LazyListScope

Receiver scope which is used by LazyColumn and LazyRow.

Summary

Public functions
open Unit
item(key: Any?, contentType: Any?, content: @Composable LazyItemScope.() -> Unit)

Adds a single item.
Cmn
open Unit
items(
    count: Int,
    key: ((index: Int) -> Any)?,
    contentType: (index: Int) -> Any?,
    itemContent: @Composable LazyItemScope.(index: Int) -> Unit
)

Adds a count of items.
Cmn
Unit
stickyHeader(key: Any?, contentType: Any?, content: @Composable LazyItemScope.(Int) -> Unit)

Adds a sticky header item, which will remain pinned even when scrolling after it.
Cmn

Extension functions
inline Unit
<T : Any?> LazyListScope.items(
    items: Array<T>,
    noinline key: ((item) -> Any)?,
    noinline contentType: (item) -> Any?,
    crossinline itemContent: @Composable LazyItemScope.(item) -> Unit
)

Adds an array of items.
Cmn
inline Unit
<T : Any?> LazyListScope.items(
    items: List<T>,
    noinline key: ((item) -> Any)?,
    noinline contentType: (item) -> Any?,
    crossinline itemContent: @Composable LazyItemScope.(item) -> Unit
)

Adds a list of items.
Cmn
inline Unit
<T : Any?> LazyListScope.itemsIndexed(
    items: Array<T>,
    noinline key: ((index: Int, item) -> Any)?,
    crossinline contentType: (index: Int, item) -> Any?,
    crossinline itemContent: @Composable LazyItemScope.(index: Int, item) -> Unit
)

Adds an array of items where the content of an item is aware of its index.
Cmn
inline Unit
<T : Any?> LazyListScope.itemsIndexed(
    items: List<T>,
    noinline key: ((index: Int, item) -> Any)?,
    crossinline contentType: (index: Int, item) -> Any?,
    crossinline itemContent: @Composable LazyItemScope.(index: Int, item) -> Unit
)

Adds a list of items where the content of an item is aware of its index.
Cmn

Public functions

item

Cmn
Added in 1.2.0
open fun item(key: Any? = null, contentType: Any? = null, content: @Composable LazyItemScope.() -> Unit): Unit

Adds a single item.

Parameters
key: Any? = null

a stable and unique key representing the item. Using the same key for multiple items in the list is not allowed. Type of the key should be saveable via Bundle on Android. If null is passed the position in the list will represent the key. When you specify the key the scroll position will be maintained based on the key, which means if you add/remove items before the current visible item the item with the given key will be kept as the first visible one. This can be overridden by calling 'requestScrollToItem' on the 'LazyListState'.
contentType: Any? = null

the type of the content of this item. The item compositions of the same type could be reused more efficiently. Note that null is a valid type and items of such type will be considered compatible.
content: @Composable LazyItemScope.() -> Unit

the content of the item

items

Cmn
Added in 1.2.0
open fun items(
    count: Int,
    key: ((index: Int) -> Any)? = null,
    contentType: (index: Int) -> Any? = { null },
    itemContent: @Composable LazyItemScope.(index: Int) -> Unit
): Unit

Adds a count of items.

Parameters
count: Int

the items count
key: ((index: Int) -> Any)? = null

a factory of stable and unique keys representing the item. Using the same key for multiple items in the list is not allowed. Type of the key should be saveable via Bundle on Android. If null is passed the position in the list will represent the key. When you specify the key the scroll position will be maintained based on the key, which means if you add/remove items before the current visible item the item with the given key will be kept as the first visible one. This can be overridden by calling 'requestScrollToItem' on the 'LazyListState'.
contentType: (index: Int) -> Any? = { null }

a factory of the content types for the item. The item compositions of the same type could be reused more efficiently. Note that null is a valid type and items of such type will be considered compatible.
itemContent: @Composable LazyItemScope.(index: Int) -> Unit

the content displayed by a single item

stickyHeader

Cmn
Added in 1.8.0-alpha06
fun stickyHeader(
    key: Any? = null,
    contentType: Any? = null,
    content: @Composable LazyItemScope.(Int) -> Unit
): Unit

Adds a sticky header item, which will remain pinned even when scrolling after it. The header will remain pinned until the next header will take its place.

import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.PaddingValues
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.material.Text
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.dp

val sections = listOf("A", "B", "C", "D", "E", "F", "G")

LazyColumn(reverseLayout = true, contentPadding = PaddingValues(6.dp)) {
    sections.forEach { section ->
        stickyHeader {
            Text(
                "Section $section",
                Modifier.fillMaxWidth().background(Color.LightGray).padding(8.dp)
            )
        }
        items(10) { Text("Item $it from the section $section") }
    }
}
 
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.PaddingValues
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.LazyListState
import androidx.compose.foundation.lazy.items
import androidx.compose.foundation.lazy.rememberLazyListState
import androidx.compose.material.Text
import androidx.compose.runtime.State
import androidx.compose.runtime.derivedStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.dp

/**
 * Checks if [index] is in the sticking position, that is, it's the first visible item and its
 * offset is equal to the content padding.
 */
fun LazyListState.isSticking(index: Int): State<Boolean> {
    return derivedStateOf {
        val firstVisible = layoutInfo.visibleItemsInfo.firstOrNull()
        firstVisible?.index == index && firstVisible.offset == -layoutInfo.beforeContentPadding
    }
}

val sections = listOf("A", "B", "C", "D", "E", "F", "G")
val state = rememberLazyListState()

LazyColumn(state = state, reverseLayout = true, contentPadding = PaddingValues(6.dp)) {
    sections.forEach { section ->
        stickyHeader { headerIndex ->
            // change color when header is sticking
            val isSticking by remember(state) { state.isSticking(headerIndex) }
            Text(
                "Section $section",
                Modifier.fillMaxWidth()
                    .background(if (isSticking) Color.Red else Color.LightGray)
                    .padding(8.dp)
            )
        }
        items(10) { Text("Item $it from the section $section") }
    }
}
Parameters
key: Any? = null

a stable and unique key representing the item. Using the same key for multiple items in the list is not allowed. Type of the key should be saveable via Bundle on Android. If null is passed the position in the list will represent the key. When you specify the key the scroll position will be maintained based on the key, which means if you add/remove items before the current visible item the item with the given key will be kept as the first visible one. This can be overridden by calling 'requestScrollToItem' on the 'LazyListState'.
contentType: Any? = null

the type of the content of this item. The item compositions of the same type could be reused more efficiently. Note that null is a valid type and items of such type will be considered compatible.
content: @Composable LazyItemScope.(Int) -> Unit

the content of the header, the header index is provided, this is the item position within the total set of items in this lazy list (the global index).

Extension functions

items

Cmn 
inline fun <T : Any?> LazyListScope.items(
    items: Array<T>,
    noinline key: ((item) -> Any)? = null,
    noinline contentType: (item) -> Any? = { null },
    crossinline itemContent: @Composable LazyItemScope.(item) -> Unit
): Unit

Adds an array of items.

Parameters
items: Array<T>

the data array
noinline key: ((item) -> Any)? = null

a factory of stable and unique keys representing the item. Using the same key for multiple items in the list is not allowed. Type of the key should be saveable via Bundle on Android. If null is passed the position in the list will represent the key. When you specify the key the scroll position will be maintained based on the key, which means if you add/remove items before the current visible item the item with the given key will be kept as the first visible one. This can be overridden by calling 'requestScrollToItem' on the 'LazyListState'.
noinline contentType: (item) -> Any? = { null }

a factory of the content types for the item. The item compositions of the same type could be reused more efficiently. Note that null is a valid type and items of such type will be considered compatible.
crossinline itemContent: @Composable LazyItemScope.(item) -> Unit

the content displayed by a single item

items

Cmn 
inline fun <T : Any?> LazyListScope.items(
    items: List<T>,
    noinline key: ((item) -> Any)? = null,
    noinline contentType: (item) -> Any? = { null },
    crossinline itemContent: @Composable LazyItemScope.(item) -> Unit
): Unit

Adds a list of items.

Parameters
items: List<T>

the data list
noinline key: ((item) -> Any)? = null

a factory of stable and unique keys representing the item. Using the same key for multiple items in the list is not allowed. Type of the key should be saveable via Bundle on Android. If null is passed the position in the list will represent the key. When you specify the key the scroll position will be maintained based on the key, which means if you add/remove items before the current visible item the item with the given key will be kept as the first visible one. This can be overridden by calling 'requestScrollToItem' on the 'LazyListState'.
noinline contentType: (item) -> Any? = { null }

a factory of the content types for the item. The item compositions of the same type could be reused more efficiently. Note that null is a valid type and items of such type will be considered compatible.
crossinline itemContent: @Composable LazyItemScope.(item) -> Unit

the content displayed by a single item

itemsIndexed

Cmn 
inline fun <T : Any?> LazyListScope.itemsIndexed(
    items: Array<T>,
    noinline key: ((index: Int, item) -> Any)? = null,
    crossinline contentType: (index: Int, item) -> Any? = { _, _ -> null },
    crossinline itemContent: @Composable LazyItemScope.(index: Int, item) -> Unit
): Unit

Adds an array of items where the content of an item is aware of its index.

Parameters
items: Array<T>

the data array
noinline key: ((index: Int, item) -> Any)? = null

a factory of stable and unique keys representing the item. Using the same key for multiple items in the list is not allowed. Type of the key should be saveable via Bundle on Android. If null is passed the position in the list will represent the key. When you specify the key the scroll position will be maintained based on the key, which means if you add/remove items before the current visible item the item with the given key will be kept as the first visible one. This can be overridden by calling 'requestScrollToItem' on the 'LazyListState'.
crossinline contentType: (index: Int, item) -> Any? = { _, _ -> null }

a factory of the content types for the item. The item compositions of the same type could be reused more efficiently. Note that null is a valid type and items of such type will be considered compatible.
crossinline itemContent: @Composable LazyItemScope.(index: Int, item) -> Unit

the content displayed by a single item

itemsIndexed

Cmn 
inline fun <T : Any?> LazyListScope.itemsIndexed(
    items: List<T>,
    noinline key: ((index: Int, item) -> Any)? = null,
    crossinline contentType: (index: Int, item) -> Any? = { _, _ -> null },
    crossinline itemContent: @Composable LazyItemScope.(index: Int, item) -> Unit
): Unit

Adds a list of items where the content of an item is aware of its index.

Parameters
items: List<T>

the data list
noinline key: ((index: Int, item) -> Any)? = null

a factory of stable and unique keys representing the item. Using the same key for multiple items in the list is not allowed. Type of the key should be saveable via Bundle on Android. If null is passed the position in the list will represent the key. When you specify the key the scroll position will be maintained based on the key, which means if you add/remove items before the current visible item the item with the given key will be kept as the first visible one. This can be overridden by calling 'requestScrollToItem' on the 'LazyListState'.
crossinline contentType: (index: Int, item) -> Any? = { _, _ -> null }

a factory of the content types for the item. The item compositions of the same type could be reused more efficiently. Note that null is a valid type and items of such type will be considered compatible.
crossinline itemContent: @Composable LazyItemScope.(index: Int, item) -> Unit

the content displayed by a single item