Online Software Educational Training - IT Tutorials - Online Education Training for Computer Software

Home

JAVA APPLET

Controlling Scroll Bars

To process scroll bar events, you need to implement the AdjustmentListener interface. Each time a user interacts with a scroll bar, an AdjustMentEvent object is generated. Its getAdjustmentType() method can be used to determine the type of the event

Adjustment Event Name	Event
BLOCK_DECREMENT	A page-down event has been generated
BLOCK_INCREMENT	A page-up event has been generated
TRACK	An absolute tracking event has been generated
UNIT_DECREMENT	The line-down button in a scroll bar has been pressed
UNIT_INCREMENT	The line-up button in a scroll bar has been pressed

An example to handle scrollbars event

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class scrollhand extends Applet implements ItemListener,AdjustmentListener
{
CheckboxGroup chkgroup;
Checkbox chknet,chktv,radmale,radfemale;
Scrollbar scrage;
TextField txtsex;
TextField txttv;
TextField txtnet;
TextField txtage;

public void init()
{
chkgroup = new CheckboxGroup();
chknet = new Checkbox("NET");
chktv = new Checkbox("TV");
radmale = new Checkbox("Male",true,chkgroup);
radfemale = new Checkbox("Female",false,chkgroup);
scrage = new Scrollbar(Scrollbar.HORIZONTAL,0,5,0,100);
txtage = new TextField(10);
txttv = new TextField(10);
txtnet = new TextField(10);
txtsex = new TextField(10);
add(chknet);
chknet.addItemListener(this);
add(txtnet);
add(chktv);
chktv.addItemListener(this);
add(txttv);
add(radmale);
radmale.addItemListener(this);
add(radfemale);
radfemale.addItemListener(this);
add(txtsex);
add(txtage);
add(scrage);
scrage.addAdjustmentListener(this);
}
public void itemStateChanged(ItemEvent ie)
{
if(ie.getItemSelectable()==chknet)
{
txtnet.setText("Internet");
}
if(chknet.getState()==false)
{
txtnet.setText(" ");
}

if(ie.getItemSelectable()==chktv)
{
txttv.setText("TV");
}
if(chktv.getState()==false)
{
txttv.setText(" ");
}
if(ie.getItemSelectable()==radmale)
{
txtsex.setText("Male");
}
if(ie.getItemSelectable()==radfemale)
{
txtsex.setText("Female");
}
}
public void adjustmentValueChanged(AdjustmentEvent se)
{
if(se.getAdjustable()==scrage)
{
scrage.setValue(scrage.getValue());
txtage.setText(String.valueOf(scrage.getValue()));
}
}
}


Previous		Next