HarmonyOS鸿蒙Next中ArkUI的PinchGesture中获取的event.scale值会产生突变

使用互斥手势组（GestureMode.Exclusive），优先处理缩放手势；通过插值算法缓解event.scale突变。示例支持双指缩放+双指平移及单指平移的切换：

@Entry
@Component
struct GestureDemo {
  @State zoom: number = 1.0;
  @State offsetX: number = 0;
  @State offsetY: number = 0;
  private lastPanX: number = 0;
  private lastPanY: number = 0;
  private pinchStartZoom: number = 1.0;
  private lastPinchCenterX: number = 0;
  private lastPinchCenterY: number = 0;

  build() {
    Stack() {
      // 被操作的内容（例如图片或画布）
      Canvas(this.ctx)
        .width('100%')
        .height('100%')
        .scale({ x: this.zoom, y: this.zoom })
        .translate({ x: this.offsetX, y: this.offsetY })

    }
    .gesture(
      GestureGroup(GestureMode.Exclusive,
        // 双指缩放逻辑
        PinchGesture({ fingers: 2 })
          .onActionStart((event: GestureEvent | undefined) => {
            if (event) {
              this.pinchStartZoom = this.zoom;
              this.lastPinchCenterX = (event.fingerList.displayX + event.fingerList.displayX) / 2;
              this.lastPinchCenterY = (event.fingerList.displayY + event.fingerList.displayY) / 2;
            }
          })
          .onActionUpdate((event: GestureEvent | undefined) => {
            if (event) {
              // 平滑处理缩放值
              const smoothFactor = 0.2;
              const targetZoom = this.pinchStartZoom * event.scale;
              this.zoom += (targetZoom - this.zoom) * smoothFactor;
              
              // 根据缩放中心点调整偏移量
              const newCenterX = (event.fingerList.displayX + event.fingerList.displayX) / 2;
              const newCenterY = (event.fingerList.displayY + event.fingerList.displayY) / 2;
              this.offsetX += (newCenterX - this.lastPinchCenterX) * this.zoom;
              this.offsetY += (newCenterY - this.lastPinchCenterY) * this.zoom;
              this.lastPinchCenterX = newCenterX;
              this.lastPinchCenterY = newCenterY;
            }
          }),

        // 单指/双指平移逻辑
        PanGesture({ fingers: 1 })
          .onActionStart((event: GestureEvent | undefined) => {
            if (event) {
              this.lastPanX = event.offsetX;
              this.lastPanY = event.offsetY;
            }
          })
          .onActionUpdate((event: GestureEvent | undefined) => {
            if (event) {
              // 直接更新偏移量
              this.offsetX += (event.offsetX - this.lastPanX) * this.zoom;
              this.offsetY += (event.offsetY - this.lastPanY) * this.zoom;
              this.lastPanX = event.offsetX;
              this.lastPanY = event.offsetY;
            }
          })
      )
    )
  }
}