Request to refresh the UI after a network request

Request to refresh the UI after a network request

A problem occurred while creating the project. The synchronization request cannot refresh the interface.

Original assumption: In the synchronous request method, add a chrysanthemum before synchronizing the request. After the synchronous request obtains the result, remove the chrysanthemum.

Reality: Chrysanthemum is not displayed at all.

It has been a whole day of struggle since then. later I asked a friend. the synchronous request freeze interface. Let me try asynchronous requests. later, after an asynchronous request to the network, refresh the interface on the main thread.

I still don't understand Apple's frozen view. Why? A friend knows the answer and helps you solve the problem. Thank you.