How to find out which function is cased hang on main thread

Question

Is there any way to easy to debug out what cause my hang on main thread? when I debug without enable the breakpoint, there's a moment that the tableView will hang for a while, but how to found what cause that?

EDIT I have upload the thread status when the app is hang, and I click the Pause button. show bellow:

EDIT I have upload the Profile of Instruments, which selected duration is which the screen is hang.

Edit I have create a root problem question about this.Image download and save to file, Image read from file will cause lock?

Answer 1

You can use Instruments for that. Choose Product / Profile. Choose Time Profiler. Start profiling by pressing Record (the red circle). When the table view hangs, you'll most likely see a change in the graph. Select the region on the graph corresponding to the time when the table view hanged, and see what's being done on the main thread. You can find more info on Instruments on the web.

Another option is to start normal debugging, and then press "Pause" right when the tableView hangs. And then look at the stack trace for the main thread.