iOS 10. Dragging cell disappears

[mrikh]

Whenever i try to drag a cell by pressing on the top edge of the cell. The cell vanishes and isn't visible in the debug view heirarchy either. Here is what happens:

The delegate method for willBeginDragging gets called but didEndDraggingAt isn't called and in this particular case ONLY, the following gets printed into the logs:

"Snapshotting a view that has not been rendered results in an empty snapshot. Ensure your view has been rendered at least once before snapshotting or snapshot after screen updates."

Here is a screenshot:

[KyoheiG3]

Hi @mrikh
I tried to fix the issue on this branch.
Could you try it?

[mrikh]

Hi @KyoheiG3,
I already tried setting after screen updates to true but that doesn't seem to solve the problem :)

[KyoheiG3]

I do not know what is happening. Can you tell me the code that does not work?

[mrikh]

Basically what happens is, the draggingCell is returned nil from inside this method:

func copiedCell(at indexPath: IndexPath) -> UIView? {
        return dataSource?.dragger?(self, cellForRowAt: indexPath) ?? targetTableView?.cellForRow(at: indexPath)?.snapshotView(afterScreenUpdates: false)
    }

I tried implementing the datasource and return the cell but that still doesn't solve the problem.

I cannot provide you a sample directly from the code i am using due to well it being an official organisation project and i'll be able to provide a sample after i get the time.

This happens only when i click the boundary of the cell and try to drag, never when i long press inside the cell itself

[KyoheiG3]

Thanks for your information. I will try it.

[mrikh]

So i managed to do a hackish fix to the problem, i changed the method to this:

func copiedCell(at indexPath: IndexPath) -> UIView? {
        
        if let view = dataSource?.dragger?(self, cellForRowAt: indexPath){
            return view
        }else if let cell = targetTableView?.cellForRow(at: indexPath){
            if let view = cell.snapshotView(afterScreenUpdates: false){
                return view
            }else{
                
                let data = NSKeyedArchiver.archivedData(withRootObject: cell)
                if let tempCell = NSKeyedUnarchiver.unarchiveObject(with: data) as? UITableViewCell{
                    tempCell.frame = cell.bounds
                    return tempCell
                }else{
                    return nil
                }
            }
        }
        
        return nil
    }

And the problem seems to be resolved

[KyoheiG3]

Awesome! I did not get any problem, but I want to take your code into the method.

[KyoheiG3]

Fixed in #17. Please check it out.