选择数据库池示例的条目，并展开所有的树节点。

Select the entry for the database pool example and expand all the tree nodes.

youdao

对于较大的树型数据集，您可能只想加载可见树节点的必要数据，当用户展开一个节点后再记载该节点的子节点。

For large tree data sets you probably want to only load the necessary data for the visible nodes of the tree. When a user expands a node, it starts to load the children of that node.

youdao

如果树节点是可展开的，则将会获得“expanded”状态。

If the tree node is expandable, it will get the state of expanded.

youdao