Can't switch between dynamically created tabs in MDCTabBar.

[vedtam]

Hi guys,

In my element I'm displaying category titles as Tabs. The problem is that I can't switch between tabs which are rendered after the categories get fetched:

...
    <div class="mdc-tab-bar" role="tablist">
        <div class="mdc-tab-scroller">
          <div class="mdc-tab-scroller__scroll-area">
            <div class="mdc-tab-scroller__scroll-content">

              <button class="mdc-tab mdc-tab--active" 
                      role="tab" tabindex="0" aria-selected="true">
                <span class="mdc-tab__content">
                  <!-- <span class="mdc-tab__icon material-icons">favorite</span> -->
                  <span class="mdc-tab__text-label">VIEW ALL</span>
                </span>
                <span class="mdc-tab-indicator mdc-tab-indicator--active">
                  <span class="mdc-tab-indicator__content mdc-tab-indicator__content--underline"></span>
                </span>
                <span class="mdc-tab__ripple"></span>
              </button>

              ${Object.values(categories || []).map((category) => html`
                <button class="mdc-tab" 
                        role="tab" tabindex="0" aria-selected="false">
                  <span class="mdc-tab__content">
                    <!-- <span class="mdc-tab__icon material-icons">favorite</span> -->
                    <span class="mdc-tab__text-label">${category}</span>
                  </span>
                  <span class="mdc-tab-indicator">
                    <span class="mdc-tab-indicator__content mdc-tab-indicator__content--underline"></span>
                  </span>
                  <span class="mdc-tab__ripple"></span>
                </button>
              `)}

            </div>
          </div>
        </div>
      </div>
  `;
  }

...

stateChanged(state: RootState) {
  this.categories = state.category.items;
}

firstUpdated(){
   new MDCTabBar(this.shadowRoot.querySelector('.mdc-tab-bar'));
}

I've created a demo on glitch that demonstrates the issue, you can see the source here.

I've tried to look for answers on discord, but I got no proper answer there. Thanks!

[kfranqueiro]

Reproduction with vanilla MDC Web: https://glitch.com/edit/#!/mdc-web-4214

We're only ever instantiating tabs based on the DOM during initialize. We would probably need to add an explicit addTab (and removeTab?) API that would receive an mdc-tab element (or possibly an index for removal), or something like reinstantiateTabs that would destroy all current tab instances and reinstantiate based on the current state of the DOM.

[vedtam]

@kfranqueiro thanks for the clarification. Well as a workaround, I moved the 'static' tab inside the loop that generates the rest of the tabs after data gets fetched, now all tabs render simultaneously but I can see other cases where this wouldn't be an option so having an add/remove Tab or reinstantiateTabs method would be nice.

[Rajeshbhartia]

I think you might forget to import those files

import {MDCTabBar} from '@material/tab-bar'; const tabBar = new MDCTabBar(document.querySelector('.mdc-tab-bar'));

[KrisSodroski]

Is there any update on this.

It seems a lot of the mdc controls require that the data be statically passed to any implementation. It makes the controls rather unsuitable to use.

To work around this, I had to catch my tab-item render event, and hack the MDC tab into the tabList of the tabAdapter.

On top of this, there seems to be a global tracking of these tab items, so each tab-item must have a unique id globally.

  const anyTabBar = this.TabBar as any;

  anyTabBar.tabList.push(Tab);

  const randomId = Math.round(Math.random() * Number.MAX_VALUE);

  const id = `mdc-tab-${ randomId }`;

  Tab.id = id;

  Tab.root.id = id;

[JoshMayberry]

I am also interested in some kind of add/remove Tab or reinstantiateTabs solution.