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| import androidx.compose.foundation.ExperimentalFoundationApi | |
| import androidx.compose.foundation.gestures.FlingBehavior | |
| import androidx.compose.foundation.gestures.ScrollableDefaults | |
| import androidx.compose.foundation.layout.Arrangement | |
| import androidx.compose.foundation.layout.PaddingValues | |
| import androidx.compose.foundation.lazy.LazyColumn | |
| import androidx.compose.foundation.lazy.LazyItemScope | |
| import androidx.compose.foundation.lazy.LazyListScope | |
| import androidx.compose.foundation.lazy.LazyListState | |
| import androidx.compose.foundation.lazy.rememberLazyListState | |
| import androidx.compose.runtime.Composable | |
| import androidx.compose.runtime.Stable | |
| import androidx.compose.runtime.mutableStateMapOf | |
| import androidx.compose.runtime.remember | |
| import androidx.compose.ui.Alignment | |
| import androidx.compose.ui.Modifier | |
| import androidx.compose.ui.unit.dp | |
| @Composable | |
| fun IndexedLazyColumn( | |
| modifier: Modifier = Modifier, | |
| state: IndexedLazyListState = rememberIndexedLazyListState(), | |
| contentPadding: PaddingValues = PaddingValues(0.dp), | |
| reverseLayout: Boolean = false, | |
| verticalArrangement: Arrangement.Vertical = if (!reverseLayout) Arrangement.Top else Arrangement.Bottom, | |
| horizontalAlignment: Alignment.Horizontal = Alignment.Start, | |
| flingBehavior: FlingBehavior = ScrollableDefaults.flingBehavior(), | |
| userScrollEnabled: Boolean = true, | |
| content: IndexedLazyListScope.() -> Unit | |
| ) { | |
| LazyColumn( | |
| modifier = modifier, | |
| state = state.listState, | |
| contentPadding = contentPadding, | |
| reverseLayout = reverseLayout, | |
| verticalArrangement = verticalArrangement, | |
| horizontalAlignment = horizontalAlignment, | |
| flingBehavior = flingBehavior, | |
| userScrollEnabled = userScrollEnabled, | |
| ) { | |
| IndexedLazyListScope(this, state).content() | |
| } | |
| } | |
| @Composable | |
| fun rememberIndexedLazyListState( | |
| listState: LazyListState = rememberLazyListState(), | |
| ): IndexedLazyListState { | |
| return remember { IndexedLazyListState(listState) } | |
| } | |
| @Stable | |
| class IndexedLazyListState internal constructor( | |
| val listState: LazyListState, | |
| ) { | |
| private val itemIndexMapping = mutableStateMapOf<Any, Int>() | |
| suspend fun animateScrollToItemByKey(key: Any) { | |
| val index = itemIndexMapping[key] | |
| if (index != null) { | |
| listState.animateScrollToItem(index) | |
| } | |
| } | |
| internal fun linkKeyToIndex(key: Any, index: Int) { | |
| itemIndexMapping[key] = index | |
| } | |
| } | |
| @Stable | |
| class IndexedLazyListScope( | |
| private val lazyListScope: LazyListScope, | |
| private val state: IndexedLazyListState, | |
| ) : LazyListScope { | |
| private var currentItemLayoutIndex = 0 | |
| override fun item(key: Any?, contentType: Any?, content: @Composable LazyItemScope.() -> Unit) { | |
| lazyListScope.item(key, contentType, content) | |
| if (key != null) | |
| state.linkKeyToIndex(key, currentItemLayoutIndex) | |
| currentItemLayoutIndex++ | |
| } | |
| @Deprecated("Use the non deprecated overload", level = DeprecationLevel.HIDDEN) | |
| override fun item(key: Any?, content: @Composable LazyItemScope.() -> Unit) { | |
| item(key, null, content) | |
| } | |
| override fun items( | |
| count: Int, | |
| key: ((index: Int) -> Any)?, | |
| contentType: (index: Int) -> Any?, | |
| itemContent: @Composable LazyItemScope.(index: Int) -> Unit | |
| ) { | |
| lazyListScope.items(count, key, contentType, itemContent) | |
| repeat(count) { i -> | |
| val resolvedKey = key?.invoke(i) | |
| if (resolvedKey != null) | |
| state.linkKeyToIndex(resolvedKey, currentItemLayoutIndex) | |
| currentItemLayoutIndex++ | |
| } | |
| } | |
| @Deprecated("Use the non deprecated overload", level = DeprecationLevel.HIDDEN) | |
| override fun items( | |
| count: Int, | |
| key: ((index: Int) -> Any)?, | |
| itemContent: @Composable LazyItemScope.(index: Int) -> Unit | |
| ) { | |
| items(count, key, { null }, itemContent) | |
| } | |
| @ExperimentalFoundationApi | |
| override fun stickyHeader(key: Any?, contentType: Any?, content: @Composable LazyItemScope.(Int) -> Unit) { | |
| lazyListScope.stickyHeader(key, contentType, content) | |
| if (key != null) | |
| state.linkKeyToIndex(key, currentItemLayoutIndex) | |
| currentItemLayoutIndex++ | |
| } | |
| } |
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