当使用 LazyColumn/Row 时，其中的 item 需要指定唯一不重复的 key。无论是 Preview 中提供的数据还是运行时的数据，如果提供给 LazyColumn/Row 的 key 出现重复都会抛出相同的异常：
IllegalArgumentException: Key "1" was already used. If you are using LazyColumn/Row please make sure you provide a unique key for each item
- 如下面的例子中
Preview 提供给 items 的 key 出现重复，就会出现上图中的 Render problem 异常：
data class Item(
val id: Int,
val name: String,
)
@Composable
fun ItemGrid(items: List<Item>) {
val state = rememberLazyGridState()
LazyVerticalGrid(
modifier = Modifier.fillMaxSize(),
state = state,
columns = GridCells.Fixed(3),
contentPadding = PaddingValues(16.dp),
horizontalArrangement = Arrangement.spacedBy(8.dp),
) {
items(items, { it.id }) { item ->
Text(text = item.name)
}
}
}
@Composable
@Preview
fun PreviewItemGrid() {
ItemGrid(
items = listOf(
Item(id = 1, name = "ItemName1"),
Item(id = 2, name = "ItemName2"),
Item(id = 3, name = "ItemName2"),
),
)
}
- 下面的错误信息是如果运行时遇到重复 key 抛出的异常：
FATAL EXCEPTION: main
Process: cn.itmob.demo, PID: 6736
java.lang.IllegalArgumentException: Key "1" was already used. If you are using LazyColumn/Row please make sure you provide a unique key for each item.
at androidx.compose.ui.layout.LayoutNodeSubcompositionsState.subcompose(SubcomposeLayout.kt:410)
at androidx.compose.ui.layout.LayoutNodeSubcompositionsState$Scope.subcompose(SubcomposeLayout.kt:740)
at androidx.compose.foundation.lazy.layout.LazyLayoutMeasureScopeImpl.measure-0kLqBqw(LazyLayoutMeasureScope.kt:118)
at androidx.compose.foundation.lazy.grid.LazyMeasuredItemProvider.getAndMeasure-ednRnyU(LazyMeasuredItemProvider.kt:44)
at androidx.compose.foundation.lazy.grid.LazyMeasuredLineProvider.getAndMeasure-bKFJvoY(LazyMeasuredLineProvider.kt:78)
at androidx.compose.foundation.lazy.grid.LazyGridMeasureKt.measureLazyGrid-t5wl_D8(LazyGridMeasure.kt:154)
at androidx.compose.foundation.lazy.grid.LazyGridKt$rememberLazyGridMeasurePolicy$1$1.invoke-0kLqBqw(LazyGrid.kt:330)
at androidx.compose.foundation.lazy.grid.LazyGridKt$rememberLazyGridMeasurePolicy$1$1.invoke(LazyGrid.kt:180)
at androidx.compose.foundation.lazy.layout.LazyLayoutKt$LazyLayout$1$2$1.invoke-0kLqBqw(LazyLayout.kt:71)
at androidx.compose.foundation.lazy.layout.LazyLayoutKt$LazyLayout$1$2$1.invoke(LazyLayout.kt:69)
at androidx.compose.ui.layout.LayoutNodeSubcompositionsState$createMeasurePolicy$1.measure-3p2s80s(SubcomposeLayout.kt:598)
...