Java Astract Window Toolkit- II

 

JAVA ASTRACT WINDOW TOOLKIT- II

Layout  Managers

The AWT provides 4 basic layout managers:

vFlowLayout

vGridLayout

vBorderLayout

vCardLayout

FlowLayout

The FlowLayout class is the most basic of layout Using the flow layout,components are added to the panel one at a time ,row by row.

Constructor	Action
FlowLayout()	Constructs a new flow layout with left alignment,leaving a vertical and horizontal gap of 5 pixels.
FlowLayout(int align)	Constructs a new flow layout with the alignment,specified leaving a vertical and horizontal gap of 5 pixels.
FlowLayout(int align),constructs a new flow layout with the alignment specified,int vgap,int hgap)	constructs a new flow layout with the alignment specified,int vgap,int hgap)leaving a vertical and horizontal gap as specified

                                                 

Method	Action
getAlignment()	Gets the alignment for the layout
getHgap()	Gets the horizontal gapbetweencomponents
getVgap()	Gets the verticalgap betweencomponents
setAlignment(int align)	Sets the alignment for the specified layout
setHgap(int hgap)	Sets the horizontal gap for the specified layout
setVgap(int vgap)	Sets the vertical gap for the specified layout

  

Example

File name: FlowLayoutDemo.java

import java.applet.*;

import java.awt.*;

/*

<applet code="FlowLayoutDemo" width=300 height=200>

</applet>

*/

public class FlowLayoutDemo extends Applet

{

public void init()

{

setLayout(new FlowLayout(FlowLayout.CENTER,5,5));

for(int i=1;i<=10;i++)

{

add(new Button("BUTTON"+i));

}

}

}

Output

Grid Layout

The Grid Layout class lays out components in a way very similar to a spreadsheet-in rows and column.

The grid layout can be constructed using the constructors listed in the table below:

Constructor	Action
Gridlayout()	Creates a grid layout with a default of one columnpercomponent in a single row
Gridlayout(int rows,int cols)	Creates a grid layout with he specified rows&columns
Gridlayout(int rows,int cols,int hgap,int vgap)	Creates a grid layout with he specified rows&columns and specified horizontal and vertical gaps

 

Method	Action
getColumns()	Getsthenumber ofcolumns in corresponding layout
getRows()	Gets thenumber ofrows in corresponding layout
getHgap()	Gets thehorizontalgap for the in corresponding layout
getVgap()	Gets the verticalgap for the in corresponding layout
setColumns(int cols)	Sets the number of columns to the specified number in the corresponding layout
setHgap(int hgap)	Sets the horizontal gap to the value specified in the corresponding layout
setVgap(int vgap)	Sets the vertical gap to the value specified in the corresponding layout
setRows(int rows)	Sets the number of rows in the corresponding layout to the specified value

 

Example

File name: GridLayoutDemo.java

import java.awt.*;

import java.applet.*;

/*

<applet code="GridLayoutDemo" width=300 height=200>

</applet>

*/

public class GridLayoutDemo extends Applet{

static final int n=4;

public void init(){

setLayout(new GridLayout(n,n));

setFont(new Font("SansSerif",Font.BOLD,24));

for(int i=0;i<n;i++){

for(int j=0;j<n;j++){

int k=i*n+j;

if(k>0){

add(new Button(""+k));

}

}

}

}

}

 

Output

 

Border Layouts

Borders layouts behave differently from flow and grid layouts. When you add a component to a panel that uses a border layout, you indicate its placement as a geographic direction: north, south, east, west, and center.

Constructor	Action
BorderLayout()	Creates a new border layout with no gap between the components
BorderLayout(int hgap, int vgap)	Creates a border layout with the specified horizontal and vertical gap between components.

 The Various methods that can be used in conjunction with the border layout is given below:

Method	Action
getHgap()	Returns the horizontal gap between components
getVgap()	Returns the vertical gap between components
setHgap(int hgap)	Sets the horizontal gap between components to the value specified.

Border Layout

File name: BorderLayoutDemo.java

import java.awt.*;

import java.applet.*;

import java.util.*;

/*

<applet code="BorderLayoutDemo" width=400 height=200>

</applet>

*/

public class BorderLayoutDemo extends Applet{

public void init(){

setLayout(new BorderLayout());

add(new Button("This is across the top."),BorderLayout.NORTH);

add(new Label("The footer message might go here."),BorderLayout.SOUTH);

add(new Button("Right"),BorderLayout.EAST);

add(new Button("Left"),BorderLayout.WEST);

String msg="The reasonable man adapts"+"himself to the world;\n"+"the unreasonable one persist in"+"trying to adapt the world to himself.\n"+"Therefore all progress depends"+"On the unreasonable man.\n\n"+"             -George Bernard Shaw\n\n";

add(new TextArea(msg),BorderLayout.CENTER);

}

}

Output

Card Layouts

Card layouts are different from the other layouts. Unlike with the other three layouts, when you add components to a card layout,. they are not all displayed on the screen at once. Card  layouts are used to produce slide shows of components, one at a time.

Card Layout provides these two constructors:

Card Layout()

Card Layout (int horz, int vert)

The first form creates a default card layout. The second form allows you to specify the horizontal and vertical space left between components in horz and vert, respectively.

For example, here's how to create a card layout containing three cards:

setLayout(new Card layout());

Panel one = new Panel()

add("first",one);

Panel two = new Panel()

add ("second",two);

Panel three = new Panel()

add("third",three);

show (this,"second");

Your program activates a card by calling one of the following methods defined by Card Layout:

void first(Container deck)

void last(Container deck)

void next(Container deck)

void previous(Container deck)

void show(Container deck,String card Name)

Here, deck is a reference to the container (usually a panel)that holds the cards, and card Name is the name of a card

 Card Layout

File name: BorderText.java

import java.awt.*;

/*<applet code="BorderText" width=400 height=300>

</applet>

*/

public class BorderText extends java.applet.Applet{

public void init(){

setLayout(new BorderLayout(5,5));

add("South",new Button("Bottom of the Applet"));

add("North",new Button("Top of the Applet"));

add("East",new Button("Right"));

add("West",new Button("Left"));

add("Center",new TextArea("Appears at the centre"));

}

public Insets getInsets(){

return new Insets(20,20,10,10);

}

}

 

Output

 

Creating a Frame Window is an Applet

Insets

public Insets insets(){

return new Insets(10,10,10,10);

}

Panels

set Layout(new Grid Layout(1,2,10,10));

Panel panel1 = new Panel();

panel panel2 = new Panel();

add(panel1);

add (panel2);

File name:  Frame2.java

class Frame2 extends Frame

{

Frame2(String title)

{

super(title);

addWindowListener(new WindowAdapter()){

public void windowClosing(WindowEvent we){

dispose();

}

});

}

}

File name: FrameApplet.java

import java.applet.*;

import java.awt.*;

import java.awt.event.*;

/*

<applet code="FrameApplet" width=250 height=200>

</applet>

*/

public class FrameApplet extends Applet implements ActionListener

{

public void init(){

Button b=new Button("Create Frame");

b.addActionListener(this);

add(b);

}

public void actionPerformed(ActionEvent ae){

Frame2 f2=new Frame2("My new Window");

f2.show();

f2.setSize(300,300);

}

}

Output

 

Menus

File name:  MenuFrame.java

import java.awt.*;

import java.awt.event.*;

import java.applet.*;

//Create a subclass of Frame

class MenuFrame extends Frame

{

String msg ="";

CheckboxMenuItem debug,test;

MenuFrame(String title){

super(title);

// create menu bar and addd it to frame

MenuBar mbar = new MenuBar();

setMenuBar(mbar);

//create the menu items

Menu file = new Menu("File");

MenuItem item1,item2,item3,item4,item5;

file.add(item1=new MenuItem("New"));

file.add(item2=new MenuItem("Open"));

file.add(item3=new MenuItem("Close"));

file.add(item4=new MenuItem("-"));

file.add(item5=new MenuItem("Quit"));

mbar.add(file);

Menu edit = new Menu("Edit");

MenuItem item6,item7,item8,item9;

edit.add(item6= new MenuItem("Cut"));  

edit.add(item7= new MenuItem("Copy"));  

edit.add(item8= new MenuItem("Paste"));  

edit.add(item9= new MenuItem("-"));

Menu sub = new Menu("Special");

MenuItem item10,item11,item12;

sub.add(item10 = new MenuItem("First"));

sub.add(item11 = new MenuItem("Second"));

sub.add(item12 = new MenuItem("Third"));

edit.add(sub);

//these are checkable Menu items

debug = new CheckboxMenuItem("Debug");

edit.add(debug);

test = new CheckboxMenuItem("Testing");

edit.add(test);

mbar.add(edit);

//create an object to handle action and item events

MyMenuHandler handler = new MyMenuHandler(this);

//register  it to receive those events

item1.addActionListener(handler); 

item2.addActionListener(handler);  

item3.addActionListener(handler);  

item4.addActionListener(handler);  

item5.addActionListener(handler);  

item6.addActionListener(handler);  

item7.addActionListener(handler);  

item8.addActionListener(handler);  

item9.addActionListener(handler);  

item10.addActionListener(handler);  

item11.addActionListener(handler);  

item12.addActionListener(handler);  

debug.addItemListener(handler);

test.addItemListener(handler);

//create an object to handle window events

MyWindowAdapter adapter = new MyWindowAdapter(this);

//register it to receive those events

addWindowListener(adapter);

}

public void paint(Graphics g){

g.drawString(msg,10,220);

if(debug.getState())

g.drawString("Debug is on.",10,220);

else

g.drawString("Debug is off.",10,220);

if(test.getState())

g.drawString("Testing is on.",10,240);

else

g.drawString("Testing is off.",10,240);

}

}

File name:  MyWindowAdapter.java

import java.awt.*;

import java.awt.event.*;

import java.applet.*;

class MyWindowAdapter extends WindowAdapter{

MenuFrame menuFrame;

public MyWindowAdapter(MenuFrame menuFrame){

this.menuFrame=menuFrame;

}

public void windowClosing(WindowEvent we){

menuFrame.setVisible(false);

}

}

File name:  MyMenuHandler.java

import java.awt.*;

import java.awt.event.*;

import java.applet.*;

class MyMenuHandler implements ActionListener, ItemListener{

MenuFrame menuFrame;

 public MyMenuHandler(MenuFrame menuFrame){

 this.menuFrame = menuFrame;

}

 // Handle action events

 public void actionPerformed(ActionEvent ae){

String msg = "You selected";

String arg= (String)ae.getActionCommand();

if(arg.equals("New"))

msg+="New.";

else if(arg.equals("Open"))

msg+="open.";

else if(arg.equals("Close"))

msg+="Close.";

else if(arg.equals("Quit"))

msg+="Quit.";

else if(arg.equals("Edit"))

msg+="Edit.";

else if(arg.equals("Cut"))

 msg+="Cut.";

else if(arg.equals("Copy"))

msg+="Copy.";

else if(arg.equals("Paste"))

msg+="Paste.";

else if(arg.equals("First"))

msg+="First.";

else if(arg.equals("Second"))

msg+="Second.";        

else if(arg.equals("Third"))

msg+="Third.";        

else if(arg.equals("Debug"))

msg+="Debug.";

else if(arg.equals("Testing"))

msg+="Testing.";

menuFrame.msg = msg;

menuFrame.repaint();

}

 // Handle item events

public void itemStateChanged(ItemEvent ie){

menuFrame.repaint();

}

} 

File name :  MenuDemo.java

import java.awt.*;

import java.awt.event.*;

import java.applet.*;

/*

<applet code = "MenuDemo" width = 250 height=250>

</applet>

*/

public class MenuDemo extends Applet{

Frame f;

public void init(){

f=new MenuFrame("Menu Demo");

int width=Integer.parseInt(getParameter("width"));

int height=Integer.parseInt(getParameter("height"));

setSize(new Dimension(width,height));

f.setSize(width,height);

f.setVisible(true);

}

public void start(){

f.setVisible(true);

}

public void stop(){

f.setVisible(false);

}

}                                                                                    

Output

 

Dialog Boxes

File name:  MessageBox.java

import java.awt.*;

import java.awt.event.*;

class MessageBox extends Dialog{

MessageBox(Frame fm,String lab){

super(fm,"Message",true);

setLayout(new GridLayout(2,1,0,0));

Panel p1=new Panel();

Panel p2=new Panel();

Button b1,b2;

p1.setFont(new Font("TimesRoman",Font.BOLD,18));

p1.setLayout(new FlowLayout(FlowLayout.CENTER,20,15));

p2.setLayout(new FlowLayout(FlowLayout.CENTER,20,20));

p1.add(new Label(lab));

b1=new Button("ok");

b1.addActionListener(new B1());

p2.add(b1);

b2=new Button("cancel");

b2.addActionListener(new B1());

p1.add(b2);

add(p1);

add(p2);

setSize(350,125);

setTitle("Message Box");

addWindowListener(new WindowAdapter(){

public void windowClosing(WindowEvent w){

System.exit(0);

}

});

}

}

 

File name:  B1.java

import java.awt.*;

import java.awt.event.*;

class B1 implements ActionListener{

public void actionPerformed(ActionEvent e){

try{

Button ok=(Button)e.getSource();

String s=ok.getLabel();

if(s.equals("ok")||s.equals("cancel")){

//dispose();

System.exit(0);

}

}

catch(Exception n){}

}

}

File name:  MessageApplication.java

import java.awt.*;

import java.awt.event.*;

public class MessageApplication extends Frame{

boolean a;

MessageApplication(){

MessageBox mb=new MessageBox(this,"JAVA Alert: This is a Message Box");

mb.setLocation(200,200);

mb.setVisible(true);

a=false;

}

public static void main(String args[]){

MessageApplication fm=new MessageApplication();

System.out.println("Popping out Message Box");

fm.setVisible(true);

}

}

Output

 

File Dialogs

File name:  FileDialogDemo.java

import java.awt.*;

import java.awt.event.*;

/*

<applet code="FileDialogDemo" width=400 height=400>

</applet>

*/

class FileDialogDemo extends Frame implements ActionListener

{

Frame t;

Button b1;

Label l1;

FileDialogDemo()

{

t=new Frame("Sample Frame");

t.setLayout(new FlowLayout());

b1=new Button("Open");

l1=new Label("File selected:");

t.add(b1);

t.add(l1);

b1.addActionListener(this);

t.setSize(300,300);

t.setVisible(true);

}

public static void main(String args[])

{

FileDialogDemo fd=new FileDialogDemo();

}

public void actionPerformed(ActionEvent a){

FileDialog fd=new FileDialog(t,"File Dialog");

fd.setVisible(true);

l1.setText(l1.getText()+fd.getFile());

}

}

Output