# @ohos.application.Ability (Ability)

The **Ability** module manages the ability lifecycle and context, such as creating and destroying an ability, and dumping client information.

This module provides the following common ability-related functions:

- [Caller](#caller): implements sending of sequenceable data to the target ability when an ability (caller ability) invokes the target ability (callee ability).
- [Callee](#callee): implements callbacks for registration and deregistration of caller notifications.

> **NOTE**
>
> The APIs of this module are deprecated since API version 9. You are advised to use [@ohos.app.ability.UIAbility (UIAbility)](js-apis-app-ability-uiAbility.md) instead.
>
> 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 '@ohos.application.Ability';
```

## Attributes

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

| Name| Type| Readable| Writable| Description| 
| -------- | -------- | -------- | -------- | -------- |
| context | [UIAbilityContext](js-apis-inner-application-uiAbilityContext.md) | Yes| No| Context of an ability.| 
| launchWant | [Want](js-apis-app-ability-want.md) | Yes| No| Parameters for starting the ability.| 
| lastRequestWant | [Want](js-apis-app-ability-want.md) | Yes| No| Parameters used when the ability was started last time.| 
| callee | [Callee](#callee) | Yes| No| Object that invokes the stub service.| 

## Ability.onCreate

onCreate(want: Want, param: AbilityConstant.LaunchParam): void;

Called to initialize the service logic when an ability is created.

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

**Parameters**

  | Name| Type| Mandatory| Description| 
  | -------- | -------- | -------- | -------- |
  | want | [Want](js-apis-app-ability-want.md) | Yes| Information related to this ability, including the ability name and bundle name.| 
  | param | AbilityConstant.LaunchParam | Yes| Parameters for starting the ability, and the reason for the last abnormal exit.| 

**Example**

  ```ts
  export default class EntryAbility extends UIAbility {
      onCreate(want, param) {
          console.log('onCreate, want:' + want.abilityName);
      }
  }
  ```


## Ability.onWindowStageCreate

onWindowStageCreate(windowStage: window.WindowStage): void

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

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

**Parameters**

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

**Example**
    
  ```ts
  export default class EntryAbility extends UIAbility {
      onWindowStageCreate(windowStage) {
          console.log('onWindowStageCreate');
      }
  }
  ```


## Ability.onWindowStageDestroy

onWindowStageDestroy(): void

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

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

**Example**
    
  ```ts
  export default class EntryAbility extends UIAbility {
      onWindowStageDestroy() {
          console.log('onWindowStageDestroy');
      }
  }
  ```


## Ability.onWindowStageRestore

onWindowStageRestore(windowStage: window.WindowStage): void

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

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

**Parameters**

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

**Example**
    
  ```ts
  export default class EntryAbility extends UIAbility {
      onWindowStageRestore(windowStage) {
          console.log('onWindowStageRestore');
      }
  }
  ```


## Ability.onDestroy

onDestroy(): void;

Called when this ability is destroyed to clear resources.

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

**Example**

  ```ts
  export default class EntryAbility extends UIAbility {
      onDestroy() {
          console.log('onDestroy');
      }
  }
  ```


## Ability.onForeground

onForeground(): void;

Called when this ability is switched from the background to the foreground.

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

**Example**

  ```ts
  export default class EntryAbility extends UIAbility {
      onForeground() {
          console.log('onForeground');
      }
  }
  ```


## Ability.onBackground

onBackground(): void;

Called when this ability is switched from the foreground to the background.

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

**Example**

  ```ts
  export default class EntryAbility extends UIAbility {
      onBackground() {
          console.log('onBackground');
      }
  }
  ```


## Ability.onContinue

onContinue(wantParam : {[key: string]: any}): AbilityConstant.OnContinueResult;

Called to save data during the ability migration preparation process.

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

**Parameters**

  | Name| Type| Mandatory| Description| 
  | -------- | -------- | -------- | -------- |
  | wantParam | {[key: string]: any} | Yes| **want** parameter.| 

**Return value**

  | Type| Description| 
  | -------- | -------- |
  | AbilityConstant.OnContinueResult | Continuation result.| 

**Example**

  ```ts
  import AbilityConstant from "@ohos.app.ability.AbilityConstant";
  
  export default class EntryAbility extends UIAbility {
      onContinue(wantParams) {
          console.log('onContinue');
          wantParams["myData"] = "my1234567";
          return AbilityConstant.OnContinueResult.AGREE;
      }
  }
  ```


## Ability.onNewWant

onNewWant(want: Want, launchParams: AbilityConstant.LaunchParam): void;

Called when a new Want is passed in and this UIAbility is started again.

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

**Parameters**

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

**Example**

  ```ts
  export default class EntryAbility extends UIAbility {
      onNewWant(want, launchParams) {
          console.log('onNewWant, want:' + want.abilityName);
          console.log('onNewWant, launchParams:' + JSON.stringify(launchParams));
      }
  }
  ```

## Ability.onConfigurationUpdated

onConfigurationUpdated(config: Configuration): void;

Called when the global configuration is updated.

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

**Parameters**

  | Name| Type| Mandatory| Description| 
  | -------- | -------- | -------- | -------- |
  | config | [Configuration](js-apis-application-configuration.md) | Yes| Callback invoked when the global configuration is updated. The global configuration indicates the configuration of the environment where the application is running and includes the language and color mode.| 

**Example**

  ```ts
  export default class EntryAbility extends UIAbility {
      onConfigurationUpdated(config) {
          console.log('onConfigurationUpdated, language:' + config.language);
      }
  }
  ```

## Ability.dump

dump(params: Array\<string>): Array\<string>;

Dumps client information.

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

**Parameters**

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

**Example**

  ```ts
  export default class EntryAbility extends UIAbility {
      dump(params) {
          console.log('dump, params:' + JSON.stringify(params));
          return ["params"]
      }
  }
  ```

## Ability.onMemoryLevel

onMemoryLevel(level: AbilityConstant.MemoryLevel): void;

Called when the system has decided to adjust the memory level. For example, this API can be used when there is not enough memory to run as many background processes as possible.

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

**Parameters**

  | Name| Type| Mandatory| Description| 
  | -------- | -------- | -------- | -------- |
  | level | [AbilityConstant.MemoryLevel](js-apis-application-abilityConstant.md#abilityconstantmemorylevel) | Yes| Memory level that indicates the memory usage status. When the specified memory level is reached, a callback will be invoked and the system will start adjustment.| 

**Example**

  ```ts
  export default class EntryAbility extends UIAbility {
    onMemoryLevel(level) {
        console.log('onMemoryLevel, level:' + JSON.stringify(level));
    } 
  }
  ```

## Ability.onSaveState

onSaveState(reason: AbilityConstant.StateType, wantParam : {[key: string]: any}): AbilityConstant.OnSaveResult;

Called when the framework automatically saves the ability state in the case of an application fault. This API is used together with [appRecovery](js-apis-app-ability-appRecovery.md).  

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

**Parameters**

  | Name| Type| Mandatory| Description|
  | -------- | -------- | -------- | -------- |
  | reason | [AbilityConstant.StateType](js-apis-application-abilityConstant.md#abilityconstantstatetype) | Yes| Reason for triggering the callback to save the ability state.|
  | wantParam | {[key:&nbsp;string]:&nbsp;any} | Yes| **want** parameter.|

**Return value**

  | Type| Description|
  | -------- | -------- |
  | AbilityConstant.OnSaveResult | Whether the ability state is saved.|

**Example**

  ```ts
import AbilityConstant from '@ohos.app.ability.AbilityConstant';

export default class EntryAbility extends UIAbility {
    onSaveState(reason, wantParam) {
        console.log('onSaveState');
        wantParam["myData"] = "my1234567";
        return AbilityConstant.OnSaveResult.RECOVERY_AGREE;
    }
}
  ```

## Caller

Implements sending of sequenceable data to the target ability when an ability (caller ability) invokes the target ability (callee ability).

## Caller.call

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

Sends sequenceable data to the target ability.

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

**Parameters**

  | Name| Type| Mandatory| Description| 
  | -------- | -------- | -------- | -------- |
  | method | string | Yes| Notification message string negotiated between the two abilities. The message is used to instruct the callee to register a function to receive the sequenceable data.| 
  | data | rpc.Sequenceable | Yes| Sequenceable data. You need to customize the data.| 

**Return value**

  | Type| Description| 
  | -------- | -------- |
  | Promise&lt;void&gt; | Promise used to return a response.| 

**Error codes**

| ID| Error Message|
| ------- | -------------------------------- |
| 201 | The application does not have permission to call the interface. |
| 401 | Invalid input parameter. |
| 16200001 | Caller released. The caller has been released. |
| 16200002 | Callee invalid. The callee does not exist. |
| 16000050 | Internal Error. |

**Example**

  ```ts
  import UIAbility from '@ohos.app.ability.UIAbility';
  
  class MyMessageAble{ // Custom sequenceable data structure.
    name:""
    str:""
    num: 1
    constructor(name, str) {
      this.name = name;
      this.str = str;
    }
    marshalling(messageParcel) {
      messageParcel.writeInt(this.num);
      messageParcel.writeString(this.str);
      console.log('MyMessageAble marshalling num[' + this.num + '] str[' + this.str + ']');
      return true;
    }
    unmarshalling(messageParcel) {
      this.num = messageParcel.readInt();
      this.str = messageParcel.readString();
      console.log('MyMessageAble unmarshalling num[' + this.num + '] str[' + this.str + ']');
      return true;
    }
  };
  var method = 'call_Function'; // Notification message string negotiated by the two abilities
  var caller;
  export default class EntryAbility extends UIAbility {
    onWindowStageCreate(windowStage) {
      this.context.startAbilityByCall({
        bundleName: "com.example.myservice",
        abilityName: "EntryAbility",
        deviceId: ""
      }).then((obj) => {
        caller = obj;
        let msg = new MyMessageAble("msg", "world"); // See the definition of Sequenceable.
        caller.call(method, msg)
          .then(() => {
            console.log('Caller call() called');
          })
          .catch((callErr) => {
            console.log('Caller.call catch error, error.code: ' + JSON.stringify(callErr.code) +
              ' error.message: ' + JSON.stringify(callErr.message));
          });
      }).catch((err) => {
        console.log('Caller GetCaller error, error.code: ' + JSON.stringify(err.code) +
          ' error.message: ' + JSON.stringify(err.message));
      });
    }
  }
  ```


## Caller.callWithResult

callWithResult(method: string, data: rpc.Sequenceable): Promise&lt;rpc.MessageParcel&gt;;

Sends sequenceable data to the target ability and obtains the sequenceable data returned by the target ability.

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

**Parameters**

  | Name| Type| Mandatory| Description| 
  | -------- | -------- | -------- | -------- |
  | method | string | Yes| Notification message string negotiated between the two abilities. The message is used to instruct the callee to register a function to receive the sequenceable data.| 
  | data | rpc.Sequenceable | Yes| Sequenceable data. You need to customize the data.| 

**Return value**

  | Type| Description| 
  | -------- | -------- |
  | Promise&lt;rpc.MessageParcel&gt; | Promise used to return the sequenceable data from the target ability.| 

**Error codes**

| ID| Error Message|
| ------- | -------------------------------- |
| 201 | The application does not have permission to call the interface. |
| 401 | Invalid input parameter. |
| 16200001 | Caller released. The caller has been released. |
| 16200002 | Callee invalid. The callee does not exist. |
| 16000050 | Internal Error. |

**Example**

  ```ts
  import UIAbility from '@ohos.app.ability.UIAbility';
  
  class MyMessageAble{
    name:""
    str:""
    num: 1
    constructor(name, str) {
      this.name = name;
      this.str = str;
    }
    marshalling(messageParcel) {
      messageParcel.writeInt(this.num);
      messageParcel.writeString(this.str);
      console.log('MyMessageAble marshalling num[' + this.num + '] str[' + this.str + ']');
      return true;
    }
    unmarshalling(messageParcel) {
      this.num = messageParcel.readInt();
      this.str = messageParcel.readString();
      console.log('MyMessageAble unmarshalling num[' + this.num + '] str[' + this.str + ']');
      return true;
    }
  };
  var method = 'call_Function';
  var caller;
  export default class EntryAbility extends UIAbility {
    onWindowStageCreate(windowStage) {
      this.context.startAbilityByCall({
        bundleName: "com.example.myservice",
        abilityName: "EntryAbility",
        deviceId: ""
      }).then((obj) => {
        caller = obj;
        let msg = new MyMessageAble(1, "world");
        caller.callWithResult(method, msg)
          .then((data) => {
            console.log('Caller callWithResult() called');
            let retmsg = new MyMessageAble(0, "");
            data.readSequenceable(retmsg);
          })
          .catch((callErr) => {
            console.log('Caller.callWithResult catch error, error.code: ' + JSON.stringify(callErr.code) +
              ' error.message: ' + JSON.stringify(callErr.message));
          });
      }).catch((err) => {
        console.log('Caller GetCaller error, error.code: ' + JSON.stringify(err.code) +
          ' error.message: ' + JSON.stringify(err.message));
      });
    }
  }
  ```


## Caller.release

release(): void;

Releases the caller interface of the target ability.

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

**Error codes**

| ID| Error Message|
| ------- | -------------------------------- |
| 401 | Invalid input parameter. |
| 16200001 | Caller released. The caller has been released. |
| 16200002 | Callee invalid. The callee does not exist. |
| 16000050 | Internal Error. |

**Example**

  ```ts
  import UIAbility from '@ohos.app.ability.UIAbility';
  
  var caller;
  
  export default class EntryAbility extends UIAbility {
    onWindowStageCreate(windowStage) {
      this.context.startAbilityByCall({
        bundleName: "com.example.myservice",
        abilityName: "EntryAbility",
        deviceId: ""
      }).then((obj) => {
        caller = obj;
        try {
          caller.release();
        } catch (releaseErr) {
          console.log('Caller.release catch error, error.code: ' + JSON.stringify(releaseErr.code) +
            ' error.message: ' + JSON.stringify(releaseErr.message));
        }
      }).catch((err) => {
        console.log('Caller GetCaller error, error.code: ' + JSON.stringify(err.code) +
          ' error.message: ' + JSON.stringify(err.message));
      });
    }
  }
  ```

## Caller.onRelease

 onRelease(callback: OnReleaseCallBack): void;

Registers a callback that is invoked when the stub on the target ability is disconnected.

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

**Parameters**

  | Name| Type| Mandatory| Description| 
  | -------- | -------- | -------- | -------- |
  | callback | OnReleaseCallBack | Yes| Callback used for the **onRelease** API.| 

**Example**

  ```ts
  import UIAbility from '@ohos.app.ability.UIAbility';
  
  var caller;
  
  export default class EntryAbility extends UIAbility {
    onWindowStageCreate(windowStage) {
      this.context.startAbilityByCall({
        bundleName: "com.example.myservice",
        abilityName: "EntryAbility",
        deviceId: ""
      }).then((obj) => {
          caller = obj;
          try {
            caller.onRelease((str) => {
                console.log(' Caller OnRelease CallBack is called ' + str);
            });
          } catch (error) {
            console.log('Caller.on catch error, error.code: ' + JSON.stringify(error.code) +
              ' error.message: ' + JSON.stringify(error.message));
          }
      }).catch((err) => {
        console.log('Caller GetCaller error, error.code: ' + JSON.stringify(err.code) +
          ' error.message: ' + JSON.stringify(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 ability registers a function.

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

**Parameters**

  | Name| Type| Mandatory| Description| 
  | -------- | -------- | -------- | -------- |
  | method | string | Yes| Notification message string negotiated between the two abilities.| 
  | callback | CalleeCallBack | Yes| JS notification synchronization callback of the **rpc.MessageParcel** type. The callback must return at least one empty **rpc.Sequenceable** object. Otherwise, the function execution fails.| 

**Error codes**

| ID| Error Message|
| ------- | -------------------------------- |
| 401 | Invalid input parameter. |
| 16200004 | Method registered. The method has registered. |
| 16000050 | Internal Error. |

**Example**

  ```ts
  import UIAbility from '@ohos.app.ability.UIAbility';
  class MyMessageAble{
      name:""
      str:""
      num: 1
      constructor(name, str) {
        this.name = name;
        this.str = str;
      }
      marshalling(messageParcel) {
          messageParcel.writeInt(this.num);
          messageParcel.writeString(this.str);
          console.log('MyMessageAble marshalling num[' + this.num + '] str[' + this.str + ']');
          return true;
      }
      unmarshalling(messageParcel) {
          this.num = messageParcel.readInt();
          this.str = messageParcel.readString();
          console.log('MyMessageAble unmarshalling num[' + this.num + '] str[' + this.str + ']');
          return true;
      }
  };
  var method = 'call_Function';
  function funcCallBack(pdata) {
      console.log('Callee funcCallBack is called ' + pdata);
      let msg = new MyMessageAble("test", "");
      pdata.readSequenceable(msg);
      return new MyMessageAble("test1", "Callee test");
  }
  export default class EntryAbility extends UIAbility {
    onCreate(want, launchParam) {
      console.log('Callee onCreate is called');
      try {
        this.callee.on(method, funcCallBack);
      } catch (error) {
        console.log('Callee.on catch error, error.code: ' + JSON.stringify(error.code) +
          ' error.message: ' + JSON.stringify(error.message));
      }
    }
  }
  ```

## Callee.off

off(method: string): void;

Deregisters a caller notification callback, which is invoked when the target ability registers a function.

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

**Parameters**

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

**Error codes**

| ID| Error Message|
| ------- | -------------------------------- |
| 401 | Invalid input parameter. |
| 16200005 | Method not registered. The method has not registered. |
| 16000050 | Internal Error. |


**Example**
  ```ts
  import UIAbility from '@ohos.app.ability.UIAbility';
  
  var method = 'call_Function';
  
  export default class EntryAbility extends UIAbility {
    onCreate(want, launchParam) {
      console.log('Callee onCreate is called');
      try {
        this.callee.off(method);
      } catch (error) {
        console.log('Callee.off catch error, error.code: ' + JSON.stringify(error.code) +
          ' error.message: ' + JSON.stringify(error.message));
      }
    }
  }
  ```

## OnReleaseCallBack

(msg: string): void;

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

| Name| Type| Readable| Writable| Description| 
| -------- | -------- | -------- | -------- | -------- |
| (msg: string) | function | Yes| No| Prototype of the listener function registered by the caller.| 

## CalleeCallBack

(indata: rpc.MessageParcel): rpc.Sequenceable;

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

| Name| Type| Readable| Writable| Description| 
| -------- | -------- | -------- | -------- | -------- |
| (indata: rpc.MessageParcel) | rpc.Sequenceable | Yes| No| Prototype of the listener function registered by the callee.|