Android 레이아웃 인플레이션 이해하기

Android 레이아웃 인플레이션 이해하기 

package com.example.samplelayoutinflater1;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.LinearLayout;

public class MenuActivity extends AppCompatActivity {
    LinearLayout container;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_menu);
        container=findViewById(R.id.container);

        Button button=findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                LayoutInflater inflater=(LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                inflater.inflate(R.layout.sub1,container,true);
                CheckBox checkBox=container.findViewById(R.id.checkBox);
                checkBox.setText("로딩확인");
            }
        });

    }
}

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MenuActivity">
    <LinearLayout

        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        >
        <TextView
            android:id="@+id/textView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="버튼을 눌러 부분 화면을 추가하세요"
            android:textSize="20sp"
            />
        <Button
            android:id="@+id/button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="추가하기"
            />
        <LinearLayout
            android:id="@+id/container"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical"></LinearLayout>

    </LinearLayout>


</android.support.constraint.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="부분 화면 1"
        android:textSize="30sp"
        />
    <CheckBox
        android:id="@+id/checkBox"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="동의합니다"
        />
</LinearLayout>