java - AsynchCallback上的空指针异常

这是我的方法。

@Override
public void onSuccess(PlotSetOutput result) {
            String test = result.toString(); // this works
        controller.getScolopaxGUI().getResultsPanel().setPlots(result);
        controller.getScolopaxGUI().displayTab(1);
    }

在我的setPlots方法中，我试图在GoogleMaps上显示结果。我设定了一个断点
在setPlots内部，似乎代码在此之前失败。
我也能够成功获取ResultPanel对象。因此，我对导致此NullPointerException的原因感到困惑。

06:47:38.791 [ERROR] [scolopax] Uncaught exception escaped
java.lang.NullPointerException: null
    at edu.neu.scolopax.web.client.RetrieveSummariesAsynchCallback.onSuccess(RetrieveSummariesAsynchCallback.java:32)
    at edu.neu.scolopax.web.client.RetrieveSummariesAsynchCallback.onSuccess(RetrieveSummariesAsynchCallback.java:1)
    at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:232)
    at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:258)
    at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:412)
    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.GeneratedMethodAccessor33.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)

最佳答案

这里

以下之一为空

controller

controller.getScolopaxGUI()

controller.getScolopaxGUI().getResultsPanel()

尝试这个

    if(controller != null &&  controller.getScolopaxGUI() != null &&
 controller.getScolopaxGUI().getResultsPanel() != null)
     controller.getScolopaxGUI().getResultsPanel().setPlots(result);