android - Detail placeholder in ListDetailPaneScaffold? - Stack Overflow

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Is it possible to display a placeholder on the detail pane of a ListDetailPaneScaffold when still no item from the list has been selected? I'm displaying a route in a map when an item is selected, and whould be preferable to display an empty map on the detail pane before any item has been selected. Displaying a white empty space seems not good. I can't find how to achieve this on docs.

ListDetailPaneScaffold(
    modifier = Modifier.fillMaxSize(),
    directive = navigator.scaffoldDirective,
    value = navigator.scaffoldValue,
    listPane = {
        AnimatedPane(modifier = Modifier.fillMaxWidth(0.1f)) {
            LinesList(
                lines = uiState.lines,
                selectedIndex = uiState.lines.indexOf(uiState.selectedLine),
                onItemClick = { index ->
                    // Navigate to the detail pane with the passed item
                    navigator.navigateTo(ListDetailPaneScaffoldRole.Detail, index)
                },
            )
        }
    },
    detailPane = {
        AnimatedPane {
            // Show the detail pane content if selected item is available
            navigator.currentDestination?.content?.let { index ->
                val selectedLine = uiState.lines[index]
                vm.selectLine(selectedLine)
                Map(selectedItem = uiState.selectedLine)
            }
        }
    },
)

Is it possible to display a placeholder on the detail pane of a ListDetailPaneScaffold when still no item from the list has been selected? I'm displaying a route in a map when an item is selected, and whould be preferable to display an empty map on the detail pane before any item has been selected. Displaying a white empty space seems not good. I can't find how to achieve this on docs.

ListDetailPaneScaffold(
    modifier = Modifier.fillMaxSize(),
    directive = navigator.scaffoldDirective,
    value = navigator.scaffoldValue,
    listPane = {
        AnimatedPane(modifier = Modifier.fillMaxWidth(0.1f)) {
            LinesList(
                lines = uiState.lines,
                selectedIndex = uiState.lines.indexOf(uiState.selectedLine),
                onItemClick = { index ->
                    // Navigate to the detail pane with the passed item
                    navigator.navigateTo(ListDetailPaneScaffoldRole.Detail, index)
                },
            )
        }
    },
    detailPane = {
        AnimatedPane {
            // Show the detail pane content if selected item is available
            navigator.currentDestination?.content?.let { index ->
                val selectedLine = uiState.lines[index]
                vm.selectLine(selectedLine)
                Map(selectedItem = uiState.selectedLine)
            }
        }
    },
)

• android
• kotlin
• android-jetpack-compose
• android-jetpack-compose-scaffold

Share Improve this question Follow asked Feb 13 at 12:51 NullPointerExceptionNullPointerException 37.7k8080 gold badges230230 silver badges403403 bronze badges

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1 Answer 1

Sorted by: Reset to default 0

You already properly distinguish between a loaded entry and the unselected state by only applying the details content when navigator.currentDestination?.content is not null.

You just need to add your placeholder in the case it is null:

navigator.currentDestination?.content?.let { index ->
    // details of selected item
} ?: DetailsPlaceHolder()

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