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I create Java Desktop Project then I create JPanel (called MyJPanel), then I add to it a few controls (JLabel, JTextField, JButton). Next I create JFrame. I compile the project. Now I want to JPanel to JFrame. I am doing it in the same way as in NetBeans 5.5.1: I am adding JPanel to palette (it seems to work), then I try to add MyJPanel to the JFrame and I got warning: "The component cannot be instantiated. Please make sure it is a JavaBeans". The problem disappears when I remove from MyJPanel's constructor call to initComponents() method, which does not solve the issue obviously. It seems as if NetBeans 6 expected that no-arg constructor must be empty. I am using NetBeans 6, M10 with Java SDK 5.
I suppose there should be and exception in the log, please attach it.
Ok, I think I know what is going on. I made a test on a simple example: JPanel + JLabel on it. As long as I haven't changed label's default name the generated java code was: jLabel1.setText("jLabel1"); When I changed the name to, say, "labelka" the generated code was changed to: jLabel1.setText(application.Application.getInstance(dbapptest.DBApp.class).getContext().getResourceMap(MyPane.class).getString("jLabel1.text")); // NOI18N which causes NPE (see log below) All needed classes and files seems to exist, so this line (Application class?) must do something wrong at runtime. The relevant (i.e. produced while trying to add JPanel to JFrame) part of messages.log [WARNING] BeanSupport cannot create default instance of: pl.xoft.quiz.MyPane SEVERE org.openide.ErrorManager$AnnException: msg at org.openide.ErrorManager$AnnException.findOrCreate(ErrorManager.java:839) at org.openide.ErrorManager$DelegatingErrorManager.annotate(ErrorManager.java:628) at org.openide.ErrorManager.annotate(ErrorManager.java:430) at org.netbeans.modules.form.MetaComponentCreator.showInstErrorMessage(MetaComponentCreator.java:1317) at org.netbeans.modules.form.MetaComponentCreator.initComponentInstance(MetaComponentCreator.java:1305) at org.netbeans.modules.form.MetaComponentCreator.createVisualComponent(MetaComponentCreator.java:753) at org.netbeans.modules.form.MetaComponentCreator.access$200(MetaComponentCreator.java:62) at org.netbeans.modules.form.MetaComponentCreator$2.run(MetaComponentCreator.java:192) at org.netbeans.modules.form.FormLAF$1.run(FormLAF.java:183) at org.openide.util.Mutex.doEventAccess(Mutex.java:1201) at org.openide.util.Mutex.readAccess(Mutex.java:262) at org.netbeans.modules.form.FormLAF.executeWithLookAndFeel(FormLAF.java:168) at org.netbeans.modules.form.MetaComponentCreator.precreateVisualComponent(MetaComponentCreator.java:189) at org.netbeans.modules.form.HandleLayer$NewComponentDrag.init(HandleLayer.java:2583) at org.netbeans.modules.form.HandleLayer$NewComponentDrag.<init>(HandleLayer.java:2579) at org.netbeans.modules.form.HandleLayer$NewComponentDropListener.dragEnter(HandleLayer.java:2852) at java.awt.dnd.DropTarget.dragEnter(DropTarget.java:337) at sun.awt.dnd.SunDropTargetContextPeer.processEnterMessage(SunDropTargetContextPeer.java:295) at sun.awt.dnd.SunDropTargetContextPeer.access$500(SunDropTargetContextPeer.java:53) at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchEnterEvent(SunDropTargetContextPeer.java:759) at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchEvent(SunDropTargetContextPeer.java:727) at sun.awt.dnd.SunDropTargetEvent.dispatch(SunDropTargetEvent.java:29) at java.awt.Component.dispatchEventImpl(Component.java:3826) at java.awt.Container.dispatchEventImpl(Container.java:2024) at java.awt.Component.dispatchEvent(Component.java:3803) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212) at java.awt.LightweightDispatcher.trackMouseEnterExit(Container.java:4017) at java.awt.LightweightDispatcher.processDropTargetEvent(Container.java:3955) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3817) at java.awt.Container.dispatchEventImpl(Container.java:2010) at java.awt.Window.dispatchEventImpl(Window.java:1778) at java.awt.Component.dispatchEvent(Component.java:3803) at java.awt.EventQueue.dispatchEvent(EventQueue.java:463) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149) at java.awt.EventDispatchThread.run(EventDispatchThread.java:110) msg Caused: java.lang.NullPointerException at pl.xoft.quiz.MyPane.initComponents(MyPane.java:32) at pl.xoft.quiz.MyPane.<init>(MyPane.java:17) 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 java.lang.Class.newInstance0(Class.java:350) at java.lang.Class.newInstance(Class.java:303) at org.netbeans.modules.form.CreationFactory.createDefaultInstance(CreationFactory.java:136) at org.netbeans.modules.form.RADComponent.createBeanInstance(RADComponent.java:203) at org.netbeans.modules.form.RADComponent.initInstance(RADComponent.java:147) [catch] at org.netbeans.modules.form.MetaComponentCreator.initComponentInstance(MetaComponentCreator.java:1302) at org.netbeans.modules.form.MetaComponentCreator.createVisualComponent(MetaComponentCreator.java:753) at org.netbeans.modules.form.MetaComponentCreator.access$200(MetaComponentCreator.java:62) at org.netbeans.modules.form.MetaComponentCreator$2.run(MetaComponentCreator.java:192) at org.netbeans.modules.form.FormLAF$1.run(FormLAF.java:183) at org.openide.util.Mutex.doEventAccess(Mutex.java:1201) at org.openide.util.Mutex.readAccess(Mutex.java:262) at org.netbeans.modules.form.FormLAF.executeWithLookAndFeel(FormLAF.java:168) at org.netbeans.modules.form.MetaComponentCreator.precreateVisualComponent(MetaComponentCreator.java:189) at org.netbeans.modules.form.HandleLayer$NewComponentDrag.init(HandleLayer.java:2583) at org.netbeans.modules.form.HandleLayer$NewComponentDrag.<init>(HandleLayer.java:2579) at org.netbeans.modules.form.HandleLayer$NewComponentDropListener.dragEnter(HandleLayer.java:2852) at java.awt.dnd.DropTarget.dragEnter(DropTarget.java:337) at sun.awt.dnd.SunDropTargetContextPeer.processEnterMessage(SunDropTargetContextPeer.java:295) at sun.awt.dnd.SunDropTargetContextPeer.access$500(SunDropTargetContextPeer.java:53) at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchEnterEvent(SunDropTargetContextPeer.java:759) at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchEvent(SunDropTargetContextPeer.java:727) at sun.awt.dnd.SunDropTargetEvent.dispatch(SunDropTargetEvent.java:29) at java.awt.Component.dispatchEventImpl(Component.java:3826) at java.awt.Container.dispatchEventImpl(Container.java:2024) at java.awt.Component.dispatchEvent(Component.java:3803) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212) at java.awt.LightweightDispatcher.trackMouseEnterExit(Container.java:4017) at java.awt.LightweightDispatcher.processDropTargetEvent(Container.java:3955) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3817) at java.awt.Container.dispatchEventImpl(Container.java:2010) at java.awt.Window.dispatchEventImpl(Window.java:1778) at java.awt.Component.dispatchEvent(Component.java:3803) at java.awt.EventQueue.dispatchEvent(EventQueue.java:463) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149) at java.awt.EventDispatchThread.run(EventDispatchThread.java:110) ALL [null]: The component cannot be instantiated. Please make sure it is a JavaBean. And, for completnes, the JPanel source code: /* * MyPane.java * * Created on 16 sierpień 2007, 16:50 */ package pl.xoft.quiz; /** * * @author pi */ public class MyPane extends javax.swing.JPanel { /** Creates new form MyPane */ public MyPane() { initComponents(); } /** This method is called from within the constructor to * initialize the form. * WARNING: Do NOT modify this code. The content of this method is * always regenerated by the Form Editor. */ // <editor-fold defaultstate="collapsed" desc=" Generated Code "> private void initComponents() { jLabel1 = new javax.swing.JLabel(); jLabel1.setText(application.Application.getInstance(dbapptest.DBApp.class).getContext().getResourceMap(MyPane.class).getString("jLabel1.text")); // NOI18N org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(this); this.setLayout(layout); layout.setHorizontalGroup( layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING) .add(layout.createSequentialGroup() .addContainerGap() .add(jLabel1) .addContainerGap(348, Short.MAX_VALUE)) ); layout.setVerticalGroup( layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING) .add(layout.createSequentialGroup() .addContainerGap() .add(jLabel1) .addContainerGap(271, Short.MAX_VALUE)) ); }// </editor-fold> // Variables declaration - do not modify private javax.swing.JLabel jLabel1; // End of variables declaration }
Already fixed as issue 118842. *** This issue has been marked as a duplicate of 118842 ***