Question

I’m currently working on a drag and drop functionality and luckily I found a good tutorial. The goal of this project is to drag and drop “items” from one table view to another with the help of the UILongPressGestureRecognizer. As I have learned from this, you have to get a “snapshot” of a cell you chose in able to get the feel of dragging something out of a table. And I think, below is the method that does this.

- (void)dragAndDropTableViewController:(DragAndDropTableVC *)ddtvc draggingGestureWillBegin:(UIGestureRecognizer *)gesture forCell:(UITableViewCell *)cell
{
    // create a snapshot of the cell
    NSLog(@"draggable delegate method is called");
    UIGraphicsBeginImageContext(cell.contentView.bounds.size);
    [cell.contentView.layer renderInContext: UIGraphicsGetCurrentContext()];
    UIImage *cellImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    UIImageView *cellImageView = [[UIImageView alloc] initWithImage:cellImage];
    self.dragAndDropView = [[UIView alloc] initWithFrame:cellImageView.frame];
    [self.dragAndDropView addSubview:cellImageView];
    [self.dragAndDropView setBackgroundColor:[UIColor blueColor]];
    [self.dragAndDropView setCenter:[gesture locationInView:self.view.superview]];

    [self.view.superview addSubview:self.dragAndDropView];
}

Basically, upon getting the cell’s “snapshot”, you have to add it as a subview of a UIView. The thing that bugs me out is this part.

[self.dragAndDropView setCenter:[gesture locationInView:self.view.superview]];

This may sound easy but what I would want to do is when the long press is done, the draggable cell should appear a bit higher than the original location of the selected cell.

Enlighten me please 🙂 Thanks!

Answer 1

Actually you have to convert center point with respect to your superview then you should use one of these methods convertPoint: fromView: and convertPoint: toView: and for more information see this link.

I think it will be helpful to you.