SplitController

public final class SplitController

The controller class that gets information about the currently active activity splits and provides interaction points to customize the splits and form new splits.

A split is a pair of containers that host activities in the same or different processes, combined under the same parent window of the hosting task.

A pair of activities can be put into a split by providing a static or runtime split rule and then launching the activities in the same task using Activity.startActivity().

Summary

Nested types

A class to determine if activity splits with Activity Embedding are currently available.

Public methods
final void

Clears the callback previously set by setSplitAttributesCalculator.
static final @NonNull SplitController

Obtains an instance of SplitController.
final @NonNull SplitController.SplitSupportStatus

Indicates whether split functionality is supported on the device.
final boolean
@RequiresWindowSdkExtension(version = 5)
pinTopActivityStack(int taskId, @NonNull SplitPinRule splitPinRule)

Pins the top-most ActivityStack to keep the stack of the Activities to be always positioned on top.
final void

Sets or replaces the previously registered SplitAttributes calculator.
final @NonNull Flow<@NonNull List<@NonNull SplitInfo>>

A Flow of SplitInfo list that contains the current split states that this activity is part of.
final void

Unpins the pinned ActivityStack.
final void
@RequiresWindowSdkExtension(version = 3)
updateSplitAttributes(
    @NonNull SplitInfo splitInfo,
    @NonNull SplitAttributes splitAttributes
)

Updates the SplitAttributes of a split pair.

Public methods

clearSplitAttributesCalculator

Added in 1.1.0
@RequiresWindowSdkExtension(version = 2)
public final void clearSplitAttributesCalculator()

Clears the callback previously set by setSplitAttributesCalculator. The caller must make sure if WindowSdkExtensions.extensionVersion is greater than or equal to 2.

Throws
kotlin.UnsupportedOperationException

if WindowSdkExtensions.extensionVersion is less than 2.

getInstance

Added in 1.1.0
public static final @NonNull SplitController getInstance(@NonNull Context context)

Obtains an instance of SplitController.

Parameters
@NonNull Context context

the Context to initialize the controller with

getSplitSupportStatus

Added in 1.1.0
public final @NonNull SplitController.SplitSupportStatus getSplitSupportStatus()

Indicates whether split functionality is supported on the device. Note that devices might not enable splits in all states or conditions. For example, a foldable device with multiple screens can choose to collapse splits when apps run on the device's small display, but enable splits when apps run on the device's large display. In cases like this, splitSupportStatus always returns SplitSupportStatus.SPLIT_AVAILABLE, and if the split is collapsed, activities are launched on top, following the non-activity embedding model.

Also the androidx.window.WindowProperties.PROPERTY_ACTIVITY_EMBEDDING_SPLITS_ENABLED must be enabled in AndroidManifest within in order to get the correct state or SplitSupportStatus.SPLIT_ERROR_PROPERTY_NOT_DECLARED will be returned in some cases.

See also
SplitController.SplitSupportStatus

pinTopActivityStack

Added in 1.4.0-alpha05
@RequiresWindowSdkExtension(version = 5)
public final boolean pinTopActivityStack(int taskId, @NonNull SplitPinRule splitPinRule)

Pins the top-most ActivityStack to keep the stack of the Activities to be always positioned on top. The rest of the activities in the Task will be split with the pinned ActivityStack. The pinned ActivityStack would also have isolated activity navigation in which only the activities that are started from the pinned ActivityStack can be added on top of the ActivityStack.

The pinned ActivityStack is unpinned whenever the pinned ActivityStack is expanded. Use SplitPinRule.Builder.setSticky if the same ActivityStack should be pinned again whenever the ActivityStack is on top and split with another ActivityStack again.

The caller must make sure if WindowSdkExtensions.extensionVersion is greater than or equal to 5.

Parameters
int taskId

The id of the Task that top ActivityStack should be pinned.
@NonNull SplitPinRule splitPinRule

The SplitRule that specifies how the top ActivityStack should be split with others.
Returns
boolean

Returns true if the top ActivityStack is successfully pinned. Otherwise, false. Few examples are: 1. There's no ActivityStack. 2. There is already an existing pinned ActivityStack. 3. There's no other ActivityStack to split with the top ActivityStack.
Throws
kotlin.UnsupportedOperationException

if WindowSdkExtensions.extensionVersion is less than 5.

setSplitAttributesCalculator

Added in 1.1.0
@RequiresWindowSdkExtension(version = 2)
public final void setSplitAttributesCalculator(
    @NonNull Function1<@NonNull SplitAttributesCalculatorParams, @NonNull SplitAttributes> calculator
)

Sets or replaces the previously registered SplitAttributes calculator.

Note that it's callers' responsibility to check if this API is supported by checking WindowSdkExtensions.extensionVersion before using the this API. It is suggested to always set meaningful SplitRule.defaultSplitAttributes in case this API is not supported on some devices.

Also, replacing the calculator will only update existing split pairs after a change in the window or device state, such as orientation changes or folding state changes.

The SplitAttributes calculator is a function to compute the current SplitAttributes for the given SplitRule with the current device and window state. Then The calculator will be invoked if either:

  • An activity is started and matches a registered SplitRule.

  • A parent configuration is updated and there's an existing split pair.

By default, SplitRule.defaultSplitAttributes are applied if the parent container's WindowMetrics satisfies the SplitRule's dimensions requirements, which are SplitRule.minWidthDp, SplitRule.minHeightDp and SplitRule.minSmallestWidthDp. The SplitRule.defaultSplitAttributes can be set by

Developers may want to apply different SplitAttributes for different device or window states. For example, on foldable devices, developers may want to split the screen vertically if the device is in landscape, fill the screen if the device is in portrait and split the screen horizontally if the device is in tabletop posture. In this case, the SplitAttributes can be customized by the SplitAttributes calculator, which takes effects after calling this API. Developers can also clear the calculator by clearSplitAttributesCalculator. Then, developers could implement the SplitAttributes calculator as the sample linked below shows.

import androidx.window.embedding.EmbeddingAnimationBackground
import androidx.window.embedding.SplitAttributes
import androidx.window.embedding.SplitAttributes.SplitType.Companion.SPLIT_TYPE_EQUAL
import androidx.window.embedding.SplitAttributes.SplitType.Companion.SPLIT_TYPE_EXPAND
import androidx.window.embedding.SplitAttributes.SplitType.Companion.SPLIT_TYPE_HINGE
import androidx.window.embedding.SplitController
import androidx.window.layout.FoldingFeature

SplitController.getInstance(context).setSplitAttributesCalculator { params ->
    val tag = params.splitRuleTag
    val parentWindowMetrics = params.parentWindowMetrics
    val parentConfig = params.parentConfiguration
    val foldingFeatures =
        params.parentWindowLayoutInfo.displayFeatures.filterIsInstance<FoldingFeature>()
    val foldingState = if (foldingFeatures.size == 1) foldingFeatures[0] else null
    // Tag can be used to filter the SplitRule to apply the SplitAttributes
    if (TAG_SPLIT_RULE_MAIN != tag && params.areDefaultConstraintsSatisfied) {
        return@setSplitAttributesCalculator params.defaultSplitAttributes
    }

    // This sample will make the app show a layout to
    // - split the task bounds vertically if the device is in landscape
    // - fill the task bounds if the device is in portrait and its folding state does not
    //   split the screen
    // - split the task bounds horizontally in tabletop mode
    val bounds = parentWindowMetrics.bounds
    if (foldingState?.isSeparating == true) {
        // Split the parent container that followed by the hinge if the hinge separates the
        // parent window.
        return@setSplitAttributesCalculator SplitAttributes.Builder()
            .setSplitType(SPLIT_TYPE_HINGE)
            .setLayoutDirection(
                if (foldingState.orientation == FoldingFeature.Orientation.HORIZONTAL) {
                    SplitAttributes.LayoutDirection.TOP_TO_BOTTOM
                } else {
                    SplitAttributes.LayoutDirection.LOCALE
                }
            )
            // Optionally set the animation background to use when switching between
            // vertical and horizontal
            .setAnimationBackground(
                EmbeddingAnimationBackground.createColorBackground(Color.GRAY)
            )
            .build()
    }
    return@setSplitAttributesCalculator if (
        parentConfig.screenWidthDp >= 600 && bounds.width() >= bounds.height()
    ) {
        // Split the parent container equally and vertically if the device is in landscape.
        SplitAttributes.Builder()
            .setSplitType(SPLIT_TYPE_EQUAL)
            .setLayoutDirection(SplitAttributes.LayoutDirection.LOCALE)
            // Optionally set the animation background to use when switching between
            // vertical and horizontal
            .setAnimationBackground(
                EmbeddingAnimationBackground.createColorBackground(Color.GRAY)
            )
            .build()
    } else {
        // Expand containers if the device is in portrait or the width is less than 600 dp.
        SplitAttributes.Builder().setSplitType(SPLIT_TYPE_EXPAND).build()
    }
}
Parameters
@NonNull Function1<@NonNull SplitAttributesCalculatorParams, @NonNull SplitAttributes> calculator

the function to calculate SplitAttributes based on the SplitAttributesCalculatorParams. It will replace the previously set if it exists.
Throws
kotlin.UnsupportedOperationException

if WindowSdkExtensions.extensionVersion is less than 2.

splitInfoList

Added in 1.1.0
public final @NonNull Flow<@NonNull List<@NonNull SplitInfo>> splitInfoList(@NonNull Activity activity)

A Flow of SplitInfo list that contains the current split states that this activity is part of.

An activity can be in zero, one or more active splits. More than one active split is possible if an activity created multiple containers to side, stacked on top of each other. Or it can be in two different splits at the same time - in a secondary container for one (it was launched to the side) and in the primary for another (it launched another activity to the side). The reported splits in the list are ordered from bottom to top by their z-order, more recent splits appearing later. Guaranteed to be called at least once to report the most recent state.

Parameters
@NonNull Activity activity

The Activity that is interested in getting the split states
Returns
@NonNull Flow<@NonNull List<@NonNull SplitInfo>>

a Flow of SplitInfo list that includes this activity

unpinTopActivityStack

Added in 1.4.0-alpha05
@RequiresWindowSdkExtension(version = 5)
public final void unpinTopActivityStack(int taskId)

Unpins the pinned ActivityStack. The ActivityStack will still be the top-most ActivityStack right after unpinned, and the ActivityStack could be expanded or continue to be split with the next top ActivityStack if the current state matches any of the existing SplitPairRule. It is a no-op call if the task does not have a pinned ActivityStack.

The caller must make sure if WindowSdkExtensions.extensionVersion is greater than or equal to 5.

Parameters
int taskId

The id of the Task that top ActivityStack should be unpinned.
Throws
kotlin.UnsupportedOperationException

if WindowSdkExtensions.extensionVersion is less than 5.

updateSplitAttributes

Added in 1.2.0
@RequiresWindowSdkExtension(version = 3)
public final void updateSplitAttributes(
    @NonNull SplitInfo splitInfo,
    @NonNull SplitAttributes splitAttributes
)

Updates the SplitAttributes of a split pair. This is an alternative to using a split attributes calculator callback set in setSplitAttributesCalculator, useful when apps only need to update the splits in a few cases proactively but rely on the default split attributes most of the time otherwise.

The provided split attributes will be used instead of the associated SplitRule.defaultSplitAttributes.

Note that the split attributes may be updated if split attributes calculator callback is registered and invoked. If setSplitAttributesCalculator is used, the callback will still be applied to each SplitInfo when there's either:

  • A new Activity being launched.

  • A window or device state updates (e,g. due to screen rotation or folding state update).

In most cases it is suggested to use ActivityEmbeddingController.invalidateTopVisibleActivityStacks if a calculator has been set through setSplitAttributesCalculator.

Parameters
@NonNull SplitInfo splitInfo

the split pair to update
@NonNull SplitAttributes splitAttributes

the SplitAttributes to be applied
Throws
kotlin.UnsupportedOperationException

if WindowSdkExtensions.extensionVersion is less than 3.