Migrate CoordinatorLayout to Compose

CoordinatorLayout is a ViewGroup that enables complex, overlapping, and nested layouts. It's used as a container to enable specific Material Design interactions, such as expanding/collapsing toolbars and bottom sheets, for Views contained within it.

In Compose, the closest equivalent of a CoordinatorLayout is a Scaffold. A Scaffold provides content slots for combining Material Components into common screen patterns and interactions. This page describes how you can migrate your CoordinatorLayout implementation to use Scaffold in Compose.

Migration steps

To migrate CoordinatorLayout to Scaffold, follow these steps:

  1. In the snippet below, the CoordinatorLayout contains an AppBarLayout for containing a ToolBar, a ViewPager, and a FloatingActionButton. Comment out the CoordinatorLayout and its children from your UI hierarchy and add a ComposeView to replace it.

    <!--  <androidx.coordinatorlayout.widget.CoordinatorLayout-->
<!--      android:id="@+id/coordinator_layout"-->
<!--      android:layout_width="match_parent"-->
<!--      android:layout_height="match_parent"-->
<!--      android:fitsSystemWindows="true">-->

<!--    <androidx.compose.ui.platform.ComposeView-->
<!--        android:id="@+id/compose_view"-->
<!--        android:layout_width="match_parent"-->
<!--        android:layout_height="match_parent"-->
<!--        app:layout_behavior="@string/appbar_scrolling_view_behavior" />-->

<!--    <com.google.android.material.appbar.AppBarLayout-->
<!--        android:id="@+id/app_bar_layout"-->
<!--        android:layout_width="match_parent"-->
<!--        android:layout_height="wrap_content"-->
<!--        android:fitsSystemWindows="true"-->
<!--        android:theme="@style/Theme.Sunflower.AppBarOverlay">-->

    <!-- AppBarLayout contents here -->

<!--    </com.google.android.material.appbar.AppBarLayout>-->

<!--  </androidx.coordinatorlayout.widget.CoordinatorLayout>-->

<androidx.compose.ui.platform.ComposeView
    android:id="@+id/compose_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

  2. In your Fragment or Activity, obtain a reference to the ComposeView you just added and call the setContent method on it. In the body of the method, set a Scaffold as its content:

    composeView.setContent {
    Scaffold(Modifier.fillMaxSize()) { contentPadding ->
        // Scaffold contents
        // ...
    }
}
    MigrationCommonScenariosSnippets.kt

  3. In the content of your Scaffold, add your screen's primary content within it. Because the primary content in the XML above is a ViewPager2, we'll use a HorizontalPager, which is the Compose equivalent of it. The content lambda of the Scaffold also receives an instance of PaddingValues that should be applied to the content root. You can use Modifier.padding to apply the same PaddingValues to the HorizontalPager.

    composeView.setContent {
    Scaffold(Modifier.fillMaxSize()) { contentPadding ->
        val pagerState = rememberPagerState {
            10
        }
        HorizontalPager(
            state = pagerState,
            modifier = Modifier.padding(contentPadding)
        ) { /* Page contents */ }
    }
}
    MigrationCommonScenariosSnippets.kt

  4. Use other content slots that Scaffold provides to add more screen elements and migrate remaining child Views. You can use the topBar slot to add a TopAppBar, and the floatingActionButton slot to provide a FloatingActionButton.

    composeView.setContent {
    Scaffold(
        Modifier.fillMaxSize(),
        topBar = {
            TopAppBar(
                title = {
                    Text("My App")
                }
            )
        },
        floatingActionButton = {
            FloatingActionButton(
                onClick = { /* Handle click */ }
            ) {
                Icon(
                    Icons.Filled.Add,
                    contentDescription = "Add Button"
                )
            }
        }
    ) { contentPadding ->
        val pagerState = rememberPagerState {
            10
        }
        HorizontalPager(
            state = pagerState,
            modifier = Modifier.padding(contentPadding)
        ) { /* Page contents */ }
    }
}
    MigrationCommonScenariosSnippets.kt

Common use cases

Collapse and expand toolbars

In the View system, to collapse and expand the toolbar with CoordinatorLayout, you use an AppBarLayout as a container for the toolbar. You can then specify a Behavior through layout_behavior in XML on the associated scrollable View (like RecyclerView or NestedScrollView) to declare how the toolbar collapses/expands as you scroll.

In Compose, you can achieve a similar effect through a TopAppBarScrollBehavior. For example, to implement a collapsing/expanding toolbar so that the toolbar appears when you scroll up, follow these steps:

  1. Call TopAppBarDefaults.enterAlwaysScrollBehavior() to create a TopAppBarScrollBehavior.
  2. Provide the created TopAppBarScrollBehavior to the TopAppBar.

  3. Connect the NestedScrollConnection via Modifier.nestedScroll on the Scaffold so that the Scaffold can receive nested scroll events as the scrollable content scrolls up/down. This way, the contained app bar can appropriately collapse/expand as the content scrolls.

    // 1. Create the TopAppBarScrollBehavior
val scrollBehavior = TopAppBarDefaults.enterAlwaysScrollBehavior()

Scaffold(
    topBar = {
        TopAppBar(
            title = {
                Text("My App")
            },
            // 2. Provide scrollBehavior to TopAppBar
            scrollBehavior = scrollBehavior
        )
    },
    // 3. Connect the scrollBehavior.nestedScrollConnection to the Scaffold
    modifier = Modifier
        .fillMaxSize()
        .nestedScroll(scrollBehavior.nestedScrollConnection)
) { contentPadding ->
    /* Contents */
    // ...
}
    MigrationCommonScenariosSnippets.kt

Customize the collapsing/expanding scroll effect

You can provide several parameters for enterAlwaysScrollBehavior to customize the collapsing/expanding animation effect. TopAppBarDefaults also provides other TopAppBarScrollBehavior such as exitUntilCollapsedScrollBehavior, which only expands the app bar when the content is scrolled all the way down.

To create a completely custom effect (for example, a parallax effect), you can also create your own NestedScrollConnection and offset the toolbar manually as the content scrolls. See the Nested scroll sample on AOSP for a code example.

Drawers

With Views, you implement a navigation drawer by using a DrawerLayout as the root view. In turn, your CoordinatorLayout is a child view of the DrawerLayout. The DrawerLayout also contains another child view, such as a NavigationView, to display the navigation options in the drawer.

In Compose, you can implement a navigation drawer using the ModalNavigationDrawer composable. ModalNavigationDrawer offers a drawerContent slot for the drawer and a content slot for the screen's content.

ModalNavigationDrawer(
    drawerContent = {
        ModalDrawerSheet {
            Text("Drawer title", modifier = Modifier.padding(16.dp))
            Divider()
            NavigationDrawerItem(
                label = { Text(text = "Drawer Item") },
                selected = false,
                onClick = { /*TODO*/ }
            )
            // ...other drawer items
        }
    }
) {
    Scaffold(Modifier.fillMaxSize()) { contentPadding ->
        // Scaffold content
        // ...
    }
}
MigrationCommonScenariosSnippets.kt

See Drawers to learn more.

Snackbars

Scaffold provides a snackbarHost slot, which can accept a SnackbarHost composable to display a Snackbar.

val scope = rememberCoroutineScope()
val snackbarHostState = remember { SnackbarHostState() }
Scaffold(
    snackbarHost = {
        SnackbarHost(hostState = snackbarHostState)
    },
    floatingActionButton = {
        ExtendedFloatingActionButton(
            text = { Text("Show snackbar") },
            icon = { Icon(Icons.Filled.Image, contentDescription = "") },
            onClick = {
                scope.launch {
                    snackbarHostState.showSnackbar("Snackbar")
                }
            }
        )
    }
) { contentPadding ->
    // Screen content
    // ...
}
MigrationCommonScenariosSnippets.kt

See Snackbars to learn more.

Learn more

For more information about migrating a CoordinatorLayout to Compose, see the following resources: