Scroll

The <Scroll> component scrolls the content when the layout size of a component exceeds the size of its parent component.

NOTE

• This component is supported since API version 7. Updates will be marked with a superscript to indicate their earliest API version.
• When nesting a <List> within this component, specify the width and height for the <List> under scenarios where consistently high performance is required. If the width and height are not specified, this component will load all content of the <List>.
• This component can scroll only when the size on the main axis is less than the content size.
• This component can produce a bounce effect only when there is more than one screen of content.

Child Components

This component supports only one child component.

APIs

Scroll(scroller?: Scroller)

Parameters

Attributes

In addition to the universal attributes, the following attributes are supported.

ScrollDirection

ScrollSnapOptions¹⁰⁺

Events

NOTE

If the onScrollFrameBegin event and scrollBy method are used to implement nested scrolling, set the edgeEffect attribute of the scrollable child component to None. For example, if a <List> is nested in the <Scroll> component, edgeEffect of the <List> must be set to EdgeEffect.None.

Scroller

Implements a controller for a scrollable container component. You can bind this component to a container component and use it to control the scrolling of that component. One controller can control only one container component. The supported container components are <List>, <Scroll>, <ScrollBar>, <Grid>, and <WaterFlow>.

Objects to Import

scroller: Scroller = new Scroller()

scrollTo

scrollTo(value: { xOffset: number | string, yOffset: number | string, animation?: { duration?: number, curve?: Curve | ICurve } | boolean }): void

Scrolls to the specified position.

Parameters

scrollEdge

scrollEdge(value: Edge): void

Scrolls to the edge of the container, regardless of the scroll axis direction. Edge.Top and Edge.Start produce the same effect, and Edge.Bottom and Edge.End produce the same effect.

Parameters

scrollPage⁹⁺

scrollPage(value: { next: boolean }): void

Scrolls to the next or previous page.

Parameters

scrollPage^(deprecated)

scrollPage(value: { next: boolean, direction?: Axis }): void

Scrolls to the next or previous page. This API is deprecated since API version 9. You are advised to use scrollPage⁹⁺ instead.

Parameters

currentOffset

currentOffset(): OffsetResult

scrollToIndex

scrollToIndex(value: number, smooth?: boolean, align?: ScrollAlign): void

Scrolls to the item with the specified index.

When smooth is set to true, all passed items are loaded and counted in layout calculation. This may result in performance issues if a large number of items are involved.

NOTE

This API only works for the <Grid>, <List>, and <WaterFlow> components.

Parameters

scrollBy⁹⁺

scrollBy(dx: Length, dy: Length): void

Scrolls by the specified amount.

NOTE

This API is available for the <Scroll>, <List>, <Grid>, and <WaterFlow> components.

Parameters

isAtEnd¹⁰⁺

isAtEnd(): boolean

Checks whether the component has scrolled to the bottom.

NOTE

This API is available for the <Scroll>, <List>, <Grid>, and <WaterFlow> components.

Return value

getItemRect¹¹⁺

getItemRect(index: number): RectResult

Obtains the size and position of a child component.

NOTE

This API is available for the <Scroll>, <List>, <Grid>, and <WaterFlow> components.

Parameters

NOTE

• The value of index must be the index of a child component visible in the display area. Otherwise, the value is considered invalid.
• The size and position returned for an invalid value are both 0.

Return value

OffsetResult¹¹⁺

ScrollAlign¹⁰⁺

NestedScrollOptions¹⁰⁺

NestedScrollMode¹⁰⁺

EdgeEffectOptions¹¹⁺

Example

Example 1

// xxx.ets
import Curves from '@ohos.curves'

@Entry
@Component
struct ScrollExample {
  scroller: Scroller = new Scroller()
  private arr: number[] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

  build() {
    Stack({ alignContent: Alignment.TopStart }) {
      Scroll(this.scroller) {
        Column() {
          ForEach(this.arr, (item: number) => {
            Text(item.toString())
              .width('90%')
              .height(150)
              .backgroundColor(0xFFFFFF)
              .borderRadius(15)
              .fontSize(16)
              .textAlign(TextAlign.Center)
              .margin({ top: 10 })
          }, (item: string) => item)
        }.width('100%')
      }
      .scrollable(ScrollDirection.Vertical) // The scrollbar scrolls in the vertical direction.
      .scrollBar(BarState.On) // The scrollbar is always displayed.
      .scrollBarColor(Color.Gray) // The scrollbar color is gray.
      .scrollBarWidth(10) // The scrollbar width is 10.
      .friction(0.6)
      .edgeEffect(EdgeEffect.None)
      .onScroll((xOffset: number, yOffset: number) => {
        console.info(xOffset + ' ' + yOffset)
      })
      .onScrollEdge((side: Edge) => {
        console.info('To the edge')
      })
      .onScrollStop(() => {
        console.info('Scroll Stop')
      })

      Button('scroll 150')
        .height('5%')
        .onClick(() => { // Click to scroll down by 150.0 vp.
          this.scroller.scrollBy(0, 150)
        })
        .margin({ top: 10, left: 20 })
      Button('scroll 100')
        .height('5%')
        .onClick(() => { // Click to scroll down by 100.0 vp.
          const yOffset: number = this.scroller.currentOffset().yOffset;
          this.scroller.scrollTo({ xOffset: 0, yOffset: yOffset + 100 })
        })
        .margin({ top: 60, left: 20 })
      Button('scroll 100')
        .height('5%')
        .onClick(() => {// Click to scroll down by 100.0 vp. An animation is applied to the scrolling.
          let curve = Curves.interpolatingSpring(10, 1, 228, 30) // Create a step curve.
          const yOffset: number = this.scroller.currentOffset().yOffset;
          this.scroller.scrollTo({ xOffset: 0, yOffset: yOffset + 100, animation: { duration: 1000, curve: curve } })
        })
        .margin({ top: 110, left: 20 })
      Button('back top')
        .height('5%')
        .onClick(() => { // Click to go back to the top.
          this.scroller.scrollEdge(Edge.Top)
        })
        .margin({ top: 160, left: 20 })
      Button('next page')
        .height('5%')
        .onClick(() => { // Click to go to the next page.
          this.scroller.scrollPage({ next: true })
        })
        .margin({ top: 210, left: 20 })
    }.width('100%').height('100%').backgroundColor(0xDCDCDC)
  }
}

Example 2

@Entry
@Component
struct NestedScroll {
  @State listPosition: number = 0; // 0 indicates scrolling to the top of the list, 1 indicates scrolling to the middle of the list, and 2 indicates scrolling to the bottom of the list.
  private arr: number[] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  private scrollerForScroll: Scroller = new Scroller()
  private scrollerForList: Scroller = new Scroller()

  build() {
    Flex() {
      Scroll(this.scrollerForScroll) {
        Column() {
          Text("Scroll Area")
            .width("100%")
            .height("40%")
            .backgroundColor(0X330000FF)
            .fontSize(16)
            .textAlign(TextAlign.Center)
            .onClick(() => {
              this.scrollerForList.scrollToIndex(5)
            })

          List({ space: 20, scroller: this.scrollerForList }) {
            ForEach(this.arr, (item: number) => {
              ListItem() {
                Text("ListItem" + item)
                  .width("100%")
                  .height("100%")
                  .borderRadius(15)
                  .fontSize(16)
                  .textAlign(TextAlign.Center)
                  .backgroundColor(Color.White)
              }.width("100%").height(100)
            }, (item: string) => item)
          }
          .width("100%")
          .height("50%")
          .edgeEffect(EdgeEffect.None)
          .friction(0.6)
          .onReachStart(() => {
            this.listPosition = 0
          })
          .onReachEnd(() => {
            this.listPosition = 2
          })
          .onScrollFrameBegin((offset: number) => {
            if ((this.listPosition == 0 && offset <= 0) || (this.listPosition == 2 && offset >= 0)) {
              this.scrollerForScroll.scrollBy(0, offset)
              return { offsetRemain: 0 }
            }
            this.listPosition = 1
            return { offsetRemain: offset };
          })

          Text("Scroll Area")
            .width("100%")
            .height("40%")
            .backgroundColor(0X330000FF)
            .fontSize(16)
            .textAlign(TextAlign.Center)
        }
      }
      .width("100%").height("100%")
    }.width('100%').height('100%').backgroundColor(0xDCDCDC).padding(20)
  }
}

Example 3

@Entry
@Component
struct StickyNestedScroll {
  @State arr: number[] = []

  @Styles
  listCard() {
    .backgroundColor(Color.White)
    .height(72)
    .width("100%")
    .borderRadius(12)
  }

  build() {
    Scroll() {
      Column() {
        Text("Scroll Area")
          .width("100%")
          .height("40%")
          .backgroundColor('#0080DC')
          .textAlign(TextAlign.Center)
        Tabs({ barPosition: BarPosition.Start }) {
          TabContent() {
            List({ space: 10 }) {
              ForEach(this.arr, (item: number) => {
                ListItem() {
                  Text("item" + item)
                    .fontSize(16)
                }.listCard()
              }, (item: string) => item)
            }.width("100%")
            .edgeEffect(EdgeEffect.Spring)
            .nestedScroll({
              scrollForward: NestedScrollMode.PARENT_FIRST,
              scrollBackward: NestedScrollMode.SELF_FIRST
            })
          }.tabBar("Tab1")

          TabContent() {
          }.tabBar("Tab2")
        }
        .vertical(false)
        .height("100%")
      }.width("100%")
    }
    .edgeEffect(EdgeEffect.Spring)
    .friction(0.6)
    .backgroundColor('#DCDCDC')
    .scrollBar(BarState.Off)
    .width('100%')
    .height('100%')
  }

  aboutToAppear() {
    for (let i = 0; i < 30; i++) {
      this.arr.push(i)
    }
  }
}

Example 4

@Entry
@Component
struct Index {
  scroller: Scroller = new Scroller;
  private arr: number[] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
  build() {
    Scroll(this.scroller) {
      Column() {
        ForEach(this.arr, (item: number) => {
          Text(item.toString())
            .width('90%')
            .height(200)
            .backgroundColor(0xFFFFFF)
            .borderWidth(1)
            .borderColor(Color.Black)
            .borderRadius(15)
            .fontSize(16)
            .textAlign(TextAlign.Center)
        }, (item: string) => item)
      }.width('100%').backgroundColor(0xDCDCDC)
    }
    .backgroundColor(Color.Yellow)
    .height('100%')
    .edgeEffect(EdgeEffect.Spring)
    .scrollSnap({snapAlign:ScrollSnapAlign.START, snapPagination:400, enableSnapToStart:true, enableSnapToEnd:true})
  }
}