CODEWITHSUNDEEP
iphone
ohho
ohho

Reputation: 51921

How to check whether a CGPoint is inside a UIImageView?

In touchesBegan:

CGPoint touch_point = [[touches anyObject] locationInView:self.view];

There are tens of UIImageView around, stored in a NSMutableArray images. I'd like to know is there a built-in function to check if a CGPoint (touch_point) is inside one of the images, e.g.:

for (UIImageView *image in images) {
   // how to test if touch_point is tapped on a image?
}

Thanks

Follow up:

For unknown reason, pointInside never returns true. Here is the full code.

    - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
    { 
      UITouch *touch = [touches anyObject]; 
        touch_point = [touch locationInView:self.view];
        for (UIImageView *image in piece_images) {
            if ([image pointInside:touch_point withEvent:event]) {
                image.hidden = YES;
            } else {
                image.hidden = NO;
            }
            NSLog(@"image %.0f %.0f touch %.0f %.0f", image.center.x, image.center.y, touch_point.x, touch_point.y);
        }
    }

although I can see the two points are sometimes identical in the NSLog output.

I also tried:

  if ([image pointInside:touch_point withEvent:nil])

the result is the same. never returns a true.

To eliminate the chance of anything goes with with the images. I tried the following:

  if (YES or [image pointInside:touch_point withEvent:event])

all images are hidden after the first click on screen.

EDIT 2:

Really weird. Even I hard coded this:

        point.x = image.center.x;
        point.y = image.center.y;

the code becomes:

    - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
    { 
        UITouch *touch = [touches anyObject]; 
        CGPoint point; // = [touch locationInView:self.view];
        for (UIImageView *image in piece_images) {
            point.x = image.center.x;
            point.y = image.center.y;       
            if ([image pointInside:point withEvent:event]) {
                image.hidden = YES;
                NSLog(@"YES");
            } else {
                image.hidden = NO;
                NSLog(@"NO");
            }
            NSLog(@"image %.0f %.0f touch %.0f %.0f", image.center.x, image.center.y, point.x, point.y);
        }
    }

pointInside always returns false ...

Upvotes: 4

Views: 9420

Answers (3)

Emil
Emil

Reputation: 590

Sounds to me like the problem is you need to convert coordinates from your view's coordinates to the UIImageView's coordinates. You can use UIView's convertPoint method.

Try replacing

if ([image pointInside:touch_point withEvent:event]) {

with

if ([image pointInside: [self.view convertPoint:touch_point toView: image] withEvent:event]) {

(Note that you are allowed to pass nil instead of event.)

I guess this is a bit late for the questioner, but I hope it is of use to someone.

Upvotes: 12

ohho
ohho

Reputation: 51921

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    UITouch *touch = [touches anyObject];
    CGPoint point = [touch locationInView:self.view];

    for (UIImageView *piece in piece_images) {
        CGFloat x_min = piece.center.x - (piece.bounds.size.width / 2);
        CGFloat x_max = x_min + piece.bounds.size.width;
        CGFloat y_min = piece.center.y - (piece.bounds.size.height / 2);
        CGFloat y_max = y_min + piece.bounds.size.height;
        if (point.x > x_min && point.x < x_max && point.y > y_min && point.y < y_max ) {
            piece.hidden = YES;
        } else {
            piece.hidden = NO;
        }
    }

}

too bad, I have do it myself...

it's OS 3.2, XCode 3.2.2, tried both on simulator and iPad

Upvotes: 0

cutsoy
cutsoy

Reputation: 10251

if ([image pointInside:touch_point withEvent:event]) {
    // Point inside
}else {
    // Point isn't inside
}

In this case event is taken from :

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;

Upvotes: 0

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