基于mmkv的Constant封装

DevEco Studio 版本：DevEco Studio NEXT Developer Preview2
HarmonyOS API 版本：4.1.0(11)
mmkv 版本："@tencent/mmkv": "1.3.5"

基于 mmkv 的 Constant 封装

全局变量，支持 KV 直接保存到手机物理存储，使用超方便。

关键代码 Constant.ets封装如下：

/*
 * Copyright (c) 2022 Huawei Device Co., Ltd.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { MMKV } from "@tencent/mmkv";

export default class Constant {
  private static TAG = "Constant";
  /**
   * time millis distance between server time and local time.
   *
   * offsetTime = ${local.getTime() - server.getTime()}
   */
  public static offsetTime: number = 0;
  /**
   * session id
   *
   * record local from server response session id.
   */
  private static SESSION_ID = "SESSION_ID";

  public static get st(): string {
    return MMKV.defaultMMKV().decodeString(Constant.SESSION_ID) ?? "";
  }

  public static set st(value: string) {
    if (value != null)
      MMKV.defaultMMKV().encodeString(Constant.SESSION_ID, value);
  }
}