触摸屏时的“方法”

Question

I'm making a game using Xcode for iOS. This is a segment of code I have that makes the sprite jump up when the screen is tapped:

//tap/touch to jump (& play sound)
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *) event{
       [self playSound];
       jumpUp = 16;
}

How can I implement it so that the sprite just keeps going up whist you are touching the screen instead of just a single tap?

//Pseudo code:
while touchingScreen {
    jumpUp +=1;
}

Answer 1

You need to start some kind of loop in touchesBegan that runs while the touch is lasting. Then in touchesEnded (and cancelled!) make that loop stop. You can use a repeating NSTimer or something like the following. You may need to do some adjustments to make it smooth enough for a game.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesBegan:touches withEvent:event];

    // touching is a BOOL that keeps track of the touch event
    // YES means that a touch is happening at the moment
    touching = YES;
    dispatch_async(dispatch_get_main_queue(), ^{
        [self performSelector:@selector(up) withObject:nil afterDelay:.0];
    });
}

- (void)up {
    // move your sprite further up
    NSLog(@"up");
    if (touching) {
        // if the user is still touching repeat moving the sprite up
        [self performSelector:@selector(up) withObject:nil afterDelay:0.1];
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesEnded:touches withEvent:event];
    // The finger was lifted, stop the up movement
    touching = NO;
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesCancelled:touches withEvent:event];
    touching = NO;
}