安卓开发使用compose 版本 组件 LazyColumn 要实现拖动排序功能 Modifier.draggable() 使用示例kotlin完整代码
时间: 2024-05-01 12:21:12 浏览: 12
非常感谢您的提问!以下是您需要的 Kotlin 代码示例:
```
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.itemsIndexed
import androidx.compose.runtime.mutableStateListOf
import androidx.compose.ui.Modifier
import androidx.compose.ui.gesture.scrollorientationlocking.Orientation
import androidx.compose.ui.input.pointer.pointerInput
import androidx.compose.ui.unit.DpOffset
enum class DragState {
IDLE, DRAGGING
}
@Composable
fun LazyColumnWithDragAndDrop() {
val items = mutableStateListOf("Item 1", "Item 2", "Item 3")
var dragState = DragState.IDLE
var dragIndex by remember { mutableStateOf(-1) }
var targetIndex by remember { mutableStateOf(-1) }
LazyColumn {
itemsIndexed(items) { index, item ->
val backgroundColor = if (dragIndex == index) {
Color.Gray
} else if (targetIndex == index && dragState == DragState.DRAGGING) {
Color.LightGray
} else {
Color.White
}
Box(
Modifier
.background(backgroundColor)
.fillMaxWidth()
.height(50.dp)
.pointerInput(Unit) {
detectDragGesture { state ->
val layoutCoordinates = localLayoutCoordinates
val position = layoutCoordinates.offset(state.position)
when (state.draggedOrUp) {
Dragged -> {
dragIndex = index
dragState = DragState.DRAGGING
}
Up -> {
if (dragState == DragState.DRAGGING) {
items.move(dragIndex, targetIndex)
}
dragIndex = -1
targetIndex = -1
dragState = DragState.IDLE
}
Dragging -> {
if (dragState == DragState.DRAGGING) {
val targetY = position.y
val targetIndexTemp = if (targetY < 0) {
0
} else {
val itemCount = items.size
val lastItemPosition = layoutCoordinates.positionOf(Int.MAX_VALUE)
val maxTargetY = lastItemPosition.y
val top = layoutCoordinates.positionOf(0).y
val bottom = maxTargetY + (50.dp.toPx() / 2)
val newTargetY = targetY.coerceIn(top, bottom)
val newTargetIndex = ((newTargetY - (50.dp.toPx() / 2)) / 50.dp.toPx()).toInt()
newTargetIndex.coerceIn(0, itemCount - 1)
}
if (targetIndex != targetIndexTemp) {
targetIndex = targetIndexTemp
}
}
}
else -> {
dragIndex = -1
targetIndex = -1
dragState = DragState.IDLE
}
}
}
}
.draggable(
orientation = Orientation.Vertical,
onDragStarted = {
dragIndex = index
dragState = DragState.DRAGGING
},
onDragStopped = {
if (dragState == DragState.DRAGGING) {
items.move(dragIndex, targetIndex)
}
dragIndex = -1
targetIndex = -1
dragState = DragState.IDLE
},
onDragEnd = {
dragIndex = -1
targetIndex = -1
dragState = DragState.IDLE
}
)
) {
Text(
text = item,
modifier = Modifier.align(Alignment.CenterStart)
)
}
}
}
}
private fun <T> MutableList<T>.move(from: Int, to: Int) {
val fromItem = this[from]
removeAt(from)
add(to, fromItem)
}
```
这里是一个使用 `Modifier.draggable()` 实现拖动排序的 Android Compose 组件示例。在此代码中,我们使用 `pointerInput()` 拦截滚动事件以捕获拖动手势。拖动时,我们根据每个 item 的位置计算出应该被交换的 item 的索引,然后使用 `MutableList.move()` 实现了交换操作。您可以将此代码与您的项目中使用 Compose 的其他部分集成,以实现拖动排序的功能。
希望这个示例对您有所帮助!如果您有任何疑问,请随时问我。