HarmonyOS 鸿蒙Next如何实现下面这样的渐变过渡效果

开发者你好，可以使用颜色渐变和overlay来实现，实现思路以及示例demo可以参考：

1. 创建可滚动的主页面。

2. 利用颜色渐变通用属性，创建两端渐隐的自定义组件。

3. 通过overlay通用属性，设置子组件为遮罩层。

@Entry
@Component
struct FadingEdge {
  private textArray: number[] = [];
  // 渐变起始和终止颜色
  @State linearGradientBegin1Color: string = Const.BEGIN_COLOR;
  @State linearGradientEnd1Color: string = Const.END_COLOR;

  @State linearGradientBegin2Color: string = Const.BEGIN_COLOR;
  @State linearGradientEnd2Color: string = Const.END_COLOR;

  aboutToAppear(): void {
    for (let i = 0; i < Const.ITEM_COUNT; i++) {
      this.textArray.push(i);
    }
  }

  build() {
    Column({ space: Const.ROOT_GAP }) {
      // 主体
      List({ space: Const.EXAMPLE_IMAGE_GAP }) {
        ForEach(this.textArray, () => {
          ListItem() {
            // 图片示例，需要替换为实际资源值
            Image($r('app.media.fadingedge_example1'))
              .width(200)
              .height(120)
              .borderRadius(8);
          };
        }, (item: number) => item.toString());
      }
      .listDirection(Axis.Horizontal)
      .width('100%')
      .height(120)
      .overlay(this.fadingOverlay())
      .edgeEffect(EdgeEffect.None)
      .scrollBar(BarState.Off)
      .onScrollStart(()=>{
        this.linearGradientBegin1Color = Const.END_COLOR;
        this.linearGradientEnd1Color = Const.BEGIN_COLOR;

        this.linearGradientBegin2Color = Const.BEGIN_COLOR;
        this.linearGradientEnd2Color = Const.END_COLOR;
      })
      .onReachStart(() => {
        this.linearGradientBegin1Color = Const.BEGIN_COLOR;
        this.linearGradientEnd1Color = Const.BEGIN_COLOR;

        this.linearGradientBegin2Color = Const.BEGIN_COLOR;
        this.linearGradientEnd2Color = Const.END_COLOR;
      })
      .onReachEnd(() => {
        this.linearGradientBegin1Color = Const.END_COLOR;
        this.linearGradientEnd1Color = Const.BEGIN_COLOR;

        this.linearGradientBegin2Color = Const.BEGIN_COLOR;
        this.linearGradientEnd2Color = Const.BEGIN_COLOR;
      });
    }
    .width('100%')
    .height('100%')
    .padding(10);
  }

  // 浮层组件
  @Builder
  fadingOverlay() {
    Column()
      .width("100%")
      .height(120)
      // TODO: 知识点: linearGradient 可以设置指定范围内的颜色渐变效果
      .linearGradient({
        angle: Const.OVERLAY_LINEAR_GRADIENT_ANGLE,
        colors: [
          [this.linearGradientBegin1Color, Const.OVERLAY_LINEAR_GRADIENT_COLOR_POS[0]],
          [this.linearGradientEnd1Color, Const.OVERLAY_LINEAR_GRADIENT_COLOR_POS[1]],
          [this.linearGradientBegin2Color, Const.OVERLAY_LINEAR_GRADIENT_COLOR_POS[2]],
          [this.linearGradientEnd2Color, Const.OVERLAY_LINEAR_GRADIENT_COLOR_POS[3]],
        ]
      })
      .animation({
        curve: Curve.Ease,
        duration: Const.DURATION
      })
      .hitTestBehavior(HitTestMode.Transparent);
  }
}

class Const {
  // 示例图片间距
  public static readonly EXAMPLE_IMAGE_GAP: number = 10;
  // 示例图片数量
  public static readonly ITEM_COUNT: number = 6;
  // 动画时长
  public static readonly DURATION: number = 220;
  // 边缘渐变起始和终止颜色
  public static readonly BEGIN_COLOR: string = '#00ffffff';
  public static readonly END_COLOR: string = '#ffffffff';
  // 根容器组件默认间距
  public static readonly ROOT_GAP: number = 20;
  // 顶部菜单栏间距
  public static readonly MENU_ITEM_SPACE: number = 5;
  // 顶部菜单栏Item中文字与图片间距
  public static readonly MENU_ITEM_COL_SPACE: number = 5;
  // 渐变角度
  public static readonly OVERLAY_LINEAR_GRADIENT_ANGLE: number = 90;
  // 渐变颜色位置
  public static readonly OVERLAY_LINEAR_GRADIENT_COLOR_POS: number[] = [0.0, 0.15, 0.85, 1.0];
  // tosat提示框持续时间
  public static readonly PROMPT_TOAST_DURATION: number = 1200;
}