# Main Thread Checker: UI API called on a background thread

**URL:** <https://devforum.zoom.us/t/main-thread-checker-ui-api-called-on-a-background-thread/39345>\
**Category:** iOS\
**Created:** [December 29, 2020, 8:26am UTC](https://devforum.zoom.us/t/main-thread-checker-ui-api-called-on-a-background-thread/39345 "2020-12-29T08:26:12Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![maqianli9011](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/maqianli9011/32/19465_2.png) [@maqianli9011](https://devforum.zoom.us/u/maqianli9011)\
**Post date:** [December 29, 2020, 8:26am UTC](https://devforum.zoom.us/t/main-thread-checker-ui-api-called-on-a-background-thread/39345/1 "2020-12-29T08:26:12Z")

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**Description**

1. iOS start share . Console log " **Main Thread Checker: UI API called on a background thread: -[UIView drawViewHierarchyInRect:afterScreenUpdates:]**

**PID: 1621, TID: 261034, Thread name: (none), Queue name: us.zoom.timerqueue, QoS: 0**"

**Which version?**  
v5.2.42037.1112Latest

**To Reproduce(If applicable)**  
Steps to reproduce the behavior:

1. Open iOS demo
2. Start Share

**Screenshots**

 ![844735F3-E23C-4258-9CF5-4E8BACEB4EE1](https://us1.discourse-cdn.com/flex016/uploads/zoomdeveloper/original/3X/a/5/a50a5766f6f1357be1a2b036bbb984ff09cf0d87.jpeg)

**Smartphone (please complete the following information):**

- Device: iPhone 11
- OS: iOS 14

---

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**Author:** ![Michael\_Condon](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/michael_condon/32/13543_2.png) [@Michael\_Condon](https://devforum.zoom.us/u/Michael_Condon)\
**Post date:** [December 29, 2020, 6:19pm UTC](https://devforum.zoom.us/t/main-thread-checker-ui-api-called-on-a-background-thread/39345/2 "2020-12-29T18:19:59Z")

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Hey @maqianli9011,

Thank you for using the dev forum!

We are seeing the same on our end and are investigating. Thank you for bringing this to our attention.  
We will keep you updated on this.

Thanks!  
Michael