如何在Kotlin中设置值首选项？

Question

以下代码是关于Kotlin的示例项目，我可以使用Code 1来获取共享首选项的值，但是我可以设置共享首选项的值？

我无法在示例项目中找到这些代码，您能告诉我我该怎么办？谢谢！

代码1

class SettingsActivity : AppCompatActivity() { 

    companion object { 
     val ZIP_CODE = "zipCode" 
     val DEFAULT_ZIP = 94043L 
    } 

    var zipCode: Long by DelegatesExt.preference(this, ZIP_CODE, DEFAULT_ZIP) 
} 

代码2

object DelegatesExt { 
    fun <T> notNullSingleValue() = NotNullSingleValueVar<T>() 
    fun <T> preference(context: Context, name: String, default: T) = Preference(context, name, default) 
} 

class NotNullSingleValueVar<T> { 

    private var value: T? = null 

    operator fun getValue(thisRef: Any?, property: KProperty<*>): T { 
     return value ?: throw IllegalStateException("${property.name} not initialized") 
    } 

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T) { 
     this.value = if (this.value == null) value 
     else throw IllegalStateException("${property.name} already initialized") 
    } 
} 

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

    val prefs: SharedPreferences by lazy { context.getSharedPreferences("default", Context.MODE_PRIVATE) } 

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

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

    @Suppress("UNCHECKED_CAST") 
    private fun findPreference(name: String, default: T): T = 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 -> throw IllegalArgumentException("This type can be saved into Preferences") 
     } 

     res as T 
    } 

    private fun putPreference(name: String, value: T) = 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 -> throw IllegalArgumentException("This type can't be saved into Preferences") 
     }.apply() 
    } 
} 

和更多

如果函数putPreference是公共的，我可以使用设置的共享偏好的值下面的代码，但它的丑陋

class SettingsActivity : AppCompatActivity() { 

    companion object { 
     val ZIP_CODE = "zipCode" 
     val DEFAULT_ZIP = 94043L 
    } 

    DelegatesExt.Preference(this, ZIP_CODE, DEFAULT_ZIP).putPreference(ZIP_CODE,"99999L"); 
} 

Answer 1

这operator fun setValue是什么：你只写

activity.zipCode = 1L 

（其中activity是SettingsActivity）或

zipCode = 1L 

（内SettingsActivity或类扩展它），它我们将致电，致电putPreference("zipCode", 1L)。有关更多信息，请参见https://kotlinlang.org/docs/reference/delegated-properties.html。