Jetpack Compose Material3 ActionMenu

ActionMenu.kt

import androidx.annotation.StringRes
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Call
import androidx.compose.material.icons.filled.Delete
import androidx.compose.material.icons.filled.Email
import androidx.compose.material.icons.filled.Menu
import androidx.compose.material.icons.filled.MoreVert
import androidx.compose.material3.ButtonDefaults
import androidx.compose.material3.DropdownMenu
import androidx.compose.material3.DropdownMenuItem
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.LocalContentColor
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Text
import androidx.compose.material3.TextButton
import androidx.compose.material3.TopAppBar
import androidx.compose.material3.TopAppBarDefaults
import androidx.compose.runtime.Composable
import androidx.compose.runtime.MutableState
import androidx.compose.runtime.key
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.res.stringResource
import androidx.compose.ui.graphics.vector.ImageVector
import androidx.compose.ui.tooling.preview.PreviewLightDark

// Essentially a wrapper around a lambda function to give it a name and icon
// akin to Android menu XML entries.
// As an item on the action bar, the action will be displayed with an IconButton
// with the given icon, if not null. Otherwise, the string from the name resource is used.
// In overflow menu, item will always be displayed as text.
data class ActionItem(
    @StringRes
    val nameRes: Int,
    val icon: ImageVector? = null,
    val overflowMode: OverflowMode = OverflowMode.IF_NECESSARY,
    val doAction: () -> Unit,
) {
    // allow 'calling' the action like a function
    operator fun invoke() = doAction()
}

// Whether action items are allowed to overflow into a dropdown menu - or NOT SHOWN to hide
enum class OverflowMode {
    NEVER_OVERFLOW, IF_NECESSARY, ALWAYS_OVERFLOW, NOT_SHOWN
}

@OptIn(ExperimentalMaterial3Api::class)
@PreviewLightDark
@Composable
fun PreviewActionMenu() {
    val items = listOf(
        ActionItem(R.string.call, Icons.Default.Call, OverflowMode.NEVER_OVERFLOW) {},
        ActionItem(R.string.send, /* Icons.Default.Send */ null, OverflowMode.IF_NECESSARY) {},
        ActionItem(R.string.email, Icons.Default.Email, OverflowMode.IF_NECESSARY) {},
        ActionItem(R.string.delete, Icons.Default.Delete, OverflowMode.IF_NECESSARY) {},
    )
    TopAppBar(
        title = { Text("App bar") },
        navigationIcon = {
            IconButton(onClick = {}) {
                Icon(Icons.Default.Menu, "Menu")
            }
        },
        colors = TopAppBarDefaults.topAppBarColors(
            containerColor = MaterialTheme.colorScheme.surface,
            navigationIconContentColor = MaterialTheme.colorScheme.onSurface,
            titleContentColor = MaterialTheme.colorScheme.onSurface,
            actionIconContentColor = MaterialTheme.colorScheme.onSurface,
        ),
        actions = {
            ActionMenu(items, numIcons = 3)
        }
    )
}

// Note: should be used in a RowScope
@Composable
fun ActionMenu(
    items: List<ActionItem>,
    numIcons: Int = 3, // includes overflow menu icon; may be overridden by NEVER_OVERFLOW
    menuVisible: MutableState<Boolean> = remember { mutableStateOf(false) }
) {
    if (items.isEmpty()) {
        return
    }
    // decide how many action items to show as icons
    val (appbarActions, overflowActions) = remember(items, numIcons) {
        separateIntoIconAndOverflow(items, numIcons)
    }

    for (i in appbarActions.indices) {
        val item = appbarActions[i]
        key(item.hashCode()) {
            val name = stringResource(item.nameRes)
            if (item.icon != null) {
                IconButton(onClick = item.doAction) {
                    Icon(item.icon, name)
                }
            } else {
                TextButton(
                    onClick = item.doAction,
                    colors = ButtonDefaults.textButtonColors(contentColor = LocalContentColor.current)
                ) {
                    Text(text = name)
                }
            }
        }
    }

    if (overflowActions.isNotEmpty()) {
        IconButton(onClick = { menuVisible.value = true }) {
            Icon(Icons.Default.MoreVert, "More actions")
        }
        DropdownMenu(
            expanded = menuVisible.value,
            onDismissRequest = { menuVisible.value = false },
        ) {
            for (i in overflowActions.indices) {
                val item = overflowActions[i]
                key(item.hashCode()) {
                    DropdownMenuItem(
                        text = { Text(s(item.nameRes)) },
                        onClick = {
                            menuVisible.value = false
                            item.doAction()
                        },
                        leadingIcon = item.icon?.let {
                            { Icon(it, null) }
                        },
                    )
                }
            }
        }
    }
}

private fun separateIntoIconAndOverflow(
    items: List<ActionItem>,
    numIcons: Int
): Pair<List<ActionItem>, List<ActionItem>> {
    var (iconCount, overflowCount, preferIconCount) = Triple(0, 0, 0)
    for (i in items.indices) {
        val item = items[i]
        when (item.overflowMode) {
            OverflowMode.NEVER_OVERFLOW -> iconCount++
            OverflowMode.IF_NECESSARY -> preferIconCount++
            OverflowMode.ALWAYS_OVERFLOW -> overflowCount++
            OverflowMode.NOT_SHOWN -> {}
        }
    }

    val needsOverflow = iconCount + preferIconCount > numIcons || overflowCount > 0
    val actionIconSpace = numIcons - (if (needsOverflow) 1 else 0)

    val iconActions = ArrayList<ActionItem>()
    val overflowActions = ArrayList<ActionItem>()

    var iconsAvailableBeforeOverflow = actionIconSpace - iconCount
    for (i in items.indices) {
        val item = items[i]
        when (item.overflowMode) {
            OverflowMode.NEVER_OVERFLOW -> {
                iconActions.add(item)
            }
            OverflowMode.ALWAYS_OVERFLOW -> {
                overflowActions.add(item)
            }
            OverflowMode.IF_NECESSARY -> {
                if (iconsAvailableBeforeOverflow > 0) {
                    iconActions.add(item)
                    iconsAvailableBeforeOverflow--
                } else {
                    overflowActions.add(item)
                }
            }
            OverflowMode.NOT_SHOWN -> {
                // skip
            }
        }
    }
    return Pair(iconActions, overflowActions)
}

Hi @romsahel, thanks for the suggestions!

1. The Material3 updates are perfect, thanks. I've just updated my app to Compose Material3 and I'll publish my revisions.
2. I tested this out and couldn't notice a difference adding the Box vs not adding it. It looks fine on my app, where the overflow icon is positioned next to the right (end) edge of the screen. Maybe it's been fixed in the Material3 library since you posted this? I'm currently on version 1.2.0-beta02.