# Cannot invoke Object.getClass() because "o" is null - Error

**URL:** <https://forum.inductiveautomation.com/t/cannot-invoke-object-getclass-because-o-is-null-error/104871>\
**Category:** Ignition\
**Tags:** scripting, vision\
**Created:** [April 8, 2025, 10:15pm UTC](https://forum.inductiveautomation.com/t/cannot-invoke-object-getclass-because-o-is-null-error/104871 "2025-04-08T22:15:56Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Chris\_Koch](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/chris_koch/32/51591_2.png) [@Chris\_Koch](https://forum.inductiveautomation.com/u/Chris_Koch)\
**Post date:** [April 8, 2025, 10:15pm UTC](https://forum.inductiveautomation.com/t/cannot-invoke-object-getclass-because-o-is-null-error/104871/1 "2025-04-08T22:15:56Z")

</div>

Hi there, I'm having trouble tracking down a script that is clearly trying to open a pop-up window with a list of current alarms, this has occurred after an upgrade from 7.9 to 8.1. Were working on getting everything up and running and have hit a bit of a snag.

Full Error:

```python
Traceback (most recent call last):
  File "<event:actionPerformed>", line 2, in <module>
	at org.python.core.PyJavaType.wrapJavaObject(PyJavaType.java:120)
	at com.inductiveautomation.factorypmi.application.script.PyComponentWrapper.<init>(PyComponentWrapper.java:52)
	at com.inductiveautomation.factorypmi.application.script.builtin.WindowUtilities.lambda$getParentWindow$1(WindowUtilities.java:513)
	at com.inductiveautomation.factorypmi.application.script.builtin.WindowUtilities.doGUIAction(WindowUtilities.java:851)
	at com.inductiveautomation.factorypmi.application.script.builtin.WindowUtilities.getParentWindow(WindowUtilities.java:511)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
java.lang.NullPointerException: java.lang.NullPointerException: Cannot invoke "Object.getClass()" because "o" is null

	at org.python.core.Py.JavaError(Py.java:545)
	at org.python.core.Py.JavaError(Py.java:536)
	at org.python.core.PyReflectedFunction. __call__ (PyReflectedFunction.java:192)
	at com.inductiveautomation.ignition.common.script.ScriptManager$ReflectedInstanceFunction. __call__ (ScriptManager.java:553)
	at org.python.core.PyObject. __call__ (PyObject.java:461)
	at org.python.core.PyObject. __call__ (PyObject.java:465)
	at org.python.pycode._pyx393.f$0(<event:actionPerformed>:93)
	at org.python.pycode._pyx393.call_function(<event:actionPerformed>)
	at org.python.core.PyTableCode.call(PyTableCode.java:173)
	at org.python.core.PyCode.call(PyCode.java:18)
	at org.python.core.Py.runCode(Py.java:1703)
	at com.inductiveautomation.ignition.common.script.ScriptManager.runCode(ScriptManager.java:804)
	at com.inductiveautomation.factorypmi.application.binding.action.ActionAdapter.runActions(ActionAdapter.java:207)
	at com.inductiveautomation.factorypmi.application.binding.action.ActionAdapter.invoke(ActionAdapter.java:300)
	at com.inductiveautomation.factorypmi.application.binding.action.RelayInvocationHandler.invoke(RelayInvocationHandler.java:57)
	at jdk.proxy2/jdk.proxy2.$Proxy63.actionPerformed(Unknown Source)
	at java.desktop/javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
	at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
	at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
	at java.desktop/javax.swing.DefaultButtonModel.setPressed(Unknown Source)
	at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
	at java.desktop/java.awt.AWTEventMulticaster.mouseReleased(Unknown Source)
	at java.desktop/java.awt.Component.processMouseEvent(Unknown Source)
	at java.desktop/javax.swing.JComponent.processMouseEvent(Unknown Source)
	at java.desktop/java.awt.Component.processEvent(Unknown Source)
	at java.desktop/java.awt.Container.processEvent(Unknown Source)
	at java.desktop/java.awt.Component.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.Component.dispatchEvent(Unknown Source)
	at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
	at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
	at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
	at java.desktop/java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.Window.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.Component.dispatchEvent(Unknown Source)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.EventQueue$4.run(Unknown Source)
	at java.desktop/java.awt.EventQueue$4.run(Unknown Source)
	at java.base/java.security.AccessController.doPrivileged(Unknown Source)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.desktop/java.awt.EventQueue$5.run(Unknown Source)
	at java.desktop/java.awt.EventQueue$5.run(Unknown Source)
	at java.base/java.security.AccessController.doPrivileged(Unknown Source)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.desktop/java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.NullPointerException: Cannot invoke "Object.getClass()" because "o" is null
	at org.python.core.PyJavaType.wrapJavaObject(PyJavaType.java:120)
	at com.inductiveautomation.factorypmi.application.script.PyComponentWrapper.<init>(PyComponentWrapper.java:52)
	at com.inductiveautomation.factorypmi.application.script.builtin.WindowUtilities.lambda$getParentWindow$1(WindowUtilities.java:513)
	at com.inductiveautomation.factorypmi.application.script.builtin.WindowUtilities.doGUIAction(WindowUtilities.java:851)
	at com.inductiveautomation.factorypmi.application.script.builtin.WindowUtilities.getParentWindow(WindowUtilities.java:511)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
	at org.python.core.PyReflectedFunction. __call__ (PyReflectedFunction.java:190)
	... 49 more

Ignition v8.1.47 (b2025022612)
Java: Azul Systems, Inc. 17.0.13

```

---

<div class="post-metadata">

**Author:** ![Chris\_Koch](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/chris_koch/32/51591_2.png) [@Chris\_Koch](https://forum.inductiveautomation.com/u/Chris_Koch)\
**Post date:** [April 8, 2025, 10:30pm UTC](https://forum.inductiveautomation.com/t/cannot-invoke-object-getclass-because-o-is-null-error/104871/2 "2025-04-08T22:30:27Z")

</div>

80% sure this is the scripting that is calling and causing the above error.

```python
# Define Variables
parentWindow = system.gui.getParentWindow(event)
screen = event.source.getGraphicsConfiguration().getBounds()
screenHorPos = screen.x
screenVertPos = screen.y
buttonX = event.source.getLocationOnScreen().x

# This accounts for the height of the footer if the popup is launched from the navigation footer window
if parentWindow.name == "Footer":
	buttonY = event.source.getLocationOnScreen().y - windowHeight
else:
	buttonY = event.source.getLocationOnScreen().y
	
buttonWidth = event.source.getSize().width	
buttonHeight = event.source.getSize().height
sourceX = abs(buttonX - screenHorPos)
sourceY = abs(buttonY - screenVertPos)
windowWidth = parentWindow.getWidth()
windowHeight = parentWindow.getHeight()
try:
	requiredRoles = parentWindow.getRootContainer().requiredRoles
	print "Parent Window Roles:", requiredRoles
except:
	print parentWindow.title, "has no requiredRoles parameter configured."
	requiredRoles = 'rolesNotConfigured'
	
# Define Which Popup to Open
popupPath = event.source.parent.popupPath

# Get all of the alarm tag paths
tagPaths = [event.source.parent.alarm0Path, event.source.parent.alarm1Path, event.source.parent.alarm2Path,
			event.source.parent.alarm3Path, event.source.parent.alarm4Path, event.source.parent.alarm5Path,
			event.source.parent.alarm6Path, event.source.parent.alarm7Path, event.source.parent.alarm8Path,
			event.source.parent.alarm9Path]

# Pare down the list of tagPaths to only those that are configured
tagPaths = list(filter(lambda a: a != '', tagPaths))

# Create a dictionary of tagPaths and fullTagPaths with the prov:default:/tag: prefix appended to each tag path
fullTagPaths = {}
for tagPath in tagPaths:
	fullTagPaths[tagPath] = "prov:default:/tag:" + tagPath + "*"
	#fullTagPaths.append("prov:default:/tag:" + tagPath + "*")

# Develop the alarm state filter. Ex: ["ActiveUnacked","ActiveAcked"]
alarmState = []
alarmState.append("ActiveUnacked")
alarmState.append("ActiveAcked")

# Get the description and priority information from the tagPaths list
alarmRows = []
for tagPath, fullTagPath in fullTagPaths.iteritems():
	alarmInfo = system.alarm.queryStatus(state=alarmState, path=[fullTagPath])
	alarmData = alarmInfo.getDataset()
	pyAlarmData = system.dataset.toPyDataSet(alarmData)
	
	for row in pyAlarmData:
		alarmDescription = row["DisplayPath"]
		alarmPriority = row["Priority"]
		alarmSource = tagPath
		newRow = [alarmDescription, alarmPriority, alarmSource]
		alarmRows.append(newRow)
		
headers = ["Description", "Priority", "Source"]
alarmDataset = system.dataset.toDataSet(headers, alarmRows)

# Sort the alarmDataset by priority, highest to lowest
sortedDataset = system.dataset.sort(alarmDataset, "Priority", 0)

# Open the popup window
try:
	popupHeight = 10
	alarmRowHeight = 35
	try:
		alarmData = system.dataset.toPyDataSet(sortedDataset)
		# Determine the number of alarms that are configured and active in the dataset, this will
		# set the height of the popup window.
		alarmCount = 0
		for row in alarmData:
			if row != '':
				popupHeight += alarmRowHeight
				alarmCount += 1
			else:
				pass
		if alarmCount > 0:
			popup = system.nav.openWindowInstance(popupPath, {'alarmDataset' : sortedDataset, 'popupHeight' : popupHeight,
				'sourceX': sourceX, 'sourceY': sourceY, 'buttonWidth': buttonWidth, 'buttonHeight': buttonHeight,'sourceWidth': windowWidth, 'sourceHeight': windowHeight})
		else:
			system.gui.messageBox("No active alarms.")
	except:
		pass
except:
	pass

```

When there are active alarms, I am getting a popup saying "No active alarms.", In the designer only am I getting the OP error message.

---

<div class="post-metadata">

**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\
**Post date:** [April 8, 2025, 11:45pm UTC](https://forum.inductiveautomation.com/t/cannot-invoke-object-getclass-because-o-is-null-error/104871/3 "2025-04-08T23:45:17Z")

</div>

> [@Chris\_Koch](#):
>
> `parentWindow = system.gui.getParentWindow(event)`

This is weird.

So this call internally does this:

```java
        if (event.getSource() instanceof JComponent) {
            return IgnitionSwingUtilities.getAncestorOfClass(FPMIWindow.class, (JComponent) event.getSource());

```

Which then goes to this:

```python
return new PyComponentWrapper(o);

```

Which, inside that constructor, does this:

```python
        delegate = PyJavaType.wrapJavaObject(component);

```

Which, in Jython's internals, does this:

```python
    public static PyObject wrapJavaObject(Object o) {
        PyObject obj = new PyObjectDerived(fromClass(o.getClass()));
        setProxyAttr(obj, o);
        return obj;
    }

```

Which is where the NPE is coming from - `o` is null, so there's no way to call `getClass()` on it.

Going backwards, that means the `IgnitionSwingUtilities` call _is_ being hit, but is also returning null, meaning whatever component you passed in via the event object either was not a window or was not contained within a window.

Which should not be possible in Vision.

The stack suggests you're calling this from a button - anything funky about that button you can think of?