Multiple Threads and Touch Handling

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Multiple Threads and Touch Handling

(11 posts) (3 voices)

Started 1 year ago by tmsquasher
Latest reply from tmsquasher

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tmsquasher
Member

Hi guys -- quick question I was hoping someone could clear up for me.

In my app, I'm using an AVExportSession object for some audio work. Tapping anywhere on the screen triggers the export. The export runs - (void)exportAsynchronouslyWithCompletionHandler:(void (^)(void))handler, which uses a completion block for the end of the export process. The export is done on a separate thread (hence the completion block, which I think is unavoidable -- asynchronous seems to be the only option).

My issue is this: after the export is complete and the completion block's code has all been executed, touch handling no longer works. ccTouchesBegan/Moved/Ended/ect. no longer get called.

Any ideas on how to fix this? I don't have much experience with multithreaded programming, so please bear with me here. :)

Thanks!

Tom

Posted 1 year ago #
tmsquasher
Member

Any suggestions? I'm pretty stumped. :(

Posted 1 year ago #
hm50
Member

any code examples?

Posted 1 year ago #
araker
Moderator

Without seeing the relevant code parts it's very difficult to help you. Do you get any errors from the process, the handler is also called when writing fails.

Posted 1 year ago #
tmsquasher
Member
No errors pop up -- the program continues to run, just my touches aren't being picked up (I've put NSLog's in the touch handlers to check, as well).

After some basic initializations of my AVAssetExportSession *exporter object, here's what I call:
```
[exporter exportAsynchronouslyWithCompletionHandler:^{
	/* Completion block here is executed after export is complete
	 * To call any methods from here, I use
	 * [self performSelectorOnMainThread:withObject:waitUntilDone:];
	 */

}];
```
I have verified that this export is successful as I can get the file I have exported, and the program continues to run (I can switch scenes, for example, if done via a method on the main thread). The only issue for me is that ccTouchesBegan and ccTouchesEnded aren't being called.

Is this helpful?
Posted 1 year ago #
araker
Moderator

So you don't execute any code in your completion handler? Can you also post the code of ccTouchesBegan and ended?

Posted 1 year ago #
tmsquasher
Member
I removed the code in the completion handler to simplify things. It made no difference on the outcome: touch handling still didn't work. However, here's a little more of what I'm doing:

I do the export in ccTouchesBegan, and that all works great. I then switch scenes in the completion handler.
```
[exporter exportAsynchronouslyWithCompletionHandler:^{
	 [self performSelectorOnMainThread:@selector(nextScene) withObject:nil waitUntilDone:NO];
}];

// ...

- (void) nextScene {
          [[CCDirector sharedDirector] replaceScene:[OtherScene node]];
}
```
The app switches to the next scene no problem, and everything works. I create a CCLayer and set isTouchEnabled to YES. Still, my touch handling methods aren't printing my NSLog's:
```
- (void) ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
	NSLog(@"Touches Began");

	for(UITouch *touch in touches) {
		CGPoint location = [[CCDirector sharedDirector] convertToGL: [touch locationInView:touch.view]];
                // Haven't even gotten here yet
	}
}

- (void) ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
	NSLog(@"Touches Ended");
}
```
Does that clear things up a bit? The touch handlers don't get called in the original scene/layer either, but the above is what I'm trying to do. Thanks!

EDIT: Ah, one other thing. When I try that second scene without doing the export first, the touches all work properly and I get the NSLogs in the console.
Posted 1 year ago #

The selector is performed on the main thread, I don't really see why this wouldn't work. Instead of performSelector you could try to send a notification. In this case a distributed notification, since it is invoked on the main thread (normal notifications use the thread where they are posted in). More info link, link.

//somewhere in your init code
[[NSDistributedNotificationCenter defaultCenter] addObserver:self
    selector:@selector(nextScene)
    name:@"switchScene"
    object:nil
    suspensionBehavior:NSNotificationSuspensionBehaviorDrop
];

//..
[exporter exportAsynchronouslyWithCompletionHandler:^{
	 [[NSDistributedNotificationCenter defaultCenter] postNotificationName:@"switchScene" object:self];
}];

- (void) nextScene {
    [[NSDistributedNotificationCenter defaultCenter] removeObserver:self];
    [[CCDirector sharedDirector] replaceScene:[OtherScene node]];
}

Posted 1 year ago #

tmsquasher
Member

Thanks for the tips... hadn't thought of this before. I'll give it a go tomorrow and hope it works!

Thanks!

Posted 1 year ago #
tmsquasher
Member

Alright -- still having issues. I'm wondering if the touch handling is tied to the OpenGL context or something... I don't know much about this sort of thing, but I did have issues with my sprites becoming "white boxes" when I didn't use the performSelectorOnMainThread: method.

Perhaps a similar sort of thing is messing up the touch detection? While my AVExportSession is going, I can't change any of my textures (for example, I have a label that I want to display the export's progress, but it won't change. Sometimes it'll turn into a white box).

Any ideas on how to just get me back to the normal OpenGL context that I started the app with?

I really wish there was another way to do the audio work I'm trying to do, haha... I thought I had already gotten the hard part out of the way.

Posted 1 year ago #
tmsquasher
Member

Anyone have any ideas as to why the AVExportSession "exportAsynchronouslyWithCompletionHandler:" is disrupting the Cocos2d touch handling? Is it related to the OpenGL or the multithreaded/asynchronous aspect of the function?

I'm stuck! :(

Posted 1 year ago #

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