Method _initKeyManager

src/material/select/select.ts:1164–1196

Sets up a key manager to listen to keyboard events on the overlay panel.

()

  /** Sets up a key manager to listen to keyboard events on the overlay panel. */
  private _initKeyManager() {
    this._keyManager = new ActiveDescendantKeyManager<MatOption>(this.options)
      .withTypeAhead(this.typeaheadDebounceInterval)
      .withVerticalOrientation()
      .withHorizontalOrientation(this._isRtl() ? 'rtl' : 'ltr')
      .withHomeAndEnd()
      .withPageUpDown()
      .withAllowedModifierKeys(['shiftKey'])
      .skipPredicate(this._skipPredicate);

    this._keyManager.tabOut.subscribe(() => {
      if (this.panelOpen) {
        // Select the active item when tabbing away. This is consistent with how the native
        // select behaves. Note that we only want to do this in single selection mode.
        if (!this.multiple && this._keyManager.activeItem) {
          this._keyManager.activeItem._selectViaInteraction();
        }

        // Restore focus to the trigger before closing. Ensures that the focus
        // position won't be lost if the user got focus into the overlay.
        this.focus();
        this.close();
      }
    });

    this._keyManager.change.subscribe(() => {
      if (this._panelOpen && this.panel) {
        this._scrollOptionIntoView(this._keyManager.activeItemIndex || 0);
      } else if (!this._panelOpen && !this.multiple && this._keyManager.activeItem) {
        this._keyManager.activeItem._selectViaInteraction();
      }
    });
  }

  /** Drops current option subscriptions and IDs and resets from scratch. */
  private _resetOptions(): void {