAxisAlignment The alignment of each row's children in the cross axis direction.
* @param crossAxisSpacing The cross axis spacing between the rows of the layout.
* @param lastLineMainAxisAlignment Overrides the main axis alignment of the last row.
*/
@Composable
public fun FlowRow(
modifier: Modifier = Modifier,
mainAxisSize: SizeMode = SizeMode.Wrap,
mainAxisAlignment: FlowMainAxisAlignment = FlowMainAxisAlignment.Start,
mainAxisSpacing: Dp = 0.dp,
crossAxisAlignment: FlowCrossAxisAlignment = FlowCrossAxisAlignment.Start,
crossAxisSpacing: Dp = 0.dp,
lastLineMainAxisAlignment: FlowMainAxisAlignment = mainAxisAlignment,
content: @Composable () -> Unit
) {
Flow(
modifier = modifier,
orientation = LayoutOrientation.Horizontal,
mainAxisSize = mainAxisSize,
mainAxisAlignment = mainAxisAlignment,
mainAxisSpacing = mainAxisSpacing,
crossAxisAlignment = crossAxisAlignment,
crossAxisSpacing = crossAxisSpacing,
lastLineMainAxisAlignment = lastLineMainAxisAlignment,
content = content
)
}
/**
* A composable that places its children in a vertical flow. Unlike [Column], if the
* vertical space is too small to put all the children in one column, multiple columns may be used.
*
* Note that just like [Column], flex values cannot be used with [FlowColumn].
*
* @param modifier The modifier to be applied to the FlowColumn.
* @param mainAxisSize The size of the layout in the main axis direction.
* @param mainAxisAlignment The alignment of each column's children in the main axis direction.
* @param mainAxisSpacing The main axis spacing between the children of each column.
* @param crossAxisAlignment The alignment of each column's children in the cross axis direction.
* @param crossAxisSpacing The cross axis spacing between the columns of the layout.
* @param lastLineMainAxisAlignment Overrides the main axis alignment of the last column.
*/
@Composable
public fun FlowColumn(
modifier: Modifier = Modifier,
mainAxisSize: SizeMode = SizeMode.Wrap,
mainAxisAlignment: FlowMainAxisAlignment = FlowMainAxisAlignment.Start,
mainAxisSpacing: Dp = 0.dp,
crossAxisAlignment: FlowCrossAxisAlignment = FlowCrossAxisAlignment.Start,
crossAxisSpacing: Dp = 0.dp,
lastLineMainAxisAlignment: FlowMainAxisAlignment = mainAxisAlignment,
content: @Composable () -> Unit
) {
Flow(
modifier = modifier,
orientation = LayoutOrientation.Vertical,
mainAxisSize = mainAxisSize,
mainAxisAlignment = mainAxisAlignment,
mainAxisSpacing = mainAxisSpacing,
crossAxisAlignment = crossAxisAlignment,
crossAxisSpacing = crossAxisSpacing,
lastLineMainAxisAlignment = lastLineMainAxisAlignment,
content = content
)
}
/**
* Used to specify the alignment of a layout's children, in cross axis direction.
*/
public enum class FlowCrossAxisAlignment {
/**
* Place children such that their center is in the middle of the cross axis.
*/
Center,
/**
* Place children such that their start edge is aligned to the start edge of the cross axis.
*/
Start,
/**
* Place children such that their end edge is aligned to the end edge of the cross axis.
*/
End,
}
public typealias FlowMainAxisAlignment = MainAxisAlignment
/**
* Layout model that arranges its children in a horizontal or vertical flow.
*/
@Composable
private fun Flow(
modifier: Modifier,
orientation: LayoutOrientation,
mainAxisSize: SizeMode,
mainAxisAlignment: FlowMainAxisAlignment,
mainAxisSpacing: Dp,
crossAxisAlignment: FlowCrossAxisAlignment,
crossAxisSpacing: Dp,
lastLineMainAxisAlignment: FlowMainAxisAlignment,
content: @Composable () -> Unit
) {
fun Placeable.mainAxisSize() =
if (orientation == LayoutOrientation.Horizontal) width else height
fun Placeable.crossAxisSize() =
if (orientation == LayoutOrientation.Horizontal) height else width
Layout(content, modifier) { measurables, outerConstraints ->
val sequences = mutableListOf<List<Placeable>>()
val crossAxisSizes = mutableListOf<Int>()
val crossAxisPositions = mutableListOf<Int>()
var mainAxisSpace = 0
var crossAxisSpace = 0
val currentSequence = mutableListOf<Placeable>()
var currentMainAxisSize = 0
var currentCrossAxisSize = 0
val constraints = OrientationIndependentConstraints(outerConstraints, orientation)
val childConstraints = if (orientation == LayoutOrientation.Horizontal) {
Constraints(maxWidth = constraints.mainAxisMax)
} else {
Constraints(maxHeight = constraints.mainAxisMax)
}
// Return whether the placeable can be added to the current sequence.
fun canAddToCurrentSequence(placeable: Placeable) =
currentSequence.isEmpty() || currentMainAxisSize + mainAxisSpacing.roundToPx() +
placeable.mainAxisSize() <= constraints.mainAxisMax
// Store current sequence information and start a new sequence.
fun startNewSequence() {
if (sequences.isNotEmpty()) {
crossAxisSpace += crossAxisSpacing.roundToPx()
}
sequences += currentSequence.toList()
crossAxisSizes += currentCrossAxisSize
crossAxisPositions += crossAxisSpace
crossAxisSpace += currentCrossAxisSize
mainAxisSpace = max(mainAxisSpace, currentMainAxisSize)
currentSequence.clear()
currentMainAxisSize = 0
currentCrossAxisSize = 0
}
for (measurable in measurables) {
// Ask the child for its preferred size.
val placeable = measurable.measure(childConstraints)
// Start a new sequence if there is not enough space.
if (!canAddToCurrentSequence(placeable)) startNewSequence()
// Add the child to the current sequence.
if (currentSequence.isNotEmpty()) {
currentMainAxisSize += mainAxisSpacing.roundToPx()
}
currentSequence.add(placeable)
currentMainAxisSize += placeable.mainAxisSize()
currentCrossAxisSize = max(currentCrossAxisSize, placeable.crossAxisSize())
}
if (currentSequence.isNotEmpty()) startNewSequence()
val mainAxisLayoutSize = if (constraints.mainAxisMax != Constraints.Infinity &&
mainAxisSize == SizeMode.Expand
) {
constraints.mainAxisMax
} else {
max(mainAxisSpace, constraints.mainAxisMin)
}
val crossAxisLayoutSize = max(crossAxisSpace, constraints.crossAxisMin)
val layoutWidth = if (orientation == LayoutOrientation.Horizontal) {
mainAxisLayoutSize
} else {
crossAxisLayoutSize
}
val layoutHeight = if (orientation == LayoutOrientation.Horizontal) {
crossAxisLayoutSize
} else {
mainAxisLayoutSize
}
layout(layoutWidth, layoutHeight) {
sequences.forEachIndexed { i, placeables ->
val childrenMainAxisSizes = IntArray(placeables.size) { j ->
placeables[j].mainAxisSize() +
if (j < placeables.lastIndex) mainAxisSpacing.roundToPx() else 0
}
val alignment = if (i < sequences.lastIndex) {
mainAxisAlignment
} else {
lastLineMainAxisAlignment
}
val mainAxisPositions = IntArray(childrenMainAxisSizes.size) { 0 }
when (orientation) {
LayoutOrientation.Horizontal -> with(alignment.toHorizontalArrangement()) {
arrange(
mainAxisLayoutSize,
childrenMainAxisSizes,
layoutDirection,
mainAxisPositions
)
}
LayoutOrientation.Vertical -> with(alignment.toVerticalArrangement()) {
arrange(mainAxisLayoutSize, childrenMainAxisSizes, mainAxisPositions)
}
}
placeables.forEachIndexed { j, placeable ->
val crossAxisSize = placeable.crossAxisSize()
val crossAxis = when (crossAxisAlignment) {
FlowCrossAxisAlignment.Start -> 0
FlowCrossAxisAlignment.End ->
crossAxisSizes[i] - crossAxisSize
FlowCrossAxisAlignment.Center ->
Alignment.Center.align(
IntSize.Zero,
IntSize(
width = 0,
height = crossAxisSizes[i] - crossAxisSize
),
LayoutDirection.Ltr
).y
}
val crossAxisPosition = crossAxisPositions[i] + crossAxis
if (orientation == LayoutOrientation.Horizontal) {
placeable.place(
x = mainAxisPositions[j],
y = crossAxisPosition
)
} else {
placeable.place(
x = when (layoutDirection) {
LayoutDirection.Ltr ->
crossAxisPosition
LayoutDirection.Rtl ->
crossAxisLayoutSize - crossAxisPosition - crossAxisSize
},
y = mainAxisPositions[j]
)
}
}
}
}
}
}
private fun FlowMainAxisAlignment.toHorizontalArrangement() =
when (this) {
FlowMainAxisAlignment.Center -> Arrangement.Center
FlowMainAxisAlignment.Start -> Arrangement.Start
FlowMainAxisAlignment.End -> Arrangement.End
FlowMainAxisAlignment.SpaceEvenly -> Arrangement.SpaceEvenly
FlowMainAxisAlignment.SpaceBetween -> Arrangement.SpaceBetween
FlowMainAxisAlignment.SpaceAround -> Arrangement.SpaceAround
}
private fun FlowMainAxisAlignment.toVerticalArrangement() =
when (this) {
FlowMainAxisAlignment.Center -> Arrangement.Center
FlowMainAxisAlignment.Start -> Arrangement.Top
FlowMainAxisAlignment.End -> Arrangement.Bottom
FlowMainAxisAlignment.SpaceEvenly -> Arrangement.SpaceEvenly
FlowMainAxisAlignment.SpaceBetween -> Arrangement.SpaceBetween
FlowMainAxisAlignment.SpaceAround -> Arrangement.SpaceAround
}
/**
* Used to specify how a layout chooses its own size when multiple behaviors are possible.
*/
// TODO(popam): remove this when Flow is reworked
public enum class SizeMode {
/**
* Minimize the amount of free space by wrapping the children,
* subject to the incoming layout constraints.
*/
Wrap,
/**
* Maximize the amount of free space by expanding to fill the available space,
* subject to the incoming layout constraints.
*/
Expand
}
/**
* Used to specify the alignment of a layout's children, in main axis direction.
*/
public enum class MainAxisAlignment {
/**
* Place children such that they are as close as possible to the middle of the main axis.
*/
Center,
/**
* Place children such that they are as close as possible to the start of the main axis.
*/
Start,
/**
* Place children such that they are as close as possible to the end of the main axis.
*/
End,
/**
* Place children such that they are spaced evenly across the main axis, including free
* space before the first child and after the last child.
*/
SpaceEvenly,
/**
* Place children such that they are spaced evenly across the main axis, without free
* space before the first child or after the last child.
*/
SpaceBetween,
/**
* Place children such that they are spaced evenly across the main axis, including free
* space before the first child and after the last child, but half the amount of space
* existing otherwise between two consecutive children.
*/
SpaceAround;
}