NullPointerException when trying to hide view/layout

I am trying to hide a view/layout when one of the menu items is clicked but i keep getting a nullpointerexception.

This is how i am doing it.

RelativeLayout relativeLayout;
relativeLayout = (RelativeLayout) findViewById(R.id.layouttohide);

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case R.id.action_cog:
        if (relativeLayout.isShown() == true) {
            relativeLayout.setVisibility(relativeLayout.GONE);
        }else {
            relativeLayout.setVisibility(relativeLayout.VISIBLE);
        }

        return true;
    case R.id.action_stuff:
        Toast.makeText(getApplicationContext(),
                  item.getTitle(), Toast.LENGTH_SHORT).show();
        return true;

    default:
        return super.onOptionsItemSelected(item);
    }
}

In the XML file this is how i have the layout setup.

<RelativeLayout
    android:id="@+id/layouttohide"
    android:layout_width="match_parent"
    android:layout_height="150dp"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_marginBottom="0dp"
    android:background="#025fb6"
    android:visibility="visible" >