[Java] 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.java

package com.jwsoft.javaproject;

import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.Observer;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private TextView tvName;
    private Button btnShort;
    private Button btnLong;

    private MutableLiveData<String> liveName = new MutableLiveData();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tvName = findViewById(R.id.tvName);
        btnShort = findViewById(R.id.btnShort);
        btnLong = findViewById(R.id.btnLong);

        liveName.observe(this, new Observer<String>() {
            @Override
            public void onChanged(String s) {
                tvName.setText(s);
            }
        });

        btnLong.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                liveName.setValue("혀가 긴 개발자");
            }
        });

        btnShort.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                liveName.setValue("혀가 길지 않은 개발자");
            }
        });

    }
}

실행 결과