class MainActivity

package com.example.choi.mystudy18;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    Toast toast;


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


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        switch (item.getItemId()){
            case R.id.action_menu_01:
                tostShow("action_menu_01");
                break;

            case R.id.action_menu_02:
                tostShow("action_menu_02");
                break;
            case R.id.action_menu_03:
                tostShow("action_menu_03");
                break;
            case R.id.menu_01:
                tostShow("menu_01");
                break;
            case R.id.menu_02:
                tostShow("menu_02");
                break;
            case R.id.menu_03:
                tostShow("menu_03");
                break;

        }
        return false;
    }



    private void tostShow(String message){

        if(toast==null){
            toast=Toast.makeText(MainActivity.this, message, Toast.LENGTH_SHORT);
        }else{
            toast.setText(message);
        }
        toast.show();
    }



}

 

R.layout.activity_main

<?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:id="@+id/activity_main"
    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.choi.mystudy18.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />
</RelativeLayout>

 

 

R.menu.main

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android">


    <group app:showAsAction="always">
        <item android:title="Item1"
            android:icon="@drawable/g15"
            android:id="@+id/action_menu_01"
            android:orderInCategory="1"
            app:showAsAction="always"
            />

        <item android:title="Item2"
            app:showAsAction="always"
            android:icon="@android:drawable/presence_online"
            android:orderInCategory="2"
            android:id="@+id/action_menu_02" />

        <item android:title="Item3"
            android:icon="@android:drawable/stat_sys_vp_phone_call_on_hold"
            android:id="@+id/action_menu_03"
            android:orderInCategory="3"
            app:showAsAction="always" />

    </group>



    <group >
        <item android:title="메뉴1"
            android:id="@+id/menu_01" />
        <item android:title="메뉴2"
            android:id="@+id/menu_02" />

        <item android:title="메뉴3"
            android:id="@+id/menu_03" />
    </group>



</menu>