익명 클래스를 사용해서 버튼에 리스너 객체를 설정하기

package com.example.hojak.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity{

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

        Button button = (Button) findViewById(R.id. button);

        final EditText edit = (EditText) findViewById(R.id.edit);
        final TextView text = (TextView) findViewById(R.id.text);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                text.setText(edit.getText());
            }
        });
    }

}

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.hojak.myapplication.MainActivity">



    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="입력하세요."
        android:id="@+id/edit"/>

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:layout_below="@id/edit"/>

    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/button"
        android:id="@+id/text"/>



</RelativeLayout>

MainActivity.java 에서 익명 클래스 내에서는 문법 상 변하지 않는 값만 접근이 가능하게 되있다. 그래서 final 붙임