javafx - 在第一个控制器的第一个函数中,我从第二个控制器调用第二个函数,我得到了很多错误
问题描述
我有两个 fxml 文件,每个 fxml 文件都有一个控制器。在第一个 fxml 文件中,我有一个“基本”锚窗格,并且在此上有一个较小的“第二个”锚窗格。在第二个 fxml 文件中,我有一个“第三个”锚窗格,它与第一个 fxml 中的“第二个”锚窗格一样大。在这个“第三”锚窗格上,我有一个比“第三”锚窗格小一点的 TableView。在第一个控制器中,我使用 FXMLLoader 将“第二个”锚窗格的内容设置为第二个 fxml 文件。在第一个控制器中,我有一个方法,将“第二个”锚窗格的背景颜色设置为黄色,并从第二个控制器调用一个方法。此方法(在第二个控制器中)想要使 TableView 更大,但我收到错误消息。它出什么问题了?
第一个控制器:
public class Controller implements Initializable {
@FXML
AnchorPane baseanc;
@FXML
AnchorPane ancpane2;
@FXML
Button button;
controller2 contr2 = new controller2();
public void testMethod() {
ancpane2.setStyle("-fx-background-color: #ffff00");
contr2.testFunc();
}
public void buttonAction(ActionEvent event) {
testMethod();
}
@Override
public void initialize(URL url, ResourceBundle resourceBundle) {
try {
AnchorPane root = FXMLLoader.load(getClass().getResource("fxml2.fxml"));
ancpane2.getChildren().setAll(root);
} catch (IOException e) {
e.printStackTrace();
}
}
}
第二个控制器:
public class controller2{
@FXML
TableView table;
public void testFunc() {
table.setPrefHeight(720);
}
}
第一个 fxml:
<AnchorPane fx:id="baseanc" xmlns="http://javafx.com/javafx/8.0.221"
xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
<children>
<AnchorPane fx:id="ancpane2" prefHeight="720.0" prefWidth="640.0"/>
<Button fx:id="button" onAction="#buttonAction" text="Button" />
</children>
</AnchorPane>
第二个fxml:
<AnchorPane fx:id="ancpane3" xmlns="http://javafx.com/javafx/8.0.221" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.controller2">
<children>
<TableView fx:id="table" prefHeight="600.0" prefWidth="540.0">
<columns>
<TableColumn prefWidth="75.0" text="C1" />
<TableColumn prefWidth="75.0" text="C2" />
</columns>
</TableView>
</children>
</AnchorPane>
错误消息:
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1787)
at javafx.fxml/javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1670)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics/javafx.scene.Node.fireEvent(Node.java:8879)
at javafx.controls/javafx.scene.control.Button.fire(Button.java:200)
at javafx.controls/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:206)
at javafx.controls/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
at javafx.base/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3851)
at javafx.graphics/javafx.scene.Scene$MouseHandler.access$1200(Scene.java:3579)
at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1849)
at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2588)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:397)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:434)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:390)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:433)
at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:556)
at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:942)
at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at com.sun.javafx.reflect.Trampoline.invoke(MethodUtil.java:76)
at jdk.internal.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at javafx.base/com.sun.javafx.reflect.MethodUtil.invoke(MethodUtil.java:273)
at javafx.fxml/com.sun.javafx.fxml.MethodHelper.invoke(MethodHelper.java:83)
at javafx.fxml/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1782)
... 47 more
Caused by: java.lang.NullPointerException
at sample.controller2.testFunc(controller2.java:13)
at sample.Controller.testMethod(Controller.java:27)
at sample.Controller.buttonAction(Controller.java:31)
... 58 more
解决方案
问题是常规 JavaFX 控制器不应被视为单个实例(因为不是)。在加载 FXML 后,使用 @FXML 注释的所有内容都只会注入到控制器中
所以你的电话“新Controller2”
public class controller2{
@FXML
TableView table;
// Will be null without loading of a fxml
public void testFunc() {
table.setPrefHeight(720);
}
}
因此出现空指针异常。
在初始化之后,您应该通过 FXML 加载器注入初始化的控制器。
//Initialize a loader FOR the fxml with the ressource as Constructor parameter
FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("fxml2.fxml"));
// then load!
AnchorPane root = fxmlLoader.load();
//Inject the Controller!
controller2= (Controller2) fxmlLoader.getController();
// in that order.
那么 fxml 的初始化控制器应该是正确的实例。
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