progress bar error

[Frank-99]

I sometimes get the error call below from the progress bar of the splash screen of my app, but it does it very randomly and out of nowhere, and then it might not do it again for another twenty runs, even if I don't change any of the code...
Any clue if this can be a bug somewhere in the FlatProgressBarUI or something else unrelated?

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at java.desktop/javax.swing.plaf.basic.BasicProgressBarUI.updateSizes(BasicProgressBarUI.java:537)
	at java.desktop/javax.swing.plaf.basic.BasicProgressBarUI.getBox(BasicProgressBarUI.java:494)
	at com.formdev.flatlaf.ui.FlatProgressBarUI.paint(FlatProgressBarUI.java:230)
	at com.formdev.flatlaf.ui.FlatProgressBarUI.update(FlatProgressBarUI.java:201)
	at java.desktop/javax.swing.JComponent.paintComponent(JComponent.java:797)
	at java.desktop/javax.swing.JComponent.paint(JComponent.java:1074)
	at java.desktop/javax.swing.JComponent.paintChildren(JComponent.java:907)
	at java.desktop/javax.swing.JComponent.paint(JComponent.java:1083)
	at java.desktop/javax.swing.JComponent.paintToOffscreen(JComponent.java:5255)
	at java.desktop/javax.swing.RepaintManager$PaintManager.paintDoubleBufferedFPScales(RepaintManager.java:1707)
	at java.desktop/javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1616)
	at java.desktop/javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1556)
	at java.desktop/javax.swing.RepaintManager.paint(RepaintManager.java:1323)
	at java.desktop/javax.swing.JComponent._paintImmediately(JComponent.java:5203)
	at java.desktop/javax.swing.JComponent.paintImmediately(JComponent.java:5013)
	at java.desktop/javax.swing.RepaintManager$4.run(RepaintManager.java:865)
	at java.desktop/javax.swing.RepaintManager$4.run(RepaintManager.java:848)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.desktop/javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:848)
	at java.desktop/javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:823)
	at java.desktop/javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:772)
	at java.desktop/javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1890)
	at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

[Frank-99]

Just noticed it's very similar to #830
What I do with My JProgressBar is as follows:

private JProgressBar progress;
progress = new JProgressBar();
progress.setIndeterminate(true);
progress.setPreferredSize(new Dimension(150, 6));
progress.setBackground(Color.decode("#ADB8CE"));
progress.setForeground(Color.decode("#688FDD"));

window.addWindowListener(new WindowListener() {
	@Override
	public void windowOpened(WindowEvent e) {
		runner = Runner.run(() -> {	checkForUpdates(); }).toService();
	}
	@Override public void windowClosing(WindowEvent e) { }
	@Override public void windowClosed(WindowEvent e) { }
	@Override public void windowIconified(WindowEvent e) { }
	@Override public void windowDeiconified(WindowEvent e) { }
	@Override public void windowActivated(WindowEvent e) { }
	@Override public void windowDeactivated(WindowEvent e) { }
});

And the subsequent calls:

private static Runner run(Runnable runnable) {
	Runner handler = new Runner();
	handler.worker = new SwingWorker<Void, Void>() {
		@Override protected Void doInBackground() throws Exception {
			runnable.run();
			return null;
		}
		@Override protected void done() { }
	};
	handler.start();
	return handler;
}

private void checkForUpdates() {
	runner = UpdateManager.startUpdater(new UpdaterListener() {
		@Override public void onLookingForUpdate() {
			progress.setIndeterminate(true);
		}
		@Override public void onIsUpToDate() {
			progress.setIndeterminate(false);
			progress.setValue(100);
			Runner.sleep(100);
			cleanFiles();
		}
		@Override public boolean onUpdateFound() {
			progress.setIndeterminate(false);
			progress.setValue(100);
			return true;
		}
		@Override public void onDownloadingUpdate() {
			progress.setIndeterminate(false);
			progress.setValue(0);
		}
		@Override public void onDownloadUpdate(int progr) {
			progress.setValue(progr);
		}
		@Override public void onPreparingToIstall() {
			progress.setValue(0);
		}
		@Override public void onPreparingUpdate(int progr) {
			progress.setValue(progr);
		}
		@Override public boolean onReadyToIstall() {
			progress.setValue(100);
			Runner.sleep(100);
			progress.setIndeterminate(true);
			Runner.sleep(100);
			return true;
		}
		@Override public void onUpdateCanceled() {
			progress.setIndeterminate(false);
			progress.setValue(0);
			Runner.sleep(100);
			cleanFiles();
		}
		@Override public void onFailed() {
			progress.setIndeterminate(false);
			progress.setValue(0);
			Runner.sleep(100);
			cleanFiles();
		}
	});
	
	
private void cleanFiles() {
	runner = Runner.run(() -> {
		progress.setIndeterminate(false);
		progress.setValue(0);
		//...
		progress.setValue(100);
		checkDataUpdated();
	}).toService();
}

private void checkDataUpdated() {
	runner = Runner.run(() -> {
		progress.setIndeterminate(false);
		progress.setValue(0);
		//...
		progress.setValue(100);
		loadUser();
	}).toService();
}

private void loadUser() {
	runner = Runner.run(() -> {
		progress.setIndeterminate(false);
		progress.setValue(0);
		//...
		progress.setValue(100);
		launchApp();
	}).toService();
}

private void launchApp() {
	runner = Runner.run(() -> {
		progress.setValue(0);
		progress.setIndeterminate(true);
		Runner.run(() -> { window.dispose(); }, 100);
	}).toService();
}

What I don't understand is that it does it apparently randomly, without changing any of the code or circumstances when running it.

perhaps the progressbar can be set to null here? Runner.run(() -> { window.dispose(); }, 100); but I've never seen it happen without the FlatLaf library so far...

[DevCharly]

Looks like a threading issue.

You need to do all modifications of the progress bar on the AWT thread. Use SwingUtilities.invokeLater().

What I don't understand is that it does it apparently randomly, without changing any of the code or circumstances when running it

Because in "indeterminate" mode the progress bar repaints every 15ms on AWT thread while you modify it on another thread.

perhaps the progressbar can be set to null here? Runner.run(() -> { window.dispose(); }, 100);

You should dispose the window on AWT thread. This avoids the NPE.

but I've never seen it happen without the FlatLaf library so far...

I think this is because FlatLaf repaints progress bar in "indeterminate" mode every 15ms, but other Laf every 50ms.
So the chance that this happens in FlatLaf is much higher than in other Lafs.

[DevCharly]

I've added some logs (including stack trace) to FlatProgressBarUI that warns when modifying indeterminate progress bar not on AWT thread.

Please try latest 3.5-SNAPSHOT: https://github.com/JFormDesigner/FlatLaf#snapshots

[Frank-99]

Thank you, in the midst of it I didn't realise I was updating UI outside of AWT thread... Fixed it and will have to be more careful!

I've added some logs to FlatProgressBarUI that warns when modifying indeterminate progress bar not on AWT thread.

I also appreciate the friendly reminder for when dumb mistakes like mine are made and the promptness of which you've added this... amazing as always!