sealed class Renderer

Known direct subclasses
Renderer.CanvasRenderer

This class is deprecated. CanvasRenderer is deprecated

Renderer.GlesRenderer

This class is deprecated. GlesRenderer is deprecated

Known indirect subclasses
ListenableCanvasRenderer2

ListenableFuture-based compatibility wrapper around Renderer.CanvasRenderer2's suspending methods.

ListenableCanvasRenderer

This class is deprecated. Use ListenableCanvasRenderer2 instead

ListenableGlesRenderer2

ListenableFuture-based compatibility wrapper around Renderer.GlesRenderer's suspending methods.

ListenableGlesRenderer

This class is deprecated. Use ListenableGlesRenderer2 instead

Renderer.CanvasRenderer2

Watch faces that require Canvas rendering and are able to take advantage of SharedAssets to save memory (there can be more than once instance when editing), should extend their Renderer from this class.

Renderer.GlesRenderer2

Watch faces that require GLES20 rendering and are able to take advantage of SharedAssets to save memory (there can be more than once instance when editing), should extend their Renderer from this class.


The base class for CanvasRenderer, CanvasRenderer2, GlesRenderer, GlesRenderer2. Where possible it is recommended to use CanvasRenderer2 or GlesRenderer2 which allow memory to be saved during editing because there can be more than one watchface instance during editing.

Renderers are constructed on a background thread but all rendering is done on the UiThread. There is a memory barrier between construction and rendering so no special threading primitives are required.

It is recommended to set watchfaceColors with representative WatchFaceColors this is used by compatible systems to influence the system's color scheme.

Please note android.graphics.drawable.AnimatedImageDrawable and similar classes which rely on android.graphics.drawable.Drawable.Callback do not animate properly out of the box unless you register an implementation with android.graphics.drawable.Drawable.setCallback that calls invalidate. Even then these classes are not recommend because the ZonedDateTime passed to Renderer.CanvasRenderer.render or Renderer.GlesRenderer.render is not guaranteed to match the system time (e.g. for taking screenshots). In addition care is needed when implementing android.graphics.drawable.Drawable.Callback to ensure it does not animate in ambient mode which could lead to a significant power regression.

Summary

Nested types

This class is deprecated. CanvasRenderer is deprecated

Watch faces that require Canvas rendering and are able to take advantage of SharedAssets to save memory (there can be more than once instance when editing), should extend their Renderer from this class.

This class is deprecated. GlesRenderer is deprecated

Exception thrown if a GL call fails

Watch faces that require GLES20 rendering and are able to take advantage of SharedAssets to save memory (there can be more than once instance when editing), should extend their Renderer from this class.

Multiple WatchFaceService instances and hence Renderers can exist concurrently (e.g. a headless instance and an interactive instance) and using SharedAssets allows memory to be saved by sharing immutable data (e.g. Bitmaps and shaders) between them.

Protected constructors

@WorkerThread
Renderer(
    surfaceHolder: SurfaceHolder,
    currentUserStyleRepository: CurrentUserStyleRepository,
    watchState: WatchState,
    interactiveDrawModeUpdateDelayMillis: @IntRange(from = 0, to = 60000) Long
)

Public functions

open Rect

This method is used for accessibility support to describe the portion of the screen containing the main clock element.

Unit

Schedules a call to either CanvasRenderer.render or GlesRenderer.render to draw the next frame.

open Unit

Called when the Renderer is destroyed.

abstract Unit

Called when adb shell dumpsys is invoked for the WatchFaceService, allowing the renderer to optionally record state for debugging purposes.

Unit

Posts a message to schedule a call to either CanvasRenderer.render or GlesRenderer.render to draw the next frame.

Unit

Sends a request to the system asking it to update the preview image.

open Boolean

The system periodically (at least once per minute) calls onTimeTick() to trigger a display update.

Protected functions

open Unit

Called when the RenderParameters has been updated.

Public properties

Collection<Pair<IntContentDescriptionLabel>>

Accessibility ContentDescriptionLabel for any rendered watch face elements other than the time and ComplicationSlots which are generated automatically.

@Px Float

The center x coordinate of the SurfaceHolder this Renderer renders into.

@Px Float

The center y coordinate of the SurfaceHolder this Renderer renders into.

Long

The interval in milliseconds between frames in interactive DrawModes.

RenderParameters

The current RenderParameters.

Rect

The bounds of the SurfaceHolder this Renderer renders into.

SurfaceHolder

The SurfaceHolder that renderInternal will draw into.

WatchFaceColors?

Representative WatchFaceColors which are made available to system clients via androidx.wear.watchface.client.InteractiveWatchFaceClient.OnWatchFaceColorsListener.

Protected constructors

Renderer

@WorkerThread
protected Renderer(
    surfaceHolder: SurfaceHolder,
    currentUserStyleRepository: CurrentUserStyleRepository,
    watchState: WatchState,
    interactiveDrawModeUpdateDelayMillis: @IntRange(from = 0, to = 60000) Long
)
Parameters
surfaceHolder: SurfaceHolder

The SurfaceHolder that renderInternal will draw into.

currentUserStyleRepository: CurrentUserStyleRepository

The associated CurrentUserStyleRepository.

watchState: WatchState

The associated WatchState.

interactiveDrawModeUpdateDelayMillis: @IntRange(from = 0, to = 60000) Long

The interval in milliseconds between frames in interactive DrawModes. To render at 60hz set to 16. Note when battery is low, the frame rate will be clamped to 10fps. Watch faces are recommended to use lower frame rates if possible for better battery life. Variable frame rates can also help preserve battery life, e.g. if a watch face has a short animation once per second it can adjust the frame rate inorder to sleep when not animating. In ambient mode the watch face will be rendered once per minute.

Public functions

getMainClockElementBounds

Added in 1.0.0
@UiThread
open fun getMainClockElementBounds(): Rect

This method is used for accessibility support to describe the portion of the screen containing the main clock element. By default we assume this is contained in the central half of the watch face. Watch faces should override this to return the correct bounds for the main clock element.

Returns
Rect

A Rect describing the bounds of the watch faces' main clock element

invalidate

Added in 1.0.0
@UiThread
fun invalidate(): Unit

Schedules a call to either CanvasRenderer.render or GlesRenderer.render to draw the next frame.

onDestroy

Added in 1.0.0
@UiThread
open fun onDestroy(): Unit

Called when the Renderer is destroyed.

onDump

Added in 1.0.0
@UiThread
abstract fun onDump(writer: PrintWriter): Unit

Called when adb shell dumpsys is invoked for the WatchFaceService, allowing the renderer to optionally record state for debugging purposes.

postInvalidate

Added in 1.0.0
fun postInvalidate(): Unit

Posts a message to schedule a call to either CanvasRenderer.render or GlesRenderer.render to draw the next frame. Unlike invalidate, this method is thread-safe and may be called on any thread.

sendPreviewImageNeedsUpdateRequest

Added in 1.2.0
fun sendPreviewImageNeedsUpdateRequest(): Unit

Sends a request to the system asking it to update the preview image. This is useful for watch faces with configuration outside of the UserStyleSchema E.g. a watchface with a selectable background.

The system may choose to rate limit this method for performance reasons and the system is free to schedule when the update occurs.

Requires a compatible system to work (if the system is incompatible this does nothing). This can be called from any thread.

shouldAnimate

Added in 1.0.0
@UiThread
open fun shouldAnimate(): Boolean

The system periodically (at least once per minute) calls onTimeTick() to trigger a display update. If the watch face needs to animate with an interactive frame rate, calls to invalidate must be scheduled. This method controls whether or not we should do that and if shouldAnimate returns true we inhibit entering DrawMode.AMBIENT.

By default we remain at an interactive frame rate when the watch face is visible and we're not in ambient mode. Watch faces with animated transitions for entering ambient mode may need to override this to ensure they play smoothly.

Returns
Boolean

Whether we should schedule an onDraw call to maintain an interactive frame rate

Protected functions

onRenderParametersChanged

Added in 1.0.0
@UiThread
protected open fun onRenderParametersChanged(renderParameters: RenderParameters): Unit

Called when the RenderParameters has been updated. Will always be called before the first call to CanvasRenderer.render or GlesRenderer.render.

Public properties

additionalContentDescriptionLabels

Added in 1.0.0
var additionalContentDescriptionLabelsCollection<Pair<IntContentDescriptionLabel>>

Accessibility ContentDescriptionLabel for any rendered watch face elements other than the time and ComplicationSlots which are generated automatically.

The Int in the Pair<Int, ContentDescriptionLabel> is used to sort the ContentDescriptionLabels. Note the time piece has an accessibility traversal index of -1 and each ComplicationSlot's index is defined by its ComplicationSlot.accessibilityTraversalIndex.

centerX

Added in 1.0.0
val centerX: @Px Float

The center x coordinate of the SurfaceHolder this Renderer renders into.

centerY

Added in 1.0.0
val centerY: @Px Float

The center y coordinate of the SurfaceHolder this Renderer renders into.

interactiveDrawModeUpdateDelayMillis

Added in 1.0.0
var interactiveDrawModeUpdateDelayMillisLong

The interval in milliseconds between frames in interactive DrawModes. To render at 60hz set to 16. Note when battery is low, the frame rate will be clamped to 10fps. Watch faces are recommended to use lower frame rates if possible for better battery life. Variable frame rates can also help preserve battery life, e.g. if a watch face has a short animation once per second it can adjust the frame rate inorder to sleep when not animating. In ambient mode the watch face will be rendered once per minute.

renderParameters

Added in 1.0.0
val renderParametersRenderParameters

The current RenderParameters. Updated before every onDraw call.

screenBounds

Added in 1.0.0
val screenBoundsRect

The bounds of the SurfaceHolder this Renderer renders into. Depending on the shape of the device's screen not all of these pixels may be visible to the user (see Configuration.isScreenRound). Note also that API level 27+ devices draw indicators in the top and bottom 24dp of the screen, avoid rendering anything important there.

surfaceHolder

Added in 1.0.0
var surfaceHolderSurfaceHolder

The SurfaceHolder that renderInternal will draw into.

watchfaceColors

Added in 1.2.0
@WatchFaceExperimental
var watchfaceColorsWatchFaceColors?

Representative WatchFaceColors which are made available to system clients via androidx.wear.watchface.client.InteractiveWatchFaceClient.OnWatchFaceColorsListener.

Initially this value is null signifying that the colors are unknown. When possible the watchFace should assign non null WatchFaceColors and keep this updated when the colors change (e.g. due to a style change).