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);
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
试试这个最好的方法:
PreferenceConnector.java
import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
public class PreferenceConnector {
public static final String PREF_NAME = "ENUMERATOR_PREFERENCES";
public static final String PREF_NAME_REMEMBER = "ENUMERATOR_REMEMBER";
public static final int MODE = Context.MODE_PRIVATE;
public static final String name = "name";
public static void writeBoolean(Context context, String key, boolean value) {
getEditor(context).putBoolean(key, value).commit();
}
public static boolean readBoolean(Context context, String key,
boolean defValue) {
return getPreferences(context).getBoolean(key, defValue);
}
public static void writeInteger(Context context, String key, int value) {
getEditor(context).putInt(key, value).commit();
}
public static int readInteger(Context context, String key, int defValue) {
return getPreferences(context).getInt(key, defValue);
}
public static void writeString(Context context, String key, String value) {
getEditor(context).putString(key, value).commit();
}
public static String readString(Context context, String key, String defValue) {
return getPreferences(context).getString(key, defValue);
}
public static void writeLong(Context context, String key, long value) {
getEditor(context).putLong(key, value).commit();
}
public static long readLong(Context context, String key, long defValue) {
return getPreferences(context).getLong(key, defValue);
}
public static SharedPreferences getPreferences(Context context) {
return context.getSharedPreferences(PREF_NAME, MODE);
}
public static Editor getEditor(Context context) {
return getPreferences(context).edit();
}
}
写入值:
PreferenceConnector.writeString(this, PreferenceConnector.name,"Girish");
并获得价值使用:
String name= PreferenceConnector.readString(this, PreferenceConnector.name, "");
其他回答
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
有两个文件解决了共享首选项的所有问题
1)AppPersistence.java
public class AppPersistence {
public enum keys {
USER_NAME, USER_ID, USER_NUMBER, USER_EMAIL, USER_ADDRESS, CITY, USER_IMAGE,
DOB, MRG_Anniversary, COMPANY, USER_TYPE, support_phone
}
private static AppPersistence mAppPersistance;
private SharedPreferences sharedPreferences;
public static AppPersistence start(Context context) {
if (mAppPersistance == null) {
mAppPersistance = new AppPersistence(context);
}
return mAppPersistance;
}
private AppPersistence(Context context) {
sharedPreferences = context.getSharedPreferences(context.getString(R.string.prefrence_file_name),
Context.MODE_PRIVATE);
}
public Object get(Enum key) {
Map<String, ?> all = sharedPreferences.getAll();
return all.get(key.toString());
}
void save(Enum key, Object val) {
SharedPreferences.Editor editor = sharedPreferences.edit();
if (val instanceof Integer) {
editor.putInt(key.toString(), (Integer) val);
} else if (val instanceof String) {
editor.putString(key.toString(), String.valueOf(val));
} else if (val instanceof Float) {
editor.putFloat(key.toString(), (Float) val);
} else if (val instanceof Long) {
editor.putLong(key.toString(), (Long) val);
} else if (val instanceof Boolean) {
editor.putBoolean(key.toString(), (Boolean) val);
}
editor.apply();
}
void remove(Enum key) {
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.remove(key.toString());
editor.apply();
}
public void removeAll() {
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.clear();
editor.apply();
}
}
2)AppPreference.java
public static void setPreference(Context context, Enum Name, String Value) {
AppPersistence.start(context).save(Name, Value);
}
public static String getPreference(Context context, Enum Name) {
return (String) AppPersistence.start(context).get(Name);
}
public static void removePreference(Context context, Enum Name) {
AppPersistence.start(context).remove(Name);
}
}
现在你可以保存,删除或者获取,
保存
AppPreference.setPreference(context, AppPersistence.keys.USER_ID, userID);
删除
AppPreference.removePreference(context, AppPersistence.keys.USER_ID);
-get
AppPreference.getPreference(context, AppPersistence.keys.USER_ID);
我已经使用jackson来存储我的对象(jackson)。
添加杰克逊库到gradle:
api 'com.fasterxml.jackson.core:jackson-core:2.9.4'
api 'com.fasterxml.jackson.core:jackson-annotations:2.9.4'
api 'com.fasterxml.jackson.core:jackson-databind:2.9.4'
我的测试类:
public class Car {
private String color;
private String type;
// standard getters setters
}
Java对象转换为JSON:
ObjectMapper objectMapper = new ObjectMapper();
String carAsString = objectMapper.writeValueAsString(car);
存储在共享首选项中:
preferences.edit().car().put(carAsString).apply();
从共享首选项中恢复:
ObjectMapper objectMapper = new ObjectMapper();
Car car = objectMapper.readValue(preferences.car().get(), Car.class);
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
更好的方法是创建一个全局Constants类来保存键或变量以获取或保存数据。
要保存数据,请调用此方法保存来自任何地方的数据。
public static void saveData(Context con, String variable, String data)
{
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(con);
prefs.edit().putString(variable, data).commit();
}
用它来获取数据。
public static String getData(Context con, String variable, String defaultValue)
{
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(con);
String data = prefs.getString(variable, defaultValue);
return data;
}
像这样的方法就可以了
public static User getUserInfo(Context con)
{
String id = getData(con, Constants.USER_ID, null);
String name = getData(con, Constants.USER_NAME, null);
if(id != null && name != null)
{
User user = new User(); //Hope you will have a user Object.
user.setId(id);
user.setName(name);
//Here set other credentials.
return user;
}
else
return null;
}