简化SharedPreferences的用法

  • 通过扩展函数方式像其中添加open函数

  • 接收函数类型

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    fun SharedPreferences.open(block:SharedPreferences.Editor.()->Unit){
        val editor=edit()
        editor.block()
        editor.apply()
    }
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    //调用
    getSharedPreferences("data",Context.MODE_PRIVATE).open{
        putString("name","Tom")
        putInt("age",19)
        putBoolean("married",false)
    }

Android Studio自带扩展可以直接使用：

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getSharedPreferences("data",Context.MODE_PRIVATE).edit{
    putString("name","Tom")
    putInt("age",19)
    putBoolean("married",false)
}

简化ContentValues的用法

  • 定义cvOf方法

  • 获取ContentValues对象

  • 遍历pairs列表

  • 利用when语句意义判断数值类型

    **varage关键字：**对应java的可变参数列表

    Pair：键值对数据结构，由于数值类型多所以指定为Any?相当于java中的Object

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    fun cvOf(vararg pairs:Pair<String,Any?>):ContentValues{
        val cv=ContentValues()
        for(pair in pairs){
            val key=pair.first
            val value=pair.second
            when(value){
                is Int->cv.put(key, value)
                is Long->cv.put(key, value)
                is Short->cv.put(key, value)
                is Float->cv.put(key, value)
                is Double->cv.put(key, value)
                is Boolean->cv.put(key, value)
                is String->cv.put(key, value)
                is Byte->cv.put(key, value)
                is ByteArray->cv.put(key, value)
                null->cv.putNull(key)
            }
        }
        return cv
    }
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    //调用
    val values=cvOf("name" to "Game of Thrones","author" to "George Martin","pages" to 720,"price" to 20.85)
    db.insert("Book",null,values)

    利用apply简化

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    fun cvOf(vararg pairs:Pair<String,Any?>)=ContentValues().apply{
        for(pair in pairs){
            val key=pair.first
            val value=pair.second
            when(value){
                is Int->put(key, value)
                is Long->put(key, value)
                is Short->put(key, value)
                is Float->put(key, value)
                is Double->put(key, value)
                is Boolean->put(key, value)
                is String->put(key, value)
                is Byte->put(key, value)
                is ByteArray->put(key, value)
                null->putNull(key)
            }
        }
    }

    KTX库提供同样功能的contentValuesOf方法

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    val values=contentValuesOf("name" to "Game of Thrones","author" to "George Martin","pages" to 720,"price" to 20.85)
    db.insert("Book",null,values)