Brain.Error();

Question

hi,
i'm afraid I have a really stupid question, which I can't find in the books i've bought of by searching the net. I've only just started Java, well programming in general so I'm guessing that the reason I can't find the answer is that is incredibly obvious.
I am building an ImageJ plugin to analyse my research. To do the analysis currently I take an 8 bit XY greyscale image, crop it, save it in one format, export it to a mac program, perform one function, save it a new format, open it in a windows program, run a few functions, save a text file, open it in excel, perform a function and finally open it again in imageJ. All of which is a pain and none of which is anything more than a simple mathematical function. Hence why I'm on a crash course in Java (although, I do think it enjoyable and it certainly beats my work).
Enough prevarication: time for the stupid.
I have written some classes which do the first analysis on my data (I nick it from ImageJ as a float[][] ). I have also made some GUIs as I need to get information on how to process the image and added listeners/actions. I can open the GUI from the 'main' class, by calling for a 'new' GUI class but after is has opened the GUI the 'main' class carries on running and doesn't wait for me to put the data in.
Which I guess was fairly obvious as it has run the code.
I can think of ways to bodge this:
1) set an 'for' loop that only stops when the ok is hit.
2) put the GUI in a thread of its own and use wait/notify.
3) set a timer function to check every 5 seconds if ok has been hit.
but I think I've probably got something really basic wrong. How do you integrate a GUI into your main thread if you need to wait for the results of the user input?
ps. the books I have seem really good at explaining each individual thing, but not so much how the whole thing is patched together. Any suggestions for alternatives that do that bit well would be great. Or even a link to examples of how I should be building the classes together, rather than an individual class.
pps. I know my 'main' isn't really a 'main' as I'm writing a plug in to ImageJ, rather than an application, but for the purposes of testing I use one of the class' as a main.
thanks!!

Answer 1

puzzlebobble wrote:
1) set an 'for' loop that only stops when the ok is hit.
2) put the GUI in a thread of its own and use wait/notify.
3) set a timer function to check every 5 seconds if ok has been hit. 1) As mention a simple button with an action (listener) is enough. AWT/Swing is an event based GUI meaning you can specify a piece of code to respond to an event. In this case:
JButton button = new JButton(new AbstractAction("OK") {
  public void actionPerformed(ActionEvent e) {
    // code called by Swing when the button is pressed
    // or clicked or trigger by shortcut key, etc
}2) The GUI already runs on it own thread called the EDT for Event Dispatch Thread. This thread will automatically terminate when all frames / dialogs are disposed. Your Java program terminates when all non-deamon threads are terminate or you call System.exit() somewhere.
3) Again this is done in the action listener, for example:
package test;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
public class TestDemo {
    public static void main(String[] args) {
        // get it from your ImageJ program
        float[][] imageData = null;
        TestDemo test = new TestDemo(imageData);
        test.showGUI();
        // main thread end, but program doesn't
        // because the EDT is still alive
    private final float[][] imageData;
    public TestDemo(float[][] imageData) {
        this.imageData = imageData;
    private void doProcessImage() {
        // do something with imageData
    private void showGUI() {
        // make sure the GUI is created on the EDT
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                final JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                frame.getContentPane().add(new JButton(
                  new AbstractAction("Process image and exit") {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        // note that this will block the GUI from repainting
                        // since we are on the EDT here
                        // look into SwingWorker on how to do it
                        // on a background thread
                        doProcessImage();
                        // stop the program
                        frame.dispose();
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
}