@ohos.arkui.dragController (DragController)

The dragController module provides APIs for initiating drag actions. When receiving a gesture event, such as a touch or long-press event, an application can initiate a drag action and carry drag information therein.

NOTE

The initial APIs of this module are supported since API version 10. Newly added APIs will be marked with a superscript to indicate their earliest API version. The functionality of this module depends on UI context. This means that the APIs of this module cannot be used where the UI context is unclear. For details, see UIContext. Since API version 10, you can use the getDragController API in UIContext to obtain the DragController object associated with the current UI context. You can preview how this component looks on a real device, but not in DevEco Studio Previewer.

Modules to Import

import dragController from "@ohos.arkui.dragController";

dragController.executeDrag

executeDrag(custom: CustomBuilder | DragItemInfo, dragInfo: DragInfo, callback: AsyncCallback< {event: DragEvent, extraParams: string}>): void

Initiates a drag action, with the object to be dragged and the drag information passed in. This API uses an asynchronous callback to return the result.

System capability: SystemCapability.ArkUI.ArkUI.Full

Parameters

Error codes

Example

import dragController from "@ohos.arkui.dragController"
import UDC from '@ohos.data.unifiedDataChannel';

@Entry
@Component
struct DragControllerPage {
  @Builder DraggingBuilder() {
    Column() {
      Text("DraggingBuilder")
    }
    .width(100)
    .height(100)
    .backgroundColor(Color.Blue)
  }

  build() {
    Column() {
      Button('touch to execute drag')
        .onTouch((event?:TouchEvent) => {
          if(event){
            if (event.type == TouchType.Down) {
              let text = new UDC.Text()
              let unifiedData = new UDC.UnifiedData(text)

              let dragInfo: dragController.DragInfo = {
                pointerId: 0,
                data: unifiedData,
                extraParams: ''
              }
              class tmp{
                event:DragEvent|undefined = undefined
                extraParams:string = ''
              }
              let eve:tmp = new tmp()
              dragController.executeDrag(()=>{this.DraggingBuilder()}, dragInfo, (err, eve) => {
                if(eve.event){
                  if (eve.event.getResult() == DragResult.DRAG_SUCCESSFUL) {
                  // ...
                  } else if (eve.event.getResult() == DragResult.DRAG_FAILED) {
                  // ...
                  }
                }
              })
            }
          }
        })
    }
  }
}

dragController.executeDrag

executeDrag(custom: CustomBuilder | DragItemInfo, dragInfo: DragInfo): Promise<{event: DragEvent, extraParams: string}>

Initiates a drag action, with the object to be dragged and the drag information passed in. This API uses a promise to return the result.

System capability: SystemCapability.ArkUI.ArkUI.Full

Parameters

Return value

Error codes

Example

import dragController from "@ohos.arkui.dragController"
import componentSnapshot from '@ohos.arkui.componentSnapshot';
import image from '@ohos.multimedia.image';
import UDC from '@ohos.data.unifiedDataChannel';

@Entry
@Component
struct DragControllerPage {
  @State pixmap: image.PixelMap|null = null

  @Builder DraggingBuilder() {
    Column() {
      Text("DraggingBuilder")
    }
    .width(100)
    .height(100)
    .backgroundColor(Color.Blue)
  }

  @Builder PixmapBuilder() {
    Column() {
      Text("PixmapBuilder")
    }
    .width(100)
    .height(100)
    .backgroundColor(Color.Blue)
  }

  build() {
    Column() {
      Button('touch to execute drag')
        .onTouch((event?:TouchEvent) => {
          if(event){
            if (event.type == TouchType.Down) {
              let text = new UDC.Text()
              let unifiedData = new UDC.UnifiedData(text)

              let dragInfo: dragController.DragInfo = {
                pointerId: 0,
                data: unifiedData,
                extraParams: ''
              }
              let pb:CustomBuilder = ():void=>{this.PixmapBuilder()}
              componentSnapshot.createFromBuilder(pb).then((pix: image.PixelMap) => {
                this.pixmap = pix;
                let dragItemInfo: DragItemInfo = {
                  pixelMap: this.pixmap,
                  builder: ()=>{this.DraggingBuilder()},
                  extraInfo: "DragItemInfoTest"
                }

                class tmp{
                  event:DragResult|undefined = undefined
                  extraParams:string = ''
                }
                let eve:tmp = new tmp()
                dragController.executeDrag(dragItemInfo, dragInfo)
                  .then((eve) => {
                    if (eve.event.getResult() == DragResult.DRAG_SUCCESSFUL) {
                      // ...
                    } else if (eve.event.getResult() == DragResult.DRAG_FAILED) {
                      // ...
                    }
                  })
                  .catch((err:Error) => {
                  })
              })
            }
          }
        })
    }
    .width('100%')
    .height('100%')
  }
}

DragInfo

System capability: SystemCapability.ArkUI.ArkUI.Full

Defines the attributes required for initiating a drag action and information carried in the dragging process.

DragStatus¹¹⁺

System capability: SystemCapability.ArkUI.ArkUI.Full

Describes the dragging start and end states.

DragAndDropInfo¹¹⁺

System capability: SystemCapability.ArkUI.ArkUI.Full

Provides the data reported when the state changes during dragging.

DragAction¹¹⁺

Implements a DragAction object to subscribe to drag state changes and start the drag service.

System capability: SystemCapability.ArkUI.ArkUI.Full

startDrag¹¹⁺

startDrag(): Promise<void>

Starts the drag service. This API uses a promise to return the result.

System capability: SystemCapability.ArkUI.ArkUI.Full

Error codes

Example

import dragController from "@ohos.arkui.dragController"
import UDC from '@ohos.data.unifiedDataChannel';
let customBuilders:Array<CustomBuilder | DragItemInfo> = new Array<CustomBuilder | DragItemInfo>();
let text = new UDC.Text()
let unifiedData = new UDC.UnifiedData(text)
let dragInfo: dragController.DragInfo = {
  pointerId: 0,
  data: unifiedData,
  extraParams: ''
}
try{
  let dragAction: dragController.DragAction | null = dragController.createDragAction(customBuilders, dragInfo);
  if(!dragAction){
    console.log("listener dragAction is null");
    return
  }
  dragAction.startDrag().then(()=>{}).catch((err:Error)=>{
    console.log("start drag Error:" + err.message);
  })
}catch(err) {
  console.log("create dragAction Error:" + err.message);
}

on('statusChange')¹¹⁺

on(type: 'statusChange', callback: Callback<DragAndDropInfo>): void

Subscribes to drag state changes.

System capability: SystemCapability.ArkUI.ArkUI.Full

Parameters

Example

import dragController from "@ohos.arkui.dragController"
import UDC from '@ohos.data.unifiedDataChannel';
let customBuilders:Array<CustomBuilder | DragItemInfo> = new Array<CustomBuilder | DragItemInfo>();
let text = new UDC.Text()
let unifiedData = new UDC.UnifiedData(text)
let dragInfo: dragController.DragInfo = {
  pointerId: 0,
  data: unifiedData,
  extraParams: ''
}
try{
  let dragAction: dragController.DragAction | null = dragController.createDragAction(customBuilders, dragInfo);
  if(!dragAction){
    console.log("listener dragAction is null");
    return
  }
  dragAction.on('statusChange', (dragAndDropInfo: dragController.DragAndDropInfo)=>{
    console.info("Register to listen on drag status", JSON.stringify(dragAndDropInfo));
  })
}catch(err) {
  console.log("create dragAction Error:" + err.message);
}

off('statusChange')¹¹⁺

off(type: 'statusChange', callback?: Callback<DragAndDropInfo>): void

Unsubscribes from drag state changes.

System capability: SystemCapability.ArkUI.ArkUI.Full

Parameters

Example

import dragController from "@ohos.arkui.dragController"
import UDC from '@ohos.data.unifiedDataChannel';
let customBuilders:Array<CustomBuilder | DragItemInfo> = new Array<CustomBuilder | DragItemInfo>();
let text = new UDC.Text()
let unifiedData = new UDC.UnifiedData(text)
let dragInfo: dragController.DragInfo = {
  pointerId: 0,
  data: unifiedData,
  extraParams: ''
}
try{
  let dragAction: dragController.DragAction | null = dragController.createDragAction(customBuilders, dragInfo);
  if(!dragAction){
    console.log("listener dragAction is null");
    return
  }
  dragAction.off('statusChange', (dragAndDropInfo: dragController.DragAndDropInfo)=>{
    console.info("Cancel listening on drag status", JSON.stringify(dragAndDropInfo));
  })
}catch(err) {
  console.log("create dragAction Error:" + err.message);
}

dragController.createDragAction¹¹⁺

createDragAction(customArray: Array<CustomBuilder | DragItemInfo>, dragInfo: DragInfo): DragAction

Creates a DragAction object, by explicitly specifying one or more drag previews, drag data, and information about the dragged object. If the drag initiated by a DragAction object is not complete, no new DragAction object can be created, and calling this API will throw an exception.

NOTE
You are advised to control the number of drag previews. If too many previews are passed in, the drag efficiency may be affected.

System capability: SystemCapability.ArkUI.ArkUI.Full

Parameters

Return value

Error codes

Example

import dragController from "@ohos.arkui.dragController"
import componentSnapshot from '@ohos.arkui.componentSnapshot';
import image from '@ohos.multimedia.image';
import UDC from '@ohos.data.unifiedDataChannel';

@Entry
@Component
struct DragControllerPage {
  @State pixmap: image.PixelMap | null = null
  private dragAction: dragController.DragAction | null = null;
  customBuilders:Array<CustomBuilder | DragItemInfo> = new Array<CustomBuilder | DragItemInfo>();
  @Builder DraggingBuilder() {
    Column() {
      Text("DraggingBuilder")
    }
    .width(100)
    .height(100)
    .backgroundColor(Color.Blue)
  }

  build() {
    Column() {

      Column() {
        Text ("Test")
      }
      .width(100)
      .height(100)
      .backgroundColor(Color.Red)

      Button('Drag Multiple Objects').onTouch((event?:TouchEvent) => {
        if(event){
          if (event.type == TouchType.Down) {
            console.log("muti drag Down by listener");
            this.customBuilders.splice(0, this.customBuilders.length);
            this.customBuilders.push(()=>{this.DraggingBuilder()});
            this.customBuilders.push(()=>{this.DraggingBuilder()});
            this.customBuilders.push(()=>{this.DraggingBuilder()});
            let text = new UDC.Text()
            let unifiedData = new UDC.UnifiedData(text)
            let dragInfo: dragController.DragInfo = {
              pointerId: 0,
              data: unifiedData,
              extraParams: ''
            }
            try{
              this.dragAction = dragController.createDragAction(this.customBuilders, dragInfo)
            if(!this.dragAction){
              console.log("listener dragAction is null");
              return
            }
            this.dragAction.on('statusChange', (dragAndDropInfo: dragController.DragAndDropInfo)=>{
              if (dragAndDropInfo.status == dragController.DragStatus.STARTED) {
                console.log("drag has start");
              } else if (dragAndDropInfo.status == dragController.DragStatus.ENDED){
                console.log("drag has end");
                if (!this.dragAction) {
                  return
                }
                this.dragAction.off('statusChange')
              }
            })
            this.dragAction.startDrag().then(()=>{}).catch((err:Error)=>{
              console.log("start drag Error:" + err.message);
            })
            } catch(err) {
              console.log("create dragAction Error:" + err.message);
            }
          }
        }
      }).margin({top:20})
    }
  }
}

AnimationOptions¹¹⁺

System capability: SystemCapability.ArkUI.ArkUI.Full

Defines the attributes required for initiating a drag action and information carried in the dragging process.

dragController.getDragPreview¹¹⁺

getDragPreview(): DragPreview

Obtains the DragPreview object, which represents the preview displayed during a drag.

System capability: SystemCapability.ArkUI.ArkUI.Full

Return value

Example

For details, see animate.

DragPreview¹¹⁺

Implements a DragPreview object. This API does not work in the OnDrop and OnDragEnd callbacks.

System capability: SystemCapability.ArkUI.ArkUI.Full

setForegroundColor¹¹⁺

setForegroundColor(color: ResourceColor): void

Sets the mask color of the drag preview. This API does not work in the OnDrop and OnDragEnd callbacks.

System capability: SystemCapability.ArkUI.ArkUI.Full

Parameters

Example

For details, see animate.

animate¹¹⁺

animate(options: AnimationOptions, handler: () => void): void

Applies an animation to the background mask color changes. This API does not work in the OnDrop and OnDragEnd callbacks.

System capability: SystemCapability.ArkUI.ArkUI.Full

Parameters

Example

1. In the EntryAbility.ets file, obtain the UI context and save it to LocalStorage.

import AbilityConstant from '@ohos.app.ability.AbilityConstant';
import hilog from '@ohos.hilog';
import UIAbility from '@ohos.app.ability.UIAbility';
import Want from '@ohos.app.ability.Want';
import window from '@ohos.window';
import { UIContext } from '@ohos.arkui.UIContext';

let uiContext: UIContext;
let localStorage: LocalStorage = new LocalStorage('uiContext');

export default class EntryAbility extends UIAbility {
storage: LocalStorage = localStorage;

onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
  hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onCreate');
}

onDestroy(): void {
  hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onDestroy');
}

onWindowStageCreate(windowStage: window.WindowStage): void {
  hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageCreate');

  windowStage.loadContent('pages/Index', (err, data) => {
    if (err.code) {
      hilog.error(0x0000, 'testTag', 'Failed to load the content. Cause: %{public}s', JSON.stringify(err) ?? '');
      return;
    }
    hilog.info(0x0000, 'testTag', 'Succeeded in loading the content. Data: %{public}s', JSON.stringify(data) ?? '');
    windowStage.getMainWindow((err, data) => {
      if (err.code) {
        hilog.error(0x0000, 'Failed to abtain the main window. Cause:' + err.message, '');
        return;
      }
      let windowClass: window.Window = data;
      uiContext = windowClass.getUIContext();
      this.storage.setOrCreate<UIContext>('uiContext', uiContext);
    })
  });
}
}

2. In the Index.ets file, call LocalStorage.getShared() to obtain the UI context and then use the DragController object obtained to perform subsequent operations.

import UDC from '@ohos.data.unifiedDataChannel';
import hilog from '@ohos.hilog';
import dragController from "@ohos.arkui.dragController";
import image from '@ohos.multimedia.image';
import curves from '@ohos.curves';
import { BusinessError } from '@ohos.base';
import { UIContext } from '@ohos.arkui.UIContext';


let storages = LocalStorage.getShared();

@Entry(storages)
@Component
struct DragControllerPage {
@State pixmap: image.PixelMap|null = null

@Builder DraggingBuilder() {
  Column() {
    Text("DraggingBuilder")
  }
  .width(100)
  .height(100)
  .backgroundColor(Color.Blue)
}

@Builder PixmapBuilder() {
  Column() {
    Text("PixmapBuilder")
  }
  .width(100)
  .height(100)
  .backgroundColor(Color.Blue)
}

build() {
  Column() {
    Button('Drag Here').onDragEnter(() => {
        try {
          let uiContext: UIContext = storages.get<UIContext>('uiContext') as UIContext;
          let previewObj: dragController.DragPreview = uiContext.getDragController().getDragPreview();
          let foregroundColor: ResourceColor = Color.Green;

          let previewAnimation: dragController.AnimationOptions = {
            curve: curves.cubicBezierCurve(0.2,0,0,1),
          }
          previewObj.animate(previewAnimation, () => {
            previewObj.setForegroundColor(foregroundColor);
          });
        } catch (error) {
          let msg = (error as BusinessError).message;
          let code = (error as BusinessError).code;
          hilog.error(0x0000, `show error code is ${code}, message is ${msg}`, '');
        }
    })
    .onDrop(() => {

    })
    Button ('Drag').onTouch ((event?:TouchEvent) => {
      if(event){
        if (event.type == TouchType.Down) {
          let text = new UDC.Text()
          let unifiedData = new UDC.UnifiedData(text)
          let dragInfo: dragController.DragInfo = {
            pointerId: 0,
            data: unifiedData,
            extraParams: ''
          }
            class tmp{
              event:DragEvent|undefined = undefined
              extraParams:string = ''
            }
            let eve:tmp = new tmp()
            dragController.executeDrag(() => {
              this.DraggingBuilder()
            }, dragInfo, (err , eve) => {
              hilog.info(0x0000, `ljx ${JSON.stringify(err)}`, '')
              if (eve && eve.event) {
                if (eve.event.getResult() == DragResult.DRAG_SUCCESSFUL) {
                  hilog.info(0x0000, 'success', '');
                } else if (eve.event.getResult() == DragResult.DRAG_FAILED) {
                  hilog.info(0x0000, 'failed', '');
                }
              }
          })
        }
      }
    }).margin({top:100})
  }
  .width('100%')
  .height('100%')
}
}