Question

我有一个项目，我向用户询问他们使用什么类型的电子设备来告诉他们需要多少太阳能电池板和电池。

为了收集信息，我使用了一个包含三列的gridPane，其中有TextArea和可变数量的行。我需要收集gridPane的第二行和第三行中的信息。

我使用下面提到的另一个问题的方法。

private void calculer(ActionEvent event)
{
    double ampApp = 0;
    double heureApp = 0;
    double wattTotal = 0;
    double nbJourAuto;
    double heureSoleil;
    int nbPanneau;
    int nbBatterie;
    String stringTemp;

    for(int i =1; i < rangee; i++)
    {
        stringTemp = getNodeByRowColumnIndex( i, 1, gridApp).toString();
        ampApp += parseDouble(stringTemp);
    }

    for(int i =1; i < rangee; i++)
    {
        stringTemp = getNodeByRowColumnIndex(i, 2, gridApp).toString();
        heureApp += parseDouble(stringTemp);
    }

（这只是方法的第一部分，我知道缺少“}”）

这是getNodeByRowColumnIndex代码：

public Node getNodeByRowColumnIndex( final int row, final int column, GridPane gridPane) {
   Node result = null;
   ObservableList<Node> childrens = gridPane.getChildren();
   for(Node node : childrens) 
   {
        if(gridPane.getRowIndex(node) == row && gridPane.getColumnIndex(node) == column) 
        {
           result = node;
           break;
        }
   }
   return result;
}

我尝试了这个方法，但继续得到java.lang.NullPointerException

有谁知道为什么以及如何解决这个问题？

编辑：

这里要求的是堆栈跟踪

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
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.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:8411)
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(CompositeEventHandler.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.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$MouseHandler.process(Scene.java:3757)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:380)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:294)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:416)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:415)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
... 48 more
Caused by: java.lang.NullPointerException
at systemesolaire.FXMLDocumentController.getNodeByRowColumnIndex(FXMLDocumentController.java:111)
at systemesolaire.FXMLDocumentController.calculer(FXMLDocumentController.java:81)
... 58 more

这是我如何初始化我的孩子（我使用的是SceneBuilder所以这里是FXML文件）

<content>
        <GridPane fx:id="gridApp" prefHeight="141.0" prefWidth="452.0">
           <columnConstraints>
              <ColumnConstraints hgrow="SOMETIMES" maxWidth="226.0" minWidth="10.0" prefWidth="226.0" />
              <ColumnConstraints hgrow="SOMETIMES" maxWidth="146.0" minWidth="10.0" prefWidth="123.0" />
              <ColumnConstraints hgrow="SOMETIMES" maxWidth="113.0" minWidth="10.0" prefWidth="103.0" />
           </columnConstraints>
           <rowConstraints>
              <RowConstraints minHeight="40.0" prefHeight="40.0" vgrow="NEVER" />
              <RowConstraints minHeight="40.0" prefHeight="40.0" vgrow="NEVER" />
              <RowConstraints minHeight="40.0" prefHeight="40.0" vgrow="NEVER" />
           </rowConstraints>
           <children>
              <Label text="  Nom de l'appareil">
                 <font>
                    <Font name="Anke" size="18.0" />
                 </font>
              </Label>
              <Label text="Ampérage" GridPane.columnIndex="1">
                 <font>
                    <Font name="Anke" size="14.0" />
                 </font>
              </Label>
              <Label text="Heures utilisation" GridPane.columnIndex="2">
                 <font>
                    <Font name="Anke" size="13.0" />
                 </font>
              </Label>
              <TextArea prefHeight="200.0" prefWidth="200.0" promptText="Nom" GridPane.rowIndex="1" />
              <TextArea prefHeight="200.0" prefWidth="200.0" promptText="Amp" GridPane.columnIndex="1" GridPane.rowIndex="1" />
              <TextArea prefHeight="200.0" prefWidth="200.0" promptText="Heure" GridPane.columnIndex="2" GridPane.rowIndex="1" />
              <TextArea prefHeight="200.0" prefWidth="200.0" promptText="Nom" GridPane.rowIndex="2" />
              <TextArea prefHeight="200.0" prefWidth="200.0" promptText="Amp" GridPane.columnIndex="1" GridPane.rowIndex="2" />
              <TextArea prefHeight="200.0" prefWidth="200.0" promptText="Heure" GridPane.columnIndex="2" GridPane.rowIndex="2" />
           </children>
        </GridPane>
     </content>

以下是我如何在gridPane中添加一行

 @FXML
private void ajouteRangee(ActionEvent event) 
{

   TextArea nom =  new TextArea();
   TextArea amp = new TextArea();
   TextArea heure = new TextArea();



   nom.setPromptText("Nom");
   amp.setPromptText("Amp");
   heure.setPromptText("heure");


   gridApp.addRow(rangee, nom, amp, heure);
   gridApp.layout();
   rangee++;

}

Answer 1

我在老师的帮助下得到了答案，如果有人有同样的问题，我就是这样解决的。

getColumnIndex出现NullPointerException，解决方案绕过了问题，但我不知道为什么我首先得到这个例外。

由于行和列的数量是已知的，因此无需搜索每个节点的正确数量。此外，由于每行的子女数量相同，因此可以通过合理的方式获得特定的孩子。方法如下：

 public TextArea getNodeByRowColumnIndex( final int row, final int column, GridPane gridPane) 
{

   ObservableList<Node> childrens = gridPane.getChildren();
   TextArea result = (TextArea) childrens.get((row*3)+column);

   return result;
}

ObservableList逐行从左到右获取子项，因此您可以使用此公式（（（rowIndex + 1）*每行的对象数量）+到达列中的特定对象对象）

然后您可以通过执行以下操作获取TextArea文本：

 stringTemp = getNodeByRowColumnIndex( i, 1, gridApp).getText();

从JavaFX中的GridPane中的TextArea获取文本

1 个答案: