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)
}
}

其他回答

你可以保存对象在首选项不使用任何库,首先你的对象类必须实现Serializable:

public class callModel implements Serializable {

private long pointTime;
private boolean callisConnected;

public callModel(boolean callisConnected,  long pointTime) {
    this.callisConnected = callisConnected;
    this.pointTime = pointTime;
}
public boolean isCallisConnected() {
    return callisConnected;
}
public long getPointTime() {
    return pointTime;
}

}

然后你可以很容易地使用这两个方法来转换对象到字符串和字符串到对象:

 public static <T extends Serializable> T stringToObjectS(String string) {
    byte[] bytes = Base64.decode(string, 0);
    T object = null;
    try {
        ObjectInputStream objectInputStream = new ObjectInputStream(new ByteArrayInputStream(bytes));
        object = (T) objectInputStream.readObject();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return object;
}

 public static String objectToString(Parcelable object) {
    String encoded = null;
    try {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
        objectOutputStream.writeObject(object);
        objectOutputStream.close();
        encoded = new String(Base64.encodeToString(byteArrayOutputStream.toByteArray(), 0));
    } catch (IOException e) {
        e.printStackTrace();
    }
    return encoded;
}

保存:

SharedPreferences  mPrefs = getPreferences(MODE_PRIVATE);
Editor prefsEditor = mPrefs.edit();
prefsEditor.putString("MyObject", objectToString(callModelObject));
prefsEditor.commit();

阅读

String value= mPrefs.getString("MyObject", "");
MyObject obj = stringToObjectS(value);
// SharedPrefHelper is a class contains the get and save sharedPrefernce data
public class SharedPrefHelper {

    // save data in sharedPrefences
    public static void setSharedOBJECT(Context context, String key, 
                                           Object value) {

        SharedPreferences sharedPreferences =  context.getSharedPreferences(
                context.getPackageName(), Context.MODE_PRIVATE);

        SharedPreferences.Editor prefsEditor = sharedPreferences.edit();
        Gson gson = new Gson();
        String json = gson.toJson(value);
        prefsEditor.putString(key, json);
        prefsEditor.apply();
    }

    // get data from sharedPrefences 
    public static Object getSharedOBJECT(Context context, String key) {

         SharedPreferences sharedPreferences = context.getSharedPreferences(
                           context.getPackageName(), Context.MODE_PRIVATE);

        Gson gson = new Gson();
        String json = sharedPreferences.getString(key, "");
        Object obj = gson.fromJson(json, Object.class);
        User objData = new Gson().fromJson(obj.toString(), User.class);
        return objData;
    }
}
// save data in your activity

User user = new User("Hussein","h@h.com","3107310890983");        
SharedPrefHelper.setSharedOBJECT(this,"your_key",user);        
User data = (User) SharedPrefHelper.getSharedOBJECT(this,"your_key");

Toast.makeText(this,data.getName()+"\n"+data.getEmail()+"\n"+data.getPhone(),Toast.LENGTH_LONG).show();
// User is the class you want to save its objects

public class User {

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    private String name,email,phone;
    public User(String name,String email,String phone){
          this.name=name;
          this.email=email;
          this.phone=phone;
    }
}
// put this in gradle

compile 'com.google.code.gson:gson:2.7'

希望这对你有所帮助:)

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

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, "");

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