【ANDROID STUDIO】 Popup Menu

package com.example.popup;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.widget.PopupMenu;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private PopupMenu.OnMenuItemClickListener mOnMenuItemClickListener = new PopupMenu.OnMenuItemClickListener() {
        @Override
        public boolean onMenuItemClick(MenuItem item) {
            switch (item.getItemId()) {
                case R.id.menu_reply:
                    Toast.makeText(MainActivity.this, "Reply", Toast.LENGTH_SHORT).show();
                    return true;
                case R.id.menu_reply_all:
                    Toast.makeText(MainActivity.this, "Reply All", Toast.LENGTH_SHORT).show();
                    return true;
                case R.id.menu_forward:
                    Toast.makeText(MainActivity.this, "Forward", Toast.LENGTH_SHORT).show();
                    return true;
                default:
                    return false;
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void showPopupMenu(View view) {
        PopupMenu popupMenu = new PopupMenu(MainActivity.this, view);
        popupMenu.inflate(R.menu.menu_popup);
        popupMenu.setOnMenuItemClickListener(mOnMenuItemClickListener);
        popupMenu.show();
    }
}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity">

    <ImageButton android:id="@+id/imageButtonReply"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@android:drawable/ic_menu_revert"
        android:onClick="showPopupMenu"
        android:layout_marginLeft="8dp" />

</androidx.constraintlayout.widget.ConstraintLayout>
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/menu_reply"
        android:title="@string/menu_reply" />
    <item android:id="@+id/menu_reply_all"
        android:title="@string/menu_reply_all" />
    <item android:id="@+id/menu_forward"
        android:title="@string/menu_forward" />
</menu>