performSelector:withObject:afterDelay method not working properly? - iphone

Question

I have an app with a small uiimageview circle that fades in and out into two different locations. When the user touches the screen I want the circle to fade out immediately, and i want it to stop fading in and out into moving locations. So basically touching the screen kills the circle.
After the circle is killed though I want another circle to spawn and do the same thing (fading in and out into 2 different locations) until the user touches the screen, then i want that circle killed, and another circle to spawn and etc...
here's my simplified code:
- (void)spawnCircle {
self.circle = [[UIImageView alloc]initWithFrame:self.rectCircle];//alocate it and give it its first frame
self.circle.image=[UIImage imageNamed:#"circle.png"];//make its image the circle image
[self.view addSubView:self.circle];
[self performSelector:#selector(fadeCircleOut)withObject:self afterDelay:2];//the circle will fade out after 2 seconds
self.isFadeCircleOutNecessary=YES;
}
- (void)fadeCircleOut {
if (self.isFadeCircleOutNecessary){//because after the circle fades in this method is scheduled to occur after 2 seconds, well, if the user has touched the screen within that time frame we obviously don't want this method to be called because we already are fading it out
[UIView animateWithDuration:.5 delay:0 options:UIViewAnimationOptionCurveLinear animations:^{//the circle will fade out for a duration of .5 seconds
self.circle.alpha=0;
} completion:^(BOOL finished) {
if (finished) {
if (self.circle.frame.origin.x==self.rectCircle.origin.x) {//if its in the first location go to the second
self.circle.frame=self.rectCircle2;
}else{//if its in the second location go to the first
self.circle.frame=self.rectCircle;
}
[self fadeCircleIn];//now were going to immediately fade it in its new location
}
}];
}
}
- (void)fadeCircleIn {
[UIView animateWithDuration:.5 delay:0 options:UIViewAnimationOptionCurveLinear animations:^{//fade it in with a duration of .5 seconds
self.circle.alpha=1;
} completion:^(BOOL finished) {
if (finished) {
[self performSelector:#selector(fadeCircleOut) withObject:self afterDelay:2];//after 2 seconds the object will fade out again
}
}];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
[UIView animateWithDuration:.5 delay:0 options:UIViewAnimationCurveLinear|UIViewAnimationOptionBeginFromCurrentState animations:^(){ self.circle.alpha=0;} completion:^(BOOL completion){//begin from current state makes it stop any animations it is currently in the middle of
[self spawnCircle];//now another circle will pop up
self.isFadeCircleOutNecessary=NO;
}];
}
- (void)viewDidLoad {
[super viewDidLoad];
[self spawnCircle];
}
so the first time the circle spawns this works great but when the next circle spawns (after the user touches the screen and kills the first circle) the fade out method doesn't happen exactly after 2 seconds, it varies when it happens but it usually almost instantly fades out. so the delay part of the performSelector:withObject:afterDelay doesn't seem to work properly

Answer 1

I tried out your code, and got the same kind of results you did. I'm not sure what goes on behind the scenes with performSelector:withObject:afterDelay:, but it seems like once you get one going, it may still perform its function, even though you've created another circle.
I changed the code slightly by getting rid of the afterDelay calls, but putting the 2 second delay in the fade out method instead. See if this does what you want:
-(void)spawnCircle{
self.circle=[[UIImageView alloc]initWithFrame:self.rectCircle];//alocate it and give it its first frame
self.circle.image=[UIImage imageNamed:#"circle.png"];//make its image the circle image
[self.view addSubview:self.circle];
[self fadeCircleOut];
}
- (void)fadeCircleOut {
[UIView animateWithDuration:.5 delay:2 options:UIViewAnimationOptionCurveLinear animations:^{//the circle will fade out for a duration of .5 seconds
self.circle.alpha=0;
} completion:^(BOOL finished) {
if (finished) {
if (self.circle.frame.origin.x==self.rectCircle.origin.x) {//if its in the first location go to the second
self.circle.frame=self.rectCircle2;
}else{//if its in the second location go to the first
self.circle.frame=self.rectCircle;
}
[self fadeCircleIn];//now were going to immediately fade it in its new location
}
}];
}
- (void)fadeCircleIn {
[UIView animateWithDuration:.5 delay:0 options:UIViewAnimationOptionCurveLinear animations:^{//fade it in with a duration of .5 seconds
self.circle.alpha=1;
} completion:^(BOOL finished) {
if (finished) {
[self fadeCircleOut];
}
}];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
[UIView animateWithDuration:.5 delay:0 options:UIViewAnimationCurveLinear|UIViewAnimationOptionBeginFromCurrentState animations:^{
self.circle.alpha=0;
}
completion:^(BOOL completion){//begin from current state makes it stop any animations it is currently in the middle of
[self.circle removeFromSuperview];
self.circle = nil;
[self spawnCircle];
}];
}