GWT-Tutorial StockWatcher, not using new HTML-File - html

Question

I am currently working through the StockWatcher-Tutorial on the GWT page and come this far to Step 3: Build the User Interface.
I changed the content of the hosted HTML-page as said and done the rest of the tutorial.
But when I try to test the new page and start Run > Debug As > Web Application, I get an exception in onLoad():
onModuleLoad() threw an exception Exception while loading module
com.ma.project.client.MaWebAppProject. See Development Mode for
details.
java.lang.reflect.InvocationTargetException 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.ModuleSpace.onLoad(ModuleSpace.java:396) at
com.google.gwt.dev.shell.OophmSessionHandler.loadModule(OophmSessionHandler.java:200)
at
com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:525)
at
com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
at java.lang.Thread.run(Unknown Source) Caused by:
java.lang.NullPointerException at
com.ma.project.client.MaWebAppProject.onModuleLoad(MaWebAppProject.java:41)
... 9 more
and the Development Mode Tab in Eclipse says:
[ERROR] [mawebappproject] - Unable to load module entry point class
com.ma.project.client.MaWebAppProject (see associated exception for
details)
I have found out so far, it seems the changes I made in the HTML-file are not recognized by the development server although I saved the file and everything. I tried to use the GWT Compile Project but no effect.
Seems the Java Code is crashing because it can not find the , which is used as the RootPanel.
Does anyone have an idea?
UPDATE: After some trail and error I found out I had to refresh the page once in the browser after the error message. The it worked. I still don't know why this happened, but so far it not happened again...

Answer 1

could it be that you have replaced the whole html file with the one from the page. this can cause a problem, because on the page, it uses your project name which is certainly not stockwatcher but apparently something like this: com.ma.project.client.MaWebAppProject (guessed).
I suggest you only you restore the last running state and replace only the lines which are marked yellow, then it should work.
The other reason could be that you didn't use RootPanel.get("stockList") or gave another name to the id div (this one: <div id="stockList"></div>). These two names must be identical (and the id field unique of course), because the RootPanel get method searches for a field with that id and places the Widget inside of it. (btw: RootPanel.get() with no parameters, it uses the body element so you can also try this).
Well this are all possibilities right now^^

Answer 2

I think I had this exact issue. My problem ended up being that the word "stocklist" was lower case in the html id like so:
<div id="stocklist"></div>
but was camel cased in the java code where the stocklist is associated with the main panel:
RootPanel.get("stockList").add(mainPanel);
The solution was, of course, to make one match the other.