1The Abstract Windowing Toolkit• Since Java was first released, its user interface facilities have been a significant weakness– The Abstract Windowing Toolkit (AWT) was part of the JDK form the beginning, but it really was not sufficient to support a complex user interface• JDK 1.1 fixed a number of problems, and most notably, it introduced a new event model. It did not make any major additions to the basic componentsJava Foundation Classes• In April 1997, JavaSoft announced the Java Foundation Classes (JFC).– a major part of the JFC is a new set of user interface components called Swing.AWT Swing AccessibilityJava2DDragAndDropSwing• The Swing classes are used to build GUIs– Swing does not stand for anything– Swing is built on top of the 1.1/1.2 AWT libraries• Swing makes 3 major improvements on the AWT– does not rely on the platform’s native components– it supports “Pluggable Look-and-Feel” – it is based on the Model-View-Controller (MVC)AWTSwingJFCJDK 1.2Components• A GUI consists of different graphic Component objects that are combined into a hierarchy using Container objects.• Component class– An abstract class for GUI components such as menus, buttons, labels, lists, etc. • Container– An abstract class that extends Component. Containers can hold multiple components.2Weighing Components• Sun makes a distinction between light weight and heavyweight components– Lightweight components are not dependent on native peers to render themselves. They are coded in Java.– Heavyweight components are rendered by the host operating system. They are resources managed by the underlying window manager.Heavyweight Components• Heavyweight components were unwieldy for two reasons:– Equivalent components on different platforms do not necessarily act alike.– The look and feel of each component was tied to the host operating system• Almost all Swing components are lightweight except– JApplet, JFrame, JDialog, and JWindowAdditional Swing Features• Swing also provides– A wide variety of components (tables, trees, sliders, progress bars, internal frame, …)– Swing components can have tooltips placed over them.– Arbitrary keyboard events can be bound to components.– Additional debugging support.– Support for parsing and displaying HTML based information.Applets versus Applications• Using Swing it is possible to create two different types of GUI programs– Standalone applications• Programs that are started from the command line• Code resides on the machine on which they are run– Applets• Programs run inside a web browser• Code is downloaded from a web server• JVM is contained inside the web browser• For security purposes Applets are normally prevented from doing certain things (for example opening files).• For now we will write standalone applications3JFrame win = new JFrame( “title” );JFrames•A JFrame is a Window with all of the adornments added.•A JFrame provides the basic building block for screen-oriented applications.Creating a JFrame• SwingFrame.javaJFrame• Sizing a Frame– You can specify the size.• Height and width given in pixels.• The size of a pixel will vary based on the resolution of the device on which the frame is rendered.– The method, pack(), will set the size of the frame automatically based on the size of the components contained in the content pane• Note that pack does not look at the title bar.– SwingFrame2.javaJFrame•JFrames have several panes:• Components are placed in the content paneGlass paneLayered paneMenu barContent pane4Swing Components• JComponent– JComboBox, JLabel, JList, JMenuBar, JPanel, JPopupMenu, JScrollBar, JScrollPane, JTable,JTree, JInternalFrame, JOptionPane, JProgressBar, JRootPane, JSeparator, JSlider, JSplitPane, JTabbedPane, JToolBar, JToolTip, Jviewport, JColorChooser, JTextComponent,…label = new JLabel( ”text", JLabel.RIGHT ) ;JLabels•JLabels are components that you can put text into.• When creating a label you can specify the initial value and the alignment you wish to use within the label.• You can use getText() and setText() to retrieve and modify the value of the label.Hello World Example• SwingFrame3.java – Using a label.JButtons• JButton extends Component , displays a string and delivers an ActionEvent for each mouse click.• Normally buttons are displayed with a border.• In addition to text, JButtons can also display icons.• SwingButton.javabutton = new JButton( ”text“ ) ;5Layout Manager• Layout Manager – An interface that defines methods for positioning and sizing objects within a container. – Java defines several default implementations of LayoutManager.• Geometrical placement in a Container is controlled by a LayoutManager object Components, Containers, and Layout Managers• Containers may contain components – that means containers can contain containers!!. • All containers come equipped with a layout manager that positions and shapes (lays out) the container's components. • Much of the action in the AWT occurs between components, containers, and their layout managers. Layout Managers• Layouts allow you to format components on the screen in a platform independent manner.• The standard JDK provides five classes for implementing the LayoutManager interface:– FlowLayout – GridLayout – BorderLayout – CardLayout – GridBagLayout• Layout managers are defined in the AWT packageChanging the Layout• To change the layout used in a container the program must first create the layout. • Then the setLayout() method is invoked on the container that is to use the new layout.• The layout manager should be specified before any components are added to the container.JPanel p = new JPanel() ;p.setLayout( new FlowLayout() );6FlowLayout• FlowLayout is the default layout for the JPanel class. • When you add components to the screen, they are added from left to right (centered) based on the order added and the width of the screen. – Very similar to word wrap and full justification on a word processor. – If the screen is resized, the components' layout will change based on the new width and height.Flow Layout• SwingFlowLayout.java – Resize Window.GridLayout• The GridLayout manager arranges components in rows and columns.– If the number of rows is specified• columns = number of components / rows– If the number of columns is specified• rows = number of components /
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