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Java Applet Basics (2)
The Body Mass Index Calculator
The Applet Skeleton
import java.applet.*;import java.awt.*;
public class BodyMassApplet extends Applet{}
The HTML Page
<HTML><APPLET CODE = “XXXX.class" WIDTH=XXX HEIGHT = XXX></APPLET></HTML>
Create the Skeleton Files
Control Components
• Label
• TextField
• Button
Add a Label Controlimport java.applet.*;import java.awt.*;
public class BodyMassApplet extends Applet{ Label myLabel = new Label(“XXXXXXXX”); public void init() { add(myLabel); }}
Member Variable
Add Labels into the Skeleton
Add a TextField Controlimport java.applet.*;import java.awt.*;
public class BodyMassApplet extends Applet{ TextField myTextField = new TextField(columns); public void init() { add(myTextField); }}
Add TextFields into the Skeleton
Add a Button Controlimport java.applet.*;import java.awt.*;
public class BodyMassApplet extends Applet{ Button myButton = new Button(“Text on the Button”); public void init() { add(myButton); }}
Add Buttons into the Skeleton
Handle Action Eventsimport java.awt.event.*;
public class BodyMassApplet extends Applet implements ActionListener{ Button myButton = new Button(“my button”); public void init() { add(myButton); myButton.addActionListener(this); }
public void actionPerformed(ActionEvent e) { //handle the event here }}
Add the Event Handler
Display Text on a Label Control
• Syntax: myLabel.setText(“the text shown on the label control”);
Read Text from a TextField
• Syntax: myTextField.getText();
• E.g.String input;
input = myTextField.getText();
Read Inputs From all TextFields
Math.round(dbl)
• Rounds a real number into the nearest integer
• Syntax: integer = Math.round(dbl)• Example:
double dblIndex;int intIndex;intIndex = Math.round(dblIndex);
• Question: what’s the difference between Math.round(dbl) and (int)dbl?
Round the Body Index
