motaa motaa - 3 months ago 17
Java Question

Unexplainable behaviour of setProgress in SwingWorker

I did a quick and dirty implementation of SwingWorker to test the publish() and setProgress() methods. When I set the parameter for the setProgress() method like stated in the complete sourcecode below, everything works as expected.
However if I set the setProgress parameter like this:

setProgress((int) ((i/2000) * 100));

OR like this
setProgress((int) (i * (100/2000)));


The progressbar does not update since the propertyChange is not getting fired.

I seriously have no clue why this is since in my opinion I don't see anything mathematically wrong there...

Any ideas?

Thanks in advance!

Best regards

package test;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.util.LinkedList;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.SwingWorker;
import javax.swing.text.BadLocationException;
import javax.swing.text.StyledDocument;

public class ConsoleTest extends SwingWorker<Void, String>{

private JTextPane console;
private JProgressBar pb;

public ConsoleTest(JProgressBar pb, JTextPane out){

this.console = out;
this.pb = pb;
}

private static void createGUI(){

JFrame container = new JFrame();
container.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JTextPane console = new JTextPane();
JButton start = new JButton("start");
JButton reset = new JButton("reset");
JPanel btnpane = new JPanel();
btnpane.add(start);
btnpane.add(reset);
btnpane.add(new JCheckBox( "Click me to proof UI is responsive" ));
JProgressBar pb = new JProgressBar(0,100);
btnpane.add(pb);
container.add(btnpane, BorderLayout.SOUTH);

JScrollPane sp = new JScrollPane(console);
sp.setPreferredSize(new Dimension(800,800));
container.add(sp,BorderLayout.NORTH);

start.addActionListener(e -> { ConsoleTest test = new ConsoleTest(pb, console);
test.addPropertyChangeListener(evt -> { if ("progress".equals(evt.getPropertyName())) {
System.out.println("check");
test.getPG().setValue((int)evt.getNewValue());
}
});
test.execute();});
reset.addActionListener(e -> clear(console));
container.pack();
container.setVisible(true);


}

private static void clear(JTextPane console) {

console.setText("");
}



public JProgressBar getPG(){

return this.pb;
}

@Override
protected Void doInBackground() throws Exception {

LinkedList<Integer> list = new LinkedList<>();
for (int i = 0; i< 2000;i++){
list.add(i);
if(((i+1) % 5) == 0)
publish(Integer.toString(i+1));
setProgress((int) (i*100/2000));
Thread.sleep(1);
}
return null;
}

@Override
protected void process(List<String> chunks){

StyledDocument doc = this.console.getStyledDocument();
try {
for(String s: chunks)
doc.insertString(doc.getLength(),"- "+s+" elements added to the list\n", null);
} catch (BadLocationException e) {
e.printStackTrace();
}
}


@Override
protected void done() {

try {
System.out.println("DONE!!!");
}
catch (Exception ignore) {
}
}

public static void main(String[] args) {

createGUI();
}


}

Answer

you work with integers !!

setProgress((int) ((i/2000)*100));

is always 0 since (int)i / 2000 is always 0

same problem with

setProgress((int) (i*(100/2000)));

100 / 2000 is always 0 in integer

try

setProgress((int) (((float)i/2000)*100));

or

setProgress((int) (i*((float)100/2000)));

and it will work

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