我需要在许多地方获得用户对象,其中包含许多字段。登录后,我想保存/存储这些用户对象。我们如何实现这种场景?

我不能这样存储它:

SharedPreferences.Editor prefsEditor = myPrefs.edit();
prefsEditor.putString("BusinessUnit", strBusinessUnit);

当前回答

关于这个问题有很多很好的答案,穆罕穆德·阿米尔·阿里和穆哈默德·埃尔-班纳在Kotlin使用通用方法实现了答案。

为了节省

fun storeObjectInSharedPref(dataObject: Any, prefName: String): Boolean{
    val dataObjectInJson = Gson().toJson(dataObject)
    prefsEditor.putString(prefName, dataObjectInJson)
    return prefsEditor.commit()
}

检索

fun <T> retrieveStoredObject(prefName: String, baseClass: Class<T>): T?{
    val dataObject: String? = preferences.getString(prefName, "")
    return Gson().fromJson(dataObject, baseClass)
}

要了解Kotlin中的泛型,请访问这里

其他回答

您可以使用以下代码存储类对象,并从共享首选项检索任何对象。

将以下依赖项添加到应用gradle中

dependencies {
 implementation 'com.google.code.gson:gson:2.8.6'
 //Other dependencies of our project
} 

在共享pref文件中添加以下代码。

 /**
 * Saves object into the Preferences.
 *
 * @param `object` Object of model class (of type [T]) to save
 * @param key Key with which Shared preferences to
 **/
fun <T> put(`object`: T, key: String) {
    //Convert object to JSON String.
    val jsonString = GsonBuilder().create().toJson(`object`)
    //Save that String in SharedPreferences
    preferences.edit().putString(key, jsonString).apply()
}

/**
 * Used to retrieve object from the Preferences.
 *
 * @param key Shared Preference key with which object was saved.
 **/
inline fun <reified T> get(key: String): T? {
    //We read JSON String which was saved.
    val value = preferences.getString(key, null)
    //JSON String was found which means object can be read.
    //We convert this JSON String to model object. Parameter "c" (of
    //type Class < T >" is used to cast.
    return GsonBuilder().create().fromJson(value, T::class.java)
}
}

这么多好答案,她是我的2美分

我更喜欢使用内联函数和旧风格的put和get值

object PreferenceHelper {

    private const val PREFERENCES_KEY = "MyLocalPreference"

    private fun getPreference(context: Context): SharedPreferences {
        return context.getSharedPreferences(
            PREFERENCES_KEY,
            Context.MODE_PRIVATE
        )
    }

    fun setBoolean(appContext: Context, key: String?, value: Boolean?) =
        getPreference(appContext).edit().putBoolean(key, value!!).apply()

    fun setInteger(appContext: Context, key: String?, value: Int) =
        getPreference(appContext).edit().putInt(key, value).apply()

    fun setFloat(appContext: Context, key: String?, value: Float) =
        getPreference(appContext).edit().putFloat(key, value).apply()

    fun setString(appContext: Context, key: String?, value: String?) =
        getPreference(appContext).edit().putString(key, value).apply()

    // To retrieve values from shared preferences:
    fun getBoolean(appContext: Context, key: String?, defaultValue: Boolean?): Boolean =
        getPreference(appContext).getBoolean(key, defaultValue!!)

    fun getInteger(appContext: Context, key: String?, defaultValue: Int): Int =
        getPreference(appContext)
            .getInt(key, defaultValue)

    fun getString(appContext: Context, key: String?, defaultValue: String?): String? =
        getPreference(appContext)
            .getString(key, defaultValue)


}

使用

PreferenceHelper.setString(context,"CUSTOMER_NAME", "HITESH")

Toast.makeText(context, "Hello " + PreferenceHelper.getString(context,"CUSTOMER_NAME", "User"), Toast.LENGTH_LONG).show()

如果你的对象很复杂,我建议序列化/XML/JSON,并将这些内容保存到SD卡。你可以在这里找到关于如何保存到外部存储的其他信息: http://developer.android.com/guide/topics/data/data-storage.html#filesExternal

你还没有说明在这之后你对prefsEditor对象做了什么,但是为了持久化首选项数据,你还需要使用:

prefsEditor.commit();

使用delegate Kotlin,我们可以轻松地从共享首选项中放置和获取数据。

    inline fun <reified T> Context.sharedPrefs(key: String) = object : ReadWriteProperty<Any?, T> {

        val sharedPrefs by lazy { this@sharedPrefs.getSharedPreferences("APP_DATA", Context.MODE_PRIVATE) }
        val gson by lazy { Gson() }
        var newData: T = (T::class.java).newInstance()

        override fun getValue(thisRef: Any?, property: KProperty<*>): T {
            return getPrefs()
        }

        override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
            this.newData = value
            putPrefs(newData)
        }

        fun putPrefs(value: T?) {
            sharedPrefs.edit {
                when (value) {
                    is Int -> putInt(key, value)
                    is Boolean -> putBoolean(key, value)
                    is String -> putString(key, value)
                    is Long -> putLong(key, value)
                    is Float -> putFloat(key, value)
                    is Parcelable -> putString(key, gson.toJson(value))
                    else          -> throw Throwable("no such type exist to put data")
                }
            }
        }

        fun getPrefs(): T {
            return when (newData) {
                       is Int -> sharedPrefs.getInt(key, 0) as T
                       is Boolean -> sharedPrefs.getBoolean(key, false) as T
                       is String -> sharedPrefs.getString(key, "") as T ?: "" as T
                       is Long -> sharedPrefs.getLong(key, 0L) as T
                       is Float -> sharedPrefs.getFloat(key, 0.0f) as T
                       is Parcelable -> gson.fromJson(sharedPrefs.getString(key, "") ?: "", T::class.java)
                       else          -> throw Throwable("no such type exist to put data")
                   } ?: newData
        }

    }

    //use this delegation in activity and fragment in following way
        var ourData by sharedPrefs<String>("otherDatas")