Reordering Nested Lists
In my last project, I created a tool that allowed my clients to rearrange nested lists of articles and article categories using the jQuery UI Sortables component and the techniques I demonstrated in an earlier blog post.
My clients were very excited about the tool when they saw it in the prototype, but they ran into some difficulty when they tried to use it themselves during the final testing. They found it hard to place an item at either end of a list block because there were no visual cues outlining the borders of the list.
It was also nearly impossible for them to move an item around in the top-most list: if they tried to place it in between sibling items or at the end of the list, the item would almost always get dropped at the end of whatever sublist came at the end of the sibling item above.
Finally, the scrollable <div> element containing the nested lists would not scroll to match the drag movement of the cursor, so if they needed to move an item from one end of the nested lists to the other, the item would have to moved in steps.
I solved all of these problems by abandoning the drag-and-drop technique and replacing it with a version of my "click-to-click move" technique. So now when they need to move an item, they click on an icon associated with each item (hidden until needed), and target <div>s are created above and below each item:
They then just click on the target for the place they want the item moved to, and the item is "moved" and the targets are removed (technically, the item is cloned, the clone is put in the new position, and the original item is deleted).
They like the "click-to-click move" version a lot better, so perhaps that's a better means of reordering items when using nested lists. But I recently discovered jTree, a brand-new jQuery plugin someone wrote specifically for sorting nested lists using drag-and-drop. I tried out the demo for it, and it has visual cues to help you position items in the right list, but it does flicker a bit at times. Still, I might play with it the next time I have to deal with nested lists again.
Reordering Table Rows
Lists are nice, but they don't cut it when each item is really a collection of separate items: that's when you need a table. In my current project, I needed a way to reorder the rows in my table as a means of letting the user reorder the data records. The jQuery UI Sortables component, however, does not work on table rows.
I tried to create a pseudo-table by using <div>s within each <li> item to evenly space the data fields in each row. I got it working and looking slightly less than ugly in FireFox, but it didn't fare so well in IE.
I then went browsing through the jQuery UI discussion board on Google Groups and found a post that mentioned a plugin for sorting/rearranging table rows.
It's called TableDnD, and it's a slightly different approach to the challenge. When you click on a row and drag it, there is no drag outline and no gradual movement: if you move up far enough, the content of the row you're dragging and the row above it quickly switch places, and vice-versa if you move downward. It highlights the moving row as you move it so you can keep track of what's happening. The movement is very smooth and you can go as fast as you like.
The only drawbacks I'm aware of so far is that the dragging action will not trigger the scroll bar if you're trying to drag the row beyond the visual limit of the window or scrollable container (much like my original nested list tool), and someone pointed out to me that if you fill all of the cells in a row with other DOM elements such that you cannot click on any of the cells themselves, you won't be able to grab the row and move it. That's not a problem your table cells just contain text, but it's something to keep in mind if you plan on formatting the text with <span> tags or providing input boxes for the user to edtit the cell data.