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AWT
• Java AWT (Abstract Windowing Toolkit) is an API
to develop GUI or window-based application in java.
• Java AWT components are platform-dependent i.e.
components are displayed according to the view of
operating system. AWT is heavyweight i.e. its
components uses the resources of system.
• The java.awt package provides classes for AWT api
such as TextField, Label, TextArea, RadioButton,
CheckBox, Choice, List etc.
• AWT Classes
Windows Fundamentals
• The two most common windows are those derived from Panel,
which is used by applets, and those derived from Frame, which
creates a standard application window.
• Much of the functionality of these windows is derived from
their parent classes.
• Thus, a description of the class hierarchies relating to these
two classes is fundamental to their understanding.
The class hierarchy for Panel and Frame
• Component
• Component is an object having a graphical representation that
can be displayed on the screen and that can interact with the
user. For examples buttons, checkboxes, list and scrollbars of a
graphical user interface.
• Container
• Container object is a component that can contain other
components. Components added to a container are tracked in a
list. The order of the list will define the components' front-toback stacking order within the container. If no index is
specified when adding a component to a container, it will be
added to the end of the list.
• Panel
• Panel provides space in which an application can attach any
other components, including other panels.
• Window
• Window is a rectangular area which is displayed on the screen.
In different window we can execute different program and
display different data. Window provide us with multitasking
environment. A window must have either a frame, dialog, or
another window defined as its owner when it's constructed.
• Frame
• A Frame is a top-level window with a title and a border. The
size of the frame includes any area designated for the border.
Frame encapsulates window. It and has a title bar, menu bar,
borders, and resizing corners.
• Canvas
• Canvas component represents a blank rectangular area of the
screen onto which the application can draw. Application can
also trap input events from the use from that blank area of
Canvas component.
Working with Frame Windows
• Two of Frame’s constructors:
– Frame( )
– Frame(String title)
• The first form creates a standard window that does not
contain a title.
• The second form creates a window with the title specified
by title.
• Setting the Window’s Dimensions
• void setSize(int newWidth, int newHeight)
• void setSize(Dimension newSize)
• Dimension getSize( ) - obtain the current size of a
window
• Hiding and Showing a Window
• After a frame window has been created, it will not be visible
until setVisible( ) is called.
– void setVisible(boolean visibleFlag)
• Setting a Window’s Title
– void setTitle(String newTitle)
• Closing a Frame Window
– setVisible(false)
– windowClosing( )method of the WindowListener
interface
• Examples:
• AppletFrame.java
• WindowEvents.java
Working with Graphics
• A graphics context is encapsulated by the Graphics
class and is obtained in two ways:
– It is passed to an applet when one of its various methods,
such as paint( ) or update( ), is called.
– It is returned by the getGraphics( )method of Component
• The Graphics class defines a number of drawing
functions.
• Each shape can be drawn edge-only or filled.
• Objects are drawn and filled in the currently selected
graphics color, which is black by default.
• When a graphics object is drawn that exceeds the
dimensions of the window, output is automatically
clipped.
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Drawing Lines
void drawLine(int startX, int startY, int endX, int endY)
Eg: Lines.java
Drawing Rectangles
void drawRect(int top, int left, int width, int height)
void fillRect(int top, int left, int width, int height)
void drawRoundRect(int top, int left, int width, int height,int xDiam, int yDiam)
void fillRoundRect(int top, int left, int width, int height,int xDiam, int yDiam)
Drawing Ellipses and Circles
void drawOval(int top, int left, int width, int height)
void fillOval(int top, int left, int width, int height)
Drawing Arcs
void drawArc(int top, int left, int width, int height, int startAngle,int
sweepAngle)
void fillArc(int top, int left, int width, int height, int startAngle,int sweepAngle)
Drawing Polygons
void drawPolygon(intx[ ], inty[ ], int numPoints)
void fillPolygon(intx[ ], inty[ ], int numPoints)
Eg: HourGlass.java
• Sizing Graphics
• getSize( ) - returns the dimensions of the
window encapsulated within a Dimension
object.
• Eg. ResizeMe.java
Working with Colors - portable, device-independent
fashion eg: ColorDemo.java
• Color defines several constants to specify a number of common colors.
• Own color creation. Three commonly used forms are shown here:
– Color(int red, int green, int blue)
– Color(int rgbValue)
– Color(float red, float green, float blue)
– Eg: new Color(255, 100, 100);
• Color Methods
– Using Hue, Saturation, and Brightness
• static int HSBtoRGB(float hue, float saturation, float brightness)
• static float[ ] RGBtoHSB(int red, int green, int blue, float values[ ])
• int getRed( )
• int getGreen( )
• int getBlue( ) - returns the RGB color component found in the
invoking Color object in the lower 8 bits of an integer.
• int getRGB( )
• Setting the Current Graphics Color
– void setColor(Color newColor)
– Color getColor( )
• Setting the Paint Mode eg: XOR.java
• The paint mode determines how objects are drawn in a
window.
• New output to a window overwrites any preexisting contents.
• void setXORMode(Color xorColor)
• The advantage of XOR mode is that the new object is always
guaranteed to be visible no matter what color the object is
drawn over.
• To return to overwrite mode, call setPaintMode(),void
setPaintMode( )
Working with Fonts
• The AWT provides flexibility by
– abstracting font-manipulation operations and
– allowing for dynamic selection of fonts.
• Fonts have a family name, a logical font name, and a face
name.
• The family name is the general name of the font, such as
Courier.
• The logical name specifies a category of font, such as
Monospaced.
• The face name specifies a specific font, such as Courier Italic.
• Fonts are encapsulated by the Font class.
• Determining the Available Fonts eg: ShowFonts.java
– String[ ] getAvailableFontFamilyNames( )
– Font[ ] getAllFonts( )
– static GraphicsEnvironment
getLocalGraphicsEnvironment( )
• Creating and Selecting a Font eg SampleFonts.java
– Font(String fontName, int fontStyle, int pointSize)
• Font style: Font.PLAIN,Font.BOLD, andFont.ITALIC.
– void setFont(Font fontObj)
• Obtaining Font Information eg: FontInfo.java
– Font getFont( )
Managing Text output using
FontMetrics
• FontMetrics defines several methods that help
you manage text output.
– Displaying Multiple Lines of Text
– Centering Text
– Multiline Text Alignment