列表下拉刷新、上拉加载更多，不管在web时代还是鸿蒙应用都是一个非常常用的功能，基于ArkUI中TS扩展的声明式开发范式实现一个下拉刷新，上拉加载。

上拉加载、下拉刷新

如果数据量过大，可以使用LazyForEach代替ForEach

高阶组件-上拉加载，下拉刷新https://gitee.com/bingtengaoyu/harmonyos-advanced-componen/tree/master/UpDownRefresh 

1、涉及的知识点

• 列表容器（List）
• 触摸事件（onTouch）
• 位置设置（offset）
• 显示动画（animateTo）

2、效果图

3、实现思路

根据触摸事件onTouch()处理下拉和上拉，通过记录手指按下的y坐标和move移动的距离判断属于刷拉还是下滑，从而展示不同的内容。

4、关键代码

4.1 生成下拉刷新/上拉加载DOM

  @Builder UpDownRefreshBuilder(text: string, state: string) {
    Row() {
      Image($r('app.media.refreshing'))
        .width(32)
        .height(32)
      Text(text).fontSize(16)
    }
    .justifyContent(FlexAlign.Center)
    .position({
      y: state === 'down' ? 20 : -20
    })
    .zIndex(999)
    .width('94%')
    .height('8%')
  }

4.2 onTouch处理事件

  private currentOffsetY: number = 0;
  private timer: number = 0;
  @State refreshStatus: boolean = false;
  @State upRefreshStatus: boolean = false;

  aboutToDisappear() {
    this.timer = null
  }

  putDownRefresh(event?: TouchEvent): void {
    if (event === undefined) {
      return;
    }
    switch (event.type) {
      case TouchType.Down:
        this.currentOffsetY = event.touches[0].y;
        break;
      case TouchType.Move:
        if(this.scroller.currentOffset().yOffset < 50) {
          this.refreshStatus = event.touches[0].y - this.currentOffsetY > 50;
        }
        this.upRefreshStatus = event.touches[0].y - this.currentOffsetY < -50;
        break;
      case TouchType.Cancel:
        break;
      case TouchType.Up:
        // Only simulation effect, no data request
        this.timer = setTimeout(() => {
          if (this.upRefreshStatus) {
            this.scroller.scrollTo({           // 调用scrollTo滚动到具体位置
              xOffset: 0,                    // 竖直方向滚动，该值不起作用
              yOffset: 680,    // 滚动到底部
              animation: {                     // 滚动动画
                duration: 1500,
                curve: Curve.EaseOut
              }
            })
          }
          this.refreshStatus = false;
          this.upRefreshStatus = false;
        }, 1500);
        break;
    }
  }

5、完整代码

兵腾傲宇/harmonyos-healthy-live - Gitee.com

import router from '@ohos.router'
import curves from '@ohos.curves'
import { BreakpointSystem, BreakPointType } from '../common/BreakpointSystem'
import { FoodInfo, Category } from '../model/DataModels'
import { getFoods, getFoodCategories, getSortedFoodData } from '../model/DataUtil'
import { Records } from './components/DietRecord'
import { PersonalCenter } from './PersonalCenter'

interface FoodId {
  foodId: FoodInfo;
}

@Component
struct FoodListItem {
  private foodItem?: FoodInfo

  build() {
    Navigator({ target: 'pages/FoodDetail' }) {
      Row() {
        Image(this.foodItem!.image!)
          .objectFit(ImageFit.Contain)
          .autoResize(false)
          .height(40)
          .width(40)
          .backgroundColor('#FFf1f3f5')
          .margin({ right: 16 })
          .borderRadius(6)
          .sharedTransition(this.foodItem!.letter, {
            duration: 400,
            curve: curves.cubicBezier(0.2, 0.2, 0.1, 1.0),
            delay: 100
          })
        Text(this.foodItem?.name)
          .fontSize(14)
        Blank()
        Text($r('app.string.calorie_with_kcal_unit', this.foodItem?.calories.toString()))
          .fontSize(14)
      }
      .height(64)
      .width('100%')
    }
    .params({ foodId: this.foodItem } as FoodId)
    .margin({ right: 24, left: 32 })
  }
}

@Component
struct ListModeFoods {
  private foodItems: Array<FoodInfo | string> = getSortedFoodData()
  private currentOffsetY: number = 0;
  private timer: number = 0;
  @State refreshStatus: boolean = false;
  @State upRefreshStatus: boolean = false;

  aboutToDisappear() {
    this.timer = null
  }

  putDownRefresh(event?: TouchEvent): void {
    if (event === undefined) {
      return;
    }
    switch (event.type) {
      case TouchType.Down:
        this.currentOffsetY = event.touches[0].y;
        break;
      case TouchType.Move:
        if(this.scroller.currentOffset().yOffset < 50) {
          this.refreshStatus = event.touches[0].y - this.currentOffsetY > 50;
        }
        this.upRefreshStatus = event.touches[0].y - this.currentOffsetY < -50;
        break;
      case TouchType.Cancel:
        break;
      case TouchType.Up:
        // Only simulation effect, no data request
        this.timer = setTimeout(() => {
          if (this.upRefreshStatus) {
            this.scroller.scrollTo({           // 调用scrollTo滚动到具体位置
              xOffset: 0,                    // 竖直方向滚动，该值不起作用
              yOffset: 680,    // 滚动到底部
              animation: {                     // 滚动动画
                duration: 1500,
                curve: Curve.EaseOut
              }
            })
          }
          this.refreshStatus = false;
          this.upRefreshStatus = false;
        }, 1500);
        break;
    }
  }

  @Builder DownRefreshBuilder(text: string, state: string) {
    Row() {
      Image($r('app.media.refreshing'))
        .width(32)
        .height(32)
      Text(text).fontSize(16)
    }
    .justifyContent(FlexAlign.Center)
    .position({
      y: state === 'down' ? 20 : -20
    })
    .zIndex(999)
    .width('94%')
    .height('8%')
  }

  private scroller: Scroller = new Scroller(); // 创建一个滚动控制器

  build() {
    Column() {
      Text($r("app.string.title_food_list"))
        .width('100%')
        .height(56)
        .padding({ left: 20 })
        .backgroundColor('#FF1f3f5')
        .fontSize(20)

      Scroll(this.scroller) {
        if(this.refreshStatus) {
          this.DownRefreshBuilder('正在刷新', 'down')
        }
        List() {
          ForEach(this.foodItems, (item: FoodInfo) => {
            ListItem() {
              if (item.letter !== undefined) {
                FoodListItem({ foodItem: item })
              } else {
                if (typeof (item) === 'string') {
                  Text(item)
                    .fontSize(14)
                    .height(48)
                    .margin({ left: 24 })
                    .width('100%')
                }
              }
            }
          })
          if(this.upRefreshStatus) {
            ListItem(){
              this.DownRefreshBuilder('正在加载', 'up')
            }
          }
        }
        .layoutWeight(1)
      }
      .scrollBar(BarState.Off)
      .edgeEffect(EdgeEffect.Spring)
      .width('100%')
      .height('90%')
      .onTouch((event?: TouchEvent) => {
        this.putDownRefresh(event);
      })
    }
  }
}

@Component
struct FoodGridItem {
  private foodItem?: FoodInfo

  build() {
    Column() {
      Image(this.foodItem!.image!)
        .objectFit(ImageFit.Contain)
        .backgroundColor('#f1f3f5')
        .width('100%')
        .height(152)
        .sharedTransition(this.foodItem!.letter, {
          duration: 400,
          curve: curves.cubicBezier(0.2, 0.2, 0.1, 1.0),
          delay: 100
        })
      Row() {
        Text(this.foodItem?.name)
          .fontSize(14)
        Blank()
        Text($r('app.string.calorie_with_kcal_unit', this.foodItem?.calories.toString()))
          .fontSize(14)
          .fontColor(0x99000000)
      }
      .padding({ left: 12, right: 12 })
      .width('100%')
      .height(32)
      .backgroundColor('#E5E5E5')
    }
    .height(184)
    .clip(new Rect({ width: '100%', height: '100%', radius: 12 }))
    .onClick(() => {
      router.pushUrl({ url: 'pages/FoodDetail', params: { foodId: this.foodItem } })
    })
  }
}

@Component
struct FoodGrid {
  @StorageProp('currentBreakpoint') currentBreakpoint: string = 'sm'
  private foodItems?: FoodInfo[]

  build() {
    Grid() {
      ForEach(this.foodItems!, (item: FoodInfo) => {
        GridItem() {
          FoodGridItem({ foodItem: item })
        }
      })
    }
    .columnsTemplate(new BreakPointType({
      sm: '1fr 1fr',
      md: '1fr 1fr 1fr',
      lg: '1fr 1fr 1fr 1fr'
    }).getValue(this.currentBreakpoint) as string)
    .columnsGap(8)
    .rowsGap(8)
    .padding({ left: 16, right: 16 })
  }
}

@Component
struct CategoryModeFoods {
  @State currentTabIndex: number = 0
  private foodItems: FoodInfo[] = getFoods()
  private foodCategories: Category[] = getFoodCategories()

  /* *
   * 头部分类导航栏
   *
   * */
  @Builder
  tabBarItemBuilder(value: Resource, index: number) {
    Text(value)
      .fontColor(this.currentTabIndex === index ? Color.Blue : 'rgba(0,0,0,0.6)')
      .fontSize(this.currentTabIndex === index ? 20 : 18)
      .fontWeight(this.currentTabIndex === index ? FontWeight.Bold : FontWeight.Normal)
      .margin({ top: 2 })
      .height(56)
  }

  build() {
    Tabs() {
      TabContent() {
        FoodGrid({ foodItems: this.foodItems })
      }.tabBar(this.tabBarItemBuilder($r('app.string.category_all'), 0))

      ForEach(this.foodCategories, (foodCategory: Category, index?: number) => {
        TabContent() {
          FoodGrid({ foodItems: this.foodItems.filter(item => (item.categoryId === foodCategory.id)) })
        }.tabBar(this.tabBarItemBuilder(foodCategory.name!,
          index! + 1))
      })
    }
    .animationDuration(0)
    .barWidth('80%')
    .onChange((index) => {
      this.currentTabIndex = index
    })
  }
}

@Component
struct FoodsDisplay {
  @State isCategoryMode: boolean = true
  @State isMoreIconOnClick: boolean = false
  @State isMoreIconOnHover: boolean = false
  @State isMoreIconOnFocus: boolean = false

  getMoreIconBgColor() {
    if (this.isMoreIconOnClick) {
      return $r('sys.color.ohos_id_color_click_effect')
    } else if (this.isMoreIconOnHover) {
      return $r('sys.color.ohos_id_color_hover')
    } else {
      return this.isCategoryMode ? Color.White : '#F1F3F5' || Color.Transparent
    }
  }

  build() {
    Stack({ alignContent: Alignment.TopEnd }) {
      if (this.isCategoryMode) {
        CategoryModeFoods()
      } else {
        ListModeFoods()
      }
      Row() {
        Image($r("app.media.ic_switch"))
          .height(24)
          .width(24)
          .margin({ left: 24, right: 24 })
          .focusable(true)
      }
      .height(56)
      .backgroundColor(this.getMoreIconBgColor())
      .stateStyles({
        focused: {
          .border({
            radius: $r('sys.float.ohos_id_corner_radius_clicked'),
            color: $r('sys.color.ohos_id_color_focused_outline'),
            style: BorderStyle.Solid
          })
        },
        normal: {
          .border({
            radius: $r('sys.float.ohos_id_corner_radius_clicked'),
            width: 0
          })
        }
      })
      .onFocus(() => this.isMoreIconOnFocus = true)
      .onBlur(() => this.isMoreIconOnFocus = false)
      .onHover((isOn) => this.isMoreIconOnHover = isOn)
      .onClick(() => {
        this.isCategoryMode = !this.isCategoryMode
      })
    }
  }
}

@Entry
@Component
struct Home {
  @State currentTabIndex: number = 0
  @StorageProp('currentBreakpoint') currentBreakpoint: string = 'sm'
  private breakpointSystem: BreakpointSystem = new BreakpointSystem()

  /* *
   * 主页和记录的tabs
   * */
  @Builder
  bottomBarItemBuilder(name: Resource, icon: Resource, index: number) {
    Flex({
      direction: new BreakPointType({
        sm: FlexDirection.Column,
        md: FlexDirection.Row,
        lg: FlexDirection.Column
      }).getValue(this.currentBreakpoint),
      justifyContent: FlexAlign.Center,
      alignItems: ItemAlign.Center
    }) {
      Image(icon)
        .height(24)
        .width(24)
        .fillColor(this.getTabBarColor(index))
      Text(name)
        .margin(new BreakPointType<Padding>({
          sm: { top: 4 },
          md: { left: 8 },
          lg: { top: 4 }
        }).getValue(this.currentBreakpoint) as Padding)
        .fontSize(11)
        .fontColor(this.getTabBarColor(index))
    }
  }

  aboutToAppear() {
    this.breakpointSystem.register()
  }

  aboutToDisappear() {
    this.breakpointSystem.unregister()
  }

  build() {
    Tabs({
      barPosition: new BreakPointType({
        sm: BarPosition.End,
        md: BarPosition.End,
        lg: BarPosition.Start
      }).getValue(this.currentBreakpoint)
    }) {
      TabContent() {
        FoodsDisplay()
      }.tabBar(this.bottomBarItemBuilder($r("app.string.tab_bar_home"), $r("app.media.ic_bottom_home"), 0))

      TabContent() {
        Records()
      }.tabBar(this.bottomBarItemBuilder($r("app.string.tab_bar_record"), $r("app.media.ic_bottom_record"), 1))

      TabContent() {
        PersonalCenter()
      }.tabBar(this.bottomBarItemBuilder($r("app.string.tab_bar_me"), $r("app.media.ic_public_me"), 2))
    }
    .vertical(new BreakPointType({ sm: false, md: false, lg: true }).getValue(this.currentBreakpoint) as boolean)
    .barWidth(new BreakPointType({ sm: '100%', md: '100%', lg: '56vp' }).getValue(this.currentBreakpoint) as string)
    .barHeight(new BreakPointType({ sm: '56vp', md: '56vp', lg: '60%' }).getValue(this.currentBreakpoint) as string)
    .animationDuration(300)
    .onChange((index) => {
      this.currentTabIndex = index
    })
  }

  private getTabBarColor(index: number) {
    return this.currentTabIndex == index ? $r('app.color.tab_bar_select_color') : $r('app.color.tab_bar_normal_color')
  }
}

6、另外一个思路实现上拉加载，下拉刷新

根据List中的回调方法onScrollIndex()监听当前列表首尾索引，根据触摸事件onTouch()处理下拉和上拉。

const TopHeight = 200;

@Entry
@Component
struct Index {
  @State list: Array<number> = []
  // 列表y坐标偏移量
  @State offsetY: number = 0
  // 按下的y坐标
  private downY = 0
  // 上一次移动的y坐标
  private lastMoveY = 0
  // 当前列表首部的索引
  private startIndex = 0
  // 当前列表尾部的索引
  private endIndex = 0

  // 下拉刷新的布局高度
  private pullRefreshHeight = 70
  // 下拉刷新文字：下拉刷新、松开刷新、正在刷新、刷新成功
  @State pullRefreshText: string= '下拉刷新'
  // 下拉刷新图标：与文字对应
  @State pullRefreshImage: Resource = $r("app.media.ic_pull_refresh_down")
  // 是否可以刷新：未达到刷新条件，收缩回去
  private isCanRefresh = false
  // 是否正在刷新：刷新中不进入触摸逻辑
  private isRefreshing: boolean = false
  // 是否已经进入了下拉刷新操作
  private isPullRefreshOperation = false

  // 上拉加载的布局默认高度
  private loadMoreHeight = 70
  // 上拉加载的布局是否显示
  @State isVisibleLoadMore: boolean = false
  // 是否可以加载更多
  private isCanLoadMore = false
  // 是否加载中：加载中不进入触摸逻辑
  private isLoading: boolean = false


  // 自定义下拉刷新布局
  @Builder CustomPullRefreshLayout(){
    Flex({ justifyContent: FlexAlign.Center, alignItems: ItemAlign.Center }) {
      Image(this.pullRefreshImage)
        .width(18)
        .height(18)

      Text(this.pullRefreshText)
        .margin({ left: 7, bottom: 1 })
        .fontSize(17)
    }
    .width('100%')
    .height(this.pullRefreshHeight)
    // 布局跟着列表偏移量移动
    .offset({ x: 0, y: `${vp2px(-this.pullRefreshHeight) + this.offsetY}px` })
  }

  // 自定义加载更多布局
  @Builder CustomLoadMoreLayout(){
    Flex({ justifyContent: FlexAlign.Center, alignItems: ItemAlign.Center }) {
      Image($r("app.media.ic_loading"))
        .width(18)
        .height(18)

      Text('加载更多中...')
        .margin({ left: 7, bottom: 1 })
        .fontSize(17)
    }
    .width('100%')
    .height(this.loadMoreHeight)
    .backgroundColor('#f4f4f4')
    .visibility(this.isVisibleLoadMore ? Visibility.Visible : Visibility.None)
  }

  // 刷新测试数据
  private refreshData(){
    this.list = []
    for (var i = 0; i < 15; i++) {
      this.list.push(i)
    }
  }

  // 加载更多测试数据
  private loadMoreData(){
    let initValue = this.list[this.list.length-1] + 1
    for (var i = initValue; i < initValue + 10; i++) {
      this.list.push(i)
    }
  }

  build() {
    Column() {
      // 下拉刷新布局
      this.CustomPullRefreshLayout()

      // 列表布局
      List() {
        ForEach(this.list, item => {
          ListItem() {
            Column() {
              Text(`Item ${item}`)
                .padding(15)
                .fontSize(18)
            }
          }
        }, item => item.toString())

        // 加载更多布局
        ListItem(){
          this.CustomLoadMoreLayout()
        }
      }
      .backgroundColor(Color.White) // 背景
      .divider({ color: '#e2e2e2', strokeWidth: 1 }) // 分割线
      .edgeEffect(EdgeEffect.None) // 去掉回弹效果
      .offset({ x: 0, y: `${this.offsetY - TopHeight}px` }) // touch事件计算的偏移量单位是px，记得加上单位
      .onScrollIndex((start, end) => { // 监听当前列表首位索引
        console.info(`${start}=start============end=${end}`)
        this.startIndex = start
        this.endIndex = end
      })

    }
    .width('100%')
    .height('100%')
    .backgroundColor('#f4f4f4')
    .onTouch((event) => this.listTouchEvent(event))// 父容器设置touch事件，当列表无数据也可以下拉刷新
    .onAppear(() => {
      this.refreshData()
    })
  }

  // 触摸事件
  listTouchEvent(event: TouchEvent){
    switch (event.type) {
      case TouchType.Down: // 手指按下
      // 记录按下的y坐标
        this.downY = event.touches[0].y
        this.lastMoveY = event.touches[0].y
        break
      case TouchType.Move: // 手指移动
      // 下拉刷新中 或 加载更多中，不进入处理逻辑
        if(this.isRefreshing || this.isLoading){
          console.info('========Move刷新中，返回=========')
          return
        }
      // 判断手势
        let isDownPull = event.touches[0].y - this.lastMoveY > 0
      // 下拉手势 或 已经进入了下拉刷新操作
        if ((isDownPull || this.isPullRefreshOperation) && !this.isCanLoadMore) {
          this.touchMovePullRefresh(event)
        } else {
          this.touchMoveLoadMore(event)
        }
        this.lastMoveY = event.touches[0].y
        break
      case TouchType.Up: // 手指抬起
      case TouchType.Cancel: // 触摸意外中断：来电界面
      // 刷新中 或 加载更多中，不进入处理逻辑
        if(this.isRefreshing || this.isLoading){
          console.info('========Up刷新中，返回=========')
          return
        }
        if (this.isPullRefreshOperation) {
          this.touchUpPullRefresh()
        } else {
          this.touchUpLoadMore()
        }
        break
    }
  }

  //============================================下拉刷新==================================================
  // 手指移动，处理下拉刷新
  touchMovePullRefresh(event:TouchEvent){
    // 当首部索引位于0
    if (this.startIndex == 0) {
      this.isPullRefreshOperation = true
      // 下拉刷新布局高度
      var height = vp2px(this.pullRefreshHeight)
      // 滑动的偏移量
      this.offsetY = event.touches[0].y - this.downY

      // 偏移量大于下拉刷新布局高度，达到刷新条件
      if (this.offsetY >= height) {
        // 状态1：松开刷新
        this.pullRefreshState(1)
        // 偏移量的值缓慢增加
        this.offsetY = height + this.offsetY * 0.15
      } else {
        // 状态0：下拉刷新
        this.pullRefreshState(0)
      }

      if (this.offsetY < 0) {
        this.offsetY = 0
        this.isPullRefreshOperation = false
      }
    }
  }

  // 手指抬起，处理下拉刷新
  touchUpPullRefresh(){
    // 是否可以刷新
    if (this.isCanRefresh) {
      console.info('======执行下拉刷新========')
      // 偏移量为下拉刷新布局高度
      this.offsetY = vp2px(this.pullRefreshHeight)
      // 状态2：正在刷新
      this.pullRefreshState(2)

      // 模拟耗时操作
      setTimeout(() => {
        this.refreshData()
        this.closeRefresh()
      }, 2000)

    } else {
      console.info('======关闭下拉刷新！未达到条件========')
      // 关闭刷新
      this.closeRefresh()
    }
  }

  // 下拉刷新状态
  // 0下拉刷新、1松开刷新、2正在刷新、3刷新成功
  pullRefreshState(state:number){
    switch (state) {
      case 0:
      // 初始状态
        this.pullRefreshText = '下拉刷新'
        this.pullRefreshImage = $r("app.media.ic_pull_refresh_down")
        this.isCanRefresh = false
        this.isRefreshing = false
        break;
      case 1:
        this.pullRefreshText = '松开刷新'
        this.pullRefreshImage = $r("app.media.ic_pull_refresh_up")
        this.isCanRefresh = true
        this.isRefreshing = false
        break;
      case 2:
        this.offsetY = vp2px(this.pullRefreshHeight)
        this.pullRefreshText = '正在刷新'
        this.pullRefreshImage = $r("app.media.ic_loading")
        this.isCanRefresh = true
        this.isRefreshing = true
        break;
      case 3:
        this.pullRefreshText = '刷新成功'
        this.pullRefreshImage = $r("app.media.ic_refresh_succeed")
        this.isCanRefresh = true
        this.isRefreshing = true
        break;
    }
  }

  // 关闭刷新
  closeRefresh() {
    // 如果允许刷新，延迟进入，为了显示刷新中
    setTimeout(() => {
      var delay = 50
      if (this.isCanRefresh) {
        // 状态3：刷新成功
        this.pullRefreshState(3)
        // 为了显示刷新成功，延迟执行收缩动画
        delay = 500
      }
      animateTo({
        duration: 150, // 动画时长
        delay: delay, // 延迟时长
        onFinish: () => {
          // 状态0：下拉刷新
          this.pullRefreshState(0)
          this.isPullRefreshOperation = false
        }
      }, () => {
        this.offsetY = 0
      })
    }, this.isCanRefresh ? 500 : 0)
  }

  //============================================加载更多==================================================
  // 手指移动，处理加载更多
  touchMoveLoadMore(event:TouchEvent) {
    // 因为加载更多是在列表后面新增一个item，当一屏能够展示全部列表，endIndex 为 length+1
    if (this.endIndex == this.list.length - 1 || this.endIndex == this.list.length) {
      // 滑动的偏移量
      this.offsetY = event.touches[0].y - this.downY
      if (Math.abs(this.offsetY) > vp2px(this.loadMoreHeight)/2) {
        // 可以刷新了
        this.isCanLoadMore = true
        // 显示加载更多布局
        this.isVisibleLoadMore = true
        // 偏移量缓慢增加
        this.offsetY = - vp2px(this.loadMoreHeight) + this.offsetY * 0.1
      }
    }
  }

  // 手指抬起，处理加载更多
  touchUpLoadMore() {
    animateTo({
      duration: 200, // 动画时长
    }, () => {
      // 偏移量设置为0
      this.offsetY = 0
    })
    if (this.isCanLoadMore) {
      console.info('======执行加载更多========')
      // 加载中...
      this.isLoading = true
      // 模拟耗时操作
      setTimeout(() => {
        this.closeLoadMore()
        this.loadMoreData()
      }, 2000)
    } else {
      console.info('======关闭加载更多！未达到条件========')
      this.closeLoadMore()
    }
  }

  // 关闭加载更多
  closeLoadMore() {
    this.isCanLoadMore = false
    this.isLoading = false
    this.isVisibleLoadMore = false
  }

}