setAlpha not triggering after touchUpInside event occurs - ios

Question

I'm developing a camera app that has a video function. I want the button that the user presses to begin recording, which it does, and stop recording. This works properly. But, I want to raise the alpha of the recordButton to 1.0 when the button is pressed. This works properly, but when it is pressed again to stop recording the alpha remains at 1.0. The if...else statement that stops recording should trigger [self.recordButton setAlpha:0.50], but for some reason nothing happens, aside from recording stopping properly. Any clarification would be greatly appreciated.
- (IBAction)toggleMovieRecording:(id)sender
{
[[self recordButton] setEnabled:NO];
dispatch_async([self sessionQueue], ^{
if (![[self movieFileOutput] isRecording])
{
[self setLockInterfaceRotation:YES];
[self.recordButton setAlpha:1.0];
if ([[UIDevice currentDevice] isMultitaskingSupported])
{
// Setup background task. This is needed because the captureOutput:didFinishRecordingToOutputFileAtURL: callback is not received until the app returns to the foreground unless you request background execution time. This also ensures that there will be time to write the file to the assets library when the app is backgrounded. To conclude this background execution, -endBackgroundTask is called in -recorder:recordingDidFinishToOutputFileURL:error: after the recorded file has been saved.
[self setBackgroundRecordingID:[[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:nil]];
}
// Update the orientation on the movie file output video connection before starting recording.
[[[self movieFileOutput] connectionWithMediaType:AVMediaTypeVideo] setVideoOrientation:[[(AVCaptureVideoPreviewLayer *)[[self previewView] layer] connection] videoOrientation]];
// Turn OFF flash for video recording
[AAPLCameraViewController setFlashMode:AVCaptureFlashModeOff forDevice:[self videoDevice]];
// Start recording to a temporary file.
NSString *outputFilePath = [NSTemporaryDirectory() stringByAppendingPathComponent:[#"movie" stringByAppendingPathExtension:#"mov"]];
[[self movieFileOutput] startRecordingToOutputFileURL:[NSURL fileURLWithPath:outputFilePath] recordingDelegate:self];
}
else
{
[[self movieFileOutput] stopRecording];
[self.recordButton setAlpha:0.50];
}
});
}

Answer 1

You have to make sure that anything related to UI have to be done on the main queue. Check this answer
iPhone - Grand Central Dispatch main thread
To make sure add this block around setting alpha.
dispatch_async(dispatch_get_main_queue(), ^{
[self.recordButton setAlpha:0.50];
});
Let me know if that worked.