CoordinatorLayout

CoordinatorLayout configures relationships between children, such as an app bar and its scrolling sibling or a child that references another view as its anchor.

Use it when…

Use it when an AppBarLayout and scrolling content need the app-bar relationship provided by AppBarLayout.ScrollingViewBehavior. Both views belong directly inside the CoordinatorLayout, with the behavior attached to the scrolling sibling.

Use it when a child needs to reference another child's ID as an anchor and supply anchor gravity.

How it behaves

CoordinatorLayout is a ViewGroup. Configure child relationships through View layout-param methods called on its direct children. For example, .behavior(...) assigns a behavior to that child, while .anchorId(...) supplies the ID of its anchor.

The container's body builder can contain multiple children. Each child's layout params describe that child's relationship within the container.

Examples

Place these expressions in a main-actor UI body.

App bar and scrolling content

This configures the app-bar/scrolling-sibling relationship, with enough content to exercise scrolling inside the bounded container. The scroll flags belong to the TextView inside AppBarLayout; the scrolling sibling receives ScrollingViewBehavior.

CoordinatorLayout {
    AppBarLayout {
        TextView("Inbox")
            .width(.matchParent)
            .height(56)
            .scrollFlags(.scroll, .enterAlways)
    }
    .width(.matchParent)
    .height(.wrapContent)

    NestedScrollView {
        TextView(String(repeating: "Message\n", count: 100))
            .width(.matchParent)
            .height(.wrapContent)
    }
    .width(.matchParent)
    .height(.matchParent)
    .behavior(AppBarLayout.ScrollingViewBehavior())
}
.width(.matchParent)
.height(320)

Reference an anchor

The second child references the first child's ID, 10, and supplies combined bottom/end anchor gravity.

CoordinatorLayout {
    TextView(id: 10, "Header")
        .width(160)
        .height(56)

    TextView("Related content")
        .width(.wrapContent)
        .height(.wrapContent)
        .anchorId(10)
        .anchorGravity([.bottom, .end])
}
.width(.matchParent)
.height(160)

Initializers

init(id: Int32? = nil) creates a container without builder content. The optional ID defaults to nil.

CoordinatorLayout()
CoordinatorLayout(id: 20)

init(id: Int32? = nil, @BodyBuilder content: BodyBuilder.SingleView) accepts a content builder and the same optional ID. Despite the SingleView name, the builder can contain multiple children, as in the examples above.

CoordinatorLayout(id: 20) {
    TextView("First")
    TextView("Second")
}

Layout params

These six public View methods configure layout params on direct children of a CoordinatorLayout. Each takes an explicit value and returns the same view for chaining; the return value can also be discarded. The small snippets below show parameter calls to use on children inside the container.

behavior(_:)

Assigns a Behavior to the child. For the app-bar relationship, attach the concrete AppBarLayout.ScrollingViewBehavior to the scrolling sibling shown above.

TextView("List").behavior(AppBarLayout.ScrollingViewBehavior())

anchorId(_:)

Sets the child's anchor reference using an Int32 view ID. Give the referenced view a matching ID, as in the anchor example.

TextView("Related").anchorId(10)

anchorGravity(_:)

Supplies the child's gravity relative to its anchor. Gravity is an OptionSet: [.bottom, .end] constructs one combined Gravity value passed to this method.

TextView("Related").anchorGravity([.bottom, .end])

dodgeInsetEdges(_:)

Sets the child's dodgeInsetEdges parameter, which selects edges for inset dodging. Its current argument type is Gravity.

TextView("Inset").dodgeInsetEdges(.bottom)

insetEdge(_:)

Sets the child's insetEdge parameter to the supplied edge value. Its current argument type is also Gravity.

TextView("Top inset").insetEdge(.top)

keyline(_:)

Sets the child's keyline parameter using a raw Int32 value. This call supplies the parameter; it does not define keylines on the container.

TextView("Marker").keyline(0)

Limitations

Behavior is a global, non-generic Swift class with a public no-argument initializer, Behavior(). It maps to the Java inner class CoordinatorLayout.Behavior. The Swift API does not expose user-implementable scroll, drag, or swipe callbacks. Use an exposed concrete behavior such as AppBarLayout.ScrollingViewBehavior for the relationship it supports.

dodgeInsetEdges and insetEdge currently accept Gravity; a dedicated edge-flags type remains a source TODO. keyline accepts raw Int32, with a position type also left as a TODO. These parameter calls alone do not specify keyline units or guarantee a particular layout result.