Layout canonici

Canonical layouts are proven, versatile layouts that provide an optimal user experience on a variety of form factors.

Depiction of large screen devices showing the canonical layouts.

The canonical layouts support small screen phones as well as tablets, foldables, and ChromeOS devices. Derived from Material Design guidance, the layouts are aesthetic as well as functional.

The Android framework includes specialized components that make implementation of the layouts straightforward and reliable.

The canonical layouts create engaging, productivity‑enhancing UIs that form the foundation of great apps.

List-detail

Wireframe of list-detail layout.

The list-detail layout enables users to explore lists of items that have descriptive, explanatory, or other supplementary information—the item detail.

The layout divides the app window into two side-by-side panes: one for the list, one for the detail. Users select items from the list to display the item detail. Deep links in the detail reveal additional content in the detail pane.

Expanded-width displays (see Use window size classes) accommodate both the list and detail at the same time. Selection of a list item updates the detail pane to show the related content for the selected item.

Medium- and compact-width displays show either the list or the detail, depending on user interaction with the app. When just the list is visible, selection of a list item displays the detail in place of the list. When just the detail is visible, pressing the back button redisplays the list.

Configuration changes such as device orientation changes or app window size changes can change the display's window size class. A list‑detail layout responds accordingly, preserving app state:

If an expanded-width display showing both the list and detail panes narrows to medium or compact, the detail pane remains visible and the list pane is hidden
If a medium- or compact-width display has just the detail pane visible and the window size class widens to expanded, the list and detail are shown together, and the list indicates that the item corresponding to the content in the detail pane is selected
If a medium- or compact-width display has just the list pane visible and widens to expanded, the list and a placeholder detail pane are shown together

List-detail is ideal for messaging apps, contact managers, interactive media browsers or any app where the content can be organized as a list of items that reveal additional information.

Figure 1. Messaging app showing a list of conversations and the details of a selected conversation.

Implementation

Il paradigma dichiarativo di Compose supporta la logica della classe di dimensioni della finestra che determina se mostrare contemporaneamente i riquadri elenco e dettagli (quando la classe di dimensioni della finestra in larghezza è espansa) o solo il riquadro elenco o dettagli (quando la classe di dimensioni della finestra in larghezza è media o compatta).

Per garantire il flusso di dati unidirezionale, solleva tutto lo stato, inclusi la classe di dimensioni della finestra corrente e i dettagli dell'elemento di elenco selezionato (se presente), in modo che tutti i composable abbiano accesso ai dati e possano essere visualizzati correttamente.

Quando viene visualizzato solo il riquadro dei dettagli in finestre di piccole dimensioni, aggiungi BackHandler per rimuovere il riquadro dei dettagli e visualizzare solo il riquadro dell'elenco. BackHandler non fa parte della navigazione complessiva dell'app, poiché l'handler dipende dalla classe di dimensioni della finestra e dallo stato dei dettagli selezionato.

ListDetailPaneScaffold è un composable di alto livello che semplifica l'implementazione di layout elenco-dettagli. Gestisce automaticamente la logica dei riquadri in base alle classi di dimensioni della finestra e supporta la navigazione tra i riquadri.

Ecco un'implementazione minima che utilizza ListDetailPaneScaffold:

@OptIn(ExperimentalMaterial3AdaptiveApi::class)
@Composable
fun MyListDetailPaneScaffold() {
    val navigator = rememberListDetailPaneScaffoldNavigator()
    ListDetailPaneScaffold(
        directive = navigator.scaffoldDirective,
        value = navigator.scaffoldValue,
        listPane = {
            // Listing Pane
        },
        detailPane = {
            // Details Pane
        }
    )
}CanonicalLayoutSamples.kt

Di seguito sono riportati i componenti chiave di questo esempio:

rememberListDetailPaneScaffoldNavigator: crea un navigatore per gestire la navigazione tra i riquadri elenco e dettagli.
listPane: mostra l'elenco degli elementi.
detailPane: mostra i contenuti di un elemento selezionato.

Per esempi di implementazione dettagliati, vedi:

Guida per gli sviluppatori Creare un layout elenco-dettagli
list-detail-compose campione

Feed

Wireframe of feed layout.

A feed layout arranges equivalent content elements in a configurable grid for quick, convenient viewing of a large amount of content.

Size and position establish relationships among the content elements.

Content groups are created by making elements the same size and positioning them together. Attention is drawn to elements by making them larger than nearby elements.

Cards and lists are common components of feed layouts.

A feed layout supports displays of almost any size because the grid can adapt from a single, scrolling column to a multi‑column scrolling feed of content.

Feeds are especially well suited for news and social media apps.

Figure 2. Social media app showing posts in cards of varying sizes.

Implementation

A feed consists of a large number of content elements in a vertical scrolling container laid out in a grid. Lazy lists efficiently render a large number of items in columns or rows. Lazy grids render items in grids, supporting configuration of the item sizes and spans.

Configure the columns of the grid layout based on the available display area to set the minimum allowable width for grid items. When defining grid items, adjust column spans to emphasize some items over others.

For section headers, dividers, or other items designed to occupy the full width of the feed, use maxLineSpan to take up the full width of the layout.

On compact-width displays that don't have enough space to show more than one column, LazyVerticalGrid behaves just like a LazyColumn.

Here is a minimal implementation using LazyVerticalGrid:

@Composable
fun MyFeed(names: List<String>) {
    LazyVerticalGrid(
        // GridCells.Adaptive automatically adapts column count based on available width
        columns = GridCells.Adaptive(minSize = 180.dp),
    ) {
        items(names) { name ->
            Text(name)
        }
    }
}CanonicalLayoutSamples.kt

The key to an adaptive feed is the columns configuration. GridCells.Adaptive(minSize = 180.dp) creates a grid where each column is at least 180.dp wide. The grid then displays as many columns as can fit in the available space.

For an example implementation, see the Feed with Compose sample.

Supporting pane

Wireframe of supporting pane layout.

Supporting pane layout organizes app content into primary and secondary display areas.

The primary display area occupies the majority of the app window (typically about two thirds) and contains the main content. The secondary display area is a pane that takes up the remainder of the app window and presents content that supports the main content.

Supporting pane layouts work well on expanded-width displays (see Use window size classes) in landscape orientation. Medium- or compact‑width displays support showing both the primary and secondary display areas if the content is adaptable to narrower display spaces, or if the additional content can be initially hidden in a bottom or side sheet accessible by means of a control such as a menu or button.

A supporting pane layout differs from a list‑detail layout in the relationship of the primary and secondary content. Secondary pane content is meaningful only in relation to the primary content; for example, a supporting pane tool window is irrelevant by itself. The supplementary content in the detail pane of a list‑detail layout, however, is meaningful even without the primary content, for example, the description of a product from a product listing.

Use cases for supporting pane include:

Productivity apps: A document or spreadsheet accompanied by reviewer comments in a supporting pane
Media apps: A streaming video complemented by a list of related videos in a supporting pane, or the depiction of an album of music supplemented with a playlist
Tools and settings: A media editing tool with palettes, effects, and other settings in a support pane

Figure 3. Shopping app with product descriptions in a supporting pane.

Implementation

Compose supporta la logica delle classi di dimensioni delle finestre, che ti consente di determinare se mostrare contemporaneamente i contenuti principali e quelli di supporto o posizionare i contenuti di supporto in una posizione alternativa.

Solleva tutto lo stato, inclusa la classe di dimensione della finestra corrente e le informazioni relative ai dati nel contenuto principale e nel contenuto di supporto.

Per i display con larghezza compatta, posiziona i contenuti di supporto sotto i contenuti principali o all'interno di un foglio inferiore. Per le larghezze medie ed estese, posiziona i contenuti di supporto accanto ai contenuti principali, dimensionati in modo appropriato in base ai contenuti e allo spazio disponibile. Per la larghezza media, dividi lo spazio di visualizzazione equamente tra i contenuti principali e quelli di supporto. Per la larghezza espansa, assegna il 70% dello spazio ai contenuti principali e il 30% ai contenuti di supporto.

SupportingPaneScaffold è un componente componibile di alto livello che semplifica l'implementazione dei layout dei riquadri di supporto. Il composable gestisce automaticamente la logica dei riquadri in base alle classi di dimensioni della finestra, visualizzando i riquadri uno accanto all'altro sugli schermi di grandi dimensioni o nascondendo il riquadro di supporto sugli schermi piccoli. SupportingPaneScaffold supporta anche la navigazione tra i riquadri.

Di seguito è riportata un'implementazione minima:

@OptIn(ExperimentalMaterial3AdaptiveApi::class)
@Composable
fun MySupportingPaneScaffold() {
    // Creates and remembers a navigator to control pane visibility and navigation
    val navigator = rememberSupportingPaneScaffoldNavigator()
    SupportingPaneScaffold(
        // Directive and value help control pane visibility based on screen size and state
        directive = navigator.scaffoldDirective,
        value = navigator.scaffoldValue,
        mainPane = {
            // Main Pane for the primary content
        },
        supportingPane = {
            //Supporting Pane for supplementary content
        }
    )
}CanonicalLayoutSamples.kt

Componenti chiave nell'esempio:

rememberSupportingPaneScaffoldNavigator: composable che crea un navigatore per gestire la visibilità dei riquadri (ad esempio, nascondere o mostrare il riquadro di supporto sugli schermi compatti)
mainPane: composable che mostra i contenuti principali
supportingPane: composable che mostra i contenuti supplementari

Per esempi di implementazione dettagliati, vedi: