如何在Ionic的导航栏下面制作一个容器填满整个屏幕？

I want an iframe to fill all the space below the navigation bar. I see that Ionic is generating inline CSS and adding classes to html, body tags and it also creates div wrappers. I don't know what is the intended way to achieve what I want. Do I need to use some pre-made CSS class for this, or write my own? If so, how should I do that, to not break the layout.I want an iframe to fill all the space below th