Vaadin 瓦丁14.4.2'；s"；选择"；不能使用setItems命令再次设置框

在Vaadin Flow 14.4.2中，我能够在选择组件第一次运行时成功地对其执行setItems。但是，如果它再次运行（例如，由于文件名文本字段的更改），则会出现错误。下面是一段代码：

filename.addValueChangeListener(e -> {
           //other code (removed for SO)....
            final IntArrayList lstTrees = new IntArrayList();
            //populate lstTrees code (removed for SO)
          //  treeNum.removeAll(); //I tried this as a hack, but it too throws error
          // treeNum.clear(); //I tried this as a hack, but it too throws error
            treeNum.setItems(lstTrees); //this throws error when called the 2nd time!!!!!!!!!!!!!!!!!!!!!!!!!!!
            treeNum.setValue(0);
        });

该错误没有太大用处，但这里是anywas：

java.lang.NullPointerException
    at com.deepsearch.fe.tab2vizdb.fpsgraphicaldetails.spectratab.hslspectrachartandalts.UiSingletree.lambda$new$f28a286$1(UiSingletree.java:134)
    at com.vaadin.flow.component.internal.AbstractFieldSupport.lambda$addValueChangeListener$828eca10$1(AbstractFieldSupport.java:96)
    at com.vaadin.flow.component.ComponentEventBus.fireEventForListener(ComponentEventBus.java:205)
    at com.vaadin.flow.component.ComponentEventBus.fireEvent(ComponentEventBus.java:194)
    at com.vaadin.flow.component.Component.fireEvent(Component.java:359)
    at com.vaadin.flow.component.ComponentUtil.fireEvent(ComponentUtil.java:386)
    at com.vaadin.flow.component.internal.AbstractFieldSupport.setValue(AbstractFieldSupport.java:207)
    at com.vaadin.flow.component.internal.AbstractFieldSupport.setValue(AbstractFieldSupport.java:133)
    at com.vaadin.flow.component.AbstractField.setValue(AbstractField.java:181)
    at com.vaadin.flow.component.HasValue.clear(HasValue.java:179)
    at com.vaadin.flow.component.select.Select.reset(Select.java:724)
    at com.vaadin.flow.component.select.Select.setDataProvider(Select.java:419)
    at com.vaadin.flow.data.binder.HasDataProvider.setItems(HasDataProvider.java:50)
    at com.deepsearch.fe.tab2vizdb.fpsgraphicaldetails.spectratab.hslspectrachartandalts.UiSingletree.lambda$new$3fab9f70$1(UiSingletree.java:128)
    at com.vaadin.flow.component.internal.AbstractFieldSupport.lambda$addValueChangeListener$828eca10$1(AbstractFieldSupport.java:96)
    at com.vaadin.flow.component.ComponentEventBus.fireEventForListener(ComponentEventBus.java:205)
    at com.vaadin.flow.component.ComponentEventBus.fireEvent(ComponentEventBus.java:194)
    at com.vaadin.flow.component.Component.fireEvent(Component.java:359)
    at com.vaadin.flow.component.ComponentUtil.fireEvent(ComponentUtil.java:386)
    at com.vaadin.flow.component.internal.AbstractFieldSupport.setValue(AbstractFieldSupport.java:207)
    at com.vaadin.flow.component.internal.AbstractFieldSupport.setModelValue(AbstractFieldSupport.java:167)
    at com.vaadin.flow.component.AbstractField.setModelValue(AbstractField.java:225)
    at com.vaadin.flow.component.AbstractSinglePropertyField.handlePropertyChange(AbstractSinglePropertyField.java:352)
    at com.vaadin.flow.component.AbstractSinglePropertyField.access$200(AbstractSinglePropertyField.java:48)
    at com.vaadin.flow.component.AbstractSinglePropertyField$1.propertyChange(AbstractSinglePropertyField.java:325)
    at com.vaadin.flow.internal.nodefeature.ElementPropertyMap.lambda$fireEvent$2(ElementPropertyMap.java:454)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at com.vaadin.flow.internal.nodefeature.ElementPropertyMap.fireEvent(ElementPropertyMap.java:454)
    at com.vaadin.flow.internal.nodefeature.ElementPropertyMap.access$100(ElementPropertyMap.java:48)
    at com.vaadin.flow.internal.nodefeature.ElementPropertyMap$PutResult.run(ElementPropertyMap.java:166)
    at com.vaadin.flow.server.communication.ServerRpcHandler.runMapSyncTask(ServerRpcHandler.java:395)
    at com.vaadin.flow.server.communication.ServerRpcHandler.lambda$handleInvocations$0(ServerRpcHandler.java:389)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at com.vaadin.flow.server.communication.ServerRpcHandler.handleInvocations(ServerRpcHandler.java:389)
    at com.vaadin.flow.server.communication.ServerRpcHandler.handleRpc(ServerRpcHandler.java:317)
    at com.vaadin.flow.server.communication.UidlRequestHandler.synchronizedHandleRequest(UidlRequestHandler.java:89)
    at com.vaadin.flow.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:40)
    at com.vaadin.flow.server.VaadinService.handleRequest(VaadinService.java:1545)
    at com.vaadin.flow.server.VaadinServlet.service(VaadinServlet.java:247)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:873)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:542)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:566)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1701)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1345)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:480)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1668)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1247)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144)
    at org.eclipse.jetty.server.Dispatcher.forward(Dispatcher.java:227)
    at org.eclipse.jetty.server.Dispatcher.forward(Dispatcher.java:78)
    at com.deepsearch.fe.web.SecurityFilter.doFilter(SecurityFilter.java:121)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:540)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1701)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1345)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:480)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1668)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1247)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:220)
    at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:126)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
    at org.eclipse.jetty.server.Server.handle(Server.java:502)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:370)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:267)
    at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305)
    at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103)
    at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:117)
    at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:333)
    at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:310)
    at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:168)
    at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:126)
    at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:366)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683)

---

仅供参考：我的lstTrees数组不为空；因此空指针异常引用了一些Vaadin组件。此外，尽管我认为这与此无关，但我使用了Vaadin Designer来构建UI。仅供参考2：另外，我觉得几年前我也看到过类似的错误，“选择”组件无法“重置”到新列表，但当我四处搜索时，我找不到任何解决问题的方法。仅供参考3：作为一个黑客，我还尝试调用select组件的

clear（）

和

removeAll（）

方法，但这两个方法都出现了错误。

谢谢@MarcusHellberg我没有意识到UiSingletree.java:134指向了我的代码（duh！）。这解决了我的问题。Vaadin中没有关于这个问题的bug——这完全是开发人员的错误。

UiSingletree.java:134上有什么内容？谢谢@MarcusHellberg我没有意识到UiSingletree.java:134指向我的代码（duh！）。这解决了我的问题。对于这个问题，Vaadin中没有bug——这完全是开发人员的错误。