将值传递给Eclipse E4中的其他视图时出错

Question

I am using IEventBroker to send the events to other view synchronously

@Inject
private IEventBroker eventBroker; 

The sender part has the following code:

Map<String,List<TreeMap<Timestamp, Long>>> StatisticValue = new HashMap<String,List<TreeMap<Timestamp, Long>>>();
//some code to add values in statisticValue
eventBroker.send("value", StatisticValue);

The receiver side has the following code snippet.

@Inject
@Optional
public void getEvent(@UIEventTopic("value")HashMap<String,List<TreeMap<Timestamp, Long>>> entriesForTs)
{
System.out.println("size"+entriesForTs.size());
}

I am getting the following error in the receiving end:

 Exception while dispatching event org.osgi.service.event.Event [topic=value] to handler org.eclipse.e4.ui.internal.di.UIEventObjectSupplier$UIEventHandler@6d79dea2
!STACK 0
org.eclipse.e4.core.di.InjectionException: java.lang.NullPointerException
    at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:63)
    at org.eclipse.e4.ui.internal.di.UIEventObjectSupplier$UIEventHandler$1.run(UIEventObjectSupplier.java:49)
    at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:180)
    at org.eclipse.swt.widgets.Display.syncExec(Display.java:4688)
    at org.eclipse.e4.ui.internal.workbench.swt.E4Application$1.syncExec(E4Application.java:205)
    at org.eclipse.e4.ui.internal.di.UIEventObjectSupplier$UIEventHandler.handleEvent(UIEventObjectSupplier.java:47)
    at org.eclipse.equinox.internal.event.EventHandlerWrapper.handleEvent(EventHandlerWrapper.java:197)
    at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:197)
    at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:1)
    at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
    at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:148)
    at org.eclipse.equinox.internal.event.EventAdminImpl.dispatchEvent(EventAdminImpl.java:135)
    at org.eclipse.equinox.internal.event.EventAdminImpl.sendEvent(EventAdminImpl.java:78)
    at org.eclipse.equinox.internal.event.EventComponent.sendEvent(EventComponent.java:39)
    at org.eclipse.e4.ui.services.internal.events.EventBroker.send(EventBroker.java:80)
    at com.xyz.abc.project.parts.StatisticsPart.processFiles(StatisticsPart.java:270)
    at com.xyz.abc.project.parts.StatisticsPart$5.selectionChanged(StatisticsPart.java:205)
    at org.eclipse.jface.viewers.Viewer$2.run(Viewer.java:164)
    at org.eclipse.jface.util.SafeRunnable$1.run(SafeRunnable.java:128)
    at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
    at org.eclipse.jface.viewers.Viewer.fireSelectionChanged(Viewer.java:162)
    at org.eclipse.jface.viewers.StructuredViewer.updateSelection(StructuredViewer.java:2188)
    at org.eclipse.jface.viewers.StructuredViewer.handleSelect(StructuredViewer.java:1211)
    at org.eclipse.jface.viewers.StructuredViewer$4.widgetSelected(StructuredViewer.java:1241)
    at org.eclipse.jface.util.OpenStrategy.fireSelectionEvent(OpenStrategy.java:239)
    at org.eclipse.jface.util.OpenStrategy.access$4(OpenStrategy.java:233)
    at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:403)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1057)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4170)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3759)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1113)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:997)
    at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:138)
    at org.eclipse.e4.ui.internal.workbench.swt.E4Application.start(E4Application.java:162)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:354)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:181)
    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 org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:636)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:591)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1450)
    at org.eclipse.equinox.launcher.Main.main(Main.java:1426)
Caused by: java.lang.NullPointerException
    at com.xyz.abc.project.parts.showGraph.getEvent(showGraph.java:109)
    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 org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:56)
    ... 48 more

I am confused why am I getting this error. I have checked the size(size = 2) of the StatisticValue in the sender side. But it is showing some nullpointer exception. Can anyone please help me?

Answer 1

The exception is reporting a NullPointerException in your getEvent method because the entriesForTs is null.

The @UIEventTopic handling code seems to call the event handler once with a null value the first time it is used (and then calls it again with the correct value). So just check for null in your getEvent .

Update:

You could try using org.osgi.service.event.Event as the type of the getEvent argument in case there is some problem with resolving the argument type:

public void getEvent(@UIEventTopic("value") Event event)
{
  data = event.getProperty(IEventBroker.DATA);

You could also try IEventBroker.subscribe if the @UIEventTopic refuses to work.

Update 2:

The event broker send (and post ) methods treat Map specially and assumes it is a map containing the values you want to send. So it will be looking in the Map for an IEventBroker.DATA key. It would be best to wrap your map in a container class.