Java Swing, 2nd Edition

Tree Selections

After the tree is built and looks the way you want it to, you need to start working with selections so it does something useful. The JTree class introduced many of the selection manipulation methods already, but let’s take a closer look at the model for selecting paths in a tree and the DefaultSelectionModel provided in the javax.swing.tree package. If you’re comfortable with selection models, you probably won’t find anything surprising here and may want to skip to Section 17.7.

Selections are based on rows or paths. It’s important to realize the distinction between a “row” and a “path” for trees. A path contains the list of nodes from the root of the tree to another node. Paths exist regardless of whether or not you plan to display the tree.

Rows, however, are completely dependent on the graphical display of a tree. The easiest way to think about a row is to think of the tree as a JList object. Each item in the list is a row on the tree. That row corresponds to some particular path. As you expand and collapse folders, the number of rows associated with the tree changes. It’s the RowMapper object’s job to relate a row number to the correct path.

Depending on your application, you may find rows or paths more efficient. If your program deals mostly with the user object data, paths are a good choice. If you’re working with the graphical interface (automatically expanding folders and the like), rows may be more useful.

The RowMapper Interface

Tree selections make extensive ...