Question

I’m doing a simple game which user can throw one of the bottles against the status bar on the top and break it. I’m using touchesMoved to test if a user catch a bottle(UIView) and it will be thrown responding to the user’s finger flicking direction. For the throwing part, it works, but I want it to be broken and changed to a broken bottle png if it throws out of frame, this part gives it headache. Here is part of the codes:

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{

UITouch *aTouch = [touches anyObject];
CGPoint location = [aTouch locationInView:self.view];

throwView = [self.view hitTest:location withEvent:nil];

//if the movement not on self.view, it's on the bottle.
if (bottleView != self.view) {
CGPoint loc = [aTouch locationInView:self.bottleView];
CGPoint prevloc = [aTouch previousLocationInView:self.bottleView];

//getting the finger moment
myFrame = self.bottleView.frame;
deltaX = loc.x - prevloc.x;
deltaY = loc.y - prevloc.y;

myLocation = bottleView.center;


//Here I try to multiply the finger movement to throw the bottles
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:.5];
[UIView setAnimationCurve:UIViewAnimationCurveEaseOut];

myFrame.origin.x += deltaX*7.0;
myFrame.origin.y += deltaY*7.0; 
[self.bottleView setFrame:myFrame];
[bottleView setNeedsDisplay];
[UIView commitAnimations];


//if it hits the top of the frame..
    if (myFrame.origin.y <=20){
        [self hitTheTop];
    }
}}


   //this part gives me headache, I repeat the code again otherwise the bottle is broken before hitting the top.

-(void) hitTheTop{
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:.5];
[UIView setAnimationCurve:UIViewAnimationCurveEaseOut];

myFrame.origin.x += deltaX*7.0;
myFrame.origin.y += deltaY*7.0; 
[self.bottleView setFrame:myFrame];
[bottleView setNeedsDisplay];
[UIView commitAnimations];

//I calculate the slope and find where x should be when y is 0, 40 is half width of the bottle
myFrame.origin.x = myLocation.x + (myLocation.y / (-deltaY / deltaX)) - 40;
myFrame.origin.y = 0;

UIImageView *bottleBroken=
[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"broken.png"]];
[bottleBroken setFrame:CGRectMake(-20, -30, 130, 180)];
[self.bottleView setFrame:myFrame];
[bottleView addSubview:bottleBroken];   
}

For now, what i get is first the bottle flies out of frame, for a very short while, it appears back on the edge of the frame and is already broken, it really looks unnatural. Actually I’m thinking to put it a timer to display the throw and it may manage better. But I just want to explore if there is simpler way to do it without the timer, thx for any suggestion!!

Answer 1

Here’s how I do collision detection in my game.

NSMutableArray *collidees = [NSMutableArray arrayWithArray:[[GRSceneController sharedSceneController] sceneObjects]]; 

[collidees removeObject:self];

NSMutableArray *collisions = [[NSMutableArray alloc] init];

position.y += speed.y;

for (GRBlock *obj in collidees) {
    if ([self.collider doesCollideWithCollider:obj.collider])
        [collisions addObject:obj];
}

if ([collisions count]) {
    [(GRSceneObject<GRColliderDelegate> *)self didCollideWith:collisions collisionType:kVerticalCollision];
}

[collisions removeAllObjects];

Then I just repeat the same thing for position.x

the doesCollideWithCollider: method looks like this

-(BOOL)doesCollideWithCollider:(GRColliderObject *)aCollider {

    #if defined DEBUG_COLLIDER && defined LOG
    logRect(hitBox);
    logRect(aCollider.hitBox);
    #endif

    CGRect colliderBox = aCollider.hitBox;

    return CGRectIntersectsRect(hitBox, colliderBox);
}

hitBox is just a box that surrounds the object and acts as a collider, and didCollideWith:collisionType: handles the collision.

The main thing to take away from this is that you should have a variable for the speed and to position.y += speed.y to create some sort of velocity. And check for a vertical collision after updating position.y and a horizontal collision after updating position.x