Exception while trying to use GWT-EXT widgets

[magf]

Hello,
I created a simple class:
public class test extends Composite {
public test() {
}
and I set up the GET-EXT properly, so I can see the palette. Now, when I try to drop any component from the palette to the designer I get this exception:

eclipse.buildId=I20080617-2000
java.version=1.5.0_12
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=en_US
Command-line arguments: -os win32 -ws win32 -arch x86


Error
Mon Sep 08 12:16:41 EDT 2008
Designer [6.7.1.200809011505]: Designer is unable to create the 'panel' component at line 10 of test.java, using public com.gwtext.client.widgets.Panel() and arguments {}.This can be caused by problems evaluating the arguments of the constructor, or by any other problem that triggers an exception in the component when instantiated.
See your Eclipse <workspace>.metadata\.log file for details.
null

Product: GWT Designer Evaluation
Version: 5.1.0.200809011555
Expected: Eclipse 3.4
Actual: Eclipse 3.4.0.v20080512
Actual Eclipse Build Name:
Actual Eclipse Build ID: I20080617-2000
IDE Actual Name: Eclipse
IDE Actual Version: 3.3.100.v200806172000
IDE Actual NL: en_US
Activation Key: GWTDesignerEval-AE0SG-PM11W-JJD7G
Physical Address: 00-C0-49-F4-63-5C, HardwareAddress[00-1A-6B-D2-68-56], HardwareAddress[00-13-E8-C5-AE-11]
Code Gen: Flat Mode, Use Existing, First Assignment, Make Final
Events: Anonymous Class
GWT Home: C:/java/gwt-windows-1.5.2
Platform Product: Eclipse
Platform Version: 3.3.100.v200806172000
OS Name: Windows XP
OS Architecture: x86
OS Version: 5.1

com.swtdesigner.properties.PropertyException: Designer is unable to create the 'panel' component at line 10 of test.java, using public com.gwtext.client.widgets.Panel() and arguments {}.
This can be caused by problems evaluating the arguments of the constructor, or by any other problem that triggers an exception in the component when instantiated.
See your Eclipse <workspace>.metadata\.log file for details.
null
at com.swtdesigner.model.swt.widgets.ConstructorSourcePropertiesHelper.createObject(ConstructorSourcePropertiesHelper.java:274)
at com.swtdesigner.gwt.model.widgets.UIObjectInfo.createWidgetInstance(UIObjectInfo.java:332)
at com.swtdesigner.gwt.model.widgets.UIObjectInfo.createWidget(UIObjectInfo.java:288)
at com.swtdesigner.gwt.model.widgets.WidgetInfo.superCreateWidget(WidgetInfo.java:197)
at com.swtdesigner.gwt.model.widgets.panel.GwtExtPanelInfo.superCreateWidget(GwtExtPanelInfo.java:63)
at com.swtdesigner.gwt.model.widgets.WidgetInfo.createWidget(WidgetInfo.java:184)
at com.swtdesigner.gwt.model.widgets.panel.AbstractContainerInfo.createWidget(AbstractContainerInfo.java:182)
at com.swtdesigner.gwt.model.widgets.panel.AbstractContainerInfo.createChildrenWidgets(AbstractContainerInfo.java:202)
at com.swtdesigner.gwt.model.widgets.panel.AbstractContainerInfo.createWidget(AbstractContainerInfo.java:183)
at com.swtdesigner.gwt.model.widgets.panel.ThisCompositeInfo.createWidget(ThisCompositeInfo.java:214)
at com.swtdesigner.gwt.model.widgets.panel.ThisCompositeInfo.createGUIComponent(ThisCompositeInfo.java:206)
at com.swtdesigner.model.JavaInfo$18.execute(JavaInfo.java:5612)
at com.swtdesigner.model.swing.properties.custom.DesignTimeHelper.execute(DesignTimeHelper.java:54)
at com.swtdesigner.model.JavaInfo.notifyPropertyChanged(JavaInfo.java:5607)
at com.swtdesigner.model.JavaInfo.notifyPropertyChanged(JavaInfo.java:5588)
at com.swtdesigner.model.JavaInfo.unlockNotify(JavaInfo.java:5559)
at com.swtdesigner.model.JavaInfo.endEdit(JavaInfo.java:772)
at com.swtdesigner.gef.command.common.AddControlCommand.execute(AddControlCommand.java:28)
at org.eclipse.gef.commands.CommandStack.execute(CommandStack.java:78)
at com.swtdesigner.gef.domain.DesignerEditDomain$1.execute(DesignerEditDomain.java:54)
at org.eclipse.gef.tools.AbstractTool.executeCurrentCommand(AbstractTool.java:416)
at org.eclipse.gef.tools.CreationTool.performCreation(CreationTool.java:198)
at org.eclipse.gef.tools.CreationTool.handleButtonUp(CreationTool.java:122)
at org.eclipse.gef.tools.AbstractTool.mouseUp(AbstractTool.java:1006)
at org.eclipse.gef.EditDomain.mouseUp(EditDomain.java:229)
at com.swtdesigner.gef.domain.DesignerEditDomain.mouseUp(DesignerEditDomain.java:262)
at org.eclipse.gef.ui.parts.DomainEventDispatcher.dispatchMouseReleased(DomainEventDispatcher.java:346)
at org.eclipse.draw2d.LightweightSystem$EventHandler.mouseUp(LightweightSystem.java:511)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:207)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1003)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3823)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3422)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2382)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2346)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2198)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:493)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:288)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:488)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:193)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:382)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:549)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:504)
at org.eclipse.equinox.launcher.Main.run(Main.java:1236)
Caused by: java.lang.NoClassDefFoundError
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:494)
at com.swtdesigner.model.swt.widgets.ConstructorSourcePropertiesHelper.createObject(ConstructorSourcePropertiesHelper.java:271)
... 52 more

[Eric Clayberg]

The NoClassDefFoundError exception indicates that you don't have your project set up to use GWT-Ext properly.

What happens if you try our GWT-Ext Example Project?

[magf]

Thanks Eric for your very quick response. Your projects is working just fine. Interestingly enough, my gwt.xml file is identical to yours but it is not working. I will try to figure out the difference (hopefully within the remaining 2 evaluation days) and I will post my findings. Thanks again.

[Eric Clayberg]

See the GWT-Ext set up instructions on the GWT-Ext site.

GWT-Ext requires more than just changes to your gwt.xml file.