je n'arrive pas à installer window builder

Bonjour,
je ne parvient pas à utiliser window builder. Dès que je clique sur l'onglet design, ça me met: Unknown GUI toolkit
Et voici le rapport:
Pièce jointe 577379
org.eclipse.wb.internal.core.utils.exception.DesignerException: 103 (Unknown GUI toolkit). interfacegraphique.MyWindowBuilder
at org.eclipse.wb.internal.core.parser.JavaInfoParser.prepareParseContext(JavaInfoParser.java:1195)
at org.eclipse.wb.internal.core.parser.JavaInfoParser.parse(JavaInfoParser.java:242)
at org.eclipse.wb.internal.core.parser.JavaInfoParser.access$9(JavaInfoParser.java:238)
at org.eclipse.wb.internal.core.parser.JavaInfoParser$1.runObject(JavaInfoParser.java:153)
at org.eclipse.wb.internal.core.parser.JavaInfoParser$1.runObject(JavaInfoParser.java:1)
at org.eclipse.wb.internal.core.utils.execution.ExecutionUtils.runDesignTime(ExecutionUtils.java:159)
at org.eclipse.wb.internal.core.parser.JavaInfoParser.parse(JavaInfoParser.java:151)
at org.eclipse.wb.internal.core.editor.DesignPage.internal_refreshGEF(DesignPage.java:534)
at org.eclipse.wb.internal.core.editor.DesignPage.access$9(DesignPage.java:522)
at org.eclipse.wb.internal.core.editor.DesignPage$8$1.run(DesignPage.java:449)
at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:236)
at org.eclipse.ui.internal.UISynchronizer.syncExec(UISynchronizer.java:133)
at org.eclipse.swt.widgets.Display.syncExec(Display.java:4992)
at org.eclipse.wb.internal.core.editor.DesignPage$8.run(DesignPage.java:446)
at org.eclipse.jface.operation.ModalContext.runInCurrentThread(ModalContext.java:436)
at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:352)
at org.eclipse.jface.dialogs.ProgressMonitorDialog.run(ProgressMonitorDialog.java:469)
at org.eclipse.wb.internal.core.editor.DesignPage.internal_refreshGEF_withProgress(DesignPage.java:465)
at org.eclipse.wb.internal.core.editor.DesignPage.internal_refreshGEF(DesignPage.java:415)
at org.eclipse.wb.internal.core.editor.UndoManager.refreshDesignerEditor(UndoManager.java:381)
at org.eclipse.wb.internal.core.editor.DesignPage.refreshGEF(DesignPage.java:392)
at org.eclipse.wb.internal.core.editor.actions.RefreshAction.run(RefreshAction.java:46)
at org.eclipse.wb.internal.core.editor.actions.DesignPageAction.run(DesignPageAction.java:34)
at org.eclipse.wb.internal.core.editor.errors.JavaExceptionComposite.doRefresh(JavaExceptionComposite.java:87)
at org.eclipse.wb.internal.core.editor.errors.ExceptionComposite$3.widgetSelected(ExceptionComposite.java:129)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:252)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4385)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1512)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1535)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1520)
at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1324)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4172)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3789)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1158)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1047)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:155)
at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:658)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:557)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:154)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:150)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:137)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:107)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:657)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:594)
at org.eclipse.equinox.launcher.Main.run(Main.java:1447)
Pourriez vous m'aider:(?

Il me semble que WindowBuilder ne va reussir a afficher l'UI correspondant a une class que si cette classe etend JFrame. En gros, tu extrais ta fenetre dans une class "MyJFrame extends JFrame" et dans cette classe tu ajoutes les widgets et tout ca, tu peux l'editer avec Window Builder. Puis dans ton appli main tu remplaces "MyWindowBuilder window = new MyWindowBuilder(); window.frame.setVisible(true);" par "new MyFrame().setVisible(true);" et ca devrait etre bon.