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

Create the Skeleton Files

Control Components Label TextField Button

Add a Label Control import 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 Control import 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 Control import 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 Events import 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