Window Fundamentals

2

Window Fundamentals

Component encapsulates all of the attributes of a visual component.

All user interface elements that are displayed on the screen and that interact with the user are subclasses of Component.

A Component object is responsible for remembering the current foreground and background colors and the currently selected text font.

Window Fundamentals

Container A container is responsible for laying out (that is,

positioning) any components that it contains. It does this through the use of various layout

managers

Window Fundamentals

Panel A Panel may be thought of as a recursively

nestable, concrete screen component. Panel is the superclass for Applet. When screen

output is directed to an applet, it is drawn on the surface of a Panel object.

In essence, a Panel is a window that does not contain a title bar, menu bar, or border.

Window Fundamentals

Window The Window class creates a top-level window Generally, Window objects are not created

directly. Instead, a subclass of Window called Frame.

Window Fundamentals

Frame Frame is a subclass of Window It has a title bar, menu bar, borders, and resizing

corners. If you create a Frame object from within an

applet, it will contain a warning message, such as “Java Applet Window,” to the user that an applet window has been created.

This message warns users that the window was started by an applet.

Frames

1. Frame( )

2. Frame(String title)

void setSize(int newWidth, int newHeight) To set the dimensions of the

window

void setVisible(boolean visibleFlag) void setVisible(boolean visibleFlag)

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

Frames

import java.awt.*;

import java.awt.event.*;

class MyFrame extends Frame

{

MyFrame(String s)

{

super(s)

}

public void paint(Graphics g)

{

g.drawString("MCA Department",100,50);

}

Frames

public static void main(String args[])

{

MyFrame f = new MyFrame(“VESIT”);

f.setSize(200,100);

f.setVisible(true);

}

}

Frames// Create a child frame window from within an applet.

import java.awt.*;

import java.awt.event.*;

import java.applet.*;

/*

<applet code="AppletFrame" width=300 height=50>

</applet>

*/

class MyFrame extends Frame

{

MyFrame()

{

addWindowListener(new MyWindowAdapter(this));

}

Framespublic void paint(Graphics g)

{ g.drawString("Hello world",100,50);

}

}

class MyWindowAdapter extends WindowAdapter {

MyFrame f1;

public MyWindowAdapter(MyFrame f1)

{

this.f1 = f1;

}

public void windowClosing(WindowEvent we)

{

f1.setVisible(false);

}

}

Framespublic class AppletFrame1 extends Applet {

MyFrame f;

public void init() {

f = new MyFrame();

f.setSize(250, 250);

f.setVisible(true);

}

public void start() {

f.setVisible(true);

}

public void stop() {

f.setVisible(false);

}

public void paint(Graphics g) {

g.drawString("This is in applet window", 10, 20);

}

Frames

Color classColor(int red, int green, int blue)

1.  void setColor(Color newColor)

2.  Color getColor( )

import java.awt.*;

import java.applet.*;

/* <applet code=“ColorDemo" width=300 height=200>

</applet> */

public class ColorDemo extends Applet

{

public void paint(Graphics g) {

g.setColor(Color.green);

g.drawString(“Hello World”, 50,50);

}

}

Graphics Class

All graphics are drawn relative to a window. This can be the 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.

17

Graphics Primitives For drawing geometric shapes, texts An abstract class

– the extended class must override paint()

Oval

Rectangle

Arc

Line

RoundRectangle

Polygon

18

Drawing Lines

public void paint(Graphics g){ g.setColor(Color.blue); g.drawLine(0, 0, 100, 100); g.drawLine(0, 100, 100, 0); }

(x1,y1)

(x2,y2)

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

Drawing Rectangles

public void paint(Graphics g) { g.setColor(Color.pink);

g.drawRect(10, 10, 60, 50); g.fillRect(100, 10, 60, 50);}

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

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

Drawing Rounded Rectangles

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)

xDiam: diameter of the rounding arc along the X axis

yDiam: diameter of the rounding arc along the Y axis

public void paint(Graphics g) { g.setColor(Color.yellow);

g.drawRoundRect(190, 10, 60, 50, 15, 15); g.fillRoundRect(70, 90, 140, 100, 30, 40);}

21

Drawing Ellipses and Circles

public void paint(Graphics g) {

g.setColor(Color.blue);

g.drawOval(10, 10, 75, 50);

g.fillOval(100, 10, 50, 50);

}

void drawOval(int top, int left, int width, int height)

void fillOval(int top, int left, int width, int height)

• ellipse is drawn within a bounding rectangle specified by top,left , width

and height.

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

 Drawing Arcs1. void drawArc(int top, int left, int width, int height,

int startAngle, int sweepAngle)

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

int startAngle, int sweepAngle)

arc is bounded by the rectangle specified by top, left , width

and height.

The arc is drawn from startAngle through the angular

distance

specified by sweepAngle.

 Drawing Arcs

public void paint(Graphics g)

{

g.setColor(Color.orange);

g.drawArc(10, 40, 70, 70, 0, 75);

g.fillArc(100, 40, 70, 70, 0, 75);

}

Drawing Polygons

public void paint(Graphics g) { g.setColor(Color.green);

int xs[] = {161,161,185,209,185,161};

int ys[] = {310,334,358,334,310,310};

g.fillPolygon(xs,ys,6); }

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

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

Font class

Font(String fontName, int fontStyle, int pointSize)

 

fontStyl: Font.PLAIN, Font.BOLD, and Font.ITALIC.

To combine styles: Font.BOLD | Font.ITALIC

void setFont(Font fontObj)

Font class

public void paint(Graphics g)

{

g.setColor(Color.blue);

Font f = new Font(“TimesRoman”,Font.BOLD,20);

g.setFont(f);

g.drawString(“Hello World”, 50,50);

}

 

 

27

Using AWT Components Component

CanvasScrollbarButtonCheckboxLabelListChoiceTextComponent

TextArea TextField

Component– Container

• Panel

• Window– Dialog

» FileDialog

– Frame

MenuComponent– MenuItem

• Menu

Using AWT Components

Component add(Component compObj)

void remove(Component obj)

Labels

Label( )

Label(String str)

void setText(String str)

String getText( )

Labels

public void init()

{

Label one = new Label("One");

Label two = new Label("Two");

Label three = new Label("Three");

add(one);

add(two);

add(three);

}

Buttons

Button( )

Button(String str)

void setLabel(String str)

String getLabel( )

31

32

Buttonspublic void init()

{

Button yes = new Button("Yes");

Button no = new Button("No");

Button maybe = new Button("Undecided");

add(yes);

add(no);

add(maybe);

}

Buttons : Event Handlingimport java.awt.*;

import java.awt.event.*;

import java.applet.*;

/*

<applet code="ButtonDemo" width=250 height=150>

</applet>

*/

public class ButtonDemo extends Applet implements ActionListener

{

String msg = "";

Button yes, no, maybe;

Buttons : Event Handling public void init()

{

yes = new Button("Yes");

no = new Button("No");

maybe = new Button("Undecided");

add(yes);

add(no);

add(maybe);

yes.addActionListener(this);

no.addActionListener(this);

maybe.addActionListener(this);

}

Buttons : Event Handling

public void actionPerformed(ActionEvent ae)

{

msg = ae.getActionCommand();

repaint();

}

public void paint(Graphics g)

{

g.drawString("Pressed: "+msg, 6, 100);

}

}

Buttons : Event Handling

Checkboxes Checkbox( )

Checkbox(String str)

Checkbox(String str, boolean on)

Checkbox(String str, CheckboxGroup cbGroup, boolean on)

boolean getState( )

void setState(boolean on)

String getLabel( )

void setLabel(String str)

Checkboxes: Event Handlingpublic class CheckboxDemo extends Applet implements ItemListener {

String msg = "";

Checkbox c, cpp, java;

public void init()

{

c = new Checkbox("C", null, true);

cpp = new Checkbox("C++");

java = new Checkbox("JAVA");

add(c);

add(cpp);

add(java);

Checkboxes: Event Handling

c.addItemListener(this);

cpp.addItemListener(this);

java.addItemListener(this);

}

public void itemStateChanged(ItemEvent ie)

{

repaint();

}

Checkboxes: Event Handling

public void paint(Graphics g)

{

msg = c.getLabel()+ " : " + c.getState();

g.drawString(msg, 6, 100);

msg = cpp.getLabel()+ " : " + cpp.getState();

g.drawString(msg, 6, 120);

msg = java.getLabel()+ " : " + java.getState();

g.drawString(msg, 6, 140);

}

}

Checkboxes: Event Handling

CheckboxGroup

Checkbox getSelectedCheckbox( ) void setSelectedCheckbox(Checkbox which)

43

CheckboxGrouppublic class CBGroup extends Frame { public CBGroup(){

CheckboxGroup cbg = new CheckboxGroup();Checkbox cb1 = new Checkbox(“C”, cbg,false);Checkbox cb2 = new Checkbox(“JAVA”, cbg, true);add(cb1);add(cb2);add(cb3);

}…}

44

Choices

1. void add(String name) : To add a selection to the list

2. String getSelectedItem( )

3. int getSelectedIndex( )

45

Choicespublic class ColorChoice extends Applet implements ItemListener { Choice c1; Color color;

public void init() { c1 = new Choice(); c1.addItem("Red"); c1.addItem("Green"); c1.addItem("Blue"); c1.addItemListener(this); add(c1); }

46

Choices public void itemStateChanged(ItemEvent ie) { if(c1.getSelectedItem().equals("Red")) color = Color.red; else if(c1.getSelectedItem().equals("Green")) color = Color.green; else color = Color.blue; repaint(); } public void paint(Graphics g) { setBackground(color); }}

Lists List( )

List(int numRows)

List(int numRows, boolean multipleSelect)

void add(String name)

void add(String name, int index)

String getSelectedItem( )

int getSelectedIndex( )

Lists

public void init() {

List list = new List();

list.add("Hydrogen");

list.add("Helium");

list.add("Carbon");

list.add("Oxygen");

add(list);

}

TextField

TextField( )

TextField(int numChars)

TextField(String str)

TextField(String str, int numChars)

String getSelectedText( )

TextArea

TextArea( )

TextArea(int numLines, int numChars)

TextArea(String str)

TextArea(String str, int numLines, int numChars)

void append(String str)

MenuBar, Menu, & MenuItem

Menu bar contains one or more Menu objects.

Each Menu object contains a list of MenuItem objects.

Each MenuItem object represents something that can be

selected by the user.

MenuBar, Menu, & MenuItemMenuBar mb = new MenuBar();

setMenuBar(mb);

// Create menu A

Menu a = new Menu("A");

mb.add(a);

MenuItem a1 = new MenuItem("A1");

MenuItem a2 = new MenuItem("A2");

MenuItem a3 = new MenuItem("A3");

a.add(a1);

a.add(a2);

a.add(a3);

MenuBar, Menu, & MenuItem// Create menu B

Menu b = new Menu("B");

mb.add(b);

MenuItem b1 = new MenuItem("B1");

MenuItem b2 = new MenuItem("B2");

b.add(b1);

b.add(b2);

MenuBar, Menu, & MenuItem

// Create sub-menu for B3

Menu b3 = new Menu("B3");

b.add(b3);

MenuItem b31 = new MenuItem("B31");

MenuItem b32 = new MenuItem("B32");

b3.add(b31);

b3.add(b32);

55

Arranging components

Every Container has a layout manager

The default layout for a Panel is FlowLayout

An Applet is a Panel therefore, the default layout for a Applet

is FlowLayout

The layout manager is set by the setLayout( ) method.

void setLayout(LayoutManager layoutObj)

Layout of Components

FlowLayout– left to right & top

down

BorderLayout – north, south, west, east

& center

CardLayout– stack of panels

GridLayout– tabular form

– rows & columns

57

FlowLayout

Use add(component); to add to a component when using

a FlowLayout

Components are added left-to-right

If no room, a new row is started

FlowLayout is convenient but often ugly

58

FlowLayout1. FlowLayout( )

the default layout, which centers components and leaves five pixels of space between each component.

2. FlowLayout(int how) specify how each line is aligned. Valid values for how are as follows:

1. FlowLayout.LEFT

2. FlowLayout.CENTER

3. FlowLayout.RIGHT

3. FlowLayout(int how, int horz, int vert) horz and vert the horizontal and vertical space left between

components

59

FlowLayout

import java.awt.*;import java.applet.*;

public class FlowLayoutExample extends Applet { public void init () { setLayout (new FlowLayout ()); add (new Button ("One")); add (new Button ("Two")); add (new Button ("Three")); add (new Button ("Four")); add (new Button ("Five")); add (new Button ("Six")); }}

BorderLayout BorderLayout( ) BorderLayout(int horz, int vert)

BorderLayout defines the following constants that specify the regions:

1. BorderLayout.CENTER

2. BorderLayout.SOUTH

3. BorderLayout.EAST

4. BorderLayout.WEST

5. BorderLayout.NORTH

61

BorderLayout At most five components can be added

void add(Component compObj, Object region)

If you want more components, add a Panel, then add components to it.

add (new Button("NORTH"), BorderLayout.NORTH);

62

BorderLayout

public void init() { setLayout (new BorderLayout ()); add (new Button ("NORTH"), BorderLayout.NORTH); add (new Button ("SOUTH"), BorderLayout.SOUTH); add (new Button ("EAST"), BorderLayout.EAST); add (new Button ("WEST"), BorderLayout.WEST); add (new Button ("CENTER"), BorderLayout.CENTER);}

63

BorderLayoutimport java.awt.*;import java.applet.*;

public class BorderLayoutExample extends Applet { public void init () { setLayout (new BorderLayout()); add(new Button("One"), BorderLayout.NORTH); add(new Button("Two"), BorderLayout.WEST); add(new Button("Three"), BorderLayout.CENTER); add(new Button("Four"), BorderLayout.EAST); add(new Button("Five"), BorderLayout.SOUTH); add(new Button("Six"), BorderLayout.SOUTH); }}

64

Using a Panel

Panel p = new Panel(); add (p, BorderLayout.SOUTH); p.add (new Button ("Button 1")); p.add (new Button ("Button 2"));

65

GridLayout

The GridLayout manager divides the container up into a

given number of rows and columns:

GridLayout(int rows, int columns)

All sections of the grid are equally sized and as large as

possible

66

GridLayoutimport java.awt.*;

import java.applet.*;

public class GridLayoutExample extends Applet {

public void init () {

setLayout(new GridLayout(2, 3));

add(new Button("One"));

add(new Button("Two"));

add(new Button("Three"));

add(new Button("Four"));

add(new Button("Five"));

}

}

CardLayout

The CardLayout class can store several different layouts.

Each layout can be thought of as being on a separate index card

in a deck that can be shuffled so that any card is on top at a given

time.

Useful for user interfaces that can be dynamically enabled and

disabled upon user input.

User can keep other layouts hidden, ready to be activated when

needed.

CardLayout

CardLayout( )

CardLayout(int horz, int vert)

CardLayout : How to Use?

The cards are typically held in an object of type Panel.

The cards that form the deck are also typically objects of

type Panel.

This panel must have CardLayout selected as its layout

manager.

Thus, Create a panel that contains the deck and a panel for

each card in the deck.

CardLayout : How to Use?

Next, add components to the appropriate panel toform each card.

Add these panels to the Deck panel for which CardLayout is the

layout manager.

Finally, add Deck panel to the window.

Provide some way for the user to select between cards, common

approach is to include one push button for each card in the deck.

CardLayout: Example

CardLayout: Examplepublic class CardLayoutDemo extends Applet

implements ActionListener {

Checkbox Win98, winNT, solaris, mac;

Panel osCards;

CardLayout cardLO;

Button Win, Other;

public void init() {

Win = new Button("Windows");

Other = new Button("Other");

add(Win);

add(Other);

CardLayout: Example

cardLO = new CardLayout();

osCards = new Panel();

osCards.setLayout(cardLO); // set Deck panel layout to card layout

Win98 = new Checkbox("Windows 98", null, true);

winNT = new Checkbox("Windows NT/2000");

solaris = new Checkbox("Solaris");

mac = new Checkbox("MacOS");

// add Windows check boxes to a card panel

Panel winPan = new Panel();

winPan.add(Win98);

winPan.add(winNT);

CardLayout: Example // Add other OS check boxes to a card panel

Panel otherPan = new Panel();

otherPan.add(solaris);

otherPan.add(mac);

// add panels to card deck panel

osCards.add(winPan, "Windows");

osCards.add(otherPan, "Other");

// add cards to main applet panel

add(osCards);

// register to receive action events

Win.addActionListener(this);

Other.addActionListener(this);

}

CardLayout: Example

public void actionPerformed(ActionEvent ae)

{

if(ae.getSource() == Win)

cardLO.show(osCards, "Windows");

else

cardLO.show(osCards, "Other");

}

}