Kotlin的强悍震撼了我，android中每个应用都会用到SharedPreference在Kotlin中使用竟是如此简单！
package com.android.extkt import android.content.Context
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty /**
* Preference
*
* @author 祁连山™
* @date 2016-12-09
* @version 1.0
*/ class Preference<T>(val context: Context, val name: String, val default: T) : ReadWriteProperty<Any?, T> { val prefs by lazy { context.getSharedPreferences("default", 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 <U> findPreference(name: String, default: U): U = 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 not be saved")
}
res as U
} private fun <U> putPreference(name: String, value: U) = 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 not be saved")
}.apply()
}
}
使用时直接读取赋值，再也不用edit、commit，以我们最常用的引导页判断来说，如果是第一次进入应用跳转到GuideActivity，否则启动MainActivity，使用Kotlin码出来就是下面这个样子：
package com.android.kotlin import android.content.Intent
import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import com.android.extkt.Preference
import rx.Observable
import rx.android.schedulers.AndroidSchedulers
import rx.schedulers.Schedulers
import java.util.concurrent.TimeUnit class SplashActivity : AppCompatActivity() { private var first: Boolean by Preference(this, "first", true) override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_splash) val observable = Observable.timer(3000, TimeUnit.MILLISECONDS)
observable.observeOn(AndroidSchedulers.mainThread())
observable.subscribeOn(Schedulers.io())
observable.subscribe({ route() })
} override fun onBackPressed() {
return
} fun route(): Unit {
var intent = Intent()
if (first) {
intent.setClass(this, GuideActivity::class.java)
startActivity(intent)
// 可以在这里直接存储first的值
// first = false
this.finish()
return
}
intent.setClass(this, MainActivity::class.java)
startActivity(intent)
this.finish()
}
}
在Kotlin中，声明成员属性，除了直接赋值，还可以用 Delegate 的方式来声明，这个 Delegate 需要根据成员的类型（val 或者 var）来提供相应的 getValue 和 setValue 方法，比如一个可读写的 Delegate，需要提供下面的方法：
public interface ReadWriteProperty<in R, T> {
public operator fun getValue(thisRef: R, property: KProperty<*>): T
public operator fun setValue(thisRef: R, property: KProperty<*>, value: T)
}
-------------------------------------------------------------我是分隔线-------------------------------------------------------------
最近项目已经使用kt来完成，用到这里时，需要清除全部缓存数据，不好一个个赋值清除，Preference有clear()却没法用，这时就需要对Preference这个代理类进行改造，也没什么可多说的，只是因为上午改的时候写错了，发现没法使用，下午单独写个demo时才发现，分享出来。
package com.android.app import android.content.Context
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty /**
* Preference
*
* @author 祁连山
* @date 2016-12-09
* @version 1.0
*/ class Preference<T>(val context: Context) : ReadWriteProperty<Any?, T> { var key: String? = null
var value: T? = null constructor(context: Context, name: String, default: T) : this(context) {
key = name
value = default
} val prefs by lazy { context.getSharedPreferences("default", Context.MODE_PRIVATE) } override fun getValue(thisRef: Any?, property: KProperty<*>): T {
return findPreference(key!!, value!!)
} override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
putPreference(key!!, value)
} fun delete(vararg key: String): Unit {
if (key.size == 0) {
prefs.edit().clear().commit()
return
}
for (i in 0..key.size) {
prefs.edit().remove(key[i]).commit()
}
} private fun <U> findPreference(name: String, default: U): U = 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("The data can not be saved")
}
res as U
} private fun <U> putPreference(name: String, value: U) = 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("The data can not be saved")
}.apply()
}
}
使用方法与原来无异，只是用到Preference对象时，用主构造方法来获取，代码如下：
...
var prefs = Preference(this)
prefs.delete()
...
代码出处：http://www.jcodecraeer.com
代码下载：https://pan.baidu.com/s/1eR4i4ca其他资料：http://blog.csdn.net/TIANLANG3/article/details/53926273