Strange behavior when updating tree using asynchronous data

[lvyandev]

In some situations, we need to fetch tree children from server before expand.

late final _dynamicController = TreeViewController(
    onAboutToExpand: (TreeNode nodeAboutToExpand) async {
      if (treeController != _dynamicController) return;

      // add this line
      await Future.delayed(const Duration(milliseconds: 300));

      final children = _dynamicChildrenMap[nodeAboutToExpand.id];

      if (children != null) {
        nodeAboutToExpand.addChildren(
          children.map((child) => TreeNode(id: child, label: child)),
        );
      }
    },
    rootNode: TreeNode(id: 'Root')
      //? Initial Dynamic Nodes
      ..addChild(TreeNode(id: 'A', label: 'A'))
      ..addChild(TreeNode(id: 'B', label: 'B'))
      ..addChild(TreeNode(id: 'C', label: 'C')),
  );

Then it behave like this, I need to retap the expander to let the tree update.

SM-G9550_20210603173513.mp4

Am I using it wrong way? How should I update the treeView after load data async.

[baumths]

Hey!

I didn't plan onAboutToExpand to be a future...
So expandNode doesn't await on it.

onAboutToExpand should be syncronous for now.

I'm currently working on a refreshNode feature that's almost done, I just have to run some more tests on it.

Edit: the async part of the package is probably the next feature I'll be working on when I have some spare time.

[lvyandev]

So refreshNode should be a function that can update a specific node on the tree?

[baumths]

Yes, and the entire subtree of that node with an option to keep the expanded nodes.

[lvyandev]

With that should be enough for now.
Hope to see it soon

[baumths]

And probably with refreshNode we wouldn't need onAboutToExpand anymore because we could do children fetching from NodeWidget asynchronously showing a progress indicator and when that's done, call refreshNode and be all good.

[lvyandev]

I agree with that. Since onAboutToExpand doesn't support async.