ts-container-scroll.md

# Scroll

>  **NOTE**
> - This component is supported since API version 7. Updates will be marked with a superscript to indicate their earliest API version.
> - When a **\<List>** is nested in this component, you are advised to specify the width and height of 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>**.


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


## Required Permissions

None.


## Child Components

This component supports only one child component.


## APIs

Scroll(scroller?: Scroller)


## Attributes

| Name            | Type                                    | Default Value                     | Description       |
| -------------- | ---------------------------------------- | ------------------------ | --------- |
| scrollable     | ScrollDirection                          | ScrollDirection.Vertical | Scroll method.  |
| scrollBar      | [BarState](ts-appendix-enums.md#barstate-enums)| ScrollDirection.Auto     | Scrollbar status. |
| scrollBarColor | Color                                    | -                        | Color of the scrollbar.|
| scrollBarWidth | Length                                   | -                        | Width of the scrollbar.|

- ScrollDirection enums
  | Name        | Description        |
  | ---------- | ---------- |
  | Horizontal | Only horizontal scrolling is supported.|
  | Vertical   | Only vertical scrolling is supported.|
  | None       | Scrolling is disabled.     |

## Events

| Name                                      | Description                         |
| ---------------------------------------- | ----------------------------- |
| onScrollBegin<sup>9+</sup>(dx: number, dy: number)&nbsp;=&gt;&nbsp;{ dxRemain: number, dyRemain: number } | Invoked when scrolling starts.<br>Parameters:<br>- **dx**: amount to scroll by in the horizontal direction.<br>- **dy**: amount to scroll by in the vertical direction.<br>Return value:<br>- **dxRemain**: remaining amount to scroll by in the horizontal direction.<br>- **dyRemain**: remaining amount to scroll by in the vertical direction.|
| onScroll(xOffset:&nbsp;number,&nbsp;yOffset:&nbsp;number)&nbsp;=&gt;&nbsp;void | Invoked to return the horizontal and vertical offsets during scrolling when the specified scroll event occurs.|
| onScrollEdge(side:&nbsp;Edge)&nbsp;=&gt;&nbsp;void | Invoked when scrolling reaches the edge.                   |
| onScrollEnd()&nbsp;=&gt;&nbsp;void       | Invoked when scrolling stops.                    |

>  **NOTE**
> If the **onScrollBegin** event and **scrollBy** API are used to implement nested scrolling, you must set **edgeEffect** of the scrolling child node to **None**. For example, if a **\<List>** is nested in the **\<Scroll>** component, the **edgeEffect** attribute of the **\<List>** must be set to **EdgeEffect.None**.

## Scroller

Controller of the scrollable container component. You can bind this component to a container component and use it to control the scrolling of that component. Currently, this component can be bound to the **\<List>** and **\<Scroll>** components.


### Objects to Import

```
scroller: Scroller = new Scroller()
```


### scrollTo

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


Scrolls to the specified position.


- Parameters
  | Name      | Type                                    | Mandatory  | Default Value | Description                                    |
  | --------- | ---------------------------------------- | ---- | ---- | ---------------------------------------- |
  | xOffset   | Length                                   | Yes   | -    | Horizontal scrolling offset.                                 |
  | yOffset   | Length                                   | Yes   | -    | Vertical scrolling offset.                                 |
  | animation | {<br>duration:&nbsp;number,<br>curve:&nbsp;[Curve](ts-animatorproperty.md)&nbsp;\|<br>CubicBezier&nbsp;\|<br>SpringCurve<br>} | No   |      | Animation configuration, which includes the following:<br>- **duration**: scrolling duration.<br>- **curve**: scrolling curve.|


### scrollEdge

scrollEdge(value: Edge): void


Scrolls to the edge of the container.


- Parameters
  | Name  | Type| Mandatory  | Default Value | Description     |
  | ----- | ---- | ---- | ---- | --------- |
  | value | Edge | Yes   | -    | Edge position to scroll to.|

- Edge enums

  | Name  | Value  | Description      |
  | ------ | ---- | ---------- |
  | Top    | 0    | Top edge.|
  | Bottom | 2    | Bottom edge.|

  

### scrollPage

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

Scrolls to the next or previous page.

- Parameters
  | Name      | Type   | Mandatory  | Default Value | Description                          |
  | --------- | ------- | ---- | ---- | ------------------------------ |
  | next      | boolean | Yes   | -    | Whether to turn to the next page. The value **true** means to scroll to the next page, and **false** means to scroll to the previous page.|
  | direction | Axis    | No   | -    | Scrolling direction: horizontal or vertical.               |


### currentOffset

currentOffset(): Object


Obtains the scrolling offset.


- Return value
  | Type                                                    | Description                                                  |
  | ------------------------------------------------------- | ------------------------------------------------------------ |
  | {<br>xOffset:&nbsp;number,<br>yOffset:&nbsp;number<br>} | **xOffset**: horizontal scrolling offset.<br>**yOffset**: vertical scrolling offset. |


### scrollToIndex

scrollToIndex(value: number): void


Scrolls to the item with the specified index.


>  **NOTE**
> Only the **\<List>** component is supported.


- Parameters
  | Name  | Type  | Mandatory  | Default Value | Description             |
  | ----- | ------ | ---- | ---- | ----------------- |
  | value | number | Yes   | -    | Index of the item to be scrolled to in the list.|


### scrollBy

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


Scrolls by the specified amount.


>  **NOTE**
> Only the **\<Scroll>** component is supported.


- Parameters
  | Name  | Type  | Mandatory  | Default Value | Description             |
  | ----- | ------ | ---- | ---- | ----------------- |
  | dx | Length | Yes   | -    | Amount to scroll by in the horizontal direction.|
  | dy | Length | Yes   | -    | Amount to scroll by in the vertical direction.|


## Example

```ts
// xxx.ets
@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) => {
            Text(item.toString())
              .width('90%')
              .height(150)
              .backgroundColor(0xFFFFFF)
              .borderRadius(15)
              .fontSize(16)
              .textAlign(TextAlign.Center)
              .margin({ top: 10 })
          }, item => item)
        }.width('100%')
      }
      .scrollable(ScrollDirection.Vertical)
      .scrollBar(BarState.On)
      .scrollBarColor(Color.Gray)
      .scrollBarWidth(30)
      .onScroll((xOffset: number, yOffset: number) => {
        console.info(xOffset + ' ' + yOffset)
      })
      .onScrollEdge((side: Edge) => {
        console.info('To the edge')
      })
      .onScrollEnd(() => {
        console.info('Scroll Stop')
      })

      Button('scroll 100')
        .onClick(() => { // Click to scroll down 100.0.
          this.scroller.scrollTo({ xOffset: 0, yOffset: this.scroller.currentOffset().yOffset + 100 })
        })
        .margin({ top: 10, left: 20 })
      Button('back top')
        .onClick(() => { // Click to go back to the top.
          this.scroller.scrollEdge(Edge.Top)
        })
        .margin({ top: 60, left: 20 })
      Button('next page')
        .onClick(() => { // Click to scroll down to the bottom.
          this.scroller.scrollPage({ next: true })
        })
        .margin({ top: 110, left: 20 })
    }.width('100%').height('100%').backgroundColor(0xDCDCDC)
  }
}
```

![en-us_image_0000001256978363](figures/en-us_image_0000001256978363.gif)


```ts
@Entry
@Component
struct NestedScroll {
  @State listPosition: number = 0 // 0 indicates scrolling to the top of the list, 1 indicates scrolling to the center 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 scroller: Scroller = new Scroller()

  build() {
    Flex() {
      Scroll(this.scroller) {
        Column() {
          Text("Scroll Area")
            .width("100%").height("40%").backgroundColor(0X330000FF)
            .fontSize(16).textAlign(TextAlign.Center)

          List({ space: 20 }) {
            ForEach(this.arr, (item) => {
              ListItem() {
                Text("ListItem" + item)
                  .width("100%").height("100%").borderRadius(15)
                  .fontSize(16).textAlign(TextAlign.Center).backgroundColor(Color.White)
              }.width("100%").height(100)
            }, item => item)
          }
          .width("100%").height("50%").edgeEffect(EdgeEffect.None)
          .onReachStart(() => {
            this.listPosition = 0
          })
          .onReachEnd(() => {
            this.listPosition = 2
          })
          .onScrollBegin((dx: number, dy: number) => {
            if ((this.listPosition == 0 && dy >= 0) || (this.listPosition == 2 && dy <= 0)) {
              this.scroller.scrollBy(0, -dy)
              return { dxRemain: dx, dyRemain: 0 }
            }
            this.listPosition = 1;
            return { dxRemain: dx, dyRemain: dy }
          })

          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)
  }
}
```

![NestedScroll](figures/NestedScroll.gif)