Technical Q&A QA1091

Rendering Multi-line text in JTree nodes

Q: I've written a custom TreeCellRenderer for a JTree. When using the Aqua look and feel, cells do not render properly if their label exceeds a single line of text. Only the first line is shown. What gives?

A: You need to call setRowHeight(0) on the JTree you are using. A value of 0 or less for the JTree.rowHeight property forces the JTree to consult your custom TreeCellRenderer for the appropriate size of each row. Without this explicit call, a default value greater than zero is by used by the JTree without consulting the renderer.

The call to setRowHeight() should be made at any point where the JTree could have its updateUI() method called, which includes:

• Immediately after instantiation

• After changing the look and feel

The real problem behind this issue - which also occurs on Windows machines when using the Windows look and feel - is more complicated and involves a known bug in the Javasoft database, which is exploited by the custom borders of TextFields used in many custom look and feel's. Metal's lack of a TextField border makes the problem dormant when choosing that particular look and feel.

[Nov 02 2001]