鸿蒙开发如何通过用户首选项实现数据持久化

1.导入用户首选项模块。

import preferences from '@ohos.data.preferences';

2.要通过用户首选项实现数据持久化，首先要获取Preferences实例。读取指定文件，将数据加载到Preferences实例，用于数据操作。

所有代码实例:

import preferences from '@ohos.data.preferences';
class  PreferencesUtil{
  preMap:Map<string,preferences.Preferences>=new Map()
  async loadPreference(context,name:string){
    try {
      let pref = await  preferences.getPreferences(context,name)
      this.preMap.set(name,pref)
      console.log(`加载preference${name}成功`)
    }catch(e){
      console.log(`加载preference${name}失败`,JSON.stringify(e))
    }
  }
 
  //存储数据
  async putPreferenceVale(name:string,key:string,value:preferences.ValueType){
    if(!this.preMap.has(name)){
      console.log(`加载preference${name}失败`,`${name},尚未初始化`)
      return
    }
    try{
      console.log(JSON.stringify(value),'你好')
      let pref=this.preMap.get(name)
      // @ts-ignore
      await pref.put(key,JSON.stringify(value))
      // @ts-ignore
      await  pref.flush()
 
      console.log("成功",`保存${name}.${key}=${value}成功`)
      // return value
    }catch(e){
      console.log("保存失败",JSON.stringify(e))
    }
 
  }
 
  //读取数据
  async getPreferenceValue(name:string,key:string,defaultVale:preferences.ValueType){
    if(!this.preMap.has(name)){
      console.log(`加载preference${name}失败`,`${name},尚未初始化`)
      return
    }
    try{
      console.log(JSON.stringify(this.preMap),'hhhh')
      let pref=this.preMap.get(name)
      // @ts-ignore
      console.log(JSON.stringify(pref),"赛666666")
      let value=  await pref.get(key,defaultVale)
      console.log("testTag",`读取${name},${key}=${value}成功}`)
      return value
    }catch(e){
      console.log("读取失败",JSON.stringify(e))
    }
  }
  pref(pref: any,arg1: string) {
    throw new Error('Method not implemented.');
  }
 
}
const preferencesUtil = new PreferencesUtil();
 
export default preferencesUtil as PreferencesUtil;

注意:存储完需要pref.flush() 进行持久化.

3.项目中具体读取示例.

@State _id:string = ""
  @State username:string = ""
  @State password:string = ""
  @State imgPath:string = ""
  async aboutToAppear(){
    this._id = await SharePre.getPreferenceValue('MyPreferences','_id','666') as string
    this.username = await SharePre.getPreferenceValue('MyPreferences','username','666') as string
    this.password = await SharePre.getPreferenceValue('MyPreferences','password','666') as string
    this.imgPath = await SharePre.getPreferenceValue('MyPreferences','imgPath','666') as string
  }

4.写入

SharePre.putPreferenceVale('MyPreferences','username',val.data.data.username)
SharePre.putPreferenceVale('MyPreferences','password',val.data.data.password)
SharePre.putPreferenceVale('MyPreferences','telephone',val.data.data.telephone)
SharePre.putPreferenceVale('MyPreferences','_id',val.data.data._id)
SharePre.putPreferenceVale('MyPreferences','imgPath',val.data.data.imgPath)   

修改会替换掉上次的存储

最终拿出来数据 需要进行切割

Image(this.imgPath.slice(1,this.imgPath.length-1))