bug(mat-select): Talkback cannot navigate long dropdowns

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

When navigating through a mat-select element using Talkback on an Android mobile device, dropdowns with many options cause the page to not maintain focus and result in major jittering and page UI issues. This is not the case with a list of small options. This may be partially a mat-option issue as well.

Reproduction

StackBlitz link:
Steps to reproduce:

1. view page with Talkback on Android
2. attempt to move through the list (note the jittering and incorrectly moving content)

Expected Behavior

Swiping left and right should provide consistent navigation without large UI jumps and page jittering. The element that is being focused should be indicated to the user.

Actual Behavior

Swipping left and right with standard mobile screen reader navigation on long dropdowns results in UI reloading errors and focus issues. Occasionally, the first or last few elements will function normally but issues occur at the midpoints of these lists.

Looking at other UIs that have a similar element the Multiple Search Selection "state" field here seems very good, UI focus is maintained and there are no large reloading jumps when navigating. Though this is an arbatray dropdown example, and I am sure there are other ones that could be identified.

Environment

• Angular: 21.0.6
• CDK/Material: 20.2.9
• Browser(s): Chrome
• Operating System (e.g. Windows, macOS, Ubuntu): Android

从 mat-select 和 mat-option 入口开始，使用一个很长的选项列表，在启用 TalkBack 的 Android Chrome 中重现该问题。完成标准是，向左/向右导航始终将焦点保持在预期元素上，避免 UI 大幅跳动或抖动，并持续明确显示获得焦点的选项。