The Java Foundation Classes (JFC) are a set of packages encompassing the following APIs: Abstract Window Toolkit (AWT): native GUI components Swing: lightweight GUI components 2D: rendering two-dimensional shapes, text, and images Accessibility: allowing compatibility with, for example, screen readers and screen magnifiers Provides basic UI components: Buttons, lists, menus, textfields, etc Event handling mechanism Clipboard and data transfer Image manipulation Font manipulation Graphics Platform independence is achieved through peers, or native GUI components java.awt java.awt.accessibility java.awt.color java.awt.datatransfer java.awt.dnd java.awt.event java.awt.font java.awt.geom java.awt.im java.awt.image java.awt.peer java.awt.print java.awt.swing Basic component functionality Assistive technologies Colors and color spaces Clipboard and data transfer support Drag and drop Event classes and listeners 2D API font package 2D API geometry package Input methods Fundamental image manipulation classes Peer interfaces for component peers 2D API support for printing Swing components The first AWT (Java 1.0) was rolled out in an incredible 6 weeks using peers Thus an AWT menu on the Solaris platform, for example, actually creates a Motif menu object as its peer UI components that have peers are called heavyweight because they are rendered in their own (opaque) windows and thus are expensive to use, they must be rectangular and cannot have transparent backgrounds, and they are not amenable to being subclassed Java Program Java AWT Native Window System Peers A Java program creates and displays an AWT component, which creates and displays a native component, or peer. AWT 1.1 introduced the notion of lightweight components which: are contained within a heavyweight component's window do not have peers are rendered in their container's window rather than one of their own do not incur performance penalties and can have transparent backgrounds Almost all Swing components are lightweight ones that extend either java.awt.Component or java.awt.Container Object Component Container JComponent List Window Scrollbar Scrollpane Label Canvas Button Swing does not replace the AWT; it is built on top of it All 1.0 AWT components are heavyweight; corresponding Swing components are lightweight Swing component names begin with ``J'': Component (AWT) vs. JComponent (Swing) Button (AWT) vs. JButton (Swing) Always use Swing components; however, since Swing is built on top of AWT, you will need to know some AWT methods JComponent AbstractButton JButton JLabel JMenuItem JToggleButto n JList JScrollBar JCheckBox JFileChooser Note that JComponents are containers JComponents do not extend their AWT counterparts: For example, the JButton class is not a subclass (direct or indirect) of Button However, some Swing components are not JComponents For example, some Swing containers are direct subclasses of their AWT counterparts Container JComponent Panel ScrollPane Window Dialog Applet Frame Container JComponent Panel ScrollPane Window Dialog Frame Applet JFrame JApplet JWindow JDialog JComponent JLayeredPane JPanel JScrollPane JDesktopPane JInternalFrame JTable JTree void void void void void void void setBackground(Color c) setForeground(Color c) setEnabled(boolean b) setVisible(boolean b) setFont(Font f) setSize(Dimension d) setLocation(int x, int y) All but setSize and setLocation are overridden by the JComponent class. import java.awt.*; import javax.swing.*; public class SwingTest { public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); frame.setVisible(true); } } setSize and setLocation require java.awt.*; the rest require javax.swing.* The JFrame constructor argument is used as a title The Dimension constructor takes an integer width and height, respectively The setLocation method takes a pair of integer coordinates (x,y) where (0,0) is the upper left corner of the display The visibility of a JFrame is set to false by default This window was managed by the K Desktop Environment (KDE) Clicking the Close button (X) will cause the display to be hidden, but the program will continue since no listeners are set up yet Can use ctl-C to kill the Java Virtual Machine The java.awt.Color class has the following static fields (data members): Color.black Color.blue Color.cyan Color.darkGray Color.gray Color.green Color.lightGra y Color.magenta Color.orange Color.pink Color.red Color.white Color.yellow import java.awt.*; import javax.swing.*; public class SwingTest { public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); contentPane.setBackground(Color.red); frame.setVisible(true); } } Q: Why not just: frame.setBackground(Color.red); ? A: In order to be lightweight, Swing's top-level window objects must be built on top of a lightweight AWT Container object introduced in version 1.1 This container is called a content pane Swing top-level window classes: JWindow JFrame JApplet JDialog JInternalFrame import java.awt.*; import javax.swing.*; public class SwingTest { public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); JLabel label = new JLabel("HERE IS A LABEL"); contentPane.add(label, BorderLayout.NORTH); JButton button = new JButton("BUTTON"); contentPane.add(button, BorderLayout.SOUTH); frame.setVisible(true); } } Resized Since the frame is a top-level Swing window, components must be added to its content pane When components are added to a container, how they are placed is dependent upon the container's layout manager The default layout manager for a JFrame is a BorderLayout manager (described later) When adding to a container whose layout manager is BorderLayout, the second parameter should be a location defined in the BorderLayout class import java.awt.*; import javax.swing.*; public class SwingTest { public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); JLabel label = new JLabel("HERE IS A LABEL"); contentPane.add(label, BorderLayout.NORTH); JButton button = new JButton("BUTTON"); contentPane.add(button, BorderLayout.SOUTH); String[] options = {"Option 1", "Option 2", "Option 3"}; JList list = new JList(options); contentPane.add(list, BorderLayout.CENTER); frame.setVisible(true); } } Note that "Option 3" has been selected. public class SwingTest { public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(400,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); JLabel label = new JLabel("HERE IS A LABEL"); contentPane.add(label, BorderLayout.NORTH); JButton button = new JButton("BUTTON"); contentPane.add(button, BorderLayout.SOUTH); String[] options = {"Option 1", "Option 2", "Option 3"}; JList list = new JList(options); contentPane.add(list, BorderLayout.CENTER); JCheckBox cbox = new JCheckBox("Check"); contentPane.add(cbox, BorderLayout.WEST); JSlider slider = new JSlider(); contentPane.add(slider, BorderLayout.EAST); frame.setVisible(true); } } A layout manager determines the location and size of components placed into a container Different layout managers use different algorithms for determining size and location: BorderLayout: places at compass locations and center FlowLayout: places components in rows, left to right GridLayout: places in rectangular grid BoxLayout: places in a single row or column public class SwingTest { public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); contentPane.setLayout(new FlowLayout()); JLabel label = new JLabel("HERE IS A LABEL"); JButton button = new JButton("BUTTON"); String[] options = {"Option 1", "Option 2", "Option 3"}; JList list = new JList(options); JCheckBox cbox = new JCheckBox("Check"); JSlider slider = new JSlider(); contentPane.add(label); contentPane.add(button); contentPane.add(list); contentPane.add(cbox); contentPane.add(slider); frame.setVisible(true); } } Resized The default layout manager for content panes is BorderLayout. Recall that the following Swing components have content panes: JWindow JFrame JDialog JApplet JInternalFrame The other Swing container is the JPanel, whose default layout manager is FlowLayout. A JPanel object can be used for grouping components into a container, which can then be added to another container The JPanel constructor with no arguments creates a panel with a FlowLayout manager Another JPanel constructor takes any layout manager as an argument A JPanel can also be used a a blank area for drawing custom graphics JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); JLabel label = new JLabel("HERE ARE SOME BUTTONS", SwingConstants.CENTER); JButton button1 = new JButton("BUTTON1"); JButton button2 = new JButton("BUTTON2"); JButton button3 = new JButton("BUTTON3"); JPanel panel = new JPanel(); panel.add(button1); panel.add(button2); panel.add(button3); contentPane.add(label, BorderLayout.NORTH); contentPane.add(panel, BorderLayout.CENTER); frame.setVisible(true); Note use of SwingConstants.CENTER argument in JLabel constructor. JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); JLabel label = new JLabel("HERE ARE SOME BUTTONS", SwingConstants.CENTER); JButton button1 = new JButton("BUTTON1"); JButton button2 = new JButton("BUTTON2"); JButton button3 = new JButton("BUTTON3"); JPanel panel = new JPanel(); panel.setLayout (new BoxLayout(panel, BoxLayout.Y_AXIS)); panel.add(button1); panel.add(button2); panel.add(button3); contentPane.add(label, BorderLayout.NORTH); contentPane.add(panel, BorderLayout.CENTER); frame.setVisible(true); The button panel is to the west because no other component was placed there The BoxLayout constructor requires both the component being laid out and either: BoxLayout.X_AXIS BoxLayout.Y_AXIS Some layout constructors allow hgap and vgap, integers specifying the number of pixels separating components horizontally and vertically FlowLayout allows the specification of whether the line of components should be left-justified, right-justified, or centered new FlowLayout(int align) new FlowLayout(int align, int hgap, int vgap) new BorderLayout(int hgap, int vgap) new GridLayout(int rows, int cols) new GridLayout(int rows, int cols, int hgap, int vgap) JFrame frame = new JFrame("Test Frame"); frame.setSize(new Dimension(300,200)); frame.setLocation(100,100); Container contentPane = frame.getContentPane(); LayoutManager lm = contentPane.getLayout(); ((BorderLayout)lm).setHgap(25); JLabel label = new JLabel("HERE ARE SOME BUTTONS", SwingConstants.CENTER); JButton button1 = new JButton("BUTTON1"); JButton button2 = new JButton("BUTTON2"); JButton button3 = new JButton("BUTTON3"); JPanel panel = new JPanel(); panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS)); panel.add(button1); panel.add(button2); panel.add(button3); contentPane.add(label, BorderLayout.NORTH); contentPane.add(panel, BorderLayout.CENTER); frame.setVisible(true); The LayoutManager returned by getLayout() is an interface type that the BorderLayout class implements The setHgap method we want is in the BorderLayout class So we must cast the LayoutManager to BorderLayout in order to use setHgap Layout managers often need to resize their components to make things fit For example, the widths and heights of components in a BoxLayout are adjusted according to both preferred and maximum heights and widths If you don't like the size of the components a layout manager comes up with, you may have to give sizing hints using the following methods from the JComponent class: void setMinimumSize(Dimension d) void setPreferredSize(Dimension d) void setMaximumSize(Dimension d)