Java™ Application Development on Linux - Dator

370Chapter 16Getting in the Swing of Things: Designing a GUI for BudgetProDon’t think of it as adding scrollbars to the table. Rather, we’re puttingthe table into a container that has scrollbars, and this container is smart enoughto retrieve and display the table’s header separately from the table (thus, thetable’s data scrolls but the header stays put).Here, in one step, we create the JScrollPane object and initialize it withthe JTable that we want to be scrolled over.212 retval = new JScrollPane(list);Think of the JScrollPane as a window with scrollbars through whichwe can view the JTable. It has the convenient side effect of taking care of thetable’s heading for us. Without the scroll pane (e.g., if we just put the JTablein a JPanel) we’d get only the data and no heading, unless we also did a lot ofextra work using other objects and method calls.It is possible to set the JScrollPane to show horizontal as well as verticalscrollbars. Those scrollbars can be made to be always or never visible, or visibleonly as needed. Setting a scrollbar to “never visible” effectively turns off anyscrolling in that direction. Use the setHorizontalScrollBarPolicy() andsetVerticalScrollBarPolicy() methods to set the value to one of:JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDEDJScrollPane.HORIZONTAL_SCROLLBAR_NEVERJScrollPane.HORIZONTAL_SCROLLBAR_ALWAYSScroll panes can scroll over any GUI element—that is, any Componentobject, not just tables. For more information on scroll panes, be sure to referto the Javadoc pages.16.7.2.13 DialogsWe have covered most of the code in the main GUI functionality—the way itinitially creates its parts and lays them out for display. We have examined theJTable in some considerable detail and looked at a few actions associated withbuttons. Now we need to get to the user interaction that allows us to create anew account.Lines 244–268 of BudgetPro are the action that gets attached to thebutton for creating a new subaccount.