information about awt components

1. AWT COMPONENTS

2. Text area
 Sometimes a single line of text input is not enough
for a given task so to solve this problem we use text
area.
 TextArea is a subclass of TextComponent.

3. Text area constructors
 TextArea( )
 TextArea(int numLines, int numChars)
 TextArea(String str)
 TextArea(String str, int numLines, int numChars)

4. Text area constructor
 TextArea(String str, int numLines, int numChars, int
sBars)
 sBars have following values
 SCROLLBARS_BOTH
 SCROLLBARS_NONE
 SCROLLBARS_HORIZONTAL_ONLY
SCROLLBARS_VERTICAL_ONLY

5. Textarea functions
 getText( )
 setText( ),
 getSelectedText( )
 select( )
 isEditable( )
 setEditable( )

6. Textarea functions
 void append(String str)
 void insert(String str, int index)
 void replaceRange(String str, int startIndex, int
endIndex)

7. // Demonstrate TextArea.
import java.awt.*;
import java.applet.*;
/*
<applet code="TextAreaDemo" width=300 height=250>
</applet>
*/
public class TextAreaDemo extends Applet
{
public void init() {
String val = "There are two ways of constructing " +
"a software design.n" +
"One way is to make it so simplen" +
"that there are obviously no deficiencies.n" +
"And the other way is to make it so complicatedn" +
TextArea text = new TextArea(val, 10, 30);
add(text);
}
}

8. Check boxes
 Checkboxes are created by Mycheckbox class.
 init( ) method creates instances of MyCheckbox and
adds these to the applet

9. /*
* <applet code=CheckboxDemo2 width=300 height=100>
* </applet>
*/
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class CheckboxDemo2 extends Applet
{
MyCheckbox myCheckbox1, myCheckbox2, myCheckbox3;
public void init() {
myCheckbox1 = new MyCheckbox("Item 1");
add(myCheckbox1);
myCheckbox2 = new MyCheckbox("Item 2");
add(myCheckbox2);
myCheckbox3 = new MyCheckbox("Item 3");
add(myCheckbox3);}
}

10. Check box group
 Group of checkboxes creates checkbox.
 For this checkboxGroup class is used.

11. public class CheckboxGroupDemo2 extends Applet
{
CheckboxGroup cbg;
MyCheckbox myCheckbox1, myCheckbox2, myCheckbox3;
public void init() {
cbg = new CheckboxGroup();
myCheckbox1 = new MyCheckbox("Item 1", cbg, true);
add(myCheckbox1);
myCheckbox2 = new MyCheckbox("Item 2", cbg, false);
add(myCheckbox2);
myCheckbox3 = new MyCheckbox("Item 3", cbg, false);
add(myCheckbox3);
}

12. Radio Button or Choice
 To choose one option between many choices radio
button is used.
 For making radio buttons Mychoice class is used.

13. /*
* <applet code=ChoiceDemo2 width=300 height=100>
* </applet>
*/
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class ChoiceDemo2 extends Applet {
MyChoice choice;
public void init() {
choice = new MyChoice();
choice.add("Red");
choice.add("Green");
choice.add("Blue");
add(choice);
}

14. lists
 For creating lists Mylist class is used.
/*
* <applet code=ListDemo2 width=300 height=100>
* </applet>
*/
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class ListDemo2 extends Applet {
MyList list;
public void init() {
list = new MyList();
list.add("Red");
list.add("Green");
list.add("Blue");
add(list);
}

15. Creating an image
 createImage( ) that is used to create Image objects.
 Image createImage(ImageProducer imgProd)
 Image createImage(int width, int height)

16. Loading an image
 use the getImage( ).
 Image getImage(URL url)
 Image getImage(URL url, String imageName)

17. Displaying an image
 For dispalying an image we use drawImage(),which
is a method of object class.
 boolean drawImage(Image imgObj, int left, int top,
ImageObserver imgOb)

18. /*
* <applet code="SimpleImageLoad" width=248 height=146>
* <param name="img" value="seattle.jpg">
* </applet>
*/
import java.awt.*;
import java.applet.*;
public class SimpleImageLoad extends Applet
{
Image img;
public void init() {
img = getImage(getDocumentBase(), getParameter("img"));
}
public void paint(Graphics g) {
g.drawImage(img, 0, 0, this);
}
}

19. Conclusion

20. THANKS