Solution:
I sorted this by creating a tiny window (temporarily) in the corner of the screen that appeared for 1 second, every few minutes and also load the file i/o to create a temp file on disk at the same time.
I have since left Netbeans apps minimised for over 2 hours now and they come back to life with no problems.
This is the class I produced to do the work. You need to pass it the encapsulating frame to recognise when it is minimised or restored.
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Crispin licence can be seen at
http://www.crispindynamics.com/Licences/general-licence.txt.
*/
package com.crispin.icost;
import com.crispin.icadcore.ICadFileSystem;
import com.crispin.icost.gui.CostSummaryTopComponent;
import com.crispin.nbutils.NBUtils;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JWindow;
import org.openide.util.Exceptions;
import org.openide.windows.WindowManager;
/**
*
* @author dirving
*/
public class MinimisedChecker implements Runnable, WindowListener
{
private static MinimisedChecker checker = null;
boolean minimised = true;
JFrame frame;
boolean running = false;
long ticks = 0L;
SimpleDateFormat format;
public static MinimisedChecker getDefault()
{
if (checker == null)
{
checker = new MinimisedChecker();
Thread checkThread = new Thread(checker);
checkThread.start();
}
return checker;
}
private MinimisedChecker(JFrame frame)
{
frame.addWindowListener(checker);
minimised = findInstance.isShowing();
ticks = new Date().getTime();
format = new SimpleDateFormat("HH:mm:ss");
}
public void run()
{
running = true;
int oneMinute = 60000; // 60000; // 1 minute.
int refreshPeriod = 3 * oneMinute;
int cnt = refreshPeriod;
while (running)
{
synchronized (this)
{
try
{
wait(oneMinute);// 1 sec.
cnt -= oneMinute;
}
catch (InterruptedException ex)
{
}
}
if (!minimised)
{
cnt = refreshPeriod;
}
else
{
if (cnt < 0)
{
loadFunction();
cnt = refreshPeriod;
}
}
}
}
public void loadFunction()
{
Date date = new Date();
long time = date.getTime();
long period = time - ticks;
period /= 1000;// seconds
period /= 60; // minutes.
String timeStr = format.format(date);
String minStr = "Costing : minimised for ... " + period + " mins @ " + timeStr;
JWindow win = new JWindow();
JPanel panel = new JPanel();
win.add(panel);
panel.add(new JLabel(minStr));
win.pack();
win.setVisible(true);
synchronized (this)
{
try
{
wait(1000);// 1 sec.
}
catch (InterruptedException ex)
{
}
}
win.setVisible(false);
// access io.
String workingPath = "c:/tmp"; // create a temporary area to place a temp file
workingPath += File.separator + "minimised.txt";
FileWriter fWriter;
try
{
fWriter = new FileWriter(workingPath);
PrintWriter writer = new PrintWriter(fWriter);
String buffer = "0123456789abcdefghijklmnopqrstuvwxyz";
writer.println(minStr);
writer.println(timeStr);
for (int i=0; i<1024; i++)
{
writer.println(buffer);
}
writer.flush();
writer.close();
buffer = buffer.substring(1) + buffer.charAt(0);
}
catch (IOException ex)
{
Exceptions.printStackTrace(ex);
}
}
@Override
public void windowOpened(WindowEvent e)
{
}
@Override
public void windowClosing(WindowEvent e)
{
running = false;
}
@Override
public void windowClosed(WindowEvent e)
{
}
@Override
public void windowIconified(WindowEvent e)
{
minimised = true;
}
@Override
public void windowDeiconified(WindowEvent e)
{
minimised = false;
}
@Override
public void windowActivated(WindowEvent e)
{
}
@Override
public void windowDeactivated(WindowEvent e)
{
}
}
