如何使用 kotlin 从 android studio 中的 Firebase 读取数据？

Question

我想从数据库中获取用户的姓名和他的电子邮件，我用它来将数据设置到数据库中：

创建用户

fun createUser( name:String, email: String, password: String) {

    mProgressbar.setMessage("Please wait..")
    mProgressbar.show()


    mAuth.createUserWithEmailAndPassword(email, password)
        .addOnCompleteListener(this) { task ->
            if (task.isSuccessful) {
                val user = User(
                    name,
                    email
                )

                FirebaseDatabase.getInstance().getReference("Users")
                    .child(FirebaseAuth.getInstance().currentUser!!.uid)
                    .setValue(user).addOnCompleteListener(OnCompleteListener<Void> { task ->
                        if (task.isSuccessful) {
                            Toast.makeText(this, "Registered Successfully", Toast.LENGTH_LONG).show()
                            val Intent = Intent(applicationContext, MainActivity::class.java)
                            startActivity(Intent)
                            finish()
                            mProgressbar.dismiss()
                        } else {
                            //display a failure message
                        }
                    })
            } else {

                Toast.makeText(this, "Authentication failed.${task.exception}", Toast.LENGTH_SHORT).show()
                mProgressbar.dismiss()

            }
        }
}

用户

class User ( name: String,  email: String) {

    private var name: String? = name
    private var email: String? = email

    fun setName(Name: String) {
        this.name = Name
    }
    fun getName(): String? {
        return name
    }
    fun setEmail(Email: String) {
        this.email = Email
    }
    fun getEmail(): String? {
        return email
    }
}

我需要帮助。我需要帮助。我需要帮助。我需要帮助。我需要帮助。我需要帮助。我需要帮助。我需要帮助。

Answer 1

internal var user: User? = null  // declare user object outside onCreate Method

var ref = FirebaseDatabase.getInstance().getReference("Users").child(FirebaseAuth.getInstance().currentUser!!.uid)

val menuListener = object : ValueEventListener {
    override fun onDataChange(dataSnapshot: DataSnapshot) {
        user = dataSnapshot.getValue() as User
        textView.text = user?.getName()
    }
    override fun onCancelled(databaseError: DatabaseError) {
        // handle error
    }
}
ref.addListenerForSingleValueEvent(menuListener)

Answer 2

从数据库中获取值的代码

val menuListener = object : ValueEventListener {
    override fun onCancelled(databaseError: DatabaseError) {
        // handle error
    }
    override fun onDataChange(dataSnapshot: DataSnapshot) {
        user = dataSnapshot.getValue(User::class.java)
        textView.text = user?.name
    }
}

我必须将用户类代码更改为：

@IgnoreExtraProperties
data class User(
    var name: String? = "",
    var email: String? = ""
) {

    @Exclude
    fun toMap(): Map<String, Any?> {
        return mapOf(
            "uid" to name,
            "author" to email
        )
    }
}