1. activity_main.xml 코드

<androidx.appcompat.widget.LinearLayoutCompat
    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:id="@+id/baseLayout"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btnBackgroundChange"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="배경색 변경"
        android:layout_gravity="center" />
    <Button
        android:id="@+id/btnButtonChange"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="버튼 변경"
        android:layout_gravity="center" />

</androidx.appcompat.widget.LinearLayoutCompat>

2. MainActivity.java 코드

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity2";
    private LinearLayoutCompat baseLayout;
    private Button btnBackgroundChange, btnButtonChange;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setTitle("배경색 바꾸기(컨텍스트 메뉴)");

        init();
    }
    public void init(){
        baseLayout = (LinearLayoutCompat)findViewById(R.id.baseLayout);
        btnBackgroundChange = findViewById(R.id.btnBackgroundChange);
        registerForContextMenu(btnBackgroundChange);
        btnButtonChange = findViewById(R.id.btnButtonChange);
        registerForContextMenu(btnButtonChange);
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v,
    					ContextMenu.ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);

        MenuInflater mInflater = getMenuInflater();
        if(v == btnBackgroundChange){
            menu.setHeaderTitle("배경색 변경");
            mInflater.inflate(R.menu.menu1, menu);
        }
        if(v == btnButtonChange){
            mInflater.inflate(R.menu.menu2, menu);
        }
    }
    @Override
    public boolean onContextItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.itemRed:
                baseLayout.setBackgroundColor(Color.RED);
                return true;
            case R.id.itemGreen:
                baseLayout.setBackgroundColor(Color.GREEN);
                return true;
            case R.id.itemBlue:
                baseLayout.setBackgroundColor(Color.BLUE);
                return true;
            case R.id.subRotate:
                btnBackgroundChange.setRotation(45);
                return true;
            case R.id.subSizeUp:
                btnButtonChange.setScaleX(2);
                return true;
        }
        return false;
    }
}

3. menu1.xml 코드

<?xml version="1.0" encoding="utf-8"?>
<menu
    xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/itemRed"
        android:title="배경색(빨강)" />
    <item
        android:id="@+id/itemBlue"
        android:title="배경색(파랑)" />
    <item
        android:id="@+id/itemGreen"
        android:title="배경색(초록)" />
</menu>

4. menu2.xml 코드

<?xml version="1.0" encoding="utf-8"?>
<menu
    xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/subRotate"
        android:title="버튼 45도 회전" />
    <item
        android:id="@+id/subSizeUp"
        android:title="버튼 2배 확대" />
</menu>