方法签名不正确？

Question

我是初学者。    代码仅在android 6和upper上运行。 代码运行良好，有6个警告，但我想在Menu_Main.xml 6行中删除这6个警告，例如带有onClick = itemClick的行。

我该怎么做才能摆脱这些警告？请帮助我。

MainActivity.java

[]interface {}{main.UserCommand{User:"u1", Info:"i1"}, main.UserCommand{User:"u2", Info:"i2"}}
[]interface {}{main.ProductCommand{Name:"n1", Quantity:1}, main.ProductCommand{Name:"n2", Quantity:2}}

activity_main.xml中

package com.example.sky.my13application;

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 {

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return super.onCreateOptionsMenu(menu);
    }  
    public boolean itemClick(MenuItem item){
        Toast.makeText(this,item.getTitle() ,Toast.LENGTH_LONG).show();
        return true;
    }
}

menu_Main.xml

<?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.sky.my13application.MainActivity">

</RelativeLayout>

的strings.xml

<?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">

       <item android:title="@string/app_name1"
             android:onClick="itemClick"
             />
       <item android:title="@string/app_name2"
             android:onClick="itemClick"
             />
       <item android:title="@string/app_name3"
             android:onClick="itemClick"
             >
       <menu>
            <item android:title="@string/app_name4"
                  android:onClick="itemClick"
            />
            <item android:title="@string/app_name5"
                  android:onClick="itemClick"
             />
       </menu>
    </item>
</menu>