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

    <item
        android:id="@+id/action_name"
        android:icon="@drawable/you_resource_here"
        android:title="Text to be seen by user"
        app:showAsAction="always"
        android:orderInCategory="0"/>

</menu>

然后在你的活动中,如果你创建了一个新的文件,你需要编辑onCreateOptionsMenu

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main,menu);
    return true;
}

您可以编辑以下方法执行的操作：

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button,so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_name) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}