Java™ Application Development on Linux - Dator

348Chapter 16Getting in the Swing of Things: Designing a GUI for BudgetProhave additional space contributed to text areas. Consider a word processor:When you resize its window you only want the text area to expand, not themenus and icons.Layout managers are meant to address the issues of component placementand sizing. Some are very simple, others are much more complex. All have theiradvantages and disadvantages. We’ll use a few in our example to give you a tasteof how they work.16.6BEYOND ARTHUR MURRAY: ACTIONS, LISTENERS, EVENTSWith any serious GUI comes a lot of advanced Java, especially constructs likeanonymous inner classes. These are useful when we implement actions for ourbuttons and listeners for user selections.Keep in mind that there are three different time frames that we’re considering—compiletime, construction time, and event time. Compile time is obvious,and the compiler will complain if it cannot access what it needs due toscoping problems. Construction time is when the program constructs the GUIobjects for display in a window using the new and add() calls as well as layoutmanagers. Event time is when the user presses a button or edits text in a field,or when other external events change data.16.7GETTING DOWN TO CASES: DESIGNING A GUI FOR BUDGETPROOur goal is a GUI for the BudgetPro application. We’ve already built a command-lineversion, so we want to have the same general functions but with theconvenience and glamour of a GUI. The GUI will need to:• Display the current account (name and dollars)• Display the list of subaccounts that are part of this account• Provide a way to create a new (sub)account• Provide a way to move down into a subaccount• Provide a way to move up to the parent accountFrom this brief list we devise a simple display with a heading that containsthe current account and its dollar status, a table which lists the subaccounts,