Hide a button when drawer is opened in ionic?

I have an ionic drawer as:

<drawer side="left" class="left" canDrag="true" id="side-menu"></drawer>

and a button as:

<button ng-class="plusIconClass" class="button button-circle button-positive icon ion-plus-round margin-right-2x fright" ng-click="showFloatingActioButtons()" style="top:-23px !important; right:-10px !important;"></button>

now i want to add disabled class on my button every time drawer is opened but I am unable to trigger the event of opening and closing of drawer.

This links will help you