iPhone Game Development

Event Handling

Because our GameState class inherits from UIView, we can override its event handling functions for our purposes. To show this behavior, we will add to our example by creating a second GameState named gsTest. We will modify gsMain to change to the new state when the user double-taps the screen, and switch back again when she double-taps from gsTest:

//gsTest.h
@interface gsTest : GameState {
//no members necessary
}
@end
//gsTest.m
@class gsMain //forward declaration
@implementation gsTest

-(gsTest*) initWithFrame:(CGRect)frame andManager:(GameStateManager*)pManager
{
    if (self = [super initWithFrame:frame andManager:pManager]) {
        NSLog(@"gsTest init");
    }
    return self;
}

-(void) Render
{
    CGContextRef g = UIGraphicsGetCurrentContext();
    //fill background with blue
    CGContextSetFillColorWithColor(g, [UIColor blueColor].CGColor);
    CGContextFillRect(g,
          CGRectMake(0, 0, self.frame.size.width, self.frame.size.height));

    //draw text in black
    CGContextSetFillColorWithColor(g, [UIColor blackColor].CGColor);

    [@"it works!" drawAtPoint:CGPointMake(10.0,20.0)
                  withFont:[UIFont systemFontOfSize:[UIFont systemFontSize]]];
}

-(void)touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event
{
    UITouch* touch = [touches anyObject];
    NSUInteger numTaps = [touch tapCount];
    if( numTaps > 1 ) {
        [m_pManager doStateChange:[gsMain class]];
    }
}
@end

For the return to gsTest, we need to add the same touchesEnded function to our gsMain class, but making doStateChange call [gsTest class]. When compiled and run, ...