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尝试将.add列表添加到列表列表时出现NullPointerException

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我正在使用JavaFX Scenebuilder 2.0和Netbeans编写一些代码 . 我正在努力使UI工作，以便当在页面上按下按钮时，用户输入到页面上的字段的所有信息将被输入到ArrayList中 . 然后，我想将此ArrayList添加到将包含每个较小列表的ArrayList . 目标是稍后循环遍历列表以提取数据并使用它生成输出文件 . 但是，我无法将第一个列表正确添加到更大的列表中（我相信由于NullPointerException，尽管使用Javafx进行调试有点令人困惑所以我不完全确定） . 这是我的代码：

List singleEndSample=new ArrayList<String>();
List<List> allSamples;

@FXML
private void addSample(ActionEvent event) {
    final int index = groups1.getSelectionModel().getSelectedIndex();
    if (index == -1) {noGroupError.setVisible(true);}
    else 
    {
        String name = libName.getText();
        String CV = cVar.getText();
        String insert = insertSize.getText();
        noGroupError.setVisible(false);
        if (singleEnd.isSelected()) {
            String location = singleReadLocation.getText();
            if (libName.getText().length() != 0) {
                if (singleReadLocation.getText().length() != 0) {
                    if (insertSize.getText().length() != 0) {
                        if (cVar.getText().length() != 0) {
                            singleEndSample.clear();
                            String sample = libName.getText();
                            samplesListView.add(sample);
                            sampleList.setItems(samplesListView);
                            singleEndSample.add((String) listViewItems.get(index));
                            singleEndSample.add(name);
                            singleEndSample.add(location);
                            singleEndSample.add(insert);
                            singleEndSample.add(CV);
                            allSamples.add(singleEndSample);
                            singleReadLocation.clear();
                            cVar.clear();
                            insertSize.clear();
                            libName.clear();
                        }
                    }
                }
            }
        }
    }

这是我从“allSamples.add（singleEndSample）”行中得到的错误;

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException:    java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1762)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1645)
    at     com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at     com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8216)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at     com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEven    tHandler.java:218)
    at     com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at     com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3724)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3452)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1728)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2461)
    at     com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java    :348)
    at     com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java    :273)
    at java.security.AccessController.doPrivileged(Native Method)
    at     com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:382)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:553)
    at com.sun.glass.ui.View.notifyMouse(View.java:925)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$141(WinApplication.java:102)
    at com.sun.glass.ui.win.WinApplication$$Lambda$37/96639997.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1757)
    ... 51 more
Caused by: java.lang.NullPointerException
    at pipeline.ui.PipelineUIController.addSample(PipelineUIController.java:381)
    ... 61 more

请帮忙！

java arrays arraylist nullpointerexception javafx

1 回答

  • 0

    问题似乎是你永远不会实例化 allSamples 所以当你尝试访问 allSamples.add(singleEndSample); 行时，你试图访问 null 对象 . 因为List是抽象的而且无法实例化我'd suggest tweaking it to something like an ArrayList that can actually be implemented (isn' t abstract） .

    一种可能的实现可能如下所示：

    ArrayList singleEndSample=new ArrayList<String>();
List<ArrayList> allSamples = new ArrayList<ArrayList>();
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