How can I programmatically pause an NSTimer?

Question

I\'m using an NSTimer to do some rendering in an OpenGL based iPhone app. I have a modal dialog box that pops up and requests user input. While the user is providing input

Answer 1

The code below is for use with a scrollview, that brings content on at regular intervals, and loops back to the front on completion, but the same logic can be used for any pause/restart button.

The timer fires on load (initiateFeatureTimer), and pauses for user-interaction (will begin dragging method), allowing the user to look at content for as long as she likes. When user lifts her finger (will end dragging) the featurePaused boolean is reset, but also, you have the option of adding in a little more of a delay.

This way, the scroller doesn't move off instantly on finger lift, it's more reactive to the user.

//set vars, fire first method on load.
featureDelay = 8; //int
featureInt = featureDelay-1; //int
featurePaused = false; //boolean

-(void)initiateFeatureTimer {
    featureTimer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(moveFeatureScroller) userInfo:nil repeats:true];
    [featureTimer fire];
}
 -(void)moveFeatureScroller {

    if (!featurePaused){ //check boolean
        featureInt++;

         if (featureInt == featureDelay){
             featureInt = 0; //reset the feature int

            /*//scroll logic
            int nextPage = (featurePage + 1) * w;
            if (featurePage == features.count-1){ nextPage = 0; }
            [featureScroller setContentOffset:CGPointMake(nextPage, 0)]; */          
         }
      }
}

-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    featurePaused = true; //pause the timer
}
-(void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
    featurePaused = false; //restart the timer
    featureInt = -3; //if you want to add an additional delay
}