GWT: Exception: This widget's parent does not implement HasWidgets, but it does - gwt

Question

I am trying to create a structure where I have this larger UI with small parts that I can swap in and out and you get to more detailed areas. In essence I am making top level panels which hold smaller panels from other composites. Right now I am getting this exception:
13:50:51.479 [ERROR] [managementconsole] Uncaught exception escaped
com.google.gwt.event.shared.UmbrellaException: Exception caught: This widget's parent does not implement HasWidgets
at com.google.gwt.event.shared.HandlerManager.fireEvent(HandlerManager.java:129)
at com.google.gwt.user.client.ui.Widget.fireEvent(Widget.java:129)
at com.google.gwt.event.dom.client.DomEvent.fireNativeEvent(DomEvent.java:116)
at com.google.gwt.user.client.ui.Widget.onBrowserEvent(Widget.java:177)
at com.google.gwt.user.client.DOM.dispatchEventImpl(DOM.java:1351)
at com.google.gwt.user.client.DOM.dispatchEvent(DOM.java:1307)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:338)
at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:219)
at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:571)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:279)
at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:242)
at sun.reflect.GeneratedMethodAccessor37.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:293)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:547)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.IllegalStateException: This widget's parent does not implement HasWidgets
at com.google.gwt.user.client.ui.Widget.removeFromParent(Widget.java:204)
at com.google.gwt.user.client.ui.LayoutPanel.insert(LayoutPanel.java:188)
at com.google.gwt.user.client.ui.LayoutPanel.add(LayoutPanel.java:134)
at com.impulse.mc.client.pm.PolicyManager.Init(PolicyManager.java:58)
at com.impulse.mc.client.ManagementConsole$1.onClick(ManagementConsole.java:83)
at com.google.gwt.event.dom.client.ClickEvent.dispatch(ClickEvent.java:56)
at com.google.gwt.event.dom.client.ClickEvent.dispatch(ClickEvent.java:1)
at com.google.gwt.event.shared.GwtEvent.dispatch(GwtEvent.java:1)
at com.google.web.bindery.event.shared.EventBus.dispatchEvent(EventBus.java:40)
at com.google.web.bindery.event.shared.SimpleEventBus.doFire(SimpleEventBus.java:193)
at com.google.web.bindery.event.shared.SimpleEventBus.fireEvent(SimpleEventBus.java:88)
at com.google.gwt.event.shared.HandlerManager.fireEvent(HandlerManager.java:127)
at com.google.gwt.user.client.ui.Widget.fireEvent(Widget.java:129)
at com.google.gwt.event.dom.client.DomEvent.fireNativeEvent(DomEvent.java:116)
at com.google.gwt.user.client.ui.Widget.onBrowserEvent(Widget.java:177)
at com.google.gwt.user.client.DOM.dispatchEventImpl(DOM.java:1351)
at com.google.gwt.user.client.DOM.dispatchEvent(DOM.java:1307)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:338)
at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:219)
at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:571)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:279)
at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:242)
at sun.reflect.GeneratedMethodAccessor37.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:293)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:547)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
at java.lang.Thread.run(Unknown Source)
My top level class:
public class ManagementConsole implements EntryPoint
{
private MCConstants constants = GWT.create(MCConstants.class);
private final DockLayoutPanel dockLayoutPanel = new DockLayoutPanel(Unit.EM);
private final VerticalPanel verticalPanel = new VerticalPanel();
private final HorizontalPanel menuBar1 = new HorizontalPanel();
public final HorizontalPanel menuBar2 = new HorizontalPanel();
public final HorizontalPanel menuBar3 = new HorizontalPanel();
private final Button btnPolicyManager = new Button("#Policy Manager");
public final LayoutPanel mainPanel = new LayoutPanel();
private final AbsolutePanel absolutePanel = new AbsolutePanel();
private final TextArea txtrSplashScreenPut = new TextArea();
private PolicyManager PM = null;
private final ManagementConsole MC = this;
/**
* This is the entry point method.
*/
public void onModuleLoad()
{
ABManager.setFactory( (MyABFactory) GWT.create( MyABFactory.class ) );
ServerUtil.initServer();
RootLayoutPanel root = RootLayoutPanel.get();
root.add(dockLayoutPanel);
root.setWidgetLeftRight(dockLayoutPanel, 0.0, Unit.PX, 0.0, Unit.PX);
root.setWidgetTopHeight(dockLayoutPanel, 0.0, Unit.PX, 512.0, Unit.PX);
verticalPanel.setBorderWidth(1);
dockLayoutPanel.addNorth(verticalPanel, 7.7);
verticalPanel.setWidth("100%");
menuBar1.setStyleName("MenuBarStyle");
menuBar1.setBorderWidth(1);
verticalPanel.add(menuBar1);
menuBar1.setWidth("0px");
menuBar1.setSpacing( 10 );
btnPolicyManager.addClickHandler( new ClickHandler()
{
public void onClick( ClickEvent event )
{
if ( null == PM )
{
PM = new PolicyManager();
}
PM.Init( MC );
}
} );
btnPolicyManager.setText( constants.policyManagerButton() );
menuBar1.add( btnPolicyManager );
verticalPanel.add( menuBar2);
menuBar2.setWidth("0px");
verticalPanel.add(menuBar3);
menuBar3.setWidth("0px");
dockLayoutPanel.add(mainPanel);
mainPanel.add(absolutePanel);
mainPanel.setWidgetLeftWidth(absolutePanel, 276.0, Unit.PX, 383.0, Unit.PX);
mainPanel.setWidgetTopHeight(absolutePanel, 95.0, Unit.PX, 186.0, Unit.PX);
txtrSplashScreenPut.setReadOnly(true);
txtrSplashScreenPut.setTextAlignment(TextBoxBase.ALIGN_CENTER);
txtrSplashScreenPut.setText("Splash Screen\r\nPut a graphic or some other text here");
absolutePanel.add(txtrSplashScreenPut, 113, 57);
}
}
And the class that is causing the exception, in the Init method:
public class PolicyManager extends Composite
{
ManagementConsole MC = null;
private final DockLayoutPanel myRootPanel = new DockLayoutPanel(Unit.EM);
private final DockLayoutPanel sidePanel = new DockLayoutPanel(Unit.EM);
private final DockLayoutPanel mainPanel = new DockLayoutPanel(Unit.EM);
private final Label lblWelcomeToThe = new Label("Welcome to the Policy Manager");
// Only put in basic things that do not need the MC in the constructor
public PolicyManager()
{
initWidget(myRootPanel);
setSize("961px", "412px");
myRootPanel.setSize("100%", "412px");
myRootPanel.addWest(sidePanel, 17.3);
myRootPanel.add(mainPanel);
mainPanel.add(lblWelcomeToThe);
}
public void Init( ManagementConsole mc )
{
MC = mc;
mc.menuBar2.clear();
mc.menuBar3.clear();
mc.mainPanel.clear();
// This line causes the exception
mc.mainPanel.add( myRootPanel );
}
}
I do not understand that because the clear method is specified in HasWidgets.

Answer 1

It is very hard to follow your code as you use the same names in different class and then reference the field of the other class..
You initWidget of the composite and insert a dockLP(myRootPanel) and then insert another dockLP in that child. Then you insert the myRootPanel inside of a LayoutPanel but it has already been added to the composite PolicyManager via initWidget.
I would imagine if you cleaned this up a bit your stack trace could better point you to the problem. It looks like your PolicyManager doesn't need to be a Composite and doesn't need to initWidget. Just manipulate existing panels. However, you could probably clean up the organization further.
java.lang.IllegalStateException - if this widget's parent does not support removal (e.g. Composite)
http://google-web-toolkit.googlecode.com/svn/javadoc/latest/com/google/gwt/user/client/ui/Widget.html#removeFromParent()
------------old---------
Might be a problem with standards mode
LayoutPanel - "This widget will only work in standards mode, which requires that the HTML page in which it is run have an explicit declaration."?
http://google-web-toolkit.googlecode.com/svn/javadoc/latest/index.html
If not, Can you provide the full trace?