ts-container-scroll.md

# Scroll


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


## 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
  | 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 } | Called 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: number, yOffset: number) =&gt; void | Invoked when scrolling starts. It returns the horizontal and vertical offsets. |
| onScrollEdge(side: Edge) =&gt; void | Invoked when scrolling reaches the edge. |
| onScrollEnd() =&gt; void | Invoked when scrolling stops. |

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

## Scroller

Controller of the scrollable container component. You can bind this component to the container component and use it to control the scrolling of the container 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: number,<br>curve: Curve \|<br>CubicBezier \|<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. |


### 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 the value **false** means to scroll to the previous page. |
  | direction | Axis    | No   | -    | Scrolling direction: horizontal or vertical.               |


### currentOffset

scroller.currentOffset(): Object


Obtains the scrolling offset.


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


### scroller.scrollToIndex

scroller.scrollToIndex(value: number): void


Scrolls to 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)