1.Firebase與專案連結

2.點擊Cloud Firestore將library與google-services.json導入進專案

3.Firebase console創建資料庫

選擇(測試模式啟動) 上架前在改為(鎖定模式啟動)

4.寫入資料

private val users = mutableListOf<Map<String, String>>()
private val database = FirebaseFirestore.getInstance()

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

    users.add(insertUser("fly", "a123456"))
    users.add(insertUser("wei", "b123456"))

    for (user in users) {
        database.collection("users")
            .add(user)
            .addOnSuccessListener {
                Log.e("GGG", it.id)
            }
            .addOnFailureListener {
                Log.e("GGG", it.toString())
            }
    }
}

private fun insertUser(name: String, password: String): Map<String, String> {
    return mapOf("name" to name, "password" to password)
}

回傳的document id

5.讀取資料

private val database = FirebaseFirestore.getInstance()

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

    database.collection("users")
        .get().addOnSuccessListener {
            val users = it.toObjects(User::class.java)
            users.forEach {user ->
                Log.e("GGG", "{user.name}{user.password}")
            }
        }
}

6.Model(一定要有空建構子)

class User(val name: String, val password: String)  {
    constructor() : this("", "")
}