Andrew Andrew - 3 months ago 28
Objective-C Question

Adding drag and drop component to iOS app

I apologise if this seems very vague but I'm not sure how else to word it.

I am trying to build an ipad app that will let users populate a workspace with tools they need. I need an example of letting a user drag and drop components into the app interface. So for example if i had an app that the user can make a form and I want the user to be able to drag text boxes, lists, radio buttons etc to make the form, how would i go about doing that? The items that i am using will be in a popup menu so that the user drags up and then will see all the items that i need inside that popup. Im just not sure how to let them drag from the popup to the canvas and also be able to reuse the same item (so have 3 or 4 text boxes in the example). Is this possible? Can anyone direct me to a tutorial on this? I have searched but cant find anything.

If this is laid out wrong or is a stupid quest please let me know how to do it, this is my first time posting on here.

Thank you

Answer

There are already many answers explaining this question. Basically you can make custom UIView, which after touching will be following the touch movement. Something like this:

-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    _originalPosition = self.view.center;
    _touchOffset = CGPointMake(self.view.center.x-position.x,self.view.center.y-position.y);
}

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

    [UIView animateWithDuration:.001
                          delay:0.0
                        options:UIViewAnimationOptionCurveEaseInOut
                     animations:^ {

                         self.view.center = CGPointMake(position.x+_touchOffset.x, position.y+_touchOffset.y);
                     }
                     completion:^(BOOL finished) {}];
}

-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    CGPoint positionInView = [touch locationInView:self.view];
    CGPoint newPosition;
    if (CGRectContainsPoint(_desiredView.frame, positionInView)) {
        newPosition = positionInView;
        // _desiredView is view where the user can drag the view
    } else {
        newPosition = _originalPosition;
        // its outside the desired view so lets move the view back to start position
    }

    [UIView animateWithDuration:0.4
                          delay:0.0
                        options:UIViewAnimationOptionCurveEaseInOut
                     animations:^ {
                         self.view.center = newPosition
                         // to 
                     }
                     completion:^(BOOL finished) {}];

}

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