HarmonyOS鸿蒙Next中getContext() 为undefined问题

这种调用场景是不支持的，看下下面demo:

封装好的工具类：

// EntryAbility.ets 调用
onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
    hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onCreate');
    PreferencesUtil.loadPreference(this.context, 'MyPreferences');
}

import dataPreferences from '@ohos.data.preferences';
import { ValueType } from '@kit.ArkData';

class Preferences {
    preMap: Map<string, dataPreferences.Preferences> = new Map();

    async loadPreference(context, name: string) {
        try {
            let pref = await dataPreferences.getPreferences(context, name);
            this.preMap.set(name, pref);
            console.log('testTag', `加载Preference[${name}]成功`);
        } catch (e) {
            console.log('testTag', `加载Preference[${name}]失败`, JSON.stringify(e));
        }
    }

    async getPreferenceValue(name: string, key: string, defaultValue: dataPreferences.ValueType) {
        if (!this.preMap.has(name)) {
            console.log('testTag', `Preferences[${name}]未初始化`);
            return;
        }
        try {
            let pref = this.preMap.get(name);
            // 读取数据
            let value = await pref?.get(key, defaultValue);
            return value;
        } catch (e) {
            console.error('Error getting preference value:', e);
        }
    }

    async putPreferenceValue(name: string, key: string, value: dataPreferences.ValueType) {
        if (!this.preMap.has(name)) {
            return;
        }
        try {
            let pref = this.preMap.get(name);
            // 写入数据
            await pref?.put(key, value);
            // 刷新磁盘
            await pref?.flush();
        } catch (e) {
            console.error('Error putting preference value:', e);
        }
    }

    /**
     * 删除键值
     * @param name
     * @param key
     * @param value
     */
    async deleteKeyPreferenceValue(name: string, key: string, value: dataPreferences.ValueType) {
        if (!this.preMap.has(name)) {
            return;
        }
        try {
            let pref = this.preMap.get(name);
            // 写入数据
            await pref?.delete(key);
            // 刷新磁盘
            await pref?.flush();
        } catch (e) {
            console.error('Error deleting preference key:', e);
        }
    }

    /**
     * 删除文件的 preference 实例
     * @param context
     * @param name
     */
    async deletePreference(context, name: string) {
        if (!this.preMap.has(name)) {
            return;
        }
        try {
            await dataPreferences.deletePreferences(context, name);
        } catch (e) {
            console.error('Error deleting preferences:', e);
        }
        this.preMap.delete(name);
    }
}

const preferenceUtil = new Preferences();
export default preferenceUtil as Preferences;