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en/application-dev/reference/apis/js-apis-data-preferences.md
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# Lightweight Storage
# 首选项
Lightweight storage provides applications with data processing capability and allows applications to perform lightweight data storage and query. Data is stored in key-value (KV) pairs. Keys are of the string type, and values can be of the number, string, or Boolean type.
首选项为应用提供key-value键值型的数据处理能力，支持应用持久化轻量级数据，并对其修改和查询。数据存储形式为键值对，键的类型为字符串型，值的存储数据类型包括数字型、字符型、布尔型。
> ![icon-note.gif](public_sys-resources/icon-note.gif) **NOTE**<br/>
> 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.
> ![icon-note.gif](public_sys-resources/icon-note.gif) **说明：**
> 本模块首批接口从API version 9开始支持。后续版本的新增接口，采用上角标单独标记接口的起始版本。
## Modules to Import
## 导入模块
```
import data_preferences from '@ohos.data.preferences'
```ts
import data_preferences from '@ohos.data.preferences';
```
## Attributes
## 常量
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：以下各项对应的系统能力均为SystemCapability.DistributedDataManager.Preferences.Core
| Name| Type| Readable| Writable| Description|
| 名称 | 参数类型 | 可读 | 可写 | 说明 |
| -------- | -------- | -------- | -------- | -------- |
| MAX_KEY_LENGTH | string | Yes| No| Maximum length of a key. It is 80 bytes.|
| MAX_VALUE_LENGTH | string | Yes| No| Maximum length of a value of the string type. It is 8192 bytes.|
| MAX_KEY_LENGTH | string | 是 | 否 | key的最大长度限制，大小为80字节。 |
| MAX_VALUE_LENGTH | string | 是 | 否 | value的最大长度限制，大小为8192字节。 |
## data_preferences.getPreferences
getPreferences(context: Context, name: string, callback: AsyncCallback&lt;Preferences&gt;): void
Reads a file and loads the data to the **Preferences** instance. This method uses an asynchronous callback to return the execution result.
读取指定首选项持久化文件，将数据加载到Preferences实例，用于数据操作，该方法使用callback方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| context | Context | Yes| Context of the app or functionality.|
| name | string | Yes| Name of the app's internal data storage.|
| callback | AsyncCallback&lt;[Preferences](#preferences)&gt; | Yes| Callback used to return the execution result.|
| context | [Context](js-apis-Context.md) | 是 | 应用程序或功能的上下文。 |
| name | string | 是 | 应用程序内部数据存储名称。 |
| callback | AsyncCallback&lt;[Preferences](#preferences)&gt; | 是 | 回调函数。 |
- Example
```
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
var path = this.context.getDataBaseDir()
data_preferences.getPreferences(this.context, 'mystore', function (err, preferences) {
if (err) {
console.info("Get the preferences failed, path: " + path + '/mystore')
return;
}
preferences.put('startup', 'auto', function (err) {
export default class MainAbility extends Ability {
data_preferences.getPreferences(this.context, 'mystore', function (err, preferences) {
if (err) {
console.info("Put the value of startup failed with err: " + err)
return
console.info("Get the preferences failed")
return;
}
console.info("Put the value of startup successfully.")
preferences.flush(function (err) {
preferences.put('startup', 'auto', function (err) {
if (err) {
console.info("Flush to file failed with err: " + err)
console.info("Put the value of startup failed, err: " + err)
return
}
console.info("Flushed to file successfully.")
console.info("Put the value of startup successfully.")
preferences.flush(function (err) {
if (err) {
console.info("Flush to file failed, err: " + err)
return
}
console.info("Flushed to file successfully.")
})
})
})
})
}
```
......@@ -71,45 +73,47 @@ Reads a file and loads the data to the **Preferences** instance. This method use
getPreferences(context: Context, name: string): Promise&lt;Preferences&gt;
Reads a file and loads the data to the **Preferences** instance. This method uses a promise to return the execution result.
读取指定首选项持久化文件，将数据加载到Preferences实例，用于数据操作，该方法使用Promise方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| context | Context | Yes| Context of the app or functionality.|
| name | string | Yes| Name of the app's internal data storage.|
| context | [Context](js-apis-Context.md) | 是 | 应用程序或功能的上下文。 |
| name | string | 是 | 应用程序内部数据存储名称。 |
- Return value
| Type| Description|
- 返回值：
| 类型 | 说明 |
| -------- | -------- |
| Promise&lt;[Preferences](#preferences)&gt; | Promise used to return the result.|
| Promise&lt;[Preferences](#preferences)&gt; | Promise实例，用于异步获取结果。 |
- Example
```
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
var path = this.context.getDataBaseDir()
let promisePre = data_preferences.getPreferences(this.context, 'mystore')
promisePre.then((preferences) => {
preferences.put('startup', 'auto', function (err) {
if (err) {
console.info("Put the value of startup failed with err: " + err)
return
}
console.info("Put the value of startup successfully.")
preferences.flush(function (err) {
export default class MainAbility extends Ability {
let promise = data_preferences.getPreferences(this.context, 'mystore')
promise.then((preferences) => {
preferences.put('startup', 'auto', function (err) {
if (err) {
console.info("Flush to file failed with err: " + err)
console.info("Put the value of startup failed, err: " + err)
return
}
console.info("Flushed to file successfully.")
console.info("Put the value of startup successfully.")
preferences.flush(function (err) {
if (err) {
console.info("Flush to file failed, err: " + err)
return
}
console.info("Flushed to file successfully.")
})
})
}).catch((err) => {
console.info("Get the preferences failed")
})
}).catch((err) => {
console.info("Get the preferences failed, path: " + path + '/mystore')
})
}
```
......@@ -117,28 +121,32 @@ Reads a file and loads the data to the **Preferences** instance. This method use
deletePreferences(context: Context, name: string, callback: AsyncCallback&lt;void&gt;): void
Removes the singleton **Preferences** instance of the specified file from the memory, and deletes the specified file, its backup file, and corrupted files. After the specified files are deleted, the **Preferences** instance cannot be used for data operations. Otherwise, data inconsistency will occur. This method uses an asynchronous callback to return the execution result.
从内存中移除指定首选项持久化文件对应的Preferences单实例，并删除指定文件及其备份文件和损坏文件。
删除指定首选项持久化文件时，应用不允许再使用该实例进行数据操作，否则会出现数据一致性问题，该方法使用callback方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| context | Context | Yes| Context of the app or functionality.|
| name | string | Yes| Name of the app's internal data storage.|
| callback | AsyncCallback&lt;void&gt; | Yes| Callback used to return the execution result.|
| context | [Context](js-apis-Context.md) | 是 | 应用程序或功能的上下文。 |
| name | string | 是 | 应用程序内部数据存储名称。 |
| callback | AsyncCallback&lt;void&gt; | 是 | 回调函数。 |
- Example
```
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
data_preferences.deletePreferences(this.context, 'mystore', function (err) {
if (err) {
console.info("Deleted failed with err: " + err)
return
}
console.info("Deleted successfully.")
})
export default class MainAbility extends Ability {
data_preferences.deletePreferences(this.context, 'mystore', function (err) {
if (err) {
console.info("Deleted failed, err: " + err)
return
}
console.info("Deleted successfully.")
})
}
```
......@@ -146,31 +154,35 @@ Removes the singleton **Preferences** instance of the specified file from the me
deletePreferences(context: Context, name: string): Promise&lt;void&gt;
Removes the singleton **Preferences** instance of the specified file from the memory, and deletes the specified file, its backup file, and corrupted files. After the specified files are deleted, the **Preferences** instance cannot be used for data operations. Otherwise, data inconsistency will occur. This method uses a promise to return the execution result.
从内存中移除指定首选项持久化文件对应的Preferences单实例，并删除指定文件及其备份文件和损坏文件。
删除指定首选项持久化文件时，应用不允许再使用该实例进行数据操作，否则会出现数据一致性问题，该方法使用Promise方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| context | Context | Yes| Context of the app or functionality.|
| name | string | Yes| Name of the app's internal data storage.|
| context | [Context](js-apis-Context.md) | 是 | 应用程序或功能的上下文。 |
| name | string | 是 | 应用程序内部数据存储名称。 |
- Return value
| Type| Description|
- 返回值：
| 类型 | 说明 |
| -------- | -------- |
| Promise&lt;void&gt; | Promise used to return the result.|
| Promise&lt;void&gt; | Promise实例，用于异步获取结果。 |
- Example
```
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
let promisedelPre = data_preferences.deletePreferences(this.context, 'mystore')
promisedelPre.then(() => {
console.info("Deleted successfully.")
}).catch((err) => {
console.info("Deleted failed with err: " + err)
})
export default class MainAbility extends Ability {
let promise = data_preferences.deletePreferences(this.context, 'mystore')
promise.then(() => {
console.info("Deleted successfully.")
}).catch((err) => {
console.info("Deleted failed, err: " + err)
})
}
```
......@@ -178,30 +190,33 @@ Removes the singleton **Preferences** instance of the specified file from the me
removePreferencesFromCache(context: Context, name: string, callback: AsyncCallback&lt;void&gt;): void
Removes the singleton **Preferences** instance of a file from the cache. The removed instance cannot be used for data operations. Otherwise, data inconsistency will occur.
从内存中移除指定首选项持久化文件对应的Preferences单实例。
This method uses an asynchronous callback to return the result.
移除Preferences单实例时，应用不允许再使用该实例进行数据操作，否则会出现数据一致性问题，该方法使用callback方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| context | Context | Yes| Context of the app or functionality.|
| name | string | Yes| Name of the app's internal data storage.|
| callback | AsyncCallback&lt;void&gt; | Yes| Callback used to return the execution result.|
| context | [Context](js-apis-Context.md) | 是 | 应用程序或功能的上下文。 |
| name | string | 是 | 应用程序内部数据存储名称。 |
| callback | AsyncCallback&lt;void&gt; | 是 | 回调函数。 |
- Example
```
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
data_preferences.removePreferencesFromCache(this.context, 'mystore', function (err) {
if (err) {
console.info("Removed preferences from cache failed with err: " + err)
return
}
console.info("Removed preferences from cache successfully.")
})
export default class MainAbility extends Ability {
data_preferences.removePreferencesFromCache(this.context, 'mystore', function (err) {
if (err) {
console.info("Removed preferences from cache failed, err: " + err)
return
}
console.info("Removed preferences from cache successfully.")
})
}
```
......@@ -209,67 +224,79 @@ This method uses an asynchronous callback to return the result.
removePreferencesFromCache(context: Context, name: string): Promise&lt;void&gt;
Removes the singleton **Preferences** instance of a file from the cache. The removed instance cannot be used for data operations. Otherwise, data inconsistency will occur.
从内存中移除指定首选项持久化文件对应的Preferences单实例。
This method uses a promise to return the result.
移除Preferences单实例时，应用不允许再使用该实例进行数据操作，否则会出现数据一致性问题，该方法使用Promise方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| context | Context | Yes| Context of the app or functionality.|
| name | string | Yes| Name of the app's internal data storage.|
| context | [Context](js-apis-Context.md) | 是 | 应用程序或功能的上下文。 |
| name | string | 是 | 应用程序内部数据存储名称。 |
- Return value
| Type| Description|
- 返回值：
| 类型 | 说明 |
| -------- | -------- |
| Promise&lt;void&gt; | Promise used to return the result.|
| Promise&lt;void&gt; | Promise实例，用于异步获取结果。 |
- Example
```
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
let promiserevPre = data_preferences.removePreferencesFromCache(this.context, 'mystore')
promiserevPre.then(() => {
console.info("Removed preferences from cache successfully.")
}).catch((err) => {
console.info("Removed preferences from cache failed with err: " + err)
})
export default class MainAbility extends Ability {
let promise = data_preferences.removePreferencesFromCache(this.context, 'mystore')
promise.then(() => {
console.info("Removed preferences from cache successfully.")
}).catch((err) => {
console.info("Removed preferences from cache failed, err: " + err)
})
}
```
## Preferences
Provides APIs for obtaining and modifying storage data.
提供获取和修改存储数据的接口。
### get
get(key: string, defValue: ValueType, callback: AsyncCallback&lt;ValueType&gt;): void
Obtains the value corresponding to a key. If the value is null or not in the default value format, the default value is returned.
This method uses an asynchronous callback to return the result.
获取键对应的值，如果值为null或者非默认值类型，返回默认数据，该方法使用callback方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| key | string | Yes| Key of the data. It cannot be empty.|
| defValue | ValueType | Yes| Default value to be returned. It can be a number, string, or Boolean value.|
| callback | AsyncCallback&lt;ValueType&gt; | Yes| Callback used to return the execution result.|
| key | string | 是 | 要获取的存储key名称，不能为空。 |
| defValue | [ValueType](#valuetype) | 是 | 默认返回值。支持number、string、boolean。 |
| callback | AsyncCallback&lt;ValueType&gt; | 是 | 回调函数。 |
- Example
```
preferences.get('startup', 'default', function(err, value) {
if (err) {
console.info("Get the value of startup failed with err: " + err)
return
}
console.info("The value of startup is " + value)
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
data_preferences.getPreferences(this.context, 'mystore', function (err, preferences) {
if (err) {
console.info("Get the preferences failed, err: " + err)
return
}
preferences.get('startup', 'default', function(err, value) {
if (err) {
console.info("Get the value of startup failed, err: " + err)
return
}
console.info("The value of startup is " + value)
})
})
}
```
......@@ -277,31 +304,39 @@ This method uses an asynchronous callback to return the result.
get(key: string, defValue: ValueType): Promise&lt;ValueType&gt;
Obtains the value corresponding to a key. If the value is null or not in the default value format, the default value is returned.
获取键对应的值，如果值为null或者非默认值类型，返回默认数据，该方法使用Promise方式作为异步方法。
This method uses a promise to return the result.
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- **参数：**
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| key | string | Yes| Key of the data. It cannot be empty.|
| defValue | ValueType | Yes| Default value to be returned. It can be a number, string, or Boolean value.|
| key | string | 是 | 要获取的存储key名称，不能为空。 |
| defValue | [ValueType](#valuetype) | 是 | 默认返回值。支持number、string、boolean。 |
- Return value
| Type| Description|
- 返回值：
| 类型 | 说明 |
| -------- | -------- |
| Promise&lt;ValueType&gt; | Promise used to return the result.|
| Promise&lt;ValueType&gt; | Promise实例，用于异步获取结果。 |
- Example
```
let promiseget = preferences.get('startup', 'default')
promiseget.then((value) => {
console.info("The value of startup is " + value)
}).catch((err) => {
console.info("Get the value of startup failed with err: " + err)
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
let promise = data_preferences.getPreferences(this.context, 'mystore')
promise.then((preferences) => {
let promiseGet = preferences.get('startup', 'default')
promiseGet.then((value) => {
console.info("The value of startup is " + value)
}).catch((err) => {
console.info("Get the value of startup failed, err: " + err)
})
}).catch((err) => {
console.info("Get the preferences failed, err: " + err)
})
}
```
......@@ -309,28 +344,37 @@ This method uses a promise to return the result.
put(key: string, value: ValueType, callback: AsyncCallback&lt;void&gt;): void
Obtains the **Preferences** instance corresponding to the specified file, writes data to the **Preferences** instance using a **Preferences** API, and saves data to the file using **flush()** or **flushSync()**.
This method uses an asynchronous callback to return the result.
首先获取指定首选项持久化文件对应的Preferences实例，然后借助Preferences API将数据写入Preferences实例，通过flush或者flushSync将Preferences实例持久化，该方法使用callback方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| key | string | Yes| Key of the data to modify. It cannot be empty.|
| value | ValueType | Yes| New value to store. It can be a number, string, or Boolean value.|
| callback | AsyncCallback&lt;void&gt; | Yes| Callback used to return the execution result.|
| key | string | 是 | 要修改的存储的key，不能为空。 |
| value | [ValueType](#valuetype) | 是 | 存储的新值。支持number、string、boolean。 |
| callback | AsyncCallback&lt;void&gt; | 是 | 回调函数。 |
- Example
```
preferences.put('startup', 'auto', function (err) {
if (err) {
console.info("Put the value of startup failed with err: " + err)
return
}
console.info("Put the value of startup successfully.")
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
data_preferences.getPreferences(this.context, 'mystore', function (err, preferences) {
if (err) {
console.info("Get the preferences failed, err: " + err)
return
}
preferences.put('startup', 'auto', function (err) {
if (err) {
console.info("Put the value of startup failed, err: " + err)
return
}
console.info("Put the value of startup successfully.")
})
})
}
```
......@@ -338,31 +382,39 @@ This method uses an asynchronous callback to return the result.
put(key: string, value: ValueType): Promise&lt;void&gt;
Obtains the **Preferences** instance corresponding to the specified file, writes data to the **Preferences** instance using a **Preferences** API, and saves data to the file using **flush()** or **flushSync()**.
首先获取指定首选项持久化文件对应的Preferences实例，然后借助Preferences API将数据写入Preferences实例，通过flush或者flushSync将Preferences实例持久化，该方法使用Promise方式作为异步方法。
This method uses a promise to return the result.
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| key | string | Yes| Key of the data to modify. It cannot be empty.|
| value | ValueType | Yes| New value to store. It can be a number, string, or Boolean value.|
| key | string | 是 | 要修改的存储的key，不能为空。 |
| value | [ValueType](#valuetype) | 是 | 存储的新值。支持number、string、boolean。 |
- Return value
| Type| Description|
- 返回值：
| 类型 | 说明 |
| -------- | -------- |
| Promise&lt;void&gt; | Promise used to return the result.|
| Promise&lt;void&gt; | Promise实例，用于异步处理。 |
- Example
```
let promiseput = preferences.put('startup', 'auto')
promiseput.then(() => {
console.info("Put the value of startup successfully.")
}).catch((err) => {
console.info("Put the value of startup failed with err: " + err)
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
let promise = data_preferences.getPreferences(this.context, 'mystore')
promise.then((preferences) => {
let promisePut = preferences.put('startup', 'auto')
promisePut.then(() => {
console.info("Put the value of startup successfully.")
}).catch((err) => {
console.info("Put the value of startup failed, err: " + err)
})
}).catch((err) => {
console.info("Get the preferences failed, err: " + err)
})
}
```
......@@ -370,34 +422,45 @@ This method uses a promise to return the result.
has(key: string, callback: AsyncCallback&lt;boolean&gt;): boolean
Checks whether the **Preference** object contains data with a given key.
This method uses an asynchronous callback to return the result.
检查存储对象是否包含名为给定key的存储键值对，该方法使用callback方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| key | string | Yes| Key of the data. It cannot be empty.|
| callback | AsyncCallback&lt;boolean&gt; | Yes| Callback used to return the execution result.|
| key | string | 是 | 要检查的存储key名称，不能为空。 |
| callback | AsyncCallback&lt;boolean&gt; | 是 | 回调函数。 |
- Return value
| Type| Description|
- 返回值：
| 类型 | 说明 |
| -------- | -------- |
| boolean | Returns **true** if the **Preference** object contains data with the specified key; returns **false** otherwise.|
| boolean | true表示存在，false表示不存在。 |
- Example
```
preferences.has('startup', function (err, isExist) {
if (err) {
console.info("Check the key of startup failed with err: " + err)
return
}
if (isExist) {
console.info("The key of startup is contained.")
}
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
data_preferences.getPreferences(this.context, 'mystore', function (err, preferences) {
if (err) {
console.info("Get the preferences failed, err: " + err)
return
}
preferences.has('startup', function (err, isExist) {
if (err) {
console.info("Check the key of startup failed, err: " + err)
return
}
if (isExist) {
console.info("The key of startup is contained.")
} else {
console.info("The key of startup dose not contain.")
}
})
})
}
```
......@@ -405,32 +468,42 @@ This method uses an asynchronous callback to return the result.
has(key: string): Promise&lt;boolean&gt;
Checks whether the **Preference** object contains data with a given key.
This method uses a promise to return the result.
检查存储对象是否包含名为给定key的存储键值对，该方法使用Promise方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| key | string | Yes| Key of the data. It cannot be empty.|
| key | string | 是 | 要检查的存储key名称，不能为空。 |
- Return value
| Type| Description|
- 返回值：
| 类型 | 说明 |
| -------- | -------- |
| Promise&lt;boolean&gt; | Promise used to return the result.|
| Promise&lt;boolean&gt; | Promise实例，用于异步处理。 |
- Example
```
let promisehas = preferences.has('startup')
promisehas.then((isExist) => {
if (isExist) {
console.info("The key of startup is contained.")
}
}).catch((err) => {
console.info("Check the key of startup failed with err: " + err)
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
let promise = data_preferences.getPreferences(this.context, 'mystore')
promise.then((preferences) => {
let promiseHas = preferences.has('startup')
promiseHas.then((isExist) => {
if (isExist) {
console.info("The key of startup is contained.")
} else {
console.info("The key of startup dose not contain.")
}
}).catch((err) => {
console.info("Check the key of startup failed, err: " + err)
})
}).catch((err) => {
console.info("Get the preferences failed, err: " + err)
})
}
```
......@@ -438,27 +511,36 @@ This method uses a promise to return the result.
delete(key: string, callback: AsyncCallback&lt;void&gt;): void
Deletes data with the specified key from this **Preference** object.
从存储对象中删除名为给定key的存储键值对，该方法使用callback方式作为异步方法。
This method uses an asynchronous callback to return the result.
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| key | string | Yes| Key of the data. It cannot be empty.|
| callback | AsyncCallback&lt;void&gt; | Yes| Callback used to return the execution result.|
| key | string | 是 | 要删除的存储key名称，不能为空。 |
| callback | AsyncCallback&lt;void&gt; | 是 | 回调函数。 |
- Example
```
preferences.delete('startup', function (err) {
if (err) {
console.info("Delete startup key failed with err: " + err)
return
}
console.info("Deleted startup key successfully.")
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
data_preferences.getPreferences(this.context, 'mystore', function (err, preferences) {
if (err) {
console.info("Get the preferences failed, err: " + err)
return
}
preferences.delete('startup', function (err) {
if (err) {
console.info("Delete startup key failed, err: " + err)
return
}
console.info("Deleted startup key successfully.")
})
})
}
```
......@@ -466,30 +548,38 @@ This method uses an asynchronous callback to return the result.
delete(key: string): Promise&lt;void&gt;
Deletes data with the specified key from this **Preference** object.
This method uses a promise to return the result.
从存储对象删除名为给定key的存储键值对，该方法使用Promise方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| key | string | Yes| Key of the data.|
| key | string | 是 | 要删除的存储key名称，不能为空。 |
- Return value
| Type| Description|
- 返回值：
| 类型 | 说明 |
| -------- | -------- |
| Promise&lt;void&gt; | Promise used to return the result.|
| Promise&lt;void&gt; | Promise实例，用于异步处理。 |
- Example
```
let promisedel = preferences.delete('startup')
promisedel.then(() => {
console.info("Deleted startup key successfully.")
}).catch((err) => {
console.info("Delete startup key failed with err: " + err)
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
let promise = data_preferences.getPreferences(this.context, 'mystore')
promise.then((preferences) => {
let promiseDelete = preferences.delete('startup')
promiseDelete.then(() => {
console.info("Deleted startup key successfully.")
}).catch((err) => {
console.info("Delete startup key failed, err: " + err)
})
}).catch((err) => {
console.info("Get the preferences failed, err: " + err)
})
}
```
......@@ -497,26 +587,35 @@ This method uses a promise to return the result.
flush(callback: AsyncCallback&lt;void&gt;): void
Saves the modification of this object to the **Preferences** instance and synchronizes the modification to the file.
将当前preferences对象中的修改保存到当前的preferences，并异步存储到首选项持久化文件中，该方法使用callback方式作为异步方法。
This method uses an asynchronous callback to return the result.
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| callback | AsyncCallback&lt;void&gt; | Yes| Callback used to return the execution result.|
| callback | AsyncCallback&lt;void&gt; | 是 | 回调函数。 |
- Example
```
preferences.flush(function (err) {
if (err) {
console.info("Flush to file failed with err: " + err)
return
}
console.info("Flushed to file successfully.")
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
data_preferences.getPreferences(this.context, 'mystore', function (err, preferences) {
if (err) {
console.info("Get the preferences failed, err: " + err)
return
}
preferences.flush(function (err) {
if (err) {
console.info("Flush to file failed, err: " + err)
return
}
console.info("Flushed to file successfully.")
})
})
}
```
......@@ -524,25 +623,33 @@ This method uses an asynchronous callback to return the result.
flush(): Promise&lt;void&gt;
Saves the modification of this object to the **Preferences** instance and synchronizes the modification to the file.
This method uses a promise to return the result.
将当前preferences对象中的修改保存到当前的preferences，并异步存储到首选项持久化文件中，该方法使用Promise方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Return value
| Type| Description|
- 返回值：
| 类型 | 说明 |
| -------- | -------- |
| Promise&lt;void&gt; | Promise used to return the result.|
| Promise&lt;void&gt; | Promise实例，用于异步处理。 |
- Example
```
let promiseflush = preferences.flush()
promiseflush.then(() => {
console.info("Flushed to file successfully.")
}).catch((err) => {
console.info("Flush to file failed with err: " + err)
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
let promise = data_preferences.getPreferences(this.context, 'mystore')
promise.then((preferences) => {
let promiseFlush = preferences.flush()
promiseFlush.then(() => {
console.info("Flushed to file successfully.")
}).catch((err) => {
console.info("Flush to file failed, err: " + err)
})
}).catch((err) => {
console.info("Get the preferences failed, err: " + err)
})
}
```
......@@ -550,26 +657,35 @@ This method uses a promise to return the result.
clear(callback: AsyncCallback&lt;void&gt;): void
Clears this **Preferences** object.
清除此存储对象中的所有存储，该方法使用callback方式作为异步方法。
This method uses an asynchronous callback to return the result.
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Mandatory| Description|
- 参数：
| 参数名 | 类型 | 必填 | 说明 |
| -------- | -------- | -------- | -------- |
| callback | AsyncCallback&lt;void&gt; | Yes| Callback used to return the execution result.|
| callback | AsyncCallback&lt;void&gt; | 是 | 回调函数。 |
- Example
```
preferences.clear(function (err) {
if (err) {
console.info("Clear to file failed with err: " + err)
return
}
console.info("Cleared to file successfully.")
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
data_preferences.getPreferences(this.context, 'mystore', function (err, preferences) {
if (err) {
console.info("Get the preferences failed, err: " + err)
return
}
preferences.clear(function (err) {
if (err) {
console.info("Clear to file failed, err: " + err)
return
}
console.info("Cleared to file successfully.")
})
})
}
```
......@@ -577,25 +693,33 @@ This method uses an asynchronous callback to return the result.
clear(): Promise&lt;void&gt;
Clears this **Preferences** object.
This method uses a promise to return the result.
清除此存储对象中的所有存储，该方法使用Promise方式作为异步方法。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Return value
| Type| Description|
- 返回值：
| 类型 | 说明 |
| -------- | -------- |
| Promise&lt;void&gt; | Promise used to return the result.|
| Promise&lt;void&gt; | Promise实例，用于异步处理。 |
- Example
```
let promiseclear = preferences.clear()
promiseclear.then(() => {
console.info("Cleared to file successfully.")
}).catch((err) => {
console.info("Clear to file failed with err: " + err)
})
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
let promise = data_preferences.getPreferences(this.context, 'mystore')
promise.then((preferences) => {
let promiseClear = preferences.clear()
promiseClear.then(() => {
console.info("Cleared to file successfully.")
}).catch((err) => {
console.info("Clear to file failed, err: " + err)
})
}).catch((err) => {
console.info("Get the preferences failed, err: " + err)
})
}
```
......@@ -603,36 +727,47 @@ This method uses a promise to return the result.
on(type: 'change', callback: Callback&lt;{ key : string }&gt;): void
Subscribes to data changes. When the value of the subscribed key changes, a callback will be invoked after the **flush()** method is executed.
订阅数据变更者类，订阅的key的值发生变更后，在执行flush方法后，callback方法会被回调。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Description|
- 参数：
| 参数名 | 类型 | 说明 |
| -------- | -------- | -------- |
| type | string | Event type. The value **change** indicates data change events.|
| callback | Callback&lt;{ key : string }&gt; | Callback used to return data changes.|
| type | string | 事件类型，固定值'change'，表示数据变更。 |
| callback | Callback&lt;{ key : string }&gt; | 回调对象实例。 |
- Example
```
var observer = function (key) {
console.info("The key of " + key + " changed.")
}
preferences.on('change', observer)
preferences.put('startup', 'auto', function (err) {
if (err) {
console.info("Put the value of startup failed with err: " + err)
return
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
var observer = function (key) {
console.info("The key of " + key + " changed.")
}
console.info("Put the value of startup successfully.")
preferences.flush(function (err) {
data_preferences.getPreferences(this.context, 'mystore', function (err, preferences) {
if (err) {
console.info("Flush to file failed with err: " + err)
console.info("Get the preferences failed, err: " + err)
return
}
console.info("Flushed to file successfully.") // observer will be called.
preferences.on('change', observer)
preferences.put('startup', 'auto', function (err) {
if (err) {
console.info("Put the value of startup failed, err: " + err)
return
}
console.info("Put the value of startup successfully.")
preferences.flush(function (err) {
if (err) {
console.info("Flush to file failed, err: " + err)
return
}
console.info("Flushed to file successfully.") // observer will be called.
})
})
})
})
}
```
......@@ -640,20 +775,57 @@ Subscribes to data changes. When the value of the subscribed key changes, a call
off(type: 'change', callback: Callback&lt;{ key : string }&gt;): void
Unsubscribes from data changes.
当不再进行订阅数据变更时，使用此接口取消订阅。
**System capability**: SystemCapability.DistributedDataManager.Preferences.Core
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
- Parameters
| Name| Type| Description|
- 参数：
| 参数名 | 类型 | 说明 |
| -------- | -------- | -------- |
| type | string | Event type. The value **change** indicates data change events.|
| callback | Callback&lt;{ key : string }&gt; | Callback used to return data changes.|
| type | string | 事件类型，固定值'change'，表示数据变更。 |
| callback | Callback&lt;{ key : string }&gt; | 需要取消的回调对象实例。 |
- Example
```
var observer = function (key) {
console.info("The key of " + key + " changed.")
- 示例：
```ts
import Ability from '@ohos.application.Ability'
import data_preferences from '@ohos.data.preferences'
export default class MainAbility extends Ability {
var observer = function (key) {
console.info("The key of " + key + " changed.")
}
data_preferences.getPreferences(this.context, 'mystore', function (err, preferences) {
if (err) {
console.info("Get the preferences failed, err: " + err)
return
}
preferences.on('change', observer)
preferences.put('startup', 'auto', function (err) {
if (err) {
console.info("Put the value of startup failed, err: " + err)
return
}
console.info("Put the value of startup successfully.")
preferences.flush(function (err) {
if (err) {
console.info("Flush to file failed, err: " + err)
return
}
console.info("Flushed to file successfully.") // observer will be called.
preferences.off('change', observer)
})
})
})
}
preferences.off('change', observer)
```
## ValueType
用于表示允许的数据字段类型。
**系统能力**：SystemCapability.DistributedDataManager.Preferences.Core
| 名称 | 说明 |
| ------- | -------------------- |
| number | 表示值类型为数字。 |
| string | 表示值类型为字符。 |
| boolean | 表示值类型为布尔值。 |
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