CODEWITHSUNDEEP
objective-c
Divine Propotion
Divine Propotion

Reputation: 172

Subview constraints for dragging

The color palette is a view added to main storyboard. I have used corner radius to make a circle. The small circle inside the palette is a subview created inside the palette view. The small circle is draggable. The problem is I can drag the small circle outside the main circle (palette).

How do I stop the small circle from being dragged once it reaches the border of the main circle (palette).

enter image description here

Upvotes: 0

Views: 69

Answers (1)

Flexicoder
Flexicoder

Reputation: 8501

Calculate the distance between the centre point of the palette and the centre point of the picker circle (How to find the distance between two CG points?)

Add on the radius of the picker circle and if that exceeds the radius of the larger circle then you want to stop the dragging.

UPDATE:

enter image description here

So if the Distance + R2 is >= Radius 1 you've reached the edge of the circle and need to stop them dragging

UPDATE2

Based on the sample project you uploaded here is the correct code...

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

    for (UITouch *touch in touches){


        CGPoint newPoint = [touch locationInView:self];
        newPoint.x -= startPoint.x;
        newPoint.y -= startPoint.y;
        CGRect frm = [picker frame];
        frm.origin = newPoint;

        CGFloat xDist = abs((newPoint.x + 15) - (self.center.x - self.frame.origin.x));
        CGFloat yDist = abs((newPoint.y + 15) - (self.center.y - self.frame.origin.y));

        CGFloat distance = sqrt((xDist * xDist) + (yDist * yDist));

        if ((distance + 15) >= (self.frame.size.width /2)) {
            // EDGE REACHED SO DON'T UPDATE
        } else {
            [picker setFrame:frm];
        }

    }
}

You only want to update the frame if its still in bounds and your distance calculations weren't taking into account the offset of the containing view

HTH

Upvotes: 1

Related Questions