Java™ Application Development on Linux - Dator

358Chapter 16Getting in the Swing of Things: Designing a GUI for BudgetPro203 if (lsm.isSelectionEmpty()) {204 view.setEnabled(false);205 } else {206 view.setEnabled(true);207 }However, we start with the View Subaccount button disabled until theuser has created and selected some subaccounts worth viewing.16.7.2.6 The createStatus() RevisitedThere is one other button on the BudgetPro application, one that is not locatedin this bottom panel of buttons. It’s the one on the status line. It, too, starts updisabled or grayed out—but it has an image in it. Any JButton can containeither text or an image, or both, but we’ve chosen to do just one or the otherin our application. We declare it like any other button:private JButton upton;but for its initialization we use a variation of the JButton constructor, one thattakes an ImageIcon object as its parameter:upton = new JButton(new ImageIcon("net/multitool/gui/back.gif"));Why do we do that all in one line? When you read it, you can certainlythink of it as two steps:ImageIcon backup = new ImageIcon("net/multitool/gui/back.gif");upton = new JButton(backup);but we have no other need for the image, so we don’t need to keep a referencefor it in a variable. Some programmers prefer to write it out in two simple steps,as it is easier to read and perhaps to maintain. We’ve chosen to put it all in theJButton’s constructor to show that we’re making no other use of the image.Which style do you prefer?And what about a button that needs to contain both text and an image?There is a constructor that takes both a String and an ImageIcon. Thenyou can set certain attributes of the JButton to position the textrelative to the image. Look in the Javadoc of JButton for the methodssetVerticalTextPosition() and setHorizontalTextPosition().