悬浮窗拖拽和吸附动画

Stack({ alignContent: Alignment.Bottom }) {
  Video({
    src: $rawfile('float_window_video.mp4'),
    controller: this.videoController
  })
    .controls(false)
    .autoPlay(true)
    .loop(true)
    .muted(true)
    .width($r('app.string.float_window_full_size'))
    .onClick(() => {
      this.videoController.requestFullscreen(true);
    })
    .borderRadius($r('app.integer.float_window_content_border_radius'))
  Text($r('app.string.float_window_live_text'))
    .width($r('app.string.float_window_full_size'))
    .fontSize($r('app.string.ohos_id_text_size_body1'))
    .fontColor($r('app.color.ohos_id_color_background'))
    .textAlign(TextAlign.Center)
    .backgroundColor($r('app.color.ohos_id_color_list_alert'))
    .borderRadius({
      bottomLeft: $r('app.integer.float_window_content_border_radius'),
      bottomRight: $r('app.integer.float_window_content_border_radius')
    })
}
.clip(true)
.border({
  width: $r('app.integer.float_window_border_width'),
  color: $r('app.color.ohos_id_color_background')
})
.borderRadius($r('app.string.ohos_id_corner_radius_default_l'))
.width(Constants.FLOAT_WINDOW_WIDTH)
.height(Constants.FLOAT_WINDOW_HEIGHT)
.backgroundColor($r('app.color.ohos_id_color_foreground'))
.position(this.edge)
.onTouch((event: TouchEvent) => {
  this.onTouchEvent(event);
})

  @State edge: Edges = { top: Constants.INIT_POSITION_Y, right: Constants.PAGE_PADDING };

  // 父组件宽度
  @State containerWidth: number = 0;
  // 父组件高度
  @State containerHeight: number = 0;
                      
  .onAreaChange((oldValue: Area, newValue: Area) => {
    // TODO：性能知识点：onAreaChange是高频回调，仅在父组件尺寸改变时获取新的父组件宽高，避免性能损耗
    if (oldValue.width !== newValue.width) {
      this.containerWidth = newValue.width as number;
    }
    if (oldValue.height !== newValue.height) {
      this.containerHeight = newValue.height as number;
    }
  })

  // 拖拽移动开始时悬浮窗在窗口中的坐标，每次移动回调触发时更新
  private windowStartX: number = 0;
  private windowStartY: number = 0;

  case TouchType.Down: {
    // 获取拖拽开始时悬浮窗在窗口中的坐标
    this.windowStartX = event.touches[0].windowX;
    this.windowStartY = event.touches[0].windowY;
    break;
  }

  case TouchType.Move: {
    const windowX: number = event.touches[0].windowX;
    const windowY: number = event.touches[0].windowY;
    // TODO：知识点：跟手动画，推荐使用默认参数的弹性跟手动画曲线curves.responsiveSpringMotion。
    animateTo({ curve: curves.responsiveSpringMotion() }, () => {
      // 判断当前edge中属性left和right哪个不为undefined，用于控制悬浮窗水平方向的位置
      if (this.edge.left !== undefined) {
        this.edge.left = this.edge.left as number + (windowX - this.windowStartX);
      } else {
        this.edge.right = this.edge.right as number - (windowX - this.windowStartX);
      }
      this.edge.top = this.edge.top as number + (windowY - this.windowStartY);
      this.windowStartX = windowX;
      this.windowStartY = windowY;
    })
    break;
  }

  case TouchType.Up: {
    // 计算悬浮窗中心点在父组件中水平方向的坐标
    let centerX: number;
    if (this.edge.left !== undefined) {
      centerX = this.edge.left as number + Constants.FLOAT_WINDOW_WIDTH / 2;
    }else{
      centerX = this.containerWidth - (this.edge.right as number) - Constants.FLOAT_WINDOW_WIDTH / 2;
    }
    // TODO：知识点：通过判断悬浮窗在父组件中的位置，设置悬浮窗贴边，使用curves.springMotion()弹性动画曲线，可以实现阻尼动画效果
    animateTo({ curve: curves.springMotion() }, () => {
      // 判断悬浮窗中心在水平方向是否超过父组件宽度的一半，根据结果设置靠左或靠右
      if (centerX > (this.containerWidth / 2)) {
        this.edge.right = Constants.PAGE_PADDING;
        this.edge.left = undefined;
      } else {
        this.edge.right = undefined;
        this.edge.left = Constants.PAGE_PADDING;
      }
      // 判断悬浮窗是否超出内容区上下边界，根据结果将悬浮窗设置在边界位置
      if (this.edge.top as number < Constants.PAGE_PADDING) {
        this.edge.top = Constants.PAGE_PADDING;
      } else if (this.edge.top as number > this.containerHeight - Constants.FLOAT_WINDOW_HEIGHT - Constants.PAGE_PADDING) {
        this.edge.top = this.containerHeight - Constants.FLOAT_WINDOW_HEIGHT - Constants.PAGE_PADDING;
      }
    })
    break;
  }

floatwindow                                  // har类型
|---/src/main/ets/common                        
|   |---Constants.ets                        // 常量
|---/src/main/ets/pages                        
|   |---FloatWindowMainPage.ets              // 视图层-悬浮窗首页