CanvasRenderer

Kotlin |Java

abstract class CanvasRenderer : Renderer

kotlin.Any
↳	androidx.wear.watchface.Renderer
	↳	androidx.wear.watchface.CanvasRenderer

Watch faces that require Canvas rendering should extend their Renderer from this class.

Summary

Public constructors
`<init>(surfaceHolder: SurfaceHolder, userStyleRepository: UserStyleRepository, watchState: WatchState, canvasType: Int, @IntRange(0, 10000) interactiveDrawModeUpdateDelayMillis: Long)` Watch faces that require Canvas rendering should extend their Renderer from this class.

Public methods
abstract Unit	`render(canvas: Canvas, bounds: Rect, calendar: Calendar)` Sub-classes should override this to implement their rendering logic which should respect the current DrawMode.

Inherited functions

From class Renderer

`Rect`	`getMainClockElementBounds()` 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.
`Unit`	`invalidate()` Schedules a call to renderInternal to draw the next frame.
`Unit`	`onDestroy()` Called when the Renderer is destroyed.
`Unit`	`onRenderParametersChanged(renderParameters: RenderParameters)` Called when the DrawMode has been updated. Will always be called before the first call to onDraw().
`Unit`	`postInvalidate()` Posts a message to schedule a call to renderInternal to draw the next frame. Unlike invalidate, this method is thread-safe and may be called on any thread.
`Boolean`	`shouldAnimate()` 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. Watchfaces with animated transitions for entering ambient mode may need to override this to ensure they play smoothly.

Inherited properties

From class Renderer

`Float`	`centerX` The center x coordinate of the SurfaceHolder this Renderer renders into.
`Float`	`centerY` The center y coordinate of the SurfaceHolder this Renderer renders into.
`Long`	`interactiveDrawModeUpdateDelayMillis` 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.
`RenderParameters`	`renderParameters` The current RenderParameters. Updated before every onDraw call.
`Rect`	`screenBounds` 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 WatchState.screenShape). Note also that API level 27+ devices draw indicators in the top and bottom 24dp of the screen, avoid rendering anything important there.
`SurfaceHolder`	`surfaceHolder` The SurfaceHolder that renderInternal will draw into.

Public constructors

<init>

CanvasRenderer(
    surfaceHolder: SurfaceHolder, 
    userStyleRepository: UserStyleRepository, 
    watchState: WatchState, 
    canvasType: Int, 
    @IntRange(0, 10000) interactiveDrawModeUpdateDelayMillis: Long)

Watch faces that require Canvas rendering should extend their Renderer from this class.

Public methods

render

@UiThread abstract fun render(
    canvas: Canvas, 
    bounds: Rect, 
    calendar: Calendar
): Unit

Sub-classes should override this to implement their rendering logic which should respect the current DrawMode. For correct functioning watch faces must use the supplied Calendar and avoid using any other ways of getting the time.

Parameters
canvas: Canvas	The Canvas to render into. Don't assume this is always the canvas from the SurfaceHolder backing the display
bounds: Rect	A Rect describing the bonds of the canvas to draw into
calendar: Calendar	The current Calendar