Re: GUI crashes when call .destroy() method on Layout class

[Marco]

Dear all, after tons of tests maybe I have figured out what was the problem: I think that every exception that I have got can be caused by following elements:

1) I use .destroy() method but the best way is to use .markForDestroy() method;
2) I use .draw() methods for each element that is part of my main layout and then, at the end, I make a call on .show() method of the layout class: I have changed my code removing calls to .draw() subclasses and inserting a call of .draw() method of my main layout class (instead of using a call to .show() method);
3) I use always this. marker in order to identify variables belonging to my class but I have read that "this" marker could generate some problem if the JNSI function does not correctly map it so I have removed it.

Thank you very much.

Marco.

On Monday, January 14, 2013 10:46:04 PM UTC+1, Marco wrote:

Dear all,

I am having problems with a GWT program (it is not pure GWT but it makes use of SmartGWT framework) developed using a MVP approach and I need your support: I have created dedicated classes for each window that I want to render; every time I want to switch between "pages" I call destroy method to the "page" that I want to close (i.e. I call destroy method on Layout object) and I launch a custom event in order to load the new "page". The problem is that sometimes (I was not able to find a predefined pattern) the method MyCurrentLoadedLayout.destroy(), called from my current loaded layout, throws an exception and the program crash. 

This is the exception that has been launched:

java.lang.ClassCastException: null

    at java.lang.Class.cast(Class.java:2990)

    at com.google.gwt.dev.shell.JsValueGlue.get(JsValueGlue.java:169)

    at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:57)

    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.invokeNativeVoid(ModuleSpace.java:299)

    at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeVoid(JavaScriptHost.java:107)

    at com.smartgwt.client.widgets.BaseWidget.destroy(BaseWidget.java)

    at com.myTestClass.myTestLayout.destroyLytMain(myTestLayout.java:867)

    [...]

I am sure that the Layout class is not null because, as I wrote, the major of the time the code works correctly.

This strange behavior happens, randomly, also when I try to launch an event via EventBus:

com.google.gwt.event.shared.UmbrellaException: Exception caught: null

    at com.google.gwt.event.shared.EventBus.castFireEvent(EventBus.java:69)

    at com.google.gwt.event.shared.SimpleEventBus.fireEvent(SimpleEventBus.java:57)

    at com.myTestClass.myTestLayout$10.onSuccess(myTestLayout.java:842)

    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:232)

    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)

    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)

    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:597)

    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.GeneratedMethodAccessor139.invoke(Unknown Source)

    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

    at java.lang.reflect.Method.invoke(Method.java:597)

    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(Thread.java:680)

Please could you help me understanding which is the problem? What can I do in order to figure out what is the cause?

Thank you vey much for your help and best Regards,

Marco.