Grouping

groupBy maps each row to a group name. Rows are then rendered grouped, with optional header and summary rows around each group.

DataTable(
    // ...
    groupBy = { it.department },
    groupHeaderContent = { groupName, rows ->
        Text("$groupName (${rows.size})", fontWeight = FontWeight.Bold)
    },
    groupSummaryContent = { groupName, rows ->
        Text("Average age: ${rows.map { it.age }.average().toInt()}")
    },
)

Both content slots are optional. Supplying neither groups the rows without any visual separator, which is rarely what you want — groupHeaderContent is what makes grouping legible.

Group headers

The header receives the group name and that group's rows, and spans the full table width:

groupHeaderContent = { department, rows ->
    Surface(color = MaterialTheme.colorScheme.secondaryContainer) {
        Row(
            Modifier.fillMaxWidth().padding(horizontal = 16.dp, vertical = 8.dp),
            horizontalArrangement = Arrangement.spacedBy(8.dp),
        ) {
            Icon(Icons.Default.Folder, contentDescription = null)
            Text("$department (${rows.size})", fontWeight = FontWeight.Bold)
        }
    }
}

Summary rows

groupSummaryContent renders after the last row of each group — the natural place for subtotals:

groupSummaryContent = { _, rows ->
    Text("Total salary: $${"%,.0f".format(rows.sumOf { it.salary })}")
}

Ordering

Groups appear in the order their first row appears in the sorted, paginated data. Sorting the table therefore also reorders the groups.

Because grouping happens after sorting and pagination, a group can be split across pages — the rows on page 2 form their own groups, headers and all. If you want whole groups per page, page by group yourself with manualPagination.

Interaction with the rest of the table

Keyboard navigation follows display order, so arrow keys walk through the grouped sequence and skip over group headers and summaries rather than landing on them.

Alternating row colours and the focus indicator likewise use the display position.

Limitations

Groups are flat and always expanded

There is currently no collapse/expand for a group, no nesting of one group inside another, and no group-level selection. groupBy returns a single String, so grouping is one level deep.

For hierarchical data — a chart of accounts, a bill of materials — you want a tree table, which the library does not have yet.