Kotlin 封装万能SharedPreferences存取任何类型详解

Kotlin 封装万能SharedPreferences存取任何类型详解

class Preference(val context : Context,val name : String,val default : T) : ReadWriteProperty{

  val prefs by lazy{context.getSharedPreferences("Realnen",Context.MODE_PRIVATE)}


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

  override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
    putPreference(name,value)
  }

  
  private fun  findPreference(name :String,default: A) : A = with(prefs){
    val res : Any = when(default){
      is Long -> getLong(name,default)
      is String -> getString(name,default)
      is Int -> getInt(name,default)
      is Boolean -> getBoolean(name,default)
      is Float -> getFloat(name,default)
      else -> deSerialization(getString(name,serialize(default)))
    }
    res as A
  }

  private fun  putPreference(name :String,value: A) = with(prefs.edit()){
    when(value){
      is Long -> putLong(name,value)
      is String -> putString(name,value)
      is Int -> putInt(name,value)
      is Boolean -> putBoolean(name,value)
      is Float -> putFloat(name,value)
      else -> putString(name,serialize(value))
    }.apply()

  }

  
  fun clearPreference(){
    prefs.edit().clear().commit()
  }

  
  fun clearPreference(key : String){
    prefs.edit().remove(key).commit()
  }

  
  @Throws(IOException::class)
  private fun serialize(obj: A): String {
    val byteArrayOutputStream = ByteArrayOutputStream()
    val objectOutputStream = ObjectOutputStream(
 byteArrayOutputStream)
    objectOutputStream.writeObject(obj)
    var serStr = byteArrayOutputStream.toString("ISO-8859-1")
    serStr = java.net.URLEncoder.encode(serStr, "UTF-8")
    objectOutputStream.close()
    byteArrayOutputStream.close()
    return serStr
  }

  
  @Throws(IOException::class, ClassNotFoundException::class)
  private fun deSerialization(str: String): A {
    val redStr = java.net.URLDecoder.decode(str, "UTF-8")
    val byteArrayInputStream = ByteArrayInputStream(
 redStr.toByteArray(charset("ISO-8859-1")))
    val objectInputStream = ObjectInputStream(
 byteArrayInputStream)
    val obj = objectInputStream.readObject() as A
    objectInputStream.close()
    byteArrayInputStream.close()
    return obj
  }
}

这里主要用的是代理模式，还有数据类要实现序列化Serializable接口,使用方式：

 var save : LoginSaveBean by Preference(App.getInstance(),Constant.LOCAL_SAVE_LOGIN_MODEL_KEY, LoginSaveBean("0","0"))

注意 这条语句我们要放在全局变量来读取，当你改变值或者值被改变时，这里的值会自己提交和同步。

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