CODEWITHSUNDEEP
iosobjective-c
iDev_91
iDev_91

Reputation: 317

CGRectIntersectsRect of subviews

i'm using two UIImageViews, i have added to each UIImageView a subview (UIView). I use the CGRectIntersectsRect to detect collision, but doesn't work. So I have:

This is the first UIImageView

hand = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 13.5, 176)];
[hand setImage:[UIImage imageNamed:@"hand0.png"]];
[hand setContentMode:UIViewContentModeScaleAspectFit];

/// Add SUBVIEW which needs to be detected for collision
hView = [[UIView alloc]initWithFrame:CGRectMake(3, 12, 7, 10)];
[hView setBackgroundColor:[UIColor redColor]];
[hand addSubview:hView];
[hand bringSubviewToFront:hView];

hand.center = self.view.center;
[self.view addSubview:hand];

And here is the second UIImageView

ball = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 33.5, 176)];
[ball setImage:[UIImage imageNamed:@"ball0.png"]];
[ball setContentMode:UIViewContentModeScaleAspectFit];

/// Add SUBVIEW to detect for collision
bView = [[UIView alloc]initWithFrame:CGRectMake(3, 155, 28, 10)];
[bView setBackgroundColor:[UIColor greenColor]];
[ball addSubview:bView];
[ball bringSubviewToFront:bView];

ball.center = self.view.center;
[self.view addSubview:ball];

And here is my code for collision detection, which runs every second.

- (void)checkCollision
{
    if (CGRectIntersectsRect(bView.frame, hView.frame)) {
        //do something here
    }
}

Any ideas why it doesn't detect the collision? The only thing i have in mind is because the hView and bView are subviews of the UIImageView.

Upvotes: 0

Views: 126

Answers (1)

rmaddy
rmaddy

Reputation: 318934

The problem is that the frames of bView and hView are relative to their respective superviews. You need to convert their frames to a common ancestor so they can be compared properly. The view controller's view would be a good candidate.

- (void)checkCollision {
    CGRect hFrame = [hView convertRect:hView.bounds toView:self.view];
    CGRect bFrame = [bView convertRect:bView.bounds toView:self.view];

    if (CGRectIntersectsRect(bFrame, hFrame)) {
        //do something here
    }
}

Upvotes: 1

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