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Java Programming

Day-

Outline

• Few more GUI-Components

 Check Boxes  Radio Buttons  Choices

• Containers

 Panel  Frame

• More Layout Managers

 Grid Layout  Border Layout  Null Layout

• GUI-Based Application Development

Radio Buttons

• A special case of check box buttons

 The Checkbox are treated as radio button when using some button group

• CheckBoxgroup

 Used for grouping the checkboxes  Constructors  CheckboxGroup()  Important methods  public Checkbox getSelectedCheckbox()  public void setSelectedCheckbox(Checkbox object)

• Creating Radio buttons

 Create instance of a CheckboxGroup class  Create two or more check boxes using following constructor  public Checkbox(String label,boolean initialstate,CheckboxGroup)

radio buttons..

import java.awt.*;

import java.applet.*;

public class TestApplet extends Applet{

CheckboxGroup chgroup=new CheckboxGroup(); Checkbox chbox1=new Checkbox(“Left”,false,chgroup); Checkbox chbox2=new Checkbox(“Right”,false,chgroup);

public void init(){ add(chbox1) add(chbox2) } }

choices..

choices cont..

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

public class TestApplet2 extends Applet{

Choice countries=new Choice();

public void init(){ countries.addItem(“Pakistan”); countries.addItem(“Iran”); countries.addItem(“China”); add(countries) } }

containers cont..

• AWT Containers

 Panel  Frames  Dialog  ScrollPane

• Extensions of Containers are also containers for example

 public class myApplet extends Applet{}  public class myFrame extends Fram{}

Panels

• A panel usually have no GUI representation

 Can have different back ground color

• It is used to organized components
• Used on other containers so that more than one layouts can be used
• Constructors

 Panel()  Panel( LayoutManager initialLayout )

• Important Methods

 Refer to slide 9 Containers

• Example: Multipanel Applet

multiple panels cont..

iImport java.awt.; import java.applet.;

public class Applet2 extends Applet {

Panel p1; Panel p2;

public Applet2(){

public void init() { p1=new Panel(); p2=new Panel(new GridLayout(3,2,5,5));

for(int a=1;a<6;a++) p1.add(new Button("Button"+a));

for(int a=6;a<12;a++) p2.add(new Button("Button"+a));

p1.setBackground(Color.red); p2.setBackground(Color.blue); add(p1); add(p2); }}

Frames

• Well defined GUI
• Enable you to create separate windows

 Can develop stand alone applications (no need of browser)  Allow development of may window applications  Can be displayed or hide dynamically (can use button to open a new frame)  Provides a rich set of cursors e.g. busy,resize,crosshair etc

• Constructors

 public Frame()  public Frame(String frameTitle)

• Important methods

 void resize(int height, int width)  void show()  void hide()  void dispose()  void setTitle(), String getTitle()  setCursot( )

Displaying and hiding a Farme

Frame example

Import java.wt.; import java.applet.;

public class FrameApplet extends Applet {

Frame f=new Frame("First Frame"); Button showFrame=new Button("Show Frame"); Button hideFrame=new Button("Hide Frame"); Button closeFrame=new Button("Close Frame");

public Applet2(){ }

public void init(){

f.setSize(300,300);

add(showFrame); add(hideFrame); add(closeFrame);

} //end of init method

public boolean action(Event e,Object obj){ String s;

//getting the label of the button clicked s=(String)obj;

if(s=="Show Frame") f.show();

if(s=="Hide Frame") f.hide();

if(s=="Close Frame") f.dispose();

return true;

} //end of action method

} // end of class

grid layout..

import java.awt.*l;

import java.applet.*;

public class Applet2 extends Applet {

public void init(){ GridLayout grid=new GridLayout(2,2,5,5); setLayout(grid);

for(int a=1;a<5;a++) add(new Button("Button"+a));

} //end of init method

} //end of class

grid layout

import java.awt.l; import java.applet.;

public class Applet2 extends Applet {

public void init(){ GridLayout grid=new GridLayout(2,2); setLayout(grid);

for(int a=1;a<5;a++) add(new Button("Button"+a));

grid.setVgap(5); grid.setHgap(5);

} //end of init method

} //end of class