Applet communication (talk to each other)
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<applet code=Sender.class width=450 height=200
name="buddy">
<param name="receiverName" value="old pal">
</applet>
<p>
<applet code=Receiver.class width=450 height=35>
<param name="name" value="old pal">
</applet>
<applet code=GetApplets.class width=400 height=150>
</applet>
/*
* 1.1 version.
*/
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Enumeration;
public class Sender extends Applet
implements ActionListener {
private String myName;
private TextField nameField;
private TextArea status;
private String newline;
public void init() {
GridBagLayout gridBag = new GridBagLayout();
GridBagConstraints c = new GridBagConstraints();
setLayout(gridBag);
Label receiverLabel = new Label("Receiver name:",
Label.RIGHT);
gridBag.setConstraints(receiverLabel, c);
add(receiverLabel);
nameField = new TextField(getParameter("RECEIVERNAME"),
10);
c.fill = GridBagConstraints.HORIZONTAL;
gridBag.setConstraints(nameField, c);
add(nameField);
nameField.addActionListener(this);
Button button = new Button("Send message");
c.gridwidth = GridBagConstraints.REMAINDER; //end row
c.anchor = GridBagConstraints.WEST; //stick to the
//text field
c.fill = GridBagConstraints.NONE; //keep the button
//small
gridBag.setConstraints(button, c);
add(button);
button.addActionListener(this);
status = new TextArea(5, 60);
status.setEditable(false);
c.anchor = GridBagConstraints.CENTER; //reset to the default
c.fill = GridBagConstraints.BOTH; //make this big
c.weightx = 1.0;
c.weighty = 1.0;
gridBag.setConstraints(status, c);
add(status);
myName = getParameter("NAME");
Label senderLabel = new Label("(My name is " + myName + ".)",
Label.CENTER);
c.weightx = 0.0;
c.weighty = 0.0;
gridBag.setConstraints(senderLabel, c);
add(senderLabel);
newline = System.getProperty("line.separator");
}
public void actionPerformed(ActionEvent event) {
Applet receiver = null;
String receiverName = nameField.getText(); //Get name to
//search for.
receiver = getAppletContext().getApplet(receiverName);
if (receiver != null) {
//Use the instanceof operator to make sure the applet
//we found is a Receiver object.
if (!(receiver instanceof Receiver)) {
status.append("Found applet named "
+ receiverName + ", "
+ "but it's not a Receiver object."
+ newline);
} else {
status.append("Found applet named "
+ receiverName + newline
+ " Sending message to it."
+ newline);
//Cast the receiver to be a Receiver object
//(instead of just an Applet object) so that the
//compiler will let us call a Receiver method.
((Receiver)receiver).processRequestFrom(myName);
}
} else {
status.append("Couldn't find any applet named "
+ receiverName + "." + newline);
}
}
public Insets getInsets() {
return new Insets(3,3,3,3);
}
public void paint(Graphics g) {
g.drawRect(0, 0,
getSize().width - 1, getSize().height - 1);
}
public String getAppletInfo() {
return "Sender by Kathy Walrath";
}
}
/*
* 1.1 version.
*/
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class Receiver extends Applet
implements ActionListener {
private final String waitingMessage =
"Waiting for a message... ";
private Label label = new Label(waitingMessage,
Label.RIGHT);
public void init() {
Button button = new Button("Clear");
add(label);
add(button);
button.addActionListener(this);
add(new Label("(My name is " + getParameter("name")
+ ".)",
Label.LEFT));
}
public void actionPerformed(ActionEvent event) {
label.setText(waitingMessage);
}
public void processRequestFrom(String senderName) {
label.setText("Received message from "
+ senderName + "!");
}
public void paint(Graphics g) {
g.drawRect(0, 0,
getSize().width - 1, getSize().height - 1);
}
public String getAppletInfo() {
return "Receiver (named " + getParameter("name") +
") by Kathy Walrath";
}
}
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