@ohos.data.sendablePreferences (Shared User Preferences)

The sendablePreferences module provides APIs for processing data in the form of key-value (KV) pairs, including querying, modifying, and persisting KV pairs.

In the KV pairs, the key must be a string, and the value can be a number, a string, a Boolean value, a bigint, or a serializable object.

The persistent files of the shared user preferences are stored in the preferencesDir directory. Before creating a preferences object, ensure that the preferencesDir path can be read and written. The encryption level of the persistent file directory determines the access to the files. For details, see Application File Directory and Application File Path.

Sendable preferences can be passed between concurrent ArkTS instances (including the main thread and TaskPool or Worker threads) by reference. It allows for higher performance than user preferences. For more information, see Using Sendable Objects.

NOTE

The initial APIs of this module are supported since API version 12. Newly added APIs will be marked with a superscript to indicate their earliest API version.

The shared user preferences are not thread-safe and may cause file damage and data loss when used in multi-process scenarios. Do not use it in multi-process scenarios.

Modules to Import

import { sendablePreferences } from '@kit.ArkData';

Constant

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Name	Type	Readable	Writable	Description
MAX_KEY_LENGTH	number	Yes	No	Maximum length of a key, which is 1024 bytes.
MAX_VALUE_LENGTH	number	Yes	No	Maximum length of a value, which is 16 MB.

sendablePreferences.getPreferences

getPreferences(context: Context, options: Options): Promise<Preferences>

Obtains a Preferences instance. This API uses a promise to return the result.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
context	Context	Yes	Application context.
options	Options	Yes	Configuration options of the Preferences instance.

Return value

Type	Description
Promise<Preferences>	Promise used to return the Preferences instance obtained. This instance inherits from ISendable and can be passed between concurrent ArkTS instances (including the main thread and the TaskPool or Worker threads) by reference. For details, see Using Sendable Objects.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
801	Capability not supported.
15500000	Inner error.
15501001	The operations is supported in stage mode only.
15501002	Invalid dataGroupId.

Example

import { UIAbility } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';
import { window } from '@kit.ArkUI';

let preferences: sendablePreferences.Preferences;

class EntryAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    let options: sendablePreferences.Options = { name: 'myStore' };
    let promise = sendablePreferences.getPreferences(this.context, options);
    promise.then((object: sendablePreferences.Preferences) => {
      preferences = object;
      console.info("Succeeded in getting preferences.");
    }).catch((err: BusinessError) => {
      console.error(`Failed to get preferences. code: ${err.code}, message: ${err.message}`);
    });
  }
}

sendablePreferences.getPreferencesSync

getPreferencesSync(context: Context, options: Options): Preferences

Obtains a Preferences instance. This API returns the result synchronously.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
context	Context	Yes	Application context.
options	Options	Yes	Configuration options of the Preferences instance.

Return value

Type	Description
Preferences	Preferences instance obtained. This instance inherits from ISendable and can be passed between concurrent ArkTS instances (including the main thread and the TaskPool or Worker threads) by reference. For details, see Using Sendable Objects.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
801	Capability not supported.
15500000	Inner error.
15501001	The operations is supported in stage mode only.
15501002	Invalid dataGroupId.

Example

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

let preferences: sendablePreferences.Preferences;

class EntryAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    let options: sendablePreferences.Options = { name: 'myStore' };
    preferences = sendablePreferences.getPreferencesSync(this.context, options);
  }
}

sendablePreferences.deletePreferences

deletePreferences(context: Context, options: Options): Promise<void>

Deletes a Preferences instance from the cache. If the Preferences instance has a persistent file, the persistent file will also be deleted. This API uses a promise to return the result.

Avoid using a deleted Preferences instance to perform data operations, which may cause data inconsistency.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
context	Context	Yes	Application context.
options	Options	Yes	Configuration options of the Preferences instance.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
801	Capability not supported.
15500000	Inner error.
15500010	Failed to delete the user preferences persistence file.
15501001	The operations is supported in stage mode only.
15501002	Invalid dataGroupId.

Example

import { UIAbility } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';
import { window } from '@kit.ArkUI';

class EntryAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    let options: sendablePreferences.Options = { name: 'myStore' };
    let promise = sendablePreferences.deletePreferences(this.context, options);
    promise.then(() => {
      console.info("Succeeded in deleting preferences.");
    }).catch((err: BusinessError) => {
      console.error(`Failed to delete preferences. code: ${err.code}, message: ${err.message}`);
    });
  }
}

sendablePreferences.removePreferencesFromCache

removePreferencesFromCache(context: Context, options: Options): Promise<void>

Removes a Preferences instance from the cache. This API uses a promise to return the result.

After an application calls getPreferences for the first time to obtain a Preferences instance, the obtained Preferences instance is cached. When the application calls getPreferences again, the Preferences instance will be read from the cache instead of from the persistent file. After this API is called to remove the instance from the cache, calling getPreferences again will read data from the persistent file and create a Preferences instance.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
context	Context	Yes	Application context.
options	Options	Yes	Configuration options of the Preferences instance.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
801	Capability not supported.
15500000	Inner error.
15501001	The operations is supported in stage mode only.
15501002	Invalid dataGroupId.

Example

import { UIAbility } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';
import { window } from '@kit.ArkUI';

class EntryAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    let options: sendablePreferences.Options = { name: 'myStore' };
    let promise = sendablePreferences.removePreferencesFromCache(this.context, options);
    promise.then(() => {
      console.info("Succeeded in removing preferences.");
    }).catch((err: BusinessError) => {
      console.error(`Failed to remove preferences. code: ${err.code}, message: ${err.message}`);
    });
  }
}

sendablePreferences.removePreferencesFromCacheSync

removePreferencesFromCacheSync(context: Context, options: Options):void

Removes a Preferences instance from the cache. This API returns the result synchronously.

After an application calls getPreferences for the first time to obtain a Preferences instance, the obtained Preferences instance is cached. When the application calls getPreferences again, the Preferences instance will be read from the cache instead of from the persistent file. After this API is called to remove the instance from the cache, calling getPreferences again will read data from the persistent file and create a Preferences instance.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
context	Context	Yes	Application context.
options	Options	Yes	Configuration options of the Preferences instance.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
801	Capability not supported.
15500000	Inner error.
15501001	The operations is supported in stage mode only.
15501002	Invalid dataGroupId.

Example

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

class EntryAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage) {
    let options: sendablePreferences.Options = { name: 'myStore' };
    sendablePreferences.removePreferencesFromCacheSync(this.context, options);
  }
}

Options

Represents the configuration options of a Preferences instance.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Name	Type	Mandatory	Description
name	string	Yes	Name of the Preferences instance.
dataGroupId	string|null	No	Application group ID. Currently, this parameter is not supported. This parameter is optional. A Preferences instance will be created in the sandbox path corresponding to the specified dataGroupId. If this parameter is not specified, the Preferences instance is created in the sandbox directory of the application. Model restriction: This attribute can be used only in the stage model.

Preferences

Provides APIs for obtaining and modifying Preferences instances. Preferences inherits from ISendable and can be passed between concurrent ArkTS instances (including the main thread and the TaskPool or Worker threads) by reference.

Before calling any API of Preferences, obtain a Preferences instance by using sendablePreferences.getPreferences.

get

get(key: string, defValue: lang.ISendable): Promise<lang.ISendable>

Obtains the value of a key from this Preferences instance. This API uses a promise to return the result. If the value is null or is not of the default value type, defValue is returned.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the data to obtain. It cannot be empty.
defValue	lang.ISendable	Yes	Default value to be returned.

Return value

Type	Description
Promise<lang.ISendable>	Promise used to return the value obtained. This instance inherits from ISendable and can be passed between concurrent ArkTS instances (including the main thread and the TaskPool or Worker threads) by reference. For details, see Using Sendable Objects.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';
import { lang } from '@kit.ArkTS';

let promise = preferences.get('startup', 'default');
promise.then((data: lang.ISendable) => {
  let dataStr = data as string;
  console.info(`Succeeded in getting value of 'startup'. Data: ${dataStr}`);
}).catch((err: BusinessError) => {
  console.error(`Failed to get value of 'startup'. code: ${err.code}, message: ${err.message}`);
});

getSync

getSync(key: string, defValue: lang.ISendable): lang.ISendable

Obtains the value of a key from this Preferences instance. This API returns the result synchronously. If the value is null or is not of the default value type, defValue is returned.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the data to obtain. It cannot be empty.
defValue	lang.ISendable	Yes	Default value to be returned.

Return value

Type	Description
lang.ISendable	Value obtained. This instance inherits from ISendable and can be passed between concurrent ArkTS instances (including the main thread and the TaskPool or Worker threads) by reference. For details, see Using Sendable Objects.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

import { lang } from '@kit.ArkTS';
let value: lang.ISendable = preferences.getSync('startup', 'default');

getAll

getAll(): Promise<lang.ISendable>

Obtains all KV pairs from this Preferences instance. This API uses a promise to return the result.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Return value

Type	Description
Promise<lang.ISendable>	Promise used to return the KV pairs obtained. This object inherits from ISendable and can be passed between concurrent ArkTS instances (including the main thread and the TaskPool or Worker threads) by reference. For details, see Using Sendable Objects.

Error codes

For details about the error codes, see User Preference Error Codes.

ID	Error Message
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';
import { lang } from '@kit.ArkTS';

let promise = preferences.getAll();
promise.then((keyValues: lang.ISendable) => {
  for (let value of Object.keys(keyValues)) {
    console.info("getAll " + JSON.stringify(value));
  }
}).catch((err: BusinessError) => {
  console.error(`Failed to get all key-values. code: ${err.code}, message: ${err.message}`);
});

getAllSync

getAllSync(): lang.ISendable

Obtains all KV pairs from this Preferences instance. This API returns the result synchronously.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Return value

Type	Description
lang.ISendable	All KV pairs obtained. This object inherits from ISendable and can be passed between concurrent ArkTS instances (including the main thread and the TaskPool or Worker threads) by reference. For details, see Using Sendable Objects.

Error codes

For details about the error codes, see User Preference Error Codes.

ID	Error Message
15500000	Inner error.

Example

import { lang } from '@kit.ArkTS';

let keyValues: lang.ISendable = preferences.getAllSync();
for (let value of Object.keys(keyValues)) {
  console.info("getAll " + JSON.stringify(value));
}

put

put(key: string, value: lang.ISendable): Promise<void>

Writes data to this Preferences instance. This API uses a promise to return the result. You can use flush to persist the Preferences instance.

NOTE

If the value contains a string that is not in UTF-8 format, store it in an Uint8Array. Otherwise, the persistent file may be damaged due to format errors.

If the key already exists, put() overwrites the value. You can use hasSync() to check whether the KV pair exists.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the data. It cannot be empty.
value	lang.ISendable	Yes	Value to write.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';

let promise = preferences.put('startup', 'auto');
promise.then(() => {
  console.info("Succeeded in putting value of 'startup'.");
}).catch((err: BusinessError) => {
  console.error(`Failed to put value of 'startup'. code: ${err.code}, message: ${err.message}`);
});

putSync

putSync(key: string, value: lang.ISendable): void

Writes data to this Preferences instance. This API returns the result synchronously. You can use flush to persist the Preferences instance.

NOTE

If the value contains a string that is not in UTF-8 format, store it in an Uint8Array. Otherwise, the persistent file may be damaged due to format errors.

If the key already exists, putSync() overwrites the value. You can use hasSync() to check whether the KV pair exists.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the data. It cannot be empty.
value	lang.ISendable	Yes	Value to write.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

preferences.putSync('startup', 'auto');

has

has(key: string): Promise<boolean>

Checks whether this Preferences instance contains the KV pair of the given key. This API uses a promise to return the result.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the data to check. It cannot be empty.

Return value

Type	Description
Promise<boolean>	Promise used to return the result. The value true means the Preferences instance contains the KV pair; the value false means the opposite.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';

let promise = preferences.has('startup');
promise.then((val: boolean) => {
  if (val) {
    console.info("The key 'startup' is contained.");
  } else {
    console.error("The key 'startup' does not contain.");
  }
}).catch((err: BusinessError) => {
  console.error(`Failed to check the key 'startup'. code: ${err.code}, message: ${err.message}`);
});

hasSync

hasSync(key: string): boolean

Checks whether this Preferences instance contains the KV pair of the given key. This API returns the result synchronously.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the data to check. It cannot be empty.

Return value

Type	Description
boolean	Returns true if the Preferences instance contains the KV pair; returns false otherwise.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

let isExist: boolean = preferences.hasSync('startup');
if (isExist) {
  console.info("The key 'startup' is contained.");
} else {
  console.error("The key 'startup' does not contain.");
}

delete

delete(key: string): Promise<void>

Deletes a KV pair from this Preferences instance. This API uses a promise to return the result. You can use flush to persist the Preferences instance.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the KV pair to delete. It cannot be empty.

Return value

Type	Description
Promise<void>	Promise that returns no value.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';

let promise = preferences.delete('startup');
promise.then(() => {
  console.info("Succeeded in deleting the key 'startup'.");
}).catch((err: BusinessError) => {
  console.error(`Failed to delete the key 'startup'. code: ${err.code}, message: ${err.message}`);
});

deleteSync

deleteSync(key: string): void

Deletes a KV pair from this Preferences instance. This API returns the result synchronously. You can use flush to persist the Preferences instance.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
key	string	Yes	Key of the KV pair to delete. It cannot be empty.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

preferences.deleteSync('startup');

flush

flush(): Promise<void>

Flushes the data in this Preferences instance to the persistent file. This API uses a promise to return the result.

NOTE

If no data is modified or the modified data is the same as the cached data, the persistence file will not be updated.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Return value

Type	Description
Promise<void>	Promise that returns no value.

Error codes

For details about the error codes, see User Preference Error Codes.

ID	Error Message
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';

let promise = preferences.flush();
promise.then(() => {
  console.info("Succeeded in flushing.");
}).catch((err: BusinessError) => {
  console.error(`Failed to flush. code: ${err.code}, message: ${err.message}`);
});

flushSync¹⁴⁺

flushSync(): void

Flushes the data in the cached Preferences instance to the persistent file.

NOTE

If no data is modified or the modified data is the same as the cached data, the persistence file will not be updated.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Error codes

For details about the error codes, see User Preference Error Codes.

ID	Error Message
15500000	Inner error.

Example

preferences.flushSync();

clear

clear(): Promise<void>

Clears this Preferences instance. This API uses a promise to return the result. You can use flush to persist the Preferences instance.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Return value

Type	Description
Promise<void>	Promise that returns no value.

Error codes

For details about the error codes, see User Preference Error Codes.

ID	Error Message
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';

let promise = preferences.clear();
promise.then(() => {
  console.info("Succeeded in clearing.");
}).catch((err: BusinessError) => {
  console.error(`Failed to clear. code: ${err.code}, message: ${err.message}`);
});

clearSync

clearSync(): void

Clears this Preferences instance. This API returns the result synchronously. You can use flush to persist the Preferences instance.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Error codes

For details about the error codes, see User Preference Error Codes.

ID	Error Message
15500000	Inner error.

Example

preferences.clearSync();

on(‘change’)

on(type: ‘change’, callback: Callback<string>): void

Subscribes to data changes. The registered callback will be invoked to return the new value if the data change is flushed.

NOTE

After removePreferencesFromCache or deletePreferences is called, the data change subscription will be automatically canceled. After getPreferences is called again, you need to subscribe to data changes again.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
type	string	Yes	Event type. The value is ‘change’, which indicates data changes.
callback	Callback<string>	Yes	Callback used to return the key whose value is changed.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';

let observer = (key: string) => {
  console.info("The key " + key + " changed.");
};
preferences.on('change', observer);
preferences.putSync('startup', 'manual');
preferences.flush().then(() => {
  console.info("Succeeded in flushing.");
}).catch((err: BusinessError) => {
  console.error(`Failed to flush. code: ${err.code}, message: ${err.message}`);
});

on(‘multiProcessChange’)

on(type: ‘multiProcessChange’, callback: Callback<string>): void

Subscribes to inter-process data changes. When multiple processes hold the same preference file, calling flush in any process (including the current process) will trigger the callback in this API.

This API is provided for applications that have applied for dataGroupId. Avoid using this API for the applications that have not applied for dataGroupId because calling it in multiple process may damage the persistent files and cause data loss.

NOTE

The maximum number of subscriptions for inter-process data change of the same persistent file for the current process is 50. Once the limit is reached, the subscription will fail. You are advised to cancel the subscription in a timely manner after the callback is triggered.

After removePreferencesFromCache or deletePreferences is called, the data change subscription will be automatically canceled. After getPreferences is called again, you need to subscribe to data changes again.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
type	string	Yes	Event type. The value is ‘multiProcessChange’, which indicates inter-process data changes.
callback	Callback<string>	Yes	Callback used to return the key whose value is changed.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.
15500019	Failed to obtain the subscription service.

Example

import { BusinessError } from '@kit.BasicServicesKit';

let observer = (key: string) => {
  console.info("The key " + key + " changed.");
};
preferences.on('multiProcessChange', observer);
preferences.putSync('startup', 'manual');
preferences.flush().then(() => {
  console.info("Succeeded in flushing.");
}).catch((err: BusinessError) => {
  console.error(`Failed to flush. code: ${err.code}, message: ${err.message}`);
});

on(‘dataChange’)

on(type: ‘dataChange’, keys: Array<string>, callback: Callback<lang.ISendable>): void

Subscribes to changes of specific data. The registered callback will be invoked only after the values of the specified keys are changed and flushed.

NOTE

After removePreferencesFromCache or deletePreferences is called, the data change subscription will be automatically canceled. After getPreferences is called again, you need to subscribe to data changes again.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
type	string	Yes	Event type. The value is ‘dataChange’, which indicates data changes.
keys	Array<string>	Yes	Keys to be observed.
callback	callback: Callback<lang.ISendable>	Yes	Callback used to return the KV pairs changed. The keys are the keys observed, and the values are the new values. The values support the following types: number, string, boolean, bigint, and serializable object.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';
import { lang } from '@kit.ArkTS';

let observer = (data: lang.ISendable) => {
  console.info(`observer : ${data}`);
};
let keys = ['name', 'age'];
preferences.on('dataChange', keys, observer);
preferences.putSync('name', 'xiaohong');
preferences.putSync('weight', 125);
preferences.flush().then(() => {
  console.info("Succeeded in flushing.");
}).catch((err: BusinessError) => {
  console.error(`Failed to flush. code: ${err.code}, message: ${err.message}`);
});

off(‘change’)

off(type: ‘change’, callback?: Callback<string>): void

Unsubscribes from data changes.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
type	string	Yes	Event type. The value is ‘change’, which indicates data changes.
callback	Callback<string>	No	Callback to unregister. If this parameter is not specified, this API unregisters all callbacks for data changes.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';

let observer = (key: string) => {
  console.info("The key " + key + " changed.");
};
preferences.on('change', observer);
preferences.putSync('startup', 'auto');
preferences.flush().then(() => {
  console.info("Succeeded in flushing.");
  preferences.off('change', observer);
}).catch((err: BusinessError) => {
  console.error(`Failed to flush. code: ${err.code}, message: ${err.message}`);
});

off(‘multiProcessChange’)

off(type: ‘multiProcessChange’, callback?: Callback<string>): void

Unsubscribes from inter-process data changes.

This API is provided for applications that have applied for dataGroupId. Avoid using this API for the applications that have not applied for dataGroupId because calling it in multiple process may damage the persistent files and cause data loss.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
type	string	Yes	Event type. The value is ‘multiProcessChange’, which indicates inter-process data changes.
callback	Callback<string>	No	Callback to unregister. If this parameter is not specified, this API unregisters all callbacks for inter-process data changes.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';

let observer = (key: string) => {
  console.info("The key " + key + " changed.");
};
preferences.on('multiProcessChange', observer);
preferences.putSync('startup', 'auto');
preferences.flush().then(() => {
  console.info("Succeeded in flushing.");
  preferences.off('multiProcessChange', observer);
}).catch((err: BusinessError) => {
  console.error(`Failed to flush. code: ${err.code}, message: ${err.message}`);
});

off(‘dataChange’)

off(type: ‘dataChange’, keys: Array<string>, callback?: Callback<lang.ISendable>): void

Unsubscribes from changes of specific data.

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

System capability: SystemCapability.DistributedDataManager.Preferences.Core

Parameters

Name	Type	Mandatory	Description
type	string	Yes	Event type. The value is ‘dataChange’, which indicates data changes.
keys	Array<string>	Yes	Keys to be unsubscribed from. If this parameter is not specified, this API unsubscribes from the changes of all keys.
callback	Callback<lang.ISendable>	No	Callback to unregister. If this parameter is not specified, this API unregisters all callbacks for the changes of the specified data.

Error codes

For details about the error codes, see Universal Error Codes and User Preference Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed.
15500000	Inner error.

Example

import { BusinessError } from '@kit.BasicServicesKit';
import { lang } from '@kit.ArkTS';

let observer = (data: lang.ISendable) => {
  console.info(`observer : ${data}`);
};
let keys = ['name', 'age'];
preferences.on('dataChange', keys, observer);
preferences.putSync('name', 'xiaohong');
preferences.putSync('weight', 125);
preferences.flush().then(() => {
  console.info("Succeeded in flushing.");
  preferences.off('dataChange', keys, observer);
}).catch((err: BusinessError) => {
  console.error(`Failed to flush. code: ${err.code}, message: ${err.message}`);
});

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