DataStore-Preferences DataStore

DataStore是用來解決數據存儲，內部使用了Coroutines和Flow，提供了兩種不同的實現。
1.Preferences DataStore
儲存key,value不需要定義架構，不提供Type safety。
2.Proto DataStore
儲存Model要定義Protocol Buffers，提供Type safety。

createDataStore("資料庫名稱"):創建資料庫
preferencesKey:資料的Key
DataStore.edit:寫入資料
DataStore.data:將資料取出利用Flow傳回
Flow<T>.collect:取得資料

導入

android {
    kotlinOptions { jvmTarget = "1.8" }
}

dependencies {
    implementation "androidx.datastore:datastore-preferences:1.0.0-alpha01"
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9'
}

創建Model

data class User(var account: String?, var password: String?)

MainActivity

class MainActivity : AppCompatActivity() {

    //共用同個key
    object PreferencesKeys {
        val ACCOUNT = preferencesKey<String>("account")
        val PASSWORD = preferencesKey<String>("password")
    }

    //創建userInfo的資料庫
    private val dataStore by lazy {
        applicationContext.createDataStore(name = "userInfo")
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

         CoroutineScope(Dispatchers.IO).launch {
            val user = dataStore.data.map { user ->
                val account = user[PreferencesKeys.ACCOUNT] ?: ""
                val password = user[PreferencesKeys.PASSWORD] ?: ""
                //把值塞入Model中回傳
                User(account, password)
            }

             //從Model取出資料
            withContext(Dispatchers.Main) {
                user.collect { user ->
                    account.setText(user.account)
                    password.setText(user.password)
                }
            }
        }
    }

    //儲存資料
    fun save(view: View) {
        CoroutineScope(Dispatchers.IO).launch {
            dataStore.edit { user ->
                user[PreferencesKeys.ACCOUNT] = account.text.toString()
                user[PreferencesKeys.PASSWORD] = password.text.toString()
            }
        }
    }
}

儲存資料後可來這邊查看
Device File Explorer > data > data > Package Name > files > datastore