HarmonyOS 曲线demo

demo如下：

import { RenderNode, DrawContext, FrameNode, NodeController } from "@ohos.arkui.node"
import drawing from "@ohos.graphics.drawing"

class TextRenderNode extends RenderNode {
  async draw(context: DrawContext) {
    const canvas = context.canvas;
    const pen = new drawing.Pen();
    pen.setStrokeWidth(5);
    pen.setColor({
      alpha: 255,
      red: 255,
      green: 0,
      blue: 0
    });
    let path =
      new drawing.Path(); // path.moveTo(10,10);
    path.arcTo(10, 10, 200, 200, 0,180); // path.close();
    canvas.attachPen(pen);
    canvas.drawPath(path);
    canvas.detachPen();
  }
}

class MyNodeController extends NodeController {
  private rootNode: FrameNode | null = null;
  private nodeArray: Array<TextRenderNode> = []

  addMyNode(item: TextRenderNode) {
    this.nodeArray.push(item)
  }

  makeNode(uiContext: UIContext): FrameNode | null {
    this.rootNode = new FrameNode(uiContext);
    const renderNode = this.rootNode.getRenderNode();
    if (renderNode === null) {
      return this.rootNode;
    }
    if (renderNode) {
      renderNode.clearChildren()
      this.nodeArray.forEach((item) => {
        renderNode.appendChild(item)
      })
    }
    return this.rootNode;
  } 
}

@Entry
@Component
struct Index {
  @State newNode: TextRenderNode = new TextRenderNode();
  @State nodeCV: MyNodeController = new MyNodeController()
  tempY = 0

  build() {
    Column() {
      Column() {
        NodeContainer(this.nodeCV).width('100%').height(200)
        Button('Invalidate').onClick(() => {
          let newNode = new TextRenderNode()
          newNode.frame = {
            x: 0,
            y: this.tempY,
            width: 200,
            height: 100
          }
          this.nodeCV.addMyNode(newNode)
          this.nodeCV.rebuild()
          this.tempY += 100
        })
      }.width('100%').height('100%')
    }.height('100%')
  }
}