S& IWP notes- Java Swing Components

Notes on Java Swing Components

What is Swings in java ?

• A part of The JFC
• Swing Java consists of
  Look and feel
  Accessibility
  Java 2D
  Drag and Drop, etc

Swing is built on top of AWT and is entirely written in Java, using AWT’s lightweight component support. In particular, unlike AWT, t he architecture of Swing components makes it easy to customize both their appearance and behavior. Components from AWT and Swing can be mixed, allowing you to add Swing support to existing AWT-based programs. For example, swing components such as JSlider, JButton and JCheckbox could be used in the same program with standard AWT labels, textfields and scrollbars. You could subclass the existing Swing UI, model, or change listener classes without having to reinvent the entire implementation. Swing also has the ability to replace these objects on-the-fly.

100% Java implementation of components Pluggable Look & Feel Lightweight components Uses MVC Architecture Model represents the data View as a visual representation of the data Controller takes input and translates it to changes in data Three parts  Component set (subclasses of JComponent) Support classes Interfaces

Swing Components

1.   JFrame

The components added to the frame are referred to as its contents; these are managed by the contentPane. To add a component to a JFrame, we must use its contentPane instead.JFrame is a Window with border, title and buttons. When JFrame is set visible, an eventdispatching thread is started. JFrame objects store several objects including a Container object known as the content pane. To add a component to a JFrame, add it to the content pane.

By default, a Jframe is displayed in the upper-left corner of the screen. To display a frame
at a specified location, you can use the setLocation(x, y) method in the JFrame class. This
method places the upper-left corner of a frame at location (x, y).

The Swing API keeps improving with abstractions such as the setDefaultCloseOperation(EXIT_ON_CLOSE) method for the JFrame

JFrame Constructors

JFrame()
Constructs a new frame that is initially invisible.

JFrame(GraphicsConfiguration gc)
Creates a Frame in the specified GraphicsConfiguration of a screen device and a blank title.

JFrame(String title)
Creates a new, initially invisible Frame with the specified title.

JFrame(String title, GraphicsConfiguration gc)
Creates a JFrame with the specified title and the specified GraphicsConfiguration of a screen device.

2.   JPanel 

It is Swing’s version of the AWT class Panel and uses the same default layout, FlowLayout. JPanel is descended directly from JComponent.

3.   JInternalFrame

A JInternalFrame is confined to a visible area of a container it is placed in. JInternalFrame a top level swing component that has a contentpane.

• It can be iconified — in this case the icon remains in the main application container.
• It can be maximized — Frame consumes the main application
• It can be closed using standard popup window controls
• It can be layered

JInternalFrame Constructor

JInternalFrame()
Creates a non-resizable, non-closable, non-maximizable, non-iconifiable JInternalFrame with no title.
JInternalFrame(String title)
Creates a non-resizable, non-closable, non-maximizable, non-iconifiable JInternalFrame with the specified title.

JInternalFrame(String title, boolean resizable)
Creates a non-closable, non-maximizable, non-iconifiable JInternalFrame with the specified title and resizability.

JInternalFrame(String title, boolean resizable, boolean closable)
Creates a non-maximizable, non-iconifiable JInternalFrame with the specified title, resizability, and closability.

JInternalFrame(String title, boolean resizable, boolean closable, boolean maximizable)
Creates a non-iconifiable JInternalFrame with the specified title, resizability, closability, and maximizability.

JInternalFrame(String title, boolean resizable, boolean closable, boolean maximizable, boolean iconifiable)
Creates a JInternalFrame with the specified title, resizability, closability, maximizability

4.   JLabels

JLabel, descended from JComponent, is used to create text labels. A JLabel object provides text instructions or information on a GUI — display a single line of read-only text, an image or both text and image. We use a Swing JLabel when we need a user interface component that displays a message or an image.

JLabel Constructor

JLabel()
Creates a JLabel instance with no image and with an empty string for the title.

JLabel(Icon image)
Creates a JLabel instance with the specified image.

JLabel(Icon image, int horizontalAlignment)
Creates a JLabel instance with the specified image and horizontal alignment.

JLabel(String text)
Creates a JLabel instance with the specified text.

JLabel(String text, Icon icon, int horizontalAlignment)
Creates a JLabel instance with the specified text, image, and horizontal alignment.

JLabel(String text, int horizontalAlignment)
Creates a JLabel instance with the specified text and horizontal alignment.

5.   JTextField

JTextField allows editing/displaying of a single line of text. New features include the ability to justify the text left, right, or center, and to set the text’s font. When the user types data into them and presses the Enter key, an action event occurs. If the program registers an event listener, the listener processes the event and can use the data in the text field at the time of the event in the program. JTextField is an input area where the user can type in characters. If you want to let the user enter multiple lines of text, you cannot use JTextfield’s unless you create several of them. The solution is to use JTextArea, which enables the user to enter multiple lines of text.

JTextField Constructor

JTextField()
Constructs a new TextField.

JTextField(Document doc, String text, int columns)
Constructs a new JTextField that uses the given text storage model and the given number of columns.

JTextField(int columns)
Constructs a new empty TextField with the specified n
umber of columns.

JTextField(String text)
Constructs a new TextField initialized with the specified text.

JTextField(String text, int columns)
Constructs a new TextField initialized with the specified text and columns.

6.   JPasswordField

JPasswordField (a direct subclass of JTextField) you can suppress the display of input. Each character entered can be replaced by an echo character. This allows confidential input for passwords, for example. By default, the echo character is the asterisk, *. When the user types data into them and presses the Enter key, an action event occurs. If the program registers an event listener, the listener processes the event and can use the data in the text field at the time of the event in the program. If you need to provide an editable text field that doesn’t show the characters the user types – use the JPasswordField class.

JPasswordField Constructor

JPasswordField()
Constructs a new JPasswordField, with a default document, null starting text string, and 0 column width.

JPasswordField(Document doc, String txt, int columns)
Constructs a new JPasswordField that uses the given text storage model and the given number of columns.

JPasswordField(int columns)
Constructs a new empty JPasswordField with the specified number of columns.

JPasswordField(String text)
Constructs a new JPasswordField initialized with the specified text.

JPasswordField(String text, int columns)
Constructs a new JPasswordField initialized with the specified text and columns.

7.   JTextArea

J. JTextArea allows editing of multiple lines of text. JTextArea can be used in conjunction with class JScrollPane to achieve scrolling. The underlying JScrollPane can be forced to always or never have either the vertical or horizontal scrollbar.

JTextArea Constructor

JTextArea()
Constructs a new TextArea.

JTextArea(Document doc)
Constructs a new JTextArea with the given document model, and defaults for all of the other arguments (null, 0, 0).

JTextArea(Document doc, String text, int rows, int columns)
Constructs a new JTextArea with the specified number of rows and columns, and the given model.

JTextArea(int rows, int columns)
Constructs a new empty TextArea with the specified number of rows and columns.

JTextArea(String text)
Constructs a new TextArea with the specified text displayed.

JTextArea(String text, int rows, int columns)
Constructs a new TextArea with the specified text and number of rows and columns.

8.   JButton

The abstract class AbstractButton extends class Component and provides a foundation for a family of button classes, including JButton. A button is a component the user clicks to trigger a specific action.

There are several types of buttons in Java, all are subclasses of AbstractButton.

• command buttons: is created with class JButton. It generates ActionEvent.
• toggle buttons: have on/off or true/false values.
• check boxes: a group of buttons. It generates ItemEvent.
• radio buttons: a group of buttons in which only one can be selected. It generates ItemEvent.

JButton Constructor

JButton()
Creates a button with no set text or icon.

JButton(Action a)
Creates a button where properties are taken from the Action supplied.

JButton(Icon icon)
Creates a button with an icon.

JButton(String text)
Creates a button with text.

JButton(String text, Icon icon)
Creates a button with initial text and an icon.

9.   JCheckBox

JCheckBox is not a member of a checkbox group. A checkbox can be selected and deselected, and it also displays its current state.

10.                         JComboBox

JComboBox is like a drop down box — you can click a drop-down arrow and select an option from a list. It generates ItemEvent. For example, when the component has focus, pressing a key that corresponds to the first character in some entry’s name selects that entry. A vertical scrollbar is used for longer lists.

JComboBox Constructor

JComboBox()
Creates a JComboBox with a default data model.

JComboBox(ComboBoxModel aModel)
Creates a JComboBox that takes it’s items from an existing ComboBoxModel.

JComboBox(Object[] items)
Creates a JComboBox that contains the elements in the specified array.

JComboBox(Vector items)
Creates a JComboBox that contains the elements in the specified Vector.

11.                         JList

JList provides a scrollable set of items from which one or more may be selected. JList can be populated from an Array or Vector. JList does not support scrolling directly—instead, the list must be associated with a scrollpane. The view port used by the scrollpane can also have a user-defined border. JList actions are handled using ListSelectionListener.

JList Constructor

JList()
Constructs a JList with an empty model.

JList(ListModel dataModel)
Constructs a JList that displays the elements in the specified, non-null model.

JList(Object[] listData)
Constructs a JList that displays the elements in the specified array.

JList(Vector listData)
Constructs a JList that displays the elements in the specified Vector.