How can i switch between camera when camera is previewing to the user?

Please follow the following instructions before filing a bug:

1. Github issues under this project are only for **sample**-related issues. If you have modified the sample code in any way, then this is probably not the appropriate place to report a bug.
1. If you are trying to report a bug related to the **CameraX library** then you can do so at the Android Issue Tracker: https://issuetracker.google.com/components/618491.
1. Include the specific sample where you found the issue, in addition to device model and specific Android build number -- which can be found under Settings > About phone.
1. Include error logs from logcat, if there are any.
1. If you can, also attach a [bug report](https://developer.android.com/studio/debug/bug-report)-- but please keep in mind that personal information can sometimes be found in those, so double check before attaching.

The issue names no specific sample, file, test, device, Android build, error log, or reproduction steps. First identify the affected sample and gather the requested device and logcat details; no implementation scope or completion criteria can be established from the current report.

Written by the indexing model from the issue text.