# @ohos.app.ability.UIAbility (UIAbility)

UIAbility is an application component that has the UI. The UIAbility module, inherited from [Ability](js-apis-app-ability-ability.md), provides lifecycle callbacks such as component creation, destruction, and foreground/background switching. It also provides the following capabilities related to component collaboration:

- [Caller](#caller): an object returned by [startAbilityByCall](js-apis-inner-application-uiAbilityContext.md#uiabilitycontextstartabilitybycall). The CallerAbility (caller) uses this object to communicate with the CalleeAbility (callee).
- [Callee](#callee): an internal object of UIAbility. The CalleeAbility (callee) uses this object to communicate with the CallerAbility (caller).

For details about the inheritance relationship of each ability, see [Inheritance Relationship](./js-apis-app-ability-ability.md#ability-inheritance-relationship).

> **NOTE**
>
> The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version.
>
> The APIs of this module can be used only in the stage model.

## Modules to Import

```ts
import { UIAbility } from '@kit.AbilityKit';
```

## Properties

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

| Name| Type| Read-only| Optional| Description|
| -------- | -------- | -------- | -------- | -------- |
| context | [UIAbilityContext](js-apis-inner-application-uiAbilityContext.md) | No| No| Context of the UIAbility.<br>**Atomic service API**: This API can be used in atomic services since API version 11.|
| launchWant | [Want](js-apis-app-ability-want.md) | No| No| Parameters for starting the UIAbility.<br>**Atomic service API**: This API can be used in atomic services since API version 11.|
| lastRequestWant | [Want](js-apis-app-ability-want.md) | No| No| Parameters carried in the last request.<br>**Atomic service API**: This API can be used in atomic services since API version 11.|
| callee | [Callee](#callee) | No| No| Object that invokes the stub service.|

## UIAbility.onCreate

onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void

Called to initialize the service logic when a UIAbility instance in the completely closed state is created. In other words, a UIAbility instance enters this lifecycle callback from a [cold start](../../application-models/uiability-intra-device-interaction.md#cold-starting-uiability). This API returns the result synchronously and does not support asynchronous callback.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| want | [Want](js-apis-app-ability-want.md) | Yes| Want information, including the ability name and bundle name.|
| launchParam | [AbilityConstant.LaunchParam](js-apis-app-ability-abilityConstant.md#launchparam) | Yes| Parameters for starting the UIAbility, and the reason for the last abnormal exit.|

**Example**

```ts
import { UIAbility, AbilityConstant, Want } from '@kit.AbilityKit';

class MyUIAbility extends UIAbility {
  onCreate(want: Want, launchParam: AbilityConstant.LaunchParam) {
    console.log(`onCreate, want: ${want.abilityName}`);
  }
}
```


## UIAbility.onWindowStageCreate

onWindowStageCreate(windowStage: window.WindowStage): void

Called when a **WindowStage** is created for this UIAbility.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| windowStage | [window.WindowStage](../apis-arkui/js-apis-window.md#windowstage9) | Yes| **WindowStage** information.|

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';

class MyUIAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    console.log('onWindowStageCreate');
  }
}
```


## UIAbility.onWindowStageWillDestroy<sup>12+</sup>

onWindowStageWillDestroy(windowStage: window.WindowStage): void

Called when the **WindowStage** is about to be destroyed.

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

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| windowStage | [window.WindowStage](../apis-arkui/js-apis-window.md#windowstage9) | Yes| **WindowStage** information.|

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';

class MyUIAbility extends UIAbility {
  onWindowStageWillDestroy(windowStage: window.WindowStage) {
    console.log('onWindowStageWillDestroy');
  }
}
```


## UIAbility.onWindowStageDestroy

onWindowStageDestroy(): void

Called when the **WindowStage** is destroyed for this UIAbility.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';

class MyUIAbility extends UIAbility {
  onWindowStageDestroy() {
    console.log('onWindowStageDestroy');
  }
}
```


## UIAbility.onWindowStageRestore

onWindowStageRestore(windowStage: window.WindowStage): void

Called when the **WindowStage** is restored during the migration of this UIAbility, which is a multi-instance ability.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| windowStage | [window.WindowStage](../apis-arkui/js-apis-window.md#windowstage9) | Yes| **WindowStage** information.|

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';

class MyUIAbility extends UIAbility {
  onWindowStageRestore(windowStage: window.WindowStage) {
    console.log('onWindowStageRestore');
  }
}
```


## UIAbility.onDestroy

onDestroy(): void | Promise&lt;void&gt;

Called to clear resources when this UIAbility is destroyed. This API returns the result synchronously or uses a promise to return the result.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Return value**

| Type| Description|
| -------- | -------- |
| void&nbsp;\|&nbsp;Promise&lt;void&gt; | No return value or a Promise object that returns no result.|

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';

class MyUIAbility extends UIAbility {
  onDestroy() {
    console.log('onDestroy');
  }
}
```

After the **onDestroy()** lifecycle callback is executed, the application may exit. Consequently, the asynchronous function (for example, asynchronously writing data to the database) in **onDestroy()** may fail to be executed. You can use the asynchronous lifecycle to ensure that the subsequent lifecycle continues only after the asynchronous function in **onDestroy()** finishes the execution.

```ts
import { UIAbility } from '@kit.AbilityKit';

class MyUIAbility extends UIAbility {
  async onDestroy() {
    console.log('onDestroy');
    // Call the asynchronous function.
  }
}
```

## UIAbility.onForeground

onForeground(): void

Called when this UIAbility is switched from the background to the foreground. This API returns the result synchronously and does not support asynchronous callback.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';

class MyUIAbility extends UIAbility {
  onForeground() {
    console.log('onForeground');
  }
}
```


## UIAbility.onBackground

onBackground(): void

Called when this UIAbility is switched from the foreground to the background. This API returns the result synchronously and does not support asynchronous callback.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';

class MyUIAbility extends UIAbility {
  onBackground() {
    console.log('onBackground');
  }
}
```


## UIAbility.onContinue

onContinue(wantParam: Record&lt;string, Object&gt;): AbilityConstant.OnContinueResult | Promise&lt;AbilityConstant.OnContinueResult&gt;

Called to save data during the UIAbility migration preparation process.

> **NOTE**
> 
> Since API version 12, **UIAbility.onContinue** supports the return value in the form of Promise\<[AbilityConstant.OnContinueResult](js-apis-app-ability-abilityConstant.md#oncontinueresult)\>.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| wantParam | Record&lt;string,&nbsp;Object&gt; | Yes| **want** parameter.|

**Return value**

| Type| Description|
| -------- | -------- |
| [AbilityConstant.OnContinueResult](js-apis-app-ability-abilityConstant.md#oncontinueresult)&nbsp;\|&nbsp;Promise&lt;[AbilityConstant.OnContinueResult](js-apis-app-ability-abilityConstant.md#oncontinueresult)&gt;  | Continuation result or Promise used to return the continuation result.|

**Example**

  ```ts
  import { UIAbility, AbilityConstant } from '@kit.AbilityKit';

  class MyUIAbility extends UIAbility {
      onContinue(wantParams: Record<string, Object>) {
          console.log('onContinue');
          wantParams['myData'] = 'my1234567';
          return AbilityConstant.OnContinueResult.AGREE;
      }
  }
  ```

An asynchronous API can be used to save data during ability continuation.

  ```ts
  import { UIAbility, AbilityConstant } from '@kit.AbilityKit';

  class MyUIAbility extends UIAbility {
    async setWant(wantParams: Record<string, Object>) {
      console.log('setWant start');
      for (let time = 0; time < 1000; ++time) {
        wantParams[time] = time;
      }
      console.log('setWant end');
    }

    async onContinue(wantParams: Record<string, Object>) {
        console.log('onContinue');
        return this.setWant(wantParams).then(()=>{
          return AbilityConstant.OnContinueResult.AGREE;
        });
    }
  }
  ```


## UIAbility.onNewWant

onNewWant(want: Want, launchParam: AbilityConstant.LaunchParam): void

Called when a UIAbility instance that has undergone the following states is started again: started in the foreground, running in the foreground, and switched to the background. In other words, a UIAbility instance enters this lifecycle callback from a [hot start](../../application-models/uiability-intra-device-interaction.md#hot-starting-uiability).

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| want | [Want](js-apis-app-ability-want.md) | Yes| Want information, such as the ability name and bundle name.|
| launchParam | [AbilityConstant.LaunchParam](js-apis-app-ability-abilityConstant.md#launchparam) | Yes| Reason for the UIAbility startup and the last abnormal exit.|

**Example**

```ts
import { UIAbility, AbilityConstant, Want } from '@kit.AbilityKit';

class MyUIAbility extends UIAbility {
  onNewWant(want: Want, launchParam: AbilityConstant.LaunchParam) {
    console.log(`onNewWant, want: ${want.abilityName}`);
    console.log(`onNewWant, launchParam: ${JSON.stringify(launchParam)}`);
  }
}
```

## UIAbility.onDump

onDump(params: Array\<string>): Array\<string>

Called to dump the client information. This API can be used to dump non-sensitive information.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| params | Array\<string> | Yes| Parameters in the form of a command.|

**Return value**

| Type| Description|
| -------- | -------- |
| Array\<string> | Dumped information array.|

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';

class MyUIAbility extends UIAbility {
  onDump(params: Array<string>) {
    console.log(`dump, params: ${JSON.stringify(params)}`);
    return ['params'];
  }
}
```


## UIAbility.onSaveState

onSaveState(reason: AbilityConstant.StateType, wantParam: Record&lt;string, Object&gt;): AbilityConstant.OnSaveResult

Called when the framework automatically saves the UIAbility state in the case of an application fault. This API is used together with [appRecovery](js-apis-app-ability-appRecovery.md). When an application is faulty, the framework calls **onSaveState** to save the status of the UIAbility if auto-save is enabled.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| reason | [AbilityConstant.StateType](js-apis-app-ability-abilityConstant.md#statetype) | Yes| Reason for triggering the callback to save the UIAbility state.|
| wantParam | Record&lt;string,&nbsp;Object&gt; | Yes| **want** parameter.|

**Return value**

| Type| Description|
| -------- | -------- |
| [AbilityConstant.OnSaveResult](js-apis-app-ability-abilityConstant.md#onsaveresult) | Whether the UIAbility state is saved.|

**Example**

```ts
import { UIAbility, AbilityConstant } from '@kit.AbilityKit';

class MyUIAbility extends UIAbility {
  onSaveState(reason: AbilityConstant.StateType, wantParam: Record<string, Object>) {
    console.log('onSaveState');
    wantParam['myData'] = 'my1234567';
    return AbilityConstant.OnSaveResult.RECOVERY_AGREE;
  }
}
```

## UIAbility.onShare<sup>10+</sup>

onShare(wantParam: Record&lt;string, Object&gt;): void

Called by this UIAbility to set data to share in the cross-device sharing scenario.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| wantParam | Record&lt;string,&nbsp;Object&gt; | Yes| Data to share.|

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';

class MyUIAbility extends UIAbility {
  onShare(wantParams: Record<string, Object>) {
    console.log('onShare');
    wantParams['ohos.extra.param.key.shareUrl'] = 'example.com';
  }
}
```

## UIAbility.onPrepareToTerminate<sup>10+</sup>

onPrepareToTerminate(): boolean

Called when this UIAbility is about to terminate. It allows for additional actions to be performed before the UIAbility is officially terminated. For example, you can prompt the user to confirm whether they want to terminate the UIAbility. If the user confirms, you can call [terminateSelf](js-apis-inner-application-uiAbilityContext.md#uiabilitycontextterminateself) to terminate it.

Currently, this API takes effect only on 2-in-1 devices.

> **NOTE**
>
> Since API version 15, this callback is not executed when [UIAbility.onPrepareToTerminateAsync](#uiabilityonpreparetoterminateasync15) is implemented. When [AbilityStage.onPrepareTerminationAsync](js-apis-app-ability-abilityStage.md#abilitystageonprepareterminationasync15) or [AbilityStage.onPrepareTermination](js-apis-app-ability-abilityStage.md#abilitystageonpreparetermination15) is implemented, this callback is not executed if the user right-clicks the dock bar or system tray to close the UIAbility.

**Required permissions**: ohos.permission.PREPARE_APP_TERMINATE

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Return value**

| Type| Description|
| -- | -- |
| boolean | Whether to terminate the UIAbility. The value **true** means that the termination process is canceled. The value **false** means to continue terminating the UIAbility.|

**Example**

```ts
import { UIAbility, Want } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';

export default class EntryAbility extends UIAbility {
  onPrepareToTerminate() {
    // Define a pre-termination operation,
    // for example, starting another UIAbility and performing asynchronous termination based on the startup result.
    let want: Want = {
      bundleName: "com.example.myapplication",
      moduleName: "entry",
      abilityName: "SecondAbility"
    }
    this.context.startAbilityForResult(want)
      .then((result)=>{
        // Obtain the startup result and terminate the current UIAbility when resultCode in the return value is 0.
        console.log('startAbilityForResult success, resultCode is ' + result.resultCode);
        if (result.resultCode === 0) {
          this.context.terminateSelf();
        }
      }).catch((err: BusinessError)=>{
      // Exception handling.
      console.error('startAbilityForResult failed, err:' + JSON.stringify(err));
      this.context.terminateSelf();
    })

    return true; // The pre-termination operation is defined. The value true means that the UIAbility termination process is canceled.
  }
}
```

## UIAbility.onPrepareToTerminateAsync<sup>15+</sup>

onPrepareToTerminateAsync(): Promise\<boolean>

Called when this UIAbility is about to terminate. It allows for additional actions to be performed before the UIAbility is officially terminated. This API uses a promise to return the result. For example, you can prompt the user to confirm whether they want to terminate the UIAbility. If the user confirms, you can call [terminateSelf](js-apis-inner-application-uiAbilityContext.md#uiabilitycontextterminateself) to terminate it.

Currently, this API takes effect only on 2-in-1 devices.

> **NOTE**
>
> - When [AbilityStage.onPrepareTerminationAsync](js-apis-app-ability-abilityStage.md#abilitystageonprepareterminationasync15) or [AbilityStage.onPrepareTermination](js-apis-app-ability-abilityStage.md#abilitystageonpreparetermination15) is implemented, this callback is not executed if the user right-clicks the dock bar or system tray to close the UIAbility.
>
> - If an asynchronous callback crashes, it will be handled as a timeout. If the UIAbility does not respond within 10 seconds, it will be terminated forcibly.

**Required permissions**: ohos.permission.PREPARE_APP_TERMINATE

**Atomic service API**: This API can be used in atomic services since API version 15.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Return value**

| Type| Description|
| -- | -- |
| Promise\<boolean> | Promise used to return the result. The value **true** means that the termination process is canceled. The value **false** means to continue terminating the UIAbility.|

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';

export default class EntryAbility extends UIAbility {
  async onPrepareToTerminateAsync(): Promise<boolean> {
    await new Promise<boolean>((res, rej) => {
      setTimeout (res, 2000); // Execute the operation 2 seconds later.
    });
    return true; // The pre-termination operation is defined. The value true means that the UIAbility termination process is canceled.
  }
}
```

## UIAbility.onBackPressed<sup>10+</sup>

onBackPressed(): boolean

Called when an operation of going back to the previous page is triggered on this UIAbility. The return value determines whether to destroy the UIAbility instance.

- When the target SDK version is earlier than 12, the default return value is **false**, indicating that the UIAbility will be destroyed.
- When the target SDK version is 12 or later, the default return value is **true**, indicating that the UIAbility will be moved to the background and will not be destroyed.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Return value**

| Type| Description|
| -- | -- |
| boolean | The value **true** means that the UIAbility instance will be moved to the background and will not be destroyed, and **false** means that the UIAbility instance will be destroyed.|

**Example**

```ts
import { UIAbility } from '@kit.AbilityKit';

export default class EntryAbility extends UIAbility {
  onBackPressed() {
    return true;
  }
}
```

## UIAbility.onCollaborate<sup>18+</sup>

onCollaborate(wantParam: Record&lt;string, Object&gt;): AbilityConstant.CollaborateResult

Callback invoked to return the collaboration result in multi-device collaboration scenarios.

 **NOTE**
- This callback does not support ability launch in specified mode.
- When you use methods such as **startAbility()** to start an application, you must include **FLAG_ABILITY_ON_COLLABORATE** in [Flags](js-apis-ability-wantConstant.md#flags) in the Want object.
- During a cold start, this callback must be invoked before [onForeground](#uiabilityonforeground) or after [onBackground](#uiabilityonbackground). During a hot start, this callback must be invoked before [onNewWant](#uiabilityonnewwant).


**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name   | Type                             | Mandatory| Description                                                        |
| --------- | --------------------------------- | ---- | ------------------------------------------------------------ |
| wantParam | Record&lt;string,&nbsp;Object&gt; | Yes  | Want parameter, which supports only the key **"ohos.extra.param.key.supportCollaborateIndex"**. The key can be used to obtain the data passed by the caller and perform corresponding processing.|

**Return value**

| Name    | Value  | Description      |
| -------- | ---- | ---------- |
| [AbilityConstant.CollaborateResult](js-apis-app-ability-abilityConstant.md#collaborateresult18) | Collaborator result, that is, whether the target application accepts the collaboration request.|

**Example**

```ts
import { UIAbility, AbilityConstant } from '@kit.AbilityKit';

class MyAbility extends UIAbility {
  onCollaborate(wantParam: Record<string, Object>) {
    return AbilityConstant.CollaborateResult.ACCEPT;
  }
}
```

## Caller

Implements sending of parcelable data to the target UIAbility when the CallerAbility invokes the target UIAbility (CalleeAbility).

### Caller.call

call(method: string, data: rpc.Parcelable): Promise&lt;void&gt;

Sends parcelable data to the target UIAbility. This API uses a promise to return the result.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| method | string | Yes| Notification message string negotiated between the two UIAbilities. The message is used to instruct the callee to register a function to receive the parcelable data.|
| data | [rpc.Parcelable](../apis-ipc-kit/js-apis-rpc.md#parcelable9) | Yes| Parcelable data. You need to customize the data.|

**Return value**

| Type| Description|
| -------- | -------- |
| Promise&lt;void&gt; | Promise that returns no value.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------------------------------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types. |
| 16200001 | Caller released. The caller has been released. |
| 16200002 | The callee does not exist. |
| 16000050 | Internal error. |

**Example**

```ts
import { UIAbility, Caller } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { rpc } from '@kit.IPCKit';
import { BusinessError } from '@kit.BasicServicesKit';

class MyMessageAble implements rpc.Parcelable { // Custom parcelable data structure.
  name: string
  str: string
  num: number = 1
  constructor(name: string, str: string) {
    this.name = name;
    this.str = str;
  }
  marshalling(messageSequence: rpc.MessageSequence) {
    messageSequence.writeInt(this.num);
    messageSequence.writeString(this.str);
    console.log(`MyMessageAble marshalling num[${this.num}] str[${this.str}]`);
    return true;
  }
  unmarshalling(messageSequence: rpc.MessageSequence) {
    this.num = messageSequence.readInt();
    this.str = messageSequence.readString();
    console.log(`MyMessageAble unmarshalling num[${this.num}] str[${this.str}]`);
    return true;
  }
};
let method = 'call_Function'; // Notification message string negotiated by the two UIAbilities.
let caller: Caller;

export default class MainUIAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    this.context.startAbilityByCall({
      bundleName: 'com.example.myservice',
      abilityName: 'MainUIAbility',
      deviceId: ''
    }).then((obj) => {
      caller = obj;
      let msg = new MyMessageAble('msg', 'world'); // See the definition of Parcelable.
      caller.call(method, msg)
        .then(() => {
          console.log('Caller call() called');
        })
        .catch((callErr: BusinessError) => {
          console.error(`Caller.call catch error, error.code: ${callErr.code}, error.message: ${callErr.message}`);
        });
    }).catch((err: BusinessError) => {
      console.error(`Caller GetCaller error, error.code: ${err.code}, error.message: ${err.message}`);
    });
  }
}
```


### Caller.callWithResult

callWithResult(method: string, data: rpc.Parcelable): Promise&lt;rpc.MessageSequence&gt;

Sends parcelable data to the target UIAbility and obtains the parcelable data returned by the target UIAbility. This API uses a promise to return the result.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| method | string | Yes| Notification message string negotiated between the two UIAbilities. The message is used to instruct the callee to register a function to receive the parcelable data.|
| data | [rpc.Parcelable](../apis-ipc-kit/js-apis-rpc.md#parcelable9) | Yes| Parcelable data. You need to customize the data.|

**Return value**

| Type| Description|
| -------- | -------- |
| Promise&lt;[rpc.MessageSequence](../apis-ipc-kit/js-apis-rpc.md#messagesequence9)&gt; | Promise used to return the parcelable data from the target UIAbility.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------------------------------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types. |
| 16200001 | Caller released. The caller has been released. |
| 16200002 | The callee does not exist. |
| 16000050 | Internal error. |

**Example**

```ts
import { UIAbility, Caller } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { rpc } from '@kit.IPCKit';
import { BusinessError } from '@kit.BasicServicesKit';

class MyMessageAble implements rpc.Parcelable {
  name: string
  str: string
  num: number = 1
  constructor(name: string, str: string) {
    this.name = name;
    this.str = str;
  }
  marshalling(messageSequence: rpc.MessageSequence) {
    messageSequence.writeInt(this.num);
    messageSequence.writeString(this.str);
    console.log(`MyMessageAble marshalling num[${this.num}] str[${this.str}]`);
    return true;
  }
  unmarshalling(messageSequence: rpc.MessageSequence) {
    this.num = messageSequence.readInt();
    this.str = messageSequence.readString();
    console.log(`MyMessageAble unmarshalling num[${this.num}] str[${this.str}]`);
    return true;
  }
};
let method = 'call_Function';
let caller: Caller;

export default class MainUIAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    this.context.startAbilityByCall({
      bundleName: 'com.example.myservice',
      abilityName: 'MainUIAbility',
      deviceId: ''
    }).then((obj) => {
      caller = obj;
      let msg = new MyMessageAble('msg', 'world');
      caller.callWithResult(method, msg)
        .then((data) => {
          console.log('Caller callWithResult() called');
          let retmsg = new MyMessageAble('msg', 'world');
          data.readParcelable(retmsg);
        })
        .catch((callErr: BusinessError) => {
          console.error(`Caller.callWithResult catch error, error.code: ${callErr.code}, error.message: ${callErr.message}`);
        });
    }).catch((err: BusinessError) => {
      console.error(`Caller GetCaller error, error.code: ${err.code}, error.message: ${err.message}`);
    });
  }
}
```


### Caller.release

release(): void

Releases the caller interface of the target UIAbility.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Error codes**

For details about the error codes, see [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------------------------------- |
| 16200001 | Caller released. The caller has been released. |
| 16200002 | The callee does not exist. |

**Example**

```ts
import { UIAbility, Caller } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { BusinessError } from '@kit.BasicServicesKit';

let caller: Caller;

export default class MainUIAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    this.context.startAbilityByCall({
      bundleName: 'com.example.myservice',
      abilityName: 'MainUIAbility',
      deviceId: ''
    }).then((obj) => {
      caller = obj;
      try {
        caller.release();
      } catch (releaseErr) {
        console.error(`Caller.release catch error, error.code: ${releaseErr.code}, error.message: ${releaseErr.message}`);
      }
    }).catch((err: BusinessError) => {
      console.error(`Caller GetCaller error, error.code: ${err.code}, error.message: ${err.message}`);
    });
  }
}
```

### Caller.onRelease

 onRelease(callback: OnReleaseCallback): void

Called when the stub on the target UIAbility is disconnected. This API uses an asynchronous callback to return the result.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| callback | [OnReleaseCallback](#onreleasecallback) | Yes| Callback used to return the result.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------------------------------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types. |
| 16200001 | Caller released. The caller has been released. |

**Example**

```ts
import { UIAbility, Caller } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { BusinessError } from '@kit.BasicServicesKit';

let caller: Caller;

export default class MainUIAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    this.context.startAbilityByCall({
      bundleName: 'com.example.myservice',
      abilityName: 'MainUIAbility',
      deviceId: ''
    }).then((obj) => {
      caller = obj;
      try {
        caller.onRelease((str) => {
          console.log(`Caller OnRelease CallBack is called ${str}`);
        });
      } catch (error) {
        console.error(`Caller.onRelease catch error, error.code: $error.code}, error.message: ${error.message}`);
      }
    }).catch((err: BusinessError) => {
      console.error(`Caller GetCaller error, error.code: ${err.code}, error.message: ${err.message}`);
    });
  }
}
```

### Caller.onRemoteStateChange<sup>10+</sup>

onRemoteStateChange(callback: OnRemoteStateChangeCallback): void

Called when the remote UIAbility state changes in the collaboration scenario. This API uses an asynchronous callback to return the result.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| callback | [OnRemoteStateChangeCallback](#onremotestatechangecallback10) | Yes| Callback used to return the result.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------------------------------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types. |
| 16200001 | Caller released. The caller has been released. |

**Example**

```ts
import { UIAbility, Caller } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { BusinessError } from '@kit.BasicServicesKit';

let caller: Caller;
let dstDeviceId: string;

export default class MainAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    this.context.startAbilityByCall({
      bundleName: 'com.example.myservice',
      abilityName: 'MainUIAbility',
      deviceId: dstDeviceId
    }).then((obj) => {
      caller = obj;
      try {
        caller.onRemoteStateChange((str) => {
          console.log('Remote state changed ' + str);
        });
      } catch (error) {
        console.error(`Caller.onRemoteStateChange catch error, error.code: ${JSON.stringify(error.code)}, error.message: ${JSON.stringify(error.message)}`);
      }
    }).catch((err: BusinessError) => {
      console.error(`Caller GetCaller error, error.code: ${JSON.stringify(err.code)}, error.message: ${JSON.stringify(err.message)}`);
    })
  }
}
```

### Caller.on('release')

on(type: 'release', callback: OnReleaseCallback): void

Called when the stub on the target UIAbility is disconnected. This API uses an asynchronous callback to return the result.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| type | string | Yes| Event type. The value is fixed at **'release'**.|
| callback | [OnReleaseCallback](#onreleasecallback) | Yes| Callback used to return the result.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------------------------------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |
| 16200001 | Caller released. The caller has been released. |

**Example**

```ts
import { UIAbility, Caller } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { BusinessError } from '@kit.BasicServicesKit';

let caller: Caller;

export default class MainUIAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    this.context.startAbilityByCall({
      bundleName: 'com.example.myservice',
      abilityName: 'MainUIAbility',
      deviceId: ''
    }).then((obj) => {
      caller = obj;
      try {
        caller.on('release', (str) => {
          console.log(`Caller OnRelease CallBack is called ${str}`);
        });
      } catch (error) {
        console.error(`Caller.on catch error, error.code: ${error.code}, error.message: ${error.message}`);
      }
    }).catch((err: BusinessError) => {
      console.error(`Caller GetCaller error, error.code: ${err.code}, error.message: ${err.message}`);
    });
  }
}
```

### Caller.off('release')

off(type: 'release', callback: OnReleaseCallback): void

Unregisters a callback that is invoked when the stub on the target UIAbility is disconnected. This capability is reserved. This API uses an asynchronous callback to return the result.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| type | string | Yes| Event type. The value is fixed at **'release'**.|
| callback | [OnReleaseCallback](#onreleasecallback) | Yes| Callback used to return the result.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md).

| ID| Error Message|
| ------- | -------------------------------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |

**Example**

```ts
import { UIAbility, Caller, OnReleaseCallback } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { BusinessError } from '@kit.BasicServicesKit';

let caller: Caller;

export default class MainUIAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    this.context.startAbilityByCall({
      bundleName: 'com.example.myservice',
      abilityName: 'MainUIAbility',
      deviceId: ''
    }).then((obj) => {
      caller = obj;
      try {
        let onReleaseCallBack: OnReleaseCallback = (str) => {
          console.log(`Caller OnRelease CallBack is called ${str}`);
        };
        caller.on('release', onReleaseCallBack);
        caller.off('release', onReleaseCallBack);
      } catch (error) {
        console.error(`Caller.on or Caller.off catch error, error.code: ${error.code}, error.message: ${error.message}`);
      }
    }).catch((err: BusinessError) => {
      console.error(`Caller GetCaller error, error.code: ${err.code}, error.message: ${err.message}`);
    });
  }
}
```

### Caller.off('release')

off(type: 'release'): void

Unregisters a callback that is invoked when the stub on the target UIAbility is disconnected. This capability is reserved.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| type | string | Yes| Event type. The value is fixed at **'release'**.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md).

| ID| Error Message|
| ------- | -------------------------------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |

**Example**

```ts
import { UIAbility, Caller, OnReleaseCallback } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';
import { BusinessError } from '@kit.BasicServicesKit';

let caller: Caller;

export default class MainUIAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    this.context.startAbilityByCall({
      bundleName: 'com.example.myservice',
      abilityName: 'MainUIAbility',
      deviceId: ''
    }).then((obj) => {
      caller = obj;
      try {
        let onReleaseCallBack: OnReleaseCallback = (str) => {
          console.log(`Caller OnRelease CallBack is called ${str}`);
        };
        caller.on('release', onReleaseCallBack);
        caller.off('release');
      } catch (error) {
        console.error(`Caller.on or Caller.off catch error, error.code: ${error.code}, error.message: ${error.message}`);
      }
    }).catch((err: BusinessError) => {
      console.error(`Caller GetCaller error, error.code: ${err.code}, error.message: ${err.message}`);
    });
  }
}
```

## Callee

Implements callbacks for caller notification registration and deregistration.

### Callee.on

on(method: string, callback: CalleeCallback): void

Registers a caller notification callback, which is invoked when the target UIAbility registers a function.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| method | string | Yes| Notification message string negotiated between the two UIAbilities.|
| callback | [CalleeCallback](#calleecallback) | Yes| JS notification synchronization callback of the [rpc.MessageSequence](../apis-ipc-kit/js-apis-rpc.md#messagesequence9) type. The callback must return at least one empty [rpc.Parcelable](../apis-ipc-kit/js-apis-rpc.md#parcelable9) object. Otherwise, the function execution fails.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------------------------------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |
| 16200004 | The method has been registered. |
| 16000050 | Internal error. |

**Example**

```ts
import { UIAbility, AbilityConstant, Want } from '@kit.AbilityKit';
import { rpc } from '@kit.IPCKit';

class MyMessageAble implements rpc.Parcelable {
  name: string
  str: string
  num: number = 1
  constructor(name: string, str: string) {
    this.name = name;
    this.str = str;
  }
  marshalling(messageSequence: rpc.MessageSequence) {
    messageSequence.writeInt(this.num);
    messageSequence.writeString(this.str);
    console.log(`MyMessageAble marshalling num[${this.num}] str[${this.str}]`);
    return true;
  }
  unmarshalling(messageSequence: rpc.MessageSequence) {
    this.num = messageSequence.readInt();
    this.str = messageSequence.readString();
    console.log(`MyMessageAble unmarshalling num[${this.num}] str[${this.str}]`);
    return true;
  }
};
let method = 'call_Function';

function funcCallBack(pdata: rpc.MessageSequence) {
  console.log(`Callee funcCallBack is called ${pdata}`);
  let msg = new MyMessageAble('test', '');
  pdata.readParcelable(msg);
  return new MyMessageAble('test1', 'Callee test');
}
export default class MainUIAbility extends UIAbility {
  onCreate(want: Want, launchParam: AbilityConstant.LaunchParam) {
    console.log('Callee onCreate is called');
    try {
      this.callee.on(method, funcCallBack);
    } catch (error) {
      console.error(`Callee.on catch error, error.code: ${error.code}, error.message: ${error.message}`);
    }
  }
}
```

### Callee.off

off(method: string): void

Unregisters a caller notification callback, which is invoked when the target UIAbility registers a function.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| method | string | Yes| Registered notification message string.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------------------------------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |
| 16200005 | The method has not been registered. |
| 16000050 | Internal error. |

**Example**

```ts
import { UIAbility, AbilityConstant, Want } from '@kit.AbilityKit';

let method = 'call_Function';

export default class MainUIAbility extends UIAbility {
  onCreate(want: Want, launchParam: AbilityConstant.LaunchParam) {
    console.log('Callee onCreate is called');
    try {
      this.callee.off(method);
    } catch (error) {
      console.error(`Callee.off catch error, error.code: ${error.code}, error.message: ${error.message}`);
    }
  }
}
```

## OnReleaseCallback

### (msg: string)

(msg: string): void

Defines the callback that is invoked when the stub on the target UIAbility is disconnected.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| --- | ----- | --- | -------- |
| msg | string | Yes| Message used for disconnection.| 

## OnRemoteStateChangeCallback<sup>10+</sup>

### (msg: string)

(msg: string): void

Defines the callback that is invoked when the remote UIAbility state changes in the collaboration scenario.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| --- | ----- | --- | -------- |
| msg | string | Yes| Message used for disconnection.| 

## CalleeCallback

### (indata: rpc.MessageSequence)

(indata: rpc.MessageSequence): rpc.Parcelable

Defines the callback of the registration message notification of the UIAbility.

**System capability**: SystemCapability.Ability.AbilityRuntime.AbilityCore

**Parameters**

| Name| Type| Mandatory| Description|
| --- | ----- | --- | -------- |
| indata | [rpc.MessageSequence](../apis-ipc-kit/js-apis-rpc.md#messagesequence9) | Yes| Data to be transferred.|

**Return value**

| Type  | Description                                 |
| ------------ | ------------------------------------- |
| [rpc.Parcelable](../apis-ipc-kit/js-apis-rpc.md#parcelable9) | Returned data object.|