Popupmenu offset from right edge of screen

I'm following this tutorial to set the popupmenu to some distance away from the right side of the screen: http://ift.tt/1ddW1uv

Similar to this tutorial, my popupmenu touches the rihgt side of the screen:

The author of the tutorial says you can adjust the horizontal offset by using reflection.

I have taken his code and put it into my project but it keeps on returning an error - please note that the piece of his code relating to putting icons within the popupmenu works flawlessly:

Attempt to invoke virtual method 'java.lang.Class java.lang.Object.getClass()' on a null object reference

The faulty line that the error points to is:

        Class listPopupClass = listPopup.getClass();

I don't know enough about reflection to solve this issue, does anyone know why I'm getting a null object reference?

        // Force icons to show
        Object menuHelper;
        Class[] argTypes;
        try {
            Field fMenuHelper = PopupMenu.class.getDeclaredField("mPopup");
            fMenuHelper.setAccessible(true);
            menuHelper = fMenuHelper.get(popupMenu);
            argTypes = new Class[]{boolean.class};
            menuHelper.getClass().getDeclaredMethod("setForceShowIcon", argTypes).invoke(menuHelper, true);

        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
        // Try to force some horizontal offset
        try {
        Field fMenuHelper = PopupMenu.class.getDeclaredField("mPopup");
        fMenuHelper.setAccessible(true);
        menuHelper = fMenuHelper.get(popupMenu);
        Field fListPopup = menuHelper.getClass().getDeclaredField("mPopup");
        fListPopup.setAccessible(true);
        Object listPopup = fListPopup.get(menuHelper);
        argTypes = new Class[] { int.class };
        Class listPopupClass = listPopup.getClass();
        // Get the width of the popup window
        int width = (Integer) listPopupClass.getDeclaredMethod("getWidth").invoke(listPopup);
        // Invoke setHorizontalOffset() with the negative width to move left by that distance
        listPopupClass.getDeclaredMethod("setHorizontalOffset", argTypes).invoke(listPopup, -width);
        // Invoke show() to update the window's position
        listPopupClass.getDeclaredMethod("show").invoke(listPopup);
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (NoSuchFieldException e) {
        e.printStackTrace();
    }
        popupMenu.inflate(R.menu.popup_global);
        popupMenu.show();