1

我正在尝试通过从 fxml 文件加载来动态设置边框窗格布局的中心窗格。现在，当我调用 setCenterPane() 方法时遇到空指针异常。下面是加载和设置中心窗格的控制器代码。我尝试加载的窗格类型是 AnchorPane，我也尝试将其转换为 AnchorPane，但它的行为仍然相同。我不确定我是否遗漏了什么。谁能提供有关如何解决此问题的任何想法？

空指针异常抛出 form borderPane.setCenter(cmdPane)行。（为了便于阅读，我从代码中删除了一些行）。

public class AnalyzerController implements Initializable {

@FXML
private BorderPane borderPane;

@FXML
private void cmdMenuAction(ActionEvent event) throws IOException {
        FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("CommandQuery.fxml"));
        Pane cmdPane = (Pane) fxmlLoader.load();

        try {
            borderPane.setCenter(cmdPane);
        } catch (Exception e) {
            e.printStackTrace();
        }
}

}

下面是异常跟踪。

java.lang.NullPointerException
    at analyzer.AnalyzerController.cmdMenuAction(AnalyzerController.java:65)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:55)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:269)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1435)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:28)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.Node.fireEvent(Node.java:6863)
    at javafx.scene.control.Hyperlink.fire(Hyperlink.java:145)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:193)
    at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:336)
    at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:329)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:64)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3328)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3168)
    at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3123)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1563)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2265)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:250)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:173)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:292)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:528)
    at com.sun.glass.ui.View.notifyMouse(View.java:922)

这是 AnalyzerController 引用的 Analyzer.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.paint.*?>

<BorderPane id="BorderPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns:fx="http://javafx.com/fxml" fx:controller="analyzer.AnalyzerController">
  <center>
    <Pane prefHeight="200.0" prefWidth="200.0">
      <children>
        <Label fx:id="noDbLabel" layoutX="187.0" layoutY="99.0" text="No database selected." />
      </children>
    </Pane>
  </center>
  <left>
    <Hyperlink fx:id="cmdMenu" onAction="#cmdMenuAction" text="Command" />
  </left>
  <top>
    <MenuBar>
      <menus>
        <Menu mnemonicParsing="false" text="File">
          <items>
            <MenuItem mnemonicParsing="false" onAction="#openDbAction" text="Open Database" fx:id="OpenDb" />
          </items>
        </Menu>
      </menus>
    </MenuBar>
  </top>
</BorderPane>

这是 CommandQuery.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import java.net.*?>
<?import java.util.*?>
<?import javafx.collections.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane id="AnchorPane" prefHeight="400.0" prefWidth="600.0" styleClass="mainFxmlClass" xmlns:fx="http://javafx.com/fxml" fx:controller="analyzer.CommandQueryController">
  <children>
    <SplitPane dividerPositions="0.29396984924623115" focusTraversable="true" orientation="VERTICAL" prefHeight="400.0" prefWidth="600.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
      <items>
        <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="100.0" prefWidth="160.0">
          <children>
            <Label layoutX="36.0" layoutY="23.0" text="Find" />
            <ComboBox fx:id="cmdTypeBox" layoutX="78.0" layoutY="23.0">
              <items>
                <FXCollections fx:factory="observableArrayList">
                  <String fx:value="Item 1" />
                  <String fx:value="Item 2" />
                  <String fx:value="Item 3" />
                </FXCollections>
              </items>
            </ComboBox>
            <Label layoutX="177.0" layoutY="23.0" text="From" />
          </children>
        </AnchorPane>
        <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="100.0" prefWidth="160.0" />
      </items>
    </SplitPane>
  </children>
  <stylesheets>
    <URL value="@commandquery.css" />
  </stylesheets>
</AnchorPane>
4

1 回答 1

1

看起来您正在尝试调用一个方法，borderPane但borderPane从未初始化。该@FXML标签告诉我，您希望borderPane在加载时被初始化Analyzer.fxml。如果是这种情况，那么您需要添加fx:id="borderPane"到您的Analyzer.fxml文件中。

于 2013-04-09T13:18:05.350 回答