HarmonyOS 鸿蒙Next stage模型,arkts语言,有关[@ohos.data.preferences (用户首选项)]key-value存取值的问题，为什么存完值取不出来

HarmonyOS 鸿蒙Next stage模型,arkts语言,有关[@ohos.data.preferences (用户首选项)]key-value存取值的问题，为什么存完值取不出来

文档里写的是在EntryAbility.ts中初始化,但是那样写会崩溃!所以我在aboutToAppear中初始化,虽然不会崩溃,但是存进去的数据,点击查看的时候,不会显示出来!

文档放在评论区!(人工审核链接有点慢!)

import data_preferences from '@ohos.data.preferences';
import common from '@ohos.app.ability.common';

let preferences = null;
const context = this as common.UIAbilityContext;

@Entry
@Component
struct Application_8 {
  @State str: string = '默认'

  aboutToAppear() {
    try {
      let promise = data_preferences.getPreferences(context, 'mystore');
      promise.then((object) => {
        preferences = object;
        console.info("Succeeded in getting preferences.");
      }).catch((err) => {
        console.error("Failed to get preferences. code =" + err.code + ", message =" + err.message);
      })
    } catch(err) {
      console.error("Failed to get preferences. code =" + err.code + ", message =" + err.message);
    }
  }

  build() {

    Column() {
      Button('点击我存值').onClick(() => {
        try {
          preferences.put('startup', 'auto')
        } catch (err) {
          console.error("Failed to put value of 'startup'. code =" + err.code + ", message =" + err.message);
        }
      })

      Button('点我查看值').onClick(() => {
        this.str = preferences.get('startup', '111')
      })

      Text(this.str)
    }.width('100%').height('100%').alignItems(HorizontalAlign.Center)
  }
}