[Kotlin] LiveData

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center"
    android:background="#FFBB11"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/tvName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="James Kim"
        android:textSize="30dp"
        android:textStyle="bold" />

    <Button
        android:id="@+id/btnLong"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:text="혀가 긴 개발자"
        android:textSize="20dp"
        android:textStyle="bold"
        android:layout_marginTop="30dp"/>

    <Button
        android:id="@+id/btnShort"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:text="혀가 길지 않은 개발자"
        android:textSize="20dp"
        android:textStyle="bold" />

</LinearLayout>

activity_main.xml

 

 

 

 

 

 

 

MainActivity.kt

package com.jwsoft.kotlinproject

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.Observer
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    private var liveName: MutableLiveData<String> = MutableLiveData()

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

        liveName.observe(this, Observer {
            tvName.text = it
        })

        btnLong.setOnClickListener { liveName.value = "혀가 긴 개발자" }
        btnShort.setOnClickListener { liveName.value = "혀가 길지 않은 개발자" }

    }
}

실행 결과