topics awt classes window fundamentals working with frame windows creating a frame window in an...

Topics•AWT Classes• Window Fundamentals•Working with Frame Windows• Creating a Frame Window in an Applet•Creating a Windowed Program•Displaying Information within a Window• Working with Graphics• Working with color•Setting the Paint Mode•Working with Fonts•Managing Text Output Using Font Metrics.

AWT Classesone of Java’s largest packages

• AWT Abstract Window Toolkit

• The main purpose of the AWT is to support applet

windows

• It can also be used to create stand-alone windows

that run in a GUI environment, such as Windows.•The AWT classes are contained in the java.awt package

AWT Classes

AWT Classes - some of the original methods were deprecated and replaced by new ones when Java 1.1 was released. For backward-compatibility, Java 2 still supports all the original 1.0 methods.

AWT Classes

Window Fundamentals

• The AWT defines windows according to a class hierarchy

that adds functionality and specificity with each level.

•The two most common windows are • those derived from Panel, which is used by applets,

• those derived from Frame, which creates a standard

window.

Window Fundamentals

Much of the functionality of these windows is derived from their parent classes.

- Component

• An abstract class that

• encapsulates all of the attributes of a visual

component.(All user interface elements are subclasses)

• It defines over a hundred public methods for

managing events (such as mouse and keyboard input,

positioning and sizing the window, and repainting.)

• Remembers the current foreground and background

colors and the currently selected text font.

- Container

• A subclass of Component

• A container is responsible for laying out any

components that it contains.

• Includes methods that allow other Component

objects to be nested within it

• Other Container objects can be stored inside of a

Container

- Panel

•A Panel is a window that does not contain a title

bar, menu bar, or border.

•A concrete subclass of Container

•The superclass for Applet

•It doesn’t add any new methods; it simply

implements Container.

- Panel

• Other components can be added to a Panel

object by its add( ) method.

• add( ) method inherited from Container.

• you can position and resize the added

components manually using the setLocation( ),

setSize( ), or setBounds( ) methods defined by

Component.

- Window

•This class creates a top-level window

• A top-level window is not contained within any other

object; (it sits directly on the desktop)

• You will use a subclass of Window called Frame to create

Window objects

- Frame

•A subclass of Window and has a title bar, menu bar,

borders, and resizing corners.

• If you create a an applet window , it will contain a

warning message, such as “Java Applet Window,”

• When a Frame window is created by a program

rather than an applet, a normal window is created.

• It creates a standard-style window

•You will use it to create

• child windows within applets,

• top-level or child windows for applications.

Working with Frame Windows

Two of Frame’s constructors:

1. Frame( ) creates a standard window that does not contain a title.

2. Frame(String title) creates a window with the title specified by title

Several methods are used when working with Frame

windows.• Setting the Window’s Dimensions

1. void setSize(int newWidth, int newHeight)

2. void setSize(Dimension newSize)

newWidth and newHeight new size of the window

newSize the Dimension object contains width and height

fields The dimensions are specified in terms of pixels.

3. Dimension getSize( ) used to obtain the current size of a window

• Setting a Window’s Title void setTitle(String newTitle)

newTitle the new title for the window

• Closing a Frame Window

setVisible(false).

•you must implement the windowClosing( ) method of the

WindowListener interface

•Inside windowClosing( ), you must remove the window from

the screen

Creating a Frame Window in an AppletSTEPS:

1. Create a subclass of Frame.

2. Override any of the standard window methods (init( ), start( ), stop( ), and paint( ))

3. Finally, implement the windowClosing( ) method of

the WindowListener interface

( calling setVisible(false) when the window is closed )

you create an object of frame’s subclass. This causes a frame

window to come into existence and you make window visible by

calling setVisible( ).

Note the following :

• SampleFrame calls Frame’s constructor. (with super()).

This causes a standard frame window to be created with

the title passed in title.

•This example overrides the applet window’s start( ) and

stop( ) methods. This causes the window to be removed

automatically when you terminate the applet, when you

close the window,

Sample output

Handling Events in a Frame Window

• Since Frame is a subclass of Component, it inherits all

the capabilities defined by Component.

• So you can use and manage a frame window that you

create just like you manage your applet’s main window.

• Whenever an event occurs in a window, the event

handlers defined by that window will be called.

• Each window handles its own events.


The MouseListener Interface

1. void mouseClicked(MouseEvent me)

2. void mouseEntered(MouseEvent me)

3. void mouseExited(MouseEvent me)

4. void mousePressed(MouseEvent me)

5. void mouseReleased(MouseEvent me)

The MouseMotionListener Interface

1. void mouseDragged(MouseEvent me)

2. void mouseMoved(MouseEvent me)


The WindowListener Interface

1. void windowActivated(WindowEvent we)

2. void windowClosed(WindowEvent we)

3. void windowClosing(WindowEvent we)

4. void windowDeactivated(WindowEvent we)

5. void windowDeiconified(WindowEvent we)

6. void windowIconified(WindowEvent we)

7. void windowOpened(WindowEvent we)

•The following program creates a window that responds to mouse

events. The main applet window also responds to mouse events.

Sample output

It is possible to create stand-alone AWT-based

applications, too. To do this, simply create an instance of

the window or windows you need inside main( ).

Sample output

Once created, a frame window takes on a life of its own. Notice

that main( ) ends with the call to appwin.setVisible(true).

Working with Graphics


• All graphics are drawn relative to a window. (main window of an applet, a child window of an applet, or a stand-alone

application window.)

• The origin of each window is at the top-left corner and is 0,0.

• Coordinates are specified in pixels

• All output to a window takes place through a graphics context.


• 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.

Drawing Lines

void drawLine(int startX, int startY, int endX, int endY)

- displays a line in the current drawing color that begins at

startX,startY and ends at endX,endY

Drawing Lines

Drawing Rectangles

1. void drawRect(int top, int left, int width, int height)

2. void fillRect(int top, int left, int width, int height)

top ,left The upper-left corner of the rectangle

width and height The dimensions of the rectangle

3. void drawRoundRect(int top, int left, int width,

int height, int xDiam, int yDiam) draws rounded

rectangle xDiam The diameter of the rounding arc along the X axis yDiam The diameter of the rounding arc along the Y axis.

Drawing Rectangles

4. void fillRoundRect(int top, int left, int width, int

height, int xDiam, int yDiam) draws a filled rectangle

Drawing Rectangles

Sample output

Sample output

Drawing Ellipses and Circles

1. void drawOval(int top, int left, int width,

int height)

2. void fillOval(int top, int left, int width, int

height)The ellipse is drawn within a bounding rectangle whose upper-left

corner is specified by top, left and whose width and height are

specified by width and height

To draw a circle, specify a square as the bounding rectangle


Sample output

Drawing Arcs

1. void drawArc(int top, int left, int width, int height,

int startAngle, int sweepAngle)

2. void fillArc(int top, int left, int width, int height, int

startAngle, int sweepAngle)

top,left upper-left corner of the bounding rectangle

width and height width and height of the bounding rectangle

startAngle , sweepAngle The arc is drawn from startAngle

through the angular distance specified by sweepAngle

Drawing Arcs

• The arc is drawn counterclockwise if sweepAngle is positive,

and clockwise if sweepAngle is negative.

• Angles are specified in degrees.

•Zero degrees is on the horizontal, at the three o’clock position

To draw an arc from twelve o’clock to six o’clock, the start angle

would be 90 and the sweep angle 180.

Drawing Arcs

Drawing Arcs

Sample output

Drawing Polygons

1. void drawPolygon(int x[ ], int y[ ], int numPoints)

2. void fillPolygon(int x[ ], int y[ ], int numPoints)

•The polygon’s endpoints are specified by the coordinate pairs

contained within the x and y arrays

•numPoints The number of points defined by x and y

Drawing Polygons

Drawing Polygons

Sample output

Sizing Graphics

• To size a graphics object first obtain the current dimensions of

the window by calling getSize( ) on the window object

•Once you have the current size of the window, you can scale

your graphical output accordingly.

•getSize( ) returns the dimensions of the window encapsulated

within a Dimension object

Sizing Graphics

Working with Color

Working with Color• Java supports color in a portable, device-independent fashion

•Color is encapsulated by the Color class and defines constants for common

colors

1. Color(int red, int green, int blue)

2. Color(int rgbValue)

3. Color(float red, float green, float blue)

• You can also create your own colors, using one of the color constructors.

Working with Color

1. The first constructor takes three integers that specify the color

as a mix of red, green, and blue. These values must be between

0 and 255

2. The second color constructor takes a single integer that

contains the mix of red, green, and blue packed into an integer

•red in bits 16 to 23,

• green in bits 8 to 15, and

•blue in bits 0 to 7

3. The final constructor, takes three float values (between 0.0 and

1.0) that specify the relative mix of red, green, and blue

Using Hue, Saturation, and Brightness (HSB)

• An alternative color model to red-green-blue (RGB)

• hue specified with a number between 0.0 and 1.0

• Saturation ranges from 0.0 to 1.0, representing light

pastels to intense hues

• Brightness values also range from 0.0 to 1.0, where 1 is bright

white and 0 is black

Color Methods

The Color class defines several methods that help manipulate

colors.

1. static int HSBtoRGB(float hue, float saturation, float

brightness)

2. static float[ ] RGBtoHSB(int red, int green, int blue, float

values[ ])

3. int getRed( ) Red components of RBG

4. int getGreen( ) Green components of RBG

5. int getBlue( ) Blue components of RBG

6. int getRGB( ) packed RGB representation of a color

Setting the Current Graphics Color

You can change this color by calling the Graphics method setColor( ):

void setColor(Color newColor)

newColor specifies the new drawing color

•You can obtain the current color by calling getColor( ),

Color getColor( )

A Color Demonstration Applet

Setting the XOR Mode

• By default, new output to a window overwrites any preexisting

contents.

• However, it is possible to have new objects XORed onto the

window by using setXORMode( )

void setXORMode(Color xorColor)

xorColor specifies the color that will be XORed to the window

when an object is drawn.

Setting the Paint Mode

• To return to overwrite mode, call setPaintMode( ), shown here:

void setPaintMode( )

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

the following program displays cross hairs that track the mouse pointer. The cross hairs are XORed onto the window and are always visible, no matter what the underlying color is.

Sample output

Working with Fonts

• The AWT provides

• flexible font-manipulation

• Allows dynamic selection of fonts.

• Fonts have

1. A family name the general name of the font, such as

Courier

2. A logical font name specifies a category of font such as

Monospaced

3. A face name a specific font, such as Courier Italic.

Working with Fonts

• Fonts are encapsulated by the Font class

Working with Fonts

• Some Methods Defined by Font

Working with Fonts• Some Methods Defined by Font

Determining the Available Fonts1. To obtain font information, you can use the

getAvailableFontFamilyNames( ) method defined

by the GraphicsEnvironment class

String[ ] getAvailableFontFamilyNames( );

This method returns an array of strings that contains the names

of the available font families.

Determining the Available Fonts2. In addition, the getAllFonts( ) method is defined by the

GraphicsEnvironment classFont[ ] getAllFonts( )

This method returns an array of Font objects for all of the

available fonts.

Since these methods are members of GraphicsEnvironment, you

need a GraphicsEnvironment reference to call them. You can

obtain this reference by using

static GraphicsEnvironment getLocalGraphicsEnvironment( )

Determining the Available Fonts

Determining the Available Fonts

Sample output

Creating and Selecting a Font

To select a new font, you must first construct a Font object that

describes that font. One Font constructor has this general form:

Font(String fontName, int fontStyle, int pointSize)

• fontName specifies the name of the desired font.

• fontStyle The style of the font.

• pointSize The size, in points, of the font


• fontName All Java environments will support the following fonts: Dialog, DialogInput, SansSerif, Serif, Monospaced, and Symbol.

• fontStyle one or more of these three constants:• Font.PLAIN• Font.BOLD• Font.ITALIC.

To combine styles, OR them together.

For example, Font.BOLD | Font.ITALIC


• To use a font that you have created, you must select it using

setFont( ), which is defined by Component

void setFont(Font fontObj)

fontObj the object that contains the desired font


The following program outputs a sample of each standard font.

Each time you click the mouse within its window, a new font is

selected and its name is displayed

Obtaining Font Information

• To obtain information about the currently selected font, you

must first get the current font by calling getFont( ).

This method is defined by the Graphics class

Font getFont( )

Once you have obtained the currently selected font, you can

retrieve information about it using various methods defined by

Font.


•this applet displays the name, family, size, and style of the

currently selected font:

Managing Text Output Using FontMetrics

FontMetrics class

• Encapsulates various information about a font.

Basic Terms :

When drawString( ) method is used , the location specifies left edge of the baseline of the characters, not at the upper-left corner as is usual with other drawing methods

FontMetrics class

• FontMetrics defines several methods that help you manage text output.

Displaying Multiple Lines of Text Using FontMetrics

Centering Text

AWT Class Hierarchy

topics awt classes window fundamentals working with frame windows creating a frame window in an...

Documents

subclass of window

toplevel window

window objects

standard window

container slide

normal window

java applet window

frame windows