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

时间:2014-11-14 03:55:56

标签: java arrays arraylist nullpointerexception javafx

我正在使用JavaFX Scenebuilder 2.0和Netbeans编写一些代码。我试图让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都将输入到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地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,所以我并不完全确定)。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();
                        }
                    }
                }
            }
        }
    }

这是我从第34行开始的错误&#34; allSamples.add(singleEndSample);

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!

1 个答案:

答案 0 :(得分:0)

问题似乎是您从未实例化allSamples,因此当您尝试在行allSamples.add(singleEndSample);中访问它时,您正尝试访问null对象。因为List是抽象的并且无法实例化,所以我建议将它调整为类似于实际可以实现的ArrayList(不是抽象的)。

一种可能的实现可能如下所示:

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