harmony 鸿蒙Canvas

2022-08-09
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Canvas

The <Canvas> component can be used to customize drawings.

NOTE

This component is supported since API version 8. Updates will be marked with a superscript to indicate their earliest API version.

Child Components

Not supported

APIs

Canvas(context?: CanvasRenderingContext2D)

Since API version 9, this API is supported in ArkTS widgets.

Parameters

Name	Type	Mandatory	Default Value	Description
context	CanvasRenderingContext2D	No	-	For details, see CanvasRenderingContext2D.

Attributes

The universal attributes are supported.

Events

In addition to the universal events, the following events are supported.

Name	Parameter	Description
onReady(event: () => void)	-	Triggered when a canvas is ready or its size changes. When this event is triggered, the canvas is cleared. The width and height of the canvas can then be obtained, and you can use the canvas APIs to draw images. If the canvas is merely relocated, the onAreaChange event is triggered, but the onReady event is not. Since API version 9, this API is supported in ArkTS widgets.

Example

// xxx.ets
@Entry
@Component
struct CanvasExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() => {
          this.context.fillRect(0, 30, 100, 100)
        })
    }
    .width('100%')
    .height('100%')
  }
}

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