Friday, September 10, 2010

Throbber for Java

Have you ever wanted to do a please wait for a Java application?  Did you want a little spinny logo to animate while they waited?

As Professor Fransworth would say, "Good news everybody!"

Let's start out with a preview of the graphic that I'll be using.
Spinner Image

Now this is actually nine different images, I've just haphazardly put them into one image here so you can see what I'm doing. I made these images in about five minutes using Inkscape but you can use whatever. You do need to export the images into a format that Java understands, I usually default to png.

I've named the rotor images rotor1.png through rotor8.png and the final image (the check mark) as rotord.png. The check mark is optional and the code below is clear cut enough to be able to remove the check mark. At any rate I'm placing the images into a package called sample.img

Now here's what we need to do. We need to create a custom JFrame (of Swing fame) that will be our spinning logo. IF you are using Netbeans, DO NOT USE NEW JFrame CLASS. If you are using Netbeans select Create New Java class. This gives you a no frills attached blank document with a shell of a Java class to begin with. If you do use the JFrame class in Netbeans it adds an XML document behind the scenes that allows you to use the GUI-fied editor, which will only serve to get in your way, in this case at least.

So let's build our customer JFrame.

package sample.ui;

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Toolkit;
import javax.swing.JPanel;

* @author John Doe
public class RotorPanel extends JPanel {

private Image[] rotorImg;
private Image rotorComplete;
private boolean done;
private int current = 0;
private final int max_image = 7;

public RotorPanel() {
this.rotorImg = new Image[max_image+1];
for(int i=0; i<max_image+1; i++)
this.rotorImg[i] = Toolkit.getDefaultToolkit().createImage(getClass().getResource("/sample/img/rotor" + (i+1) + ".png"));
this.rotorComplete = Toolkit.getDefaultToolkit().createImage(getClass().getResource("/sample/img/rotord.png"));
this.done = false;

public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.drawImage(this.rotorImg[this.current], 0, 0, this);
g2.drawImage(this.rotorComplete, 0, 0, this);

public void increment() {
this.current = 0;

public void setDone(boolean done) {
this.done = done;

public boolean isDone() {
return done;


As you can see it is pretty straight forward in approach. The constructor loads the images into an array and sets the done flag to false. The increment method moves us through the images. We've overridden the paint method to draw the image.

Now let's use our JPanel. If you are using Netbeans, go ahead an use the JDialog template, that's what I'll be covering here. In Netbeans add a standard JPanel from the palette and then in the properties window click on the code tab. In the custom creation code add "new RotorPanel()". This replaces the new javax.swing.JPanel that is found in the protected area (which is controlled by the XML file behind the scenes) with this code, which is what we want.

Next in the constructor code right after the initComponents call add the following code.

this.t = new Thread() {
public void run() {
RotorPanel p = (RotorPanel) PleaseWaitDialog.this.jPanel1;
while(!p.isDone()) {
try { Thread.sleep(65); }
catch (InterruptedException ex) {}

This creates a thread that will call the increment method to rotate the image and then the repaint method which will update our image. The Thread.sleep(65) call is to sleep 65 ms and then repaint the image, this roughly controls the speed of the animation. Notice that the loop checks the done flag. When you are done and want this thread to die, simply call ((RotorPanel) this.jPanel1).setDone(true);

In 65 ms or less the thread will die because we exit the while loop and the run method of the thread returns. Of course this doesn't mean that you need to stop displaying something, just that you will no longer be rotating the image, hence the check mark image. The actual image doesn't go away until you kill the JDialog.

Pretty simple animation. If you want better control over animation and what-not, I would suggest looking into the timing framework that is located at This framework will allow you have a better control over animating something. However, this is a simple little snippit of code that you can use for simple animations.


Powered by ScribeFire.

Thursday, September 02, 2010

Websockets are cool!

I won't go into a lot of detail today, but I tried out serving up some PHP with websockets enabled. Websockets are way cool... I won't go to the end of saying, "OMG!! This will revolutionize the Internetz!!11!!" But I must say that this is will be a big game changer in terms of Internet applications. Combinded with HTML5, web sockets will be the new preferred method for messaging between server and client as opposed to AJAX and similar push technologies.

The best part of Web Sockets is the simple approach they take to passing messages between client and server combined with just how powerful they truly are. If you have ever used callback handlers then web sockets will be a very easy topic for you. You simply register what the web page should be listening for. You web page emits messages to the server and the server emits messages back. On each message received the web page checks what has been registered and the action associated with it.

This has the upshoot of being a write the handler and forget it approach which usually is a disservice to an API, but found that it serves JavaScript quite well.

The only problem will be getting frameworks to start jumping ship from AJAX to Websockets. XML can still be passed using Websockets and most likely that's the way most people will go, but any kind of data can be sent and that includes binary data which tends to be faster and more compact than XML. Most AJAX platforms already present their API as a series of callbacks for people to use in their web pages so Webdevs are already in the right thinking for Websockets.

Another barrier to websockets is the lack of servers that have support for it. The PHP version is still in beta and Apache feels that third parties will fill in the void for them. Jetty (Java server) and a few third party SilverLight stacks provide production grade Websockets at the current moment. The final barrier is the fact that the Websocket standard hasn't been approved as final by IETF, in fact it's still draft. So everything in the standard could change in a moments notice. That alone could keep vendors from adding it to their server. Browser support is Chrome, Opera, and Firefox 4. Basically all the next gen browsers, except our favorite browser to hate IE (including the latest IE 9 build).

All that said Websockets provide a new method of communicating with clients that out matches all currently existing technology and at some point full duplex communications is going to come to all browser and servers, be it websockets or something else down the road. Most likely Websockets will be the winner the biggest question will be in what shape as the standard could change as we all wait for it to become a final standard.