Question

I have this code to drag an imageView:

in touchbegan:

CGPoint point = [touch locationInView:self];
[imageView setCenter:point];

in touchmoved:

CGPoint point = [touch locationInView:self];
[imageView setCenter:point];

this code allow to have imageview ever under my finger and move it form its center.
But I want something that allow me drag an imageview not only from center of imageview but also from another point of imageview…and not drag it if I touch out of this imageView… can you help me?

Answer 1

Instead of just setting the center point to the touch point you need to work out how the touch has moved.

Store the touch point in a variable.

In touchesBegan…

storedPoint = [touchLocationInView:self];

Then in touchesMoved…

CGPoint currentPoint = [touch locationInView:self];

CGPoint vector = CGPointMake(currentPoint.x - storedPoint.x, currentPoint.y storedPoint.y);

[imageView setCenter:CGPointMake(imageView.center.x + vector.x, imageView.center.y + vecotr.y)];

storedPoint = currentPoint;

Something like this anyway.

To ignore the touch you could say in touchesBegan…

if (!CGRectContainsPoint(imageView.frame, [touch locationInView:self])
{
    //ignore touch
    trackTouches = NO;
}

trackTouches = YES;

(trackTouches is a class var)

Then in touchesMoved only do stuff if trackTouches == YES.