HarmonyOS 鸿蒙Next 使用用户首选项存取数据，存储数据的类型为对象时，重启app之后获取到的数据的类型变为了字符串
HarmonyOS 鸿蒙Next 使用用户首选项存取数据，存储数据的类型为对象时，重启app之后获取到的数据的类型变为了字符串
使用场景:
1. 创建用户首选项实例preferences.getPreferences(context, name, (error: BusinessError, onePreference: preferences.Preferences) => { if (!error) { this.mPreferences = onePreference } })
2. 持久化数据 this.mPreferences.put(“user_info”, {“name”:“jock”})
3. 读取数据 let value = this.mPreferences.getSync(“user_info”, {})
实际情况:
1. 在存储数据之后立即调用get方法，获取到的数据依然是object类型
2. 在重启app之后再次调用get方法，获取到的数据的类型就变为了string 期望的是可以返回实际的数据
2 回复
参考下这个demo：
Index.ets
~~~
import { PreferencesUtil } from './PreferencesUtil';
export class UserInfo {
name: string = ''
}
[@Entry](/user/Entry)
[@Component](/user/Component)
struct Index {
[@State](/user/State) message: string = 'Hello World';
private preferencesUtil: PreferencesUtil = new PreferencesUtil()
aboutToAppear(): void {
this.preferencesUtil.loadPreference(getContext(this), 'aaa')
}
build() {
Column() {
Text('设置')
.id('HelloWorld')
.fontSize(50)
.fontWeight(FontWeight.Bold)
.alignRules({
center: { anchor: '__container__', align: VerticalAlign.Center },
middle: { anchor: '__container__', align: HorizontalAlign.Center }
})
.onClick(async () => {
//1. 创建用户首选项实例
await this.preferencesUtil.setPreference('aaa', 'user_info', { name: "jock" } as UserInfo)
let info = await this.preferencesUtil.getPreference('aaa', 'user_info',new UserInfo() ) as UserInfo
console.info(JSON.stringify(info.name))
console.info(JSON.stringify(info))
})
Text('获取')
.id('HelloWorld')
.fontSize(50)
.fontWeight(FontWeight.Bold)
.alignRules({
center: { anchor: '__container__', align: VerticalAlign.Center },
middle: { anchor: '__container__', align: HorizontalAlign.Center }
})
.onClick(async () => {
//1. 创建用户首选项实例
let info = await this.preferencesUtil.getPreference('aaa', 'user_info',new UserInfo()) as UserInfo
console.info(JSON.stringify(info.name))
console.info(JSON.stringify(info))
})
}
.height('100%')
.width('100%')
}
}
~~~
PreferencesUtil.ets
~~~
import dataPreferences from '[@ohos](/user/ohos).data.preferences';
export class PreferencesUtil {
private prefArr: Map<string, dataPreferences.Preferences> = new Map();
/**
* 初始化一个首选项实例
*
* [@param](/user/param) context
* [@param](/user/param) name
*/
loadPreference(context: Context, name: string) {
dataPreferences.getPreferences(context, name)
.then(preference => {
this.prefArr.set(name, preference);
console.log(`首选项${name}初始化成功`);
})
.catch((error: Error) => {
console.log(`首选项${name}初始化失败：`, JSON.stringify(error));
})
}
/**
* 获取首选项实例对应键的值
*
* [@param](/user/param) name
* [@param](/user/param) key
* [@param](/user/param) defValue
* [@returns](/user/returns) Promise<dataPreferences.ValueType>
*/
async getPreference(name: string, key: string, defValue: dataPreferences.ValueType): Promise<dataPreferences.ValueType|undefined> {
if (!this.prefArr.has(name)) {
console.log(`首选项${name}尚未初始化`);
return undefined;
}
let preference = this.prefArr.get(name);
if (preference){
try{
let value = await preference?.get(key, defValue);
console.log(`获取首选项${name}[key = ${key}]的值成功`);
return value;
} catch(e) {
console.log(`获取首选项${name}[key = ${key}]的值失败:`, JSON.stringify(e));
}
}
return undefined;
}
/**
* 设置首选项实例对应键的值
*
* [@param](/user/param) name
* [@param](/user/param) key
* [@param](/user/param) value
*/
async setPreference(name: string, key: string, value: dataPreferences.ValueType) {
if (!this.prefArr.has(name)) {
console.log(`首选项${name}尚未初始化`);
return;
}
let preference = this.prefArr.get(name);
try{
await preference?.put(key, value);
preference?.flush(); // 持久化
console.log(`设置首选项${name}[key = ${key}, value = ${value}]的值成功`);
} catch(e) {
console.log(`设置首选项${name}[key = ${key}, value = ${value}]的值失败:`, JSON.stringify(e));
}
}
/**
* 删除首选项实例对应键的项
*
* [@param](/user/param) name
* [@param](/user/param) key
*/
async deletePreference(name: string, key: string) {
if (!this.prefArr.has(name)) {
console.log(`首选项${name}尚未初始化`);
return;
}
let preference = this.prefArr.get(name);
try{
await preference?.delete(key);
console.log(`删除首选项${name}[key = ${key}]成功`);
} catch(e) {
console.log(`删除首选项${name}[key = ${key}]失败:`, JSON.stringify(e));
}
}
}
