[android] Creating a button in Android Toolbar

You can actually put anything inside a toolbar. See the below code.

<android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:background="@color/colorPrimary">

</android.support.v7.widget.Toolbar>

Between the above toolbar tag you can put almost anything. That is the benefit of using a Toolbar.

Source: Android Toolbar Example