With ability continuation APIs, you can migrate the current application task, including some page data and stack information, to a remote device. If the migration is successful, the local task will be cleared. If the migration fails, the local task can be migrated again.
## Available APIs
The following table lists the API used for ability continuation. For details about the API, see the interface document.
**Table 1** Ability continuation API
|API| Description|
|:------ | :------|
| onContinue(wantParams : {[key: string]: any}) | A callback used to store the data required for migration and indicate whether the migration is accepted. The value **true** means that the migration is accepted, and **false** means the opposite.|
## How to Develop
### Migrating an Ability
1. Configure data.
- Configure the ability to support migration.
Set the **continuable** field in the **config.json** file to **true**, which indicates that migration is supported. The default value is **false**.
```
"continuable": true
```
Abilities with the **continuable** field set to **false** cannot be migrated.
* Configure the ability startup type.
Currently, only multi-instance abilities can be migrated. Therefore, you must set the **launchType** field in the **config.json** file to **standard**.
```
"launchType": "standard"
```
2. Implement the **onContinue** API.
Modules to Import
```
import Ability from '@ohos.application.Ability';
```
- To implement migration, you must implement this API and have the value **true** returned.
- Example
```javascript
onContinue(wantParams:{[key:string]:any}){
console.log("MainAbility onContinue")
returntrue;
}
```
3. Implement the migration logic in the **onCreate** API.
- On the remote device, determine whether the startup is **LaunchReason.CONTINUATION** (3) based on **launchReason** in **onCreate**.
- After data restore is complete, call **restoreWindowStage** to trigger page restoration.
* Example
```javascript
onCreate(want,launchParam){
// The ability is being created. Initialize resources for this ability.
- You can fill custom data in the key-value format in the **wantParams** parameter, through which the data will be transferred to the remote device. The **key** type is string, and therefore it is used to carry simple and lightweight data.
```javascript
onContinue(wantParams:{[key:string]:any}){
console.log("Continue My Data")
wantParams["myData"]="my1234567";
returntrue;
}
```
- If the remote device detects a migration, it obtains the custom data saved at the initiator from **want.parameters**.
You can use distributed objects to transfer more data to a remote device. For details, see the distributed object interface document.
- In **onContinue**, the initiator saves the data to be migrated to the distributed object, sets the session ID, and sends the session ID to the remote device through **wantParams**.
- The remote device obtains the session ID from **onCreate**, creates a distributed object, and associates the distributed object with the session ID. In this way, the distributed object can be synchronized. Before calling **restoreWindowStage**, ensure that all distributed objects required for migration have been associated for correct data retrieval.
