Programming Tutorials

AWT-based applications with a User Interface Window in Java

By: Kamini Printer Friendly Format    

It is possible to create stand-alone AWT-based applications with a Window. To do this, simply create an instance of the window or windows you need inside main( ). For example, the following program creates a frame window that responds to mouse clicks and keystrokes:

// Create an AWT-based application.
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
// Create a frame window.
public class AppWindow extends Frame {
String keymsg = "";
String mousemsg = "";
int mouseX=30, mouseY=30;
public AppWindow() {
addKeyListener(new MyKeyAdapter(this));
addMouseListener(new MyMouseAdapter(this));
addWindowListener(new MyWindowAdapter());
}
public void paint(Graphics g) {
g.drawString(keymsg, 10, 40);
g.drawString(mousemsg, mouseX, mouseY);
}
// Create the window.
public static void main(String args[]) {
AppWindow appwin = new AppWindow();
appwin.setSize(new Dimension(300, 200));
appwin.setTitle("An AWT-Based Application");
appwin.setVisible(true);
}
}
class MyKeyAdapter extends KeyAdapter {
AppWindow appWindow;
public MyKeyAdapter(AppWindow appWindow) {
this.appWindow = appWindow;
}
public void keyTyped(KeyEvent ke) {
appWindow.keymsg += ke.getKeyChar();
appWindow.repaint();
};
}
class MyMouseAdapter extends MouseAdapter {
AppWindow appWindow;
public MyMouseAdapter(AppWindow appWindow) {
this.appWindow = appWindow;
}
public void mousePressed(MouseEvent me) {
appWindow.mouseX = me.getX();
appWindow.mouseY = me.getY();
appWindow.mousemsg = "Mouse Down at " + appWindow.mouseX +
", " + appWindow.mouseY;
appWindow.repaint();
}
}
class MyWindowAdapter extends WindowAdapter {
public void windowClosing(WindowEvent we) {
System.exit(0);
}
}

Sample output from this program is shown here:

Once created, a frame window takes on a life of its own. Notice that main() ends with the call to appwin.setVisible(true). However, the program keeps running until you close the window. In essence, when creating a windowed application, you will use main() to launch its top-level window. After that, your program will function as a GUI-based application, not like the console-based programs used earlier.

This tutorial is an extract from the "The Complete Reference Part 2 by Herbert Schildt".