Answers: Using Swing Components

Use the information in this lesson and the component how-to sections to help you complete these questions and exercises.

问题

问题1:Find the component that best fits each of the following needs. Write down both the component's common name (such as "frame") and find the component's how-to page online.

问题1a: A component that lets the user pick a color.
答案1a: color chooser

问题1b:A component that displays an icon, but that doesn't react to user clicks.
答案1b: label

问题1c:A component that looks like a button and that, when pressed, brings up a menu of items for the user to choose from.
答案1c: uneditable combo box

问题1d:A container that looks like a frame, but that appears (usually with other, similar containers) within a real frame.
答案1d: internal frame

问题1e:A container that lets the user determine how two components share a limited amount of space.
答案1e: split pane

问题2:Which method do you use to add a menu bar to a top-level container such as a JFrame?
答案2:setJMenuBar

问题3:Which method do you use to specify the default button for a top-level container such as a JFrame or JDialog?
答案3:JRootPane's setDefaultButton method. (You get the top-level container's root pane using the getRootPane method defined by the RootPaneContainer interface, which every top-level container implements.)

问题4:Which method do you use to enable and disable components such as JButtons?What class is it defined in?
答案4:setEnabled, which is defined in the Component class

问题5a:Which Swing components use ListSelectionModel?[Hint: The "Use" link at the top of the specification for each interface and class takes you to a page showing where in the API that interface or class is referenced.]
答案5a: JList and JTable

问题5b:Do those components use any other models to handle other aspects of the components' state?If so, list the other models' types.
答案5b: JList also uses a ListModel, which holds the list's data. JTable uses a TableModel to hold its data and a TableColumnModel to manage the table's columns.

问题6:Which type of model holds a text component's content?
答案6:Document

练习

练习1.Implement a program with a GUI that looks like the one shown below. Put the main method in a class named MyDemo1.

答案1:See MyDemo1.java. Here's the code that adds the bold, italicized text:

JLabel label = new JLabel("My Demo");
frame.getContentPane().add(BorderLayout.CENTER, label);
label.setFont(label.getFont().deriveFont(Font.ITALIC | Font.BOLD));
label.setHorizontalAlignment(JLabel.CENTER)

练习2.Make a copy of MyDemo1.java named MyDemo2.java. Add a menu bar to MyDemo2.
答案2:See MyDemo2.java. The menu bar can be implemented with this code:

JMenu menu = new JMenu("Menu");
JMenuBar mb = new JMenuBar();
mb.add(menu);
frame.setJMenuBar(mb);

练习3.Copy MyDemo1.java to MyDemo3.java. Add a button (JButton) to MyDemo3.java. Make it the default button.
答案3:See MyDemo3.java. Here's the code that adds the button and makes it the default button:

JButton b = new JButton("A button");
frame.getContentPane().add(BorderLayout.PAGE_END, b);
frame.getRootPane().setDefaultButton(b);