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Updating UI Manually

Posted on 2010-08-24
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Last Modified: 2013-11-25
Hi,

Is there a way to update UI manually?
For example, I have a function which updates UI and execute some logic.
After the UI update, it will execute some logic that will take a long time and update of UI has to be wait until the execution of logic is finished.
Is there a way to update UI manually befor even the logic is even executed?

It seems that thread can be used in here.
But Is there a way to solve this by not using thread?
Also, using if thread can be used, what is the best practice?

Thanks!
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Question by:privateson
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pgnatyuk earned 2000 total points
ID: 33514471
In this thread:
http://www.experts-exchange.com/Apple/Programming/Objective-C/Q_26411565.html?sfQueryTermInfo=1+10+30+setneedsdisplai

I've told to use
[theView setNeedsDisplay:YES];

in case you need to update the view. You can do it from the main thread.
Do you understand this way? Maybe, I do not understand your questions?

About the threads. Yes, any long operation in any language, for any device, should be launched in a separate thread. In iOS you can use POSIX threads and NSThread.
iOS Reference Library. Thread Management
http://developer.apple.com/iphone/library/documentation/cocoa/conceptual/Multithreading/CreatingThreads/CreatingThreads.html

I'd say to use NSThread. Here are two simple tutorials:
http://www.xprogress.com/post-36-threading-tutorial-using-nsthread-in-iphone-sdk-objective-c/
http://www.eigo.co.uk/Programming-threaded-processes-in-iPhone.aspx

The idea is simple. You create new thread:
[NSThread detachNewThreadSelector:@selector(threadMethod) toTarget:self withObject:nil];
The thread method should be like that:
- (void)threadMethod {
      NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
      //Here is the code.
      [pool release];
}

If you need to do something in the main thread from this new thread:
[self performSelectorOnMainThread:@selector(UpdateUIMethod) withObject:nil waitUntilDone:false];
In that method (it will be called in the main thread), you can update the UI.

You can try:
[theView performSelectorOnMainThread:@selector(setNeedsDisplay:YES) withObject:myText waitUntilDone:NO];

(I just wrote it here without testing, but it gives an idea)




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by:privateson
ID: 33532600
thanks!
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LVL 33

Expert Comment

by:pgnatyuk
ID: 33532638
You are welcome
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