Swing and Graphical User Interface in Java
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The document provides information about the Swing graphical user interface library in Java. It describes that Swing is the official GUI toolkit for Java, released as part of Java Foundation Classes. It discusses the key components, layout managers like BorderLayout and GridLayout, and event handling in Swing using interfaces, anonymous inner classes, and adapter classes.
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Swing and Graphical User Interface in Java
- 2. Introduction • Swing library is an official Java GUI toolkit released by Sun Microsystems • Swing is a part of JFC, Java Foundation Classes • Used to create Graphical user interfaces with Java. • It is a collection of packages for creating full featured desktop applications. • JFC consists of AWT, Swing, Accessibility, Java 2D, and Drag and Drop. • Swing was released in 1997 with JDK 1.2
- 3. Introduction (contd) • Platform independent • Customizable • Extensible • Configurable • Lightweight
- 4. Swing API packages • Swing API has 18 public packages • javax.accessibility • javax.swing • javax.swing.border • javax.swing.colorchooser • javax.swing.event • javax.swing.filechooser • javax.swing.plaf • javax.swing.plaf.basic • javax.swing.plaf.metal
- 5. Swing API packages (contd) • javax.swing.plaf.multi • javax.swing.plaf.synth • javax.swing.table • javax.swing.text • javax.swing.text.html • javax.swing.text.html.parser • javax.swing.text.rtf • javax.swing.tree • javax.swing.undo
- 8. Layout Management • Java Swing toolkit has two kind of components – Container Components – Children Components • The containers group children into suitable layouts • To create layouts, we use layout managers
- 9. Layout Management (contd) • BorderLayout • BoxLayout • CardLayout • FlowLayout • GridBagLayout • GridLayout • GroupLayout • SpringLayout
- 10. Absolute Positioning • If a container holds components whose size is not affected by the container's size or by font, look- and-feel, or language changes • Creating a container without a layout manager involves the following steps. 1.Set the container's layout manager to null by calling setLayout(null). 2.Call the Component class's setbounds method for each of the container's children. 3.Call the Component class's repaint method.
- 11. Absolute Positioning (contd) • Creating containers with absolutely positioned containers can cause problems if the window containing the container is resized
- 12. FlowLayout • The FlowLayout class provides a very simple layout manager that is used, by default, by the JPanel objects • The FlowLayout class puts components in a row, sized at their preferred size • If the horizontal space in the container is too small to put all the components in one row, the FlowLayout class uses multiple rows • If the container is wider than necessary for a row of components, the row is, by default, centered horizontally within the container
- 13. FlowLayout (contd) • To specify that the row is to aligned either to the left or right, use a FlowLayout constructor that takes an alignment argument – public FlowLayout(int align) • Another constructor of the FlowLayout class specifies how much vertical or horizontal padding is put around the components – public FlowLayout(int align, int hgap, int vgap)
- 15. BorderLayout • A BorderLayout object has five areas specified by the BorderLayout constants: – PAGE_START – PAGE_END – LINE_START – LINE_END – CENTER
- 16. BorderLayout (contd) • If the window is enlarged, the center area gets as much of the available space as possible • Other areas expand only as much as necessary to fill all available space • Often a container uses only one or two of the areas of the BorderLayout object — just the center, or the center and the bottom.
- 18. GridLayout • A GridLayout object places components in a grid of cells • Each component takes all the available space within its cell, and each cell is exactly the same size • If the window is resized, the GridLayout object changes the cell size so that the cells are as large as possible, given the space available to the container
- 20. Event Handling
- 21. Introduction • All GUI applications are event-driven • An application reacts to different event types which are generated during its life • Events are generated mainly by the user of an application • But they can be generated by other means as well. e.g. internet connection, window manager, timer
- 22. Introduction (contd) • In the event model, there are three participants: – event source – event object – event listener • The Event source is the object whose state changes and generates Events • The Event object (Event) encapsulates the state changes in the event source • The Event listener is the object that wants to be notified. Event source object delegates the task of handling an event to the event listener.
- 23. Event Object • When something happens in the application, an event object is created • There are several types of events, e.g ActionEvent, TextEvent, FocusEvent, ComponentEvent etc, created under specific conditions. • Event object has information about an event, that has happened
- 24. Implementation • There are several ways, how we can implement event handling in Java Swing toolkit – Anonymous inner class – Inner class – Derived class
- 25. Anonymous Inner Class • The button is the event source and it will generate events closeButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { System.exit(0); } }); • Here we register an action listener with the button • This way, the events are sent to the event target • The event target in our case is ActionListener
- 26. Inner Class • The listener is defined inside an inner class, which has a name ButtonCloseListener listener = new ButtonCloseListener(); closeButton.addActionListener(listener); • Here we have a non anonymous inner class class ButtonCloseListener implements ActionListener { public void actionPerformed(ActionEvent e) { System.exit(0); } } • The button listener is defined here.
- 27. Derived Class • We create a MyButton class, that implements the action listener MyButton closeButton = new MyButton("Close"); • Now create the MyButton custom class class MyButton extends JButton implements ActionListener { • The MyButton class is extended from the JButton class and implements the ActionListener interface • This way, the event handling is managed within the MyButton class. addActionListener(this); • Here we add the action listener to the MyButton class.
- 28. Adapter Classes • Time consuming to define all interface methods • WindowListener has seven methods • What if we only want to use one? • Required to define all methods in interface • Adapter class implements an interface • Does anyone recognize a design pattern here? • Default implementation ({ }, empty body) for all methods
- 29. Adapter Classes (contd) • You then extend adapter class, • overriding methods for events you care about, such as windowClosing. • Has "is a" relationship with interface • WindowAdapter is a WindowListener • MouseAdapter is a MouseListener