# FolderStack

The **FolderStack** component extends the **Stack** component by adding the hover feature for foldable devices. With the **upperItems** parameter set, it can automatically avoid the crease area of the foldable device and move the content to the upper half screen.

>  **NOTE**
>
>  This component is supported since API version 11. Updates will be marked with a superscript to indicate their earliest API version.


## Child Components

Multiple child components are supported.


## APIs

FolderStack(options?: FolderStackOptions)

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

**Parameters**

| Name      | Type                                   | Mandatory| Description                                                                |
| ------------ | ------------------------------------------- | ---- |----------------------------------------------------------------------|
| options |  [FolderStackOptions](#folderstackoptions14) | No  | Configuration of the **FolderStack** component.|

## FolderStackOptions<sup>14+</sup>

**Atomic service API**: This API can be used in atomic services since API version 14.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

| Name      | Type        | Mandatory| Description                      |
| ------------ | -------------------------- | ---- |----------------------------|
| upperItems |    Array<string\>  | No  | Configuration of the **FolderStack** component.<br>**upperItems**: array of IDs of child components that will be moved to the upper half screen in the hover state. On hover, child components with IDs in this array automatically shift away from the folding screen's crease area and move to the upper half screen, while other components are stacked in the lower half screen.|

## Attributes

In addition to the [universal attributes](ts-universal-attributes-size.md), the following attributes are supported.

### alignContent

alignContent(value: Alignment)

Alignment of child components in the container. When both this attribute and the universal attribute [align](ts-universal-attributes-location.md) are set, whichever is set last takes effect.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

**Parameters**

| Name| Type                                       | Mandatory| Description                                                   |
| ------ | ------------------------------------------- | ---- | ------------------------------------------------------- |
| value  | [Alignment](ts-appendix-enums.md#alignment) | Yes  | Alignment of child components in the container.<br>Default value: **Alignment.Center**|

### enableAnimation

enableAnimation(value: boolean)

Whether to enable the default animation.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

**Parameters**

| Name| Type                                       | Mandatory| Description                               |
| ------ | ------------------------------------------- | ---- | ----------------------------------- |
| value  | boolean | Yes  | Whether to enable the default animation.<br>Default value: **true**|

### autoHalfFold

autoHalfFold(value: boolean)

Sets whether to enable auto rotation. This attribute is effective only when auto rotation is disabled in device system settings.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

**Parameters**

| Name| Type   | Mandatory| Description                               |
| ------ | ------- | ---- | ----------------------------------- |
| value  | boolean | Yes  | Whether to enable auto rotation.<br>Default value: **true**|

>  **NOTE**
>
>  Setting the **offset** and **margin** attributes may cause the upper and lower half screens to block the crease area. Therefore, avoid setting these attributes with this component.

## Events

In addition to the [universal events](ts-universal-events-click.md), the following events are supported.

### onFolderStateChange

onFolderStateChange(callback: OnFoldStatusChangeCallback)

Called when the folding state changes. This API takes effect only in landscape mode.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

**Parameters**

| Name    | Type                                           | Mandatory| Description                |
| ---------- | ----------------------------------------------- | ---- | -------------------- |
| callback | [OnFoldStatusChangeCallback](#onfoldstatuschangecallback14) | Yes  | Current fold state of the device.|


### onHoverStatusChange<sup>12+</sup>

onHoverStatusChange(handler: OnHoverStatusChangeCallback)

Invoked when the hover status changes.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

**Parameters**

| Name    | Type                                           | Mandatory| Description                |
| ---------- | ----------------------------------------------- | ---- | -------------------- |
| handler | [OnHoverStatusChangeCallback](#onhoverstatuschangecallback14) | Yes  | Callback invoked when the hover status changes.|

## OnHoverStatusChangeCallback<sup>14+</sup>

type OnHoverStatusChangeCallback = (param: HoverEventParam) => void

Callback invoked when the hover status changes.

**Atomic service API**: This API can be used in atomic services since API version 14.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

| Name    | Type                                           | Mandatory| Description                |
| ---------- | ----------------------------------------------- | ---- | -------------------- |
| param | [HoverEventParam](#hovereventparam12) | Yes  | Callback invoked when the hover status changes.|

## OnFoldStatusChangeCallback<sup>14+</sup>

type OnFoldStatusChangeCallback = (event: OnFoldStatusChangeInfo) => void

Current fold state of the device.

**Atomic service API**: This API can be used in atomic services since API version 14.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

| Name    | Type                                           | Mandatory| Description                |
| ---------- | ----------------------------------------------- | ---- | -------------------- |
| callback | [OnFoldStatusChangeInfo](#onfoldstatuschangeinfo14) | Yes  | Current fold state of the device.|


## OnFoldStatusChangeInfo<sup>14+</sup>

Called when the folding state changes. This API takes effect only in landscape mode.

**Atomic service API**: This API can be used in atomic services since API version 14.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

| Name    | Type                                           | Mandatory| Description                |
| ---------- | ----------------------------------------------- | ---- | -------------------- |
| foldStatus | [FoldStatus](ts-appendix-enums.md#foldstatus11) | Yes  | Current fold state of the device.|

## HoverEventParam<sup>12+</sup>

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

| Name             | Type                                                         | Mandatory| Description        |
|------------------|-------------------------------------------------------------| --- |------------|
| foldStatus       | [FoldStatus](ts-appendix-enums.md#foldstatus11)             | Yes  | Current fold state of the device.|
| isHoverMode      | boolean                                                     | Yes  | Whether the device is in hover state. |
| appRotation      | [AppRotation](ts-appendix-enums.md#approtation12)           | Yes  | Current orientation.   |
| windowStatusType | [WindowStatusType<sup>12+</sup>](#windowstatustype12) | Yes  | Window mode.   |

## WindowStatusType<sup>12+</sup>

type WindowStatusType = WindowStatusType

Enumerates the window modes.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

| Type       | Description                |
| ---------- | ---------------------|
| [WindowStatusType](../js-apis-window.md#windowstatustype11)  | Window mode.|


## Example

This example implements the foldable device hover capability.

```ts
@Entry
@Component
struct Index {
  @State len_wid: number = 480
  @State w: string = "40%"

  build() {
    Column() {
      // Set upperItems to IDs of the child components to be moved to the upper half screen in the hover state. Other components are stacked in the lower half screen.
      FolderStack({ upperItems: ["upperitemsId"] }) {
        // This column is automatically moved up to the upper half screen.
        Column() {
          Text("video zone").height("100%").width("100%").textAlign(TextAlign.Center).fontSize(25)
        }.backgroundColor('rgb(0, 74, 175)').width("100%").height("100%").id("upperitemsId")

        // The following two columns are stacked in the lower half screen.
        Column() {
          Text("video title")
            .width("100%")
            .height(50)
            .textAlign(TextAlign.Center)
            .backgroundColor('rgb(213, 213, 213)')
            .fontSize(25)
        }.width("100%").height("100%").justifyContent(FlexAlign.Start)

        Column() {
          Text("video bar ")
            .width("100%")
            .height(50)
            .textAlign(TextAlign.Center)
            .backgroundColor('rgb(213, 213, 213)')
            .fontSize(25)
        }.width("100%").height("100%").justifyContent(FlexAlign.End)
      }
      .backgroundColor('rgb(39, 135, 217)')
      // Set whether to enable animation.
      .enableAnimation(true)
      // Set whether to enable auto-rotate.
      .autoHalfFold(true)
      // Called when the folding status changes.
      .onFolderStateChange((msg) => {
        if (msg.foldStatus === FoldStatus.FOLD_STATUS_EXPANDED) {
          console.info("The device is currently in the expanded state")
        } else if (msg.foldStatus === FoldStatus.FOLD_STATUS_HALF_FOLDED) {
          console.info("The device is currently in the half folded state")
        } else {
          // .............
        }
      })
      // The hoverStatusChange callback is invoked when the hover status changes.
      .onHoverStatusChange((msg) => {
        console.log('this foldStatus:' + msg.foldStatus);
        console.log('this isHoverMode:' + msg.isHoverMode);
        console.log('this appRotation:' + msg.appRotation);
        console.log('this windowStatusType:' + msg.windowStatusType);
      })
      // If the folderStack component does not occupy the full screen, it is used as a common stack.
      .alignContent(Alignment.Bottom)
      .height("100%")
      .width("100%")
      .backgroundColor('rgb(39, 135, 217)')

    }
    .height("100%")
    .width("100%")
    .borderWidth(1)
    .borderColor('rgb(213, 213, 213)')
    .backgroundColor('rgb(0, 74, 175)')
    .expandSafeArea([SafeAreaType.SYSTEM], [SafeAreaEdge.BOTTOM])
  }
}
```
**Figure 1** Expanded state in landscape mode
<br> ![FolderStack01.png](figures/FolderStack01.png)
<br> **Figure 2** Half-folded state in landscape mode
<br> ![FolderStack02.png](figures/FolderStack02.png)