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是否可以從每個班級添加/創建新的歷史記號？我遇到問題，如果我嘗試在主類外部創建新的令牌（History.newItem("infoTab")）（主類包含onModuleLoad（）方法），我得到NullPointerException。這裏的錯誤消息：GWT歷史問題
09:45:11.890 [ERROR] [com.mycompany.client.AdminInterface] Unable to load module entry
point class com.mycompany.client.entries.MainEntry (see associated exception for details)
編輯：在index.html的，不添加iframe的一部分。加入之後，我得到如下：
11:16:48.885 [ERROR] [com.mycompany.client.AdminInterface] Error while executing the JavaScript provider for property 'user.agent'
com.google.gwt.core.client.JavaScriptException: (null): null
at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:195)
at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:120)
at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:507)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:264)
at com.google.gwt.dev.shell.ModuleSpacePropertyOracle.computePropertyValue(ModuleSpacePropertyOracle.java:189)
at com.google.gwt.dev.shell.ModuleSpacePropertyOracle.getSelectionProperty(ModuleSpacePropertyOracle.java:127)
at com.google.gwt.dev.cfg.ConditionWhenPropertyIs.doEval(ConditionWhenPropertyIs.java:58)
at com.google.gwt.dev.cfg.Condition.isTrue(Condition.java:49)
at com.google.gwt.dev.cfg.ConditionAny.doEval(ConditionAny.java:37)
at com.google.gwt.dev.cfg.Condition.isTrue(Condition.java:49)
at com.google.gwt.dev.cfg.ConditionAll.doEval(ConditionAll.java:38)
at com.google.gwt.dev.cfg.Condition.isTrue(Condition.java:49)
at com.google.gwt.dev.cfg.Rule.isApplicable(Rule.java:36)
at com.google.gwt.dev.shell.StandardRebindOracle$Rebinder.tryRebind(StandardRebindOracle.java:98)
at com.google.gwt.dev.shell.StandardRebindOracle$Rebinder.rebind(StandardRebindOracle.java:54)
at com.google.gwt.dev.shell.StandardRebindOracle.rebind(StandardRebindOracle.java:154)
at com.google.gwt.dev.shell.ShellModuleSpaceHost.rebind(ShellModuleSpaceHost.java:119)
at com.google.gwt.dev.shell.ModuleSpace.rebind(ModuleSpace.java:531)
at com.google.gwt.dev.shell.ModuleSpace.rebindAndCreate(ModuleSpace.java:414)
at com.google.gwt.dev.shell.GWTBridgeImpl.create(GWTBridgeImpl.java:39)
at com.google.gwt.core.client.GWT.create(GWT.java:98)
at com.google.gwt.user.client.ui.Hyperlink.<clinit>(Hyperlink.java:65)
at com.mycompany.client.entries.MainEntry.onModuleLoad(MainEntry.java:110)
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.ModuleSpace.onLoad(ModuleSpace.java:369)
at com.google.gwt.dev.shell.OophmSessionHandler.loadModule(OophmSessionHandler.java:185)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:380)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:222)
at java.lang.Thread.run(Thread.java:662)
110線從MainEntry是：
searchButton = new Hyperlink("Search", SEARCH_ID);
，所以我不能真正理解，什麼是錯的...在內部消除IFRAME我送五個的歷史標記成功添加如下http://localhost:8080/client/index.html#token1。