Method _handleClosedKeydown

src/material/select/select.ts:904–933

Handles keyboard events while the select is closed.

(event: KeyboardEvent)

  /** Handles keyboard events while the select is closed. */
  private _handleClosedKeydown(event: KeyboardEvent): void {
    const keyCode = event.keyCode;
    const isArrowKey =
      keyCode === DOWN_ARROW ||
      keyCode === UP_ARROW ||
      keyCode === LEFT_ARROW ||
      keyCode === RIGHT_ARROW;
    const isOpenKey = keyCode === ENTER || keyCode === SPACE;
    const manager = this._keyManager;

    // Open the select on ALT + arrow key to match the native <select>
    if (
      (!manager.isTyping() && isOpenKey && !hasModifierKey(event)) ||
      ((this.multiple || event.altKey) && isArrowKey)
    ) {
      event.preventDefault(); // prevents the page from scrolling down when pressing space
      this.open();
    } else if (!this.multiple) {
      const previouslySelectedOption = this.selected;
      manager.onKeydown(event);
      const selectedOption = this.selected;

      // Since the value has changed, we need to announce it ourselves.
      if (selectedOption && previouslySelectedOption !== selectedOption) {
        // We set a duration on the live announcement, because we want the live element to be
        // cleared after a while so that users can't navigate to it using the arrow keys.
        this._liveAnnouncer.announce((selectedOption as MatOption).viewValue, 10000);
      }
    }
  }

  /** Handles keyboard events when the selected is open. */
  private _handleOpenKeydown(event: KeyboardEvent): void {