ios UI unresponsive during viewdidappear

Question

I have a table view, and when the user selects a row, i push them to a new ViewController. At first, I initialized all my view objects in the ViewDidLoad method (involving web service calls) but I saw that it made the transition from my tableview to my new viewcontroller very long.

Instead, I moved most of my UI initialization in the ViewDidAppear method, and I like that it sped up my transition from tableview to new viewcontroller.

However, I cannot press any buttons in my NavigationBar at the top of the screen (like the back button) until my ViewDidAppear method completes and the UI is loaded.

What's the solution for this? Is there another way for me to load my UI without it preventing the user from interacting with the buttons in my NavigationBar?

Thanks!!

yes, i tried it. it slows down my transition from tableview to the new ViewController, which I don't like. I still want the smooth transition. — user1467188, Jul 12 '12 at 05:24

Matt Cooper · Answer 1 · 2014-06-03T12:43:04.223

0

You could use grand central dispatch to make your web service calls asynchronously, which will keep the UI on the main thread responsive.

//create new queue
dispatch_queue_t backgroundQueue = dispatch_queue_create("com.siteName.projectName.bgqueue", NULL);

//run requests in background on new queue
dispatch_async(backgroundQueue, ^{
    //insert web service requests here
});

Here's a more in-depth tutorial:

http://www.raywenderlich.com/4295/multithreading-and-grand-central-dispatch-on-ios-for-beginners-tutorial

edited Jun 03 '14 at 12:43

answered Jun 02 '14 at 15:55

Matt Cooper

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that would keep them on the main thread - I don't think thats what you meant – Daij-Djan Jun 02 '14 at 15:59
@Daij-Djan You're right, thanks -- should be fixed now – Matt Cooper Jun 03 '14 at 12:43

score 0 · Answer 2 · answered Jun 02 '14 at 16:05

you do too much on the main thread. off load your longer operations like IO or longer computations BUT take care to not mess with the UI in the background thread.

Only touch the UI on the main thread. (Note sometimes it might seem safe, but in the long run it always end up producing weird issues)

one easy way is to use GCD:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0),^{
    //insert web service requests / computations / IO here 

    dispatch_async(dispatch_get_main_queue(),^{
        //back to the main thread for UI Work
    });
});

score -2 · Accepted Answer · answered Jul 12 '12 at 05:28

-2

Try to initialize your UI in the background by using the following method

[self performSelectorInBackground:@selector(initYourUI) withObject:yourObj];

You can call this in the ViewDidLoad

answered Jul 12 '12 at 05:28

lu yuan

7,207
9
44
78

1

Working with the UI in background might lead to crashes. So this is not a good ideea. – Daniel Jun 02 '14 at 15:29

ios UI unresponsive during viewdidappear

3 Answers3