Convert SharePreferences Android sang kotlin

Những gì cần tìm hiểu đã có hết trong bài viết này rồi:

https://viblo.asia/p/toi-uu-android-shared-preferences-924lJM8bZPM

Hôm nay mình sẽ mạn phép dùng bài viết của tác giả ở trên để hướng dẫn các bạn convert SharePreferences của Android sang Kotlin

1.1. Phần khởi tạo SharedPrefs

companion object {
        private val PREFS_NAME = "share_prefs"
        private var mInstance: SharedPrefs? = null
        val instance: SharedPrefs
            get() {
                if (mInstance == null) {
                    mInstance = SharedPrefs()
                }
                return mInstance as SharedPrefs
            }
    }

1.2. Put data vào shared preferences

Cần truyền vào key và gía trị vào -> function sẽ check type data và put vào đúng type

fun <T> put(key: String, data: T) {
        val editor = mSharedPreferences.edit()
        when (data) {
            is String -> editor.putString(key, data as String)
            is Boolean -> editor.putBoolean(key, data as Boolean)
            is Float -> editor.putFloat(key, data as Float)
            is Int -> editor.putInt(key, data as Int)
            is Long -> editor.putLong(key, data as Long)
            else -> editor.putString(key, App.self()?.gSon?.toJson(data))
        }
        editor.apply()
    }

1.3. Get data từ shared preferencesype

• Cần truyền vào key và type class vào -> function sẽ check type class và get ra đúng giá trị
• Có 2 cách get data ra là get có giá trị mặc định được truyền vào và get có giá trị mặc định sẵn

 @Suppress("UNCHECKED_CAST")
    operator fun <T> get(key: String, anonymousClass: Class<T>): T {
        return when (anonymousClass) {
            String::class.java -> mSharedPreferences.getString(key, "") as T
            Boolean::class.java -> java.lang.Boolean.valueOf(mSharedPreferences.getBoolean(key, false)) as T
            Float::class.java -> java.lang.Float.valueOf(mSharedPreferences.getFloat(key, 0f)) as T
            Int::class.java -> Integer.valueOf(mSharedPreferences.getInt(key, 0)) as T
            Long::class.java -> java.lang.Long.valueOf(mSharedPreferences.getLong(key, 0)) as T
            else -> App.self()?.gSon?.fromJson(mSharedPreferences.getString(key, ""), anonymousClass)!!
        }
    }

    @Suppress("UNCHECKED_CAST")
    operator fun <T> get(key: String, anonymousClass: Class<T>, defaultValue: T): T {
        return when (anonymousClass) {
            String::class.java -> mSharedPreferences.getString(key, defaultValue as String) as T
            Boolean::class.java -> java.lang.Boolean.valueOf(mSharedPreferences.getBoolean(key, defaultValue as Boolean)) as T
            Float::class.java -> java.lang.Float.valueOf(mSharedPreferences.getFloat(key, defaultValue as Float)) as T
            Int::class.java -> Integer.valueOf(mSharedPreferences.getInt(key, defaultValue as Int)) as T
            Long::class.java -> java.lang.Long.valueOf(mSharedPreferences.getLong(key, defaultValue as Long)) as T
            else -> App.self()?.gSon?.fromJson(mSharedPreferences.getString(key, ""), anonymousClass)!!
        }
    }

Full code :

class SharedPrefs private constructor() {
    private val mSharedPreferences: SharedPreferences

    init {
        mSharedPreferences = App.self()!!.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)
    }

    @Suppress("UNCHECKED_CAST")
    operator fun <T> get(key: String, anonymousClass: Class<T>): T {
        return when (anonymousClass) {
            String::class.java -> mSharedPreferences.getString(key, "") as T
            Boolean::class.java -> java.lang.Boolean.valueOf(mSharedPreferences.getBoolean(key, false)) as T
            Float::class.java -> java.lang.Float.valueOf(mSharedPreferences.getFloat(key, 0f)) as T
            Int::class.java -> Integer.valueOf(mSharedPreferences.getInt(key, 0)) as T
            Long::class.java -> java.lang.Long.valueOf(mSharedPreferences.getLong(key, 0)) as T
            else -> App.self()?.gSon?.fromJson(mSharedPreferences.getString(key, ""), anonymousClass)!!
        }
    }

    @Suppress("UNCHECKED_CAST")
    operator fun <T> get(key: String, anonymousClass: Class<T>, defaultValue: T): T {
        return when (anonymousClass) {
            String::class.java -> mSharedPreferences.getString(key, defaultValue as String) as T
            Boolean::class.java -> java.lang.Boolean.valueOf(mSharedPreferences.getBoolean(key, defaultValue as Boolean)) as T
            Float::class.java -> java.lang.Float.valueOf(mSharedPreferences.getFloat(key, defaultValue as Float)) as T
            Int::class.java -> Integer.valueOf(mSharedPreferences.getInt(key, defaultValue as Int)) as T
            Long::class.java -> java.lang.Long.valueOf(mSharedPreferences.getLong(key, defaultValue as Long)) as T
            else -> App.self()?.gSon?.fromJson(mSharedPreferences.getString(key, ""), anonymousClass)!!
        }
    }

    fun <T> put(key: String, data: T) {
        val editor = mSharedPreferences.edit()
        when (data) {
            is String -> editor.putString(key, data as String)
            is Boolean -> editor.putBoolean(key, data as Boolean)
            is Float -> editor.putFloat(key, data as Float)
            is Int -> editor.putInt(key, data as Int)
            is Long -> editor.putLong(key, data as Long)
            else -> editor.putString(key, App.self()?.gSon?.toJson(data))
        }
        editor.apply()
    }

    fun clear() {
        mSharedPreferences.edit().clear().apply()
    }

    companion object {
        private val PREFS_NAME = "share_prefs"
        private var mInstance: SharedPrefs? = null
        val instance: SharedPrefs
            get() {
                if (mInstance == null) {
                    mInstance = SharedPrefs()
                }
                return mInstance as SharedPrefs
            }
    }

class App : Application() {
    var gSon: Gson? = null
    override fun onCreate() {
        super.onCreate()
        mSelf = this
        gSon = Gson()
    }

    companion object {
        private var mSelf: App? = null
        fun self(): App? {
            return mSelf
        }
    }
}

và chú ý khai báo trong AndroidManifest nhé

android:name=".App"

cũng như import thư viện gson trong build.gradle của app nữa nhé

implementation 'com.google.code.gson:gson:2.8.2'

3.1. Tạo model Employee

Kotlin hỗ trợ chúng ta rất nhiều trong việc loại bỏ các hàm get set như trong java cũ

class Employee(var id: Long, var name: String?) {

    override fun toString(): String {
        return "Employee {" +
                "id = " + id +
                ", name = '" + name + ' +
                '}'
    }
}

3.2. MainActivity

class MainActivity : AppCompatActivity() {
    private val tag = this@MainActivity.javaClass.name!!
    private val firstStaff = "first_staff"
    private val secondStaff = "second_staff"
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val employee = Employee(1, "Nguyen Viet Manh")
        val employee2 = Employee(2, "Do Xuan Duc")

        SharedPrefs.instance.put(firstStaff, employee)
        SharedPrefs.instance.put(secondStaff, employee2)

        Log.e(tag, SharedPrefs.instance[firstStaff, Employee::class.java].toString())
        Log.e(tag, SharedPrefs.instance[secondStaff, Employee::class.java].toString())

        Log.e(tag, SharedPrefs.instance["hello", Int::class.java, 2].toString())
    }
}

https://viblo.asia/p/toi-uu-android-shared-preferences-924lJM8bZPM