Method _takeFocus

src/material/sidenav/drawer.ts:435–468

* Moves focus into the drawer. Note that this works even if * the focus trap is disabled in `side` mode.

()

   * the focus trap is disabled in `side` mode.
   */
  private _takeFocus() {
    if (!this._focusTrap) {
      return;
    }

    const element = this._elementRef.nativeElement;

    // When autoFocus is not on the sidenav, if the element cannot be focused or does
    // not exist, focus the sidenav itself so the keyboard navigation still works.
    // We need to check that `focus` is a function due to Universal.
    switch (this.autoFocus) {
      case false:
      case 'dialog':
        return;
      case true:
      case 'first-tabbable':
        afterNextRender(
          () => {
            const hasMovedFocus = this._focusTrap!.focusInitialElement();
            if (!hasMovedFocus && typeof element.focus === 'function') {
              element.focus();
            }
          },
          {injector: this._injector},
        );
        break;
      case 'first-heading':
        this._focusByCssSelector('h1, h2, h3, h4, h5, h6, [role="heading"]');
        break;
      default:
        this._focusByCssSelector(this.autoFocus!);
        break;
    }
  }

  /**
   * Restores focus to the element that was originally focused when the drawer opened.