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

您可以使用gson.jar将类对象存储到SharedPreferences中。 你可以从google-gson下载这个罐子

或者在Gradle文件中添加GSON依赖项:

implementation 'com.google.code.gson:gson:2.8.8'

你可以在这里找到最新的版本

创建共享首选项:

SharedPreferences  mPrefs = getPreferences(MODE_PRIVATE);

保存:

MyObject myObject = new MyObject;
//set variables of 'myObject', etc.

Editor prefsEditor = mPrefs.edit();
Gson gson = new Gson();
String json = gson.toJson(myObject);
prefsEditor.putString("MyObject", json);
prefsEditor.commit();

检索:

Gson gson = new Gson();
String json = mPrefs.getString("MyObject", "");
MyObject obj = gson.fromJson(json, MyObject.class);

其他回答

下面是我从这里获得的Kotlin Delegated Properties的使用方法,但扩展了它,并允许使用一种简单的机制来获取/设置SharedPreference属性。

对于String, Int, Long, Float或Boolean,它使用标准的SharePreference getter和setter。然而,对于所有其他数据类,它使用GSON序列化为一个String,用于setter。然后为getter反序列化为数据对象。

与其他解决方案类似,这需要在gradle文件中添加GSON作为依赖项:

implementation 'com.google.code.gson:gson:2.8.6'

下面是一个简单的数据类的例子,我们希望能够保存并存储到SharedPreferences:

data class User(val first: String, val last: String)

下面是一个实现属性委托的类:

object UserPreferenceProperty : PreferenceProperty<User>(
    key = "USER_OBJECT",
    defaultValue = User(first = "Jane", last = "Doe"),
    clazz = User::class.java)

object NullableUserPreferenceProperty : NullablePreferenceProperty<User?, User>(
    key = "NULLABLE_USER_OBJECT",
    defaultValue = null,
    clazz = User::class.java)

object FirstTimeUser : PreferenceProperty<Boolean>(
        key = "FIRST_TIME_USER",
        defaultValue = false,
        clazz = Boolean::class.java
)

sealed class PreferenceProperty<T : Any>(key: String,
                                         defaultValue: T,
                                         clazz: Class<T>) : NullablePreferenceProperty<T, T>(key, defaultValue, clazz)

@Suppress("UNCHECKED_CAST")
sealed class NullablePreferenceProperty<T : Any?, U : Any>(private val key: String,
                                                           private val defaultValue: T,
                                                           private val clazz: Class<U>) : ReadWriteProperty<Any, T> {

    override fun getValue(thisRef: Any, property: KProperty<*>): T = HandstandApplication.appContext().getPreferences()
            .run {
                when {
                    clazz.isAssignableFrom(String::class.java) -> getString(key, defaultValue as String?) as T
                    clazz.isAssignableFrom(Int::class.java) -> getInt(key, defaultValue as Int) as T
                    clazz.isAssignableFrom(Long::class.java) -> getLong(key, defaultValue as Long) as T
                    clazz.isAssignableFrom(Float::class.java) -> getFloat(key, defaultValue as Float) as T
                    clazz.isAssignableFrom(Boolean::class.java) -> getBoolean(key, defaultValue as Boolean) as T
                    else -> getObject(key, defaultValue, clazz)
                }
            }

    override fun setValue(thisRef: Any, property: KProperty<*>, value: T) = HandstandApplication.appContext().getPreferences()
            .edit()
            .apply {
                when {
                    clazz.isAssignableFrom(String::class.java) -> putString(key, value as String?) as T
                    clazz.isAssignableFrom(Int::class.java) -> putInt(key, value as Int) as T
                    clazz.isAssignableFrom(Long::class.java) -> putLong(key, value as Long) as T
                    clazz.isAssignableFrom(Float::class.java) -> putFloat(key, value as Float) as T
                    clazz.isAssignableFrom(Boolean::class.java) -> putBoolean(key, value as Boolean) as T
                    else -> putObject(key, value)
                }
            }
            .apply()

    private fun Context.getPreferences(): SharedPreferences = getSharedPreferences(APP_PREF_NAME, Context.MODE_PRIVATE)

    private fun <T, U> SharedPreferences.getObject(key: String, defValue: T, clazz: Class<U>): T =
            Gson().fromJson(getString(key, null), clazz) as T ?: defValue

    private fun <T> SharedPreferences.Editor.putObject(key: String, value: T) = putString(key, Gson().toJson(value))

    companion object {
        private const val APP_PREF_NAME = "APP_PREF"
    }
}

注意:您不需要更新密封类中的任何内容。委托的属性是对象/单例的UserPreferenceProperty, NullableUserPreferenceProperty和FirstTimeUser。

为了从SharedPreferences中保存/获取一个新的数据对象,现在只需要添加四行就可以了:

object NewPreferenceProperty : PreferenceProperty<String>(
        key = "NEW_PROPERTY",
        defaultValue = "",
        clazz = String::class.java)

最后,你可以通过使用by关键字来读取/写入SharedPreferences的值:

private var user: User by UserPreferenceProperty
private var nullableUser: User? by NullableUserPreferenceProperty
private var isFirstTimeUser: Boolean by 

Log.d("TAG", user) // outputs the `defaultValue` for User the first time
user = User(first = "John", last = "Doe") // saves this User to the Shared Preferences
Log.d("TAG", user) // outputs the newly retrieved User (John Doe) from Shared Preferences

您可以使用gson.jar将类对象存储到SharedPreferences中。 你可以从google-gson下载这个罐子

或者在Gradle文件中添加GSON依赖项:

implementation 'com.google.code.gson:gson:2.8.8'

你可以在这里找到最新的版本

创建共享首选项:

SharedPreferences  mPrefs = getPreferences(MODE_PRIVATE);

保存:

MyObject myObject = new MyObject;
//set variables of 'myObject', etc.

Editor prefsEditor = mPrefs.edit();
Gson gson = new Gson();
String json = gson.toJson(myObject);
prefsEditor.putString("MyObject", json);
prefsEditor.commit();

检索:

Gson gson = new Gson();
String json = mPrefs.getString("MyObject", "");
MyObject obj = gson.fromJson(json, MyObject.class);

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

在SharedPreferences中存储Model的数组列表

Add this dependency implementation 'com.google.code.gson:gson:2.8.8' Then after you convert your Model Class into JSON using Gson. Gson gson = new Gson(); String json = gson.toJson(chModelArrayList); //here chModelArrayList is a ArrayList<Model> of Model Class Then after you can add this string to SharedPreferences SharedPreferences preferences; //Create Object of SharedPreferences SharedPreferences.Editor editor; //Create Object of SharedPreferences.Editor //initialize SharedPreferences preferences = activity.getPreferences(Context.MODE_PRIVATE); editor = preferences.edit(); //Add-In SharedPreferences editor.putString(key, json); editor.commit(); for your list from SharedPreferences String json = preferences.getString(key, defVal); Gson gson = new Gson(); //Pass Your Model ArrayList in TypeToken Type type = new TypeToken<ArrayList<ChModel>>() {}.getType(); //here you get your list ArrayList<ChModel> switchGroup1 = gson.fromJson(json, type);

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)
}
}