[mdExpansionPanel] Expand/collapse all functionality

[henetiriki]

Bug, feature request, or proposal:

Feature request

What is the expected behavior?

Expand all/collapse all

What is the current behavior?

Unable to expand or collapse multiple expansion panels in a single operation, unless it is possible and I am missing something.

PS Thanks for the great effort so far - was super excited to discover that expansion panels have been added!

[henetiriki]

Hey @josephperrott - I've been looking at implementing this feature and just want to run my idea past you before opening a PR.

I propose a couple of public functions on CdkAccordion (expandAll() and collapseAll() or maybe a parameterised one expandAll(expanded: boolean)) which can then be accessed via @ViewChild(MdAccordion) in any implementing components.

These functions, in turn, emits expand/collapse events via an rxjs/Subject to which the MdExpansionPanelHeader subscribe via an rxjs/Subscription. The reasoning here is that the accordion item should only respond to expand/collapse all events if the panel is part of an accordion, with multi enabled, and also exclude any panels which may be disabled.

Hope this makes sense.

[henetiriki]

@josephperrott - I'm working on a PR for this feature. I'm unable to figure out how to ensure the material-examples content is working as expected - is there a gulp task I'm not seeing?

[willshowell]

@ouq77 I don't know the official answer, but if you're running material.angular.io locally, you can run gulp fetch-local in that repo to build the assets from your local material2 clone. I think that should pull in your new example.

[josephperrott]

How @willshowell described is the way we check it locally.