Re: Updating a Static Text and Slider From High Priority Thread While Resizing a Window
Re: Updating a Static Text and Slider From High Priority Thread While Resizing a Window
- Subject: Re: Updating a Static Text and Slider From High Priority Thread While Resizing a Window
- From: Andrew Merenbach <email@hidden>
- Date: Sat, 18 Oct 2008 19:36:01 -0700
On Oct 18, 2008, at 7:27 PM, Andrew Merenbach wrote:
On Oct 18, 2008, at 4:23 AM, Peter Zegelin wrote:
Hi,
Still fairly new to Cocoa here.
I have a high priority thread that that for the moment just calls
back as often as possible to a method that updates a static text
object with the current time. A slider is also updated to a new
value. Its a bit like a stop watch with a position indicator. This
all works well until I resize a window or invoke a menu when the
whole thing just grinds to a halt. If I call std::cout with the
value the debugger shows a continuous stream of data so I know the
thread is still being called as often as possible but the text and
slider aren't updating. Is there any way to get these items to
update under these circumstances? I tried calling [label
setNeedsDisplay] but that just caused a crash.
thanks!
Peter Zegelin
Hi, Peter,
Is it possible that your GUI objects are being updated from the
secondary thread? You'll need to use -performSelectorOnMainThread:
to channel updates from the high-priority thread to the main thread,
since only the main thread is allowed to touch the graphical AppKit
classes (which are generally not threadsafe, with the possible
exception of NSProgressIndicators). Hopefully this solves your issue!
Cheers,
Andrew
Erm, sorry to respond to myself, but I was lazy -- just for clarity,
the full methods available are (from the docs):
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg
waitUntilDone:(BOOL)wait;
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg
waitUntilDone:(BOOL)wait modes:(NSArray *)array;
-- Andrew
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