javafxstarter:从主窗口修改其他窗口上的标签文本
我是一个使用Scenebuilder和MVC初学者的新javaFx 我有一个问题如下: 我试图制作一个主窗口来提醒一个新窗口。我试图在警报窗口中对标签文本进行MIDI。但我不能那样做。我得到了这个错误:javafxstarter:从主窗口修改其他窗口上的标签文本,java,javafx,window,label,fxml,Java,Javafx,Window,Label,Fxml,我是一个使用Scenebuilder和MVC初学者的新javaFx 我有一个问题如下: 我试图制作一个主窗口来提醒一个新窗口。我试图在警报窗口中对标签文本进行MIDI。但我不能那样做。我得到了这个错误: Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException at javafx.fxml.FXMLLoade
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$MouseEventNotification.run(GlassViewEventHandler.java:352)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$355(GlassViewEventHandler.java:388)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:387)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$149(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1771)
... 48 more
Caused by: java.lang.NullPointerException
at controller.AlertController.setAlertLabel(AlertController.java:36)
at controller.MainController.onMainButtonClicked(MainController.java:24)
... 58 more
我有一个包含maincontroller、alertController和main.fxml以及alert.fxml的主窗口,如下所示:
主要内容:
package app;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class Main extends Application {
@Override
public void start(Stage primaryStage) throws Exception{
Parent root = FXMLLoader.load(getClass().getResource("../view/Main.fxml"));
primaryStage.setTitle("Hello World");
primaryStage.setScene(new Scene(root));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
主控制器:
package controller;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
public class MainController {
AlertController alertController = new AlertController();
@FXML
public Label mainLabel;
@FXML
public TextField mainTextField;
@FXML
public Button mainButton;
@FXML
public void onMainButtonClicked() {
alertController.displayAlert();
alertController.setAlertLabel("Hello from MainController!");
}
}
Main.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controller.MainController">
<children>
<VBox prefHeight="400.0" prefWidth="600.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<children>
<HBox alignment="CENTER" prefHeight="154.0" prefWidth="600.0">
<children>
<Label fx:id="mainLabel" alignment="CENTER" contentDisplay="TOP" prefHeight="31.0" prefWidth="115.0" text="Main Text" />
</children>
</HBox>
<HBox alignment="CENTER" centerShape="false" layoutX="10.0" layoutY="10.0">
<children>
<TextField fx:id="mainTextField" alignment="TOP_LEFT" prefHeight="25.0" prefWidth="331.0" />
</children>
</HBox>
<HBox alignment="CENTER" layoutX="10.0" layoutY="10.0" prefHeight="100.0" prefWidth="200.0">
<children>
<Button fx:id="mainButton" mnemonicParsing="false" onAction="#onMainButtonClicked" text="Display Alert && Set Message Text" />
</children>
</HBox>
</children>
</VBox>
</children>
</AnchorPane>
和Alert.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.VBox?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="210.0" prefWidth="380.0" xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controller.AlertController">
<children>
<VBox prefHeight="210.0" prefWidth="380.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<children>
<HBox alignment="BOTTOM_CENTER" prefHeight="100.0" prefWidth="200.0">
<children>
<Label fx:id="alertLabel" text="Alert Message" />
</children>
</HBox>
<HBox alignment="CENTER" prefHeight="100.0" prefWidth="200.0">
<children>
<Button fx:id="alertButton" mnemonicParsing="false" onAction="#onAlertButtonClicked" text="Close" />
</children>
</HBox>
</children>
</VBox>
</children>
</AnchorPane>
请帮助我解决这个问题,并解释为什么这不起作用。谢谢您的建议。有两个
AlertController
实例:一个是您在MainController
中创建的
AlertController alertController = new AlertController();
以及在displayAlert()
中加载Alert.fxml
时由fxmloader
创建的
@FXML
-注释字段由它创建的实例上的fxmloader
初始化。但是,您正在对不是由FXMLLoader
创建的AlertController
实例调用setAlertLabel(…)
。所以当你打电话的时候
alertController.setAlertLabel("Hello from MainController!");
属于alertController
的alertLabel
尚未初始化,您会收到一个空指针异常
简单解决方案
最简单的修复方法是在MainController
中加载Alert.fxml
,并检索正确的控制器实例:
public class MainController {
@FXML
public Label mainLabel;
@FXML
public TextField mainTextField;
@FXML
public Button mainButton;
@FXML
public void onMainButtonClicked() {
FXMLLoader loader = new FXMLLoader(getClass().getResource("../view/Alert.fxml"));
Parent root = loader.load();
AlertController alertController = loader.getController();
alertController.setAlertLabel("Hello from MainController!");
Scene scene = new Scene(root);
window.setScene(scene);
window.setTitle("Alert");
window.show();
}
}
并从AlertController
中删除displayAlert()
方法
自定义组件解决方案 另一种在结构上更接近原始版本的方法是将
AlertController
替换为
Alert.fxml(注意对根元素的更改,并且fx:controller
已被删除):
AlertController.java:
package controller;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.stage.Stage;
import java.io.IOException;
public class AlertController extends AnchorPane {
Stage window;
@FXML
public Label alertLabel;
@FXML
Button alertButton;
public AlertController() {
window = new Stage();
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("../view/Alert.fxml"));
loader.setController(this);
loader.setRoot(this);
loader.load();
Scene scene = new Scene(this);
window.setScene(scene);
window.setTitle("Alert");
} catch (IOException e) {
e.printStackTrace();
}
}
public void displayAlert() {
window.show();
}
public void setAlertLabel(String str) {
alertLabel.setText(str);
}
@FXML
public void onAlertButtonClicked() {
window.close();
}
}
现在,您的主控制器可以如下所示:
package controller;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
public class MainController {
AlertController alertController = new AlertController();
@FXML
public Label mainLabel;
@FXML
public TextField mainTextField;
@FXML
public Button mainButton;
@FXML
public void onMainButtonClicked() {
alertController.displayAlert();
alertController.setAlertLabel("Hello from MainController!");
}
}
AlertController
有两个实例:一个是在MainController
中创建的
AlertController alertController = new AlertController();
以及在displayAlert()
中加载Alert.fxml
时由fxmloader
创建的
@FXML
-注释字段由它创建的实例上的fxmloader
初始化。但是,您正在对不是由FXMLLoader
创建的AlertController
实例调用setAlertLabel(…)
。所以当你打电话的时候
alertController.setAlertLabel("Hello from MainController!");
属于alertController
的alertLabel
尚未初始化,您会收到一个空指针异常
简单解决方案
最简单的修复方法是在MainController
中加载Alert.fxml
,并检索正确的控制器实例:
public class MainController {
@FXML
public Label mainLabel;
@FXML
public TextField mainTextField;
@FXML
public Button mainButton;
@FXML
public void onMainButtonClicked() {
FXMLLoader loader = new FXMLLoader(getClass().getResource("../view/Alert.fxml"));
Parent root = loader.load();
AlertController alertController = loader.getController();
alertController.setAlertLabel("Hello from MainController!");
Scene scene = new Scene(root);
window.setScene(scene);
window.setTitle("Alert");
window.show();
}
}
并从AlertController
中删除displayAlert()
方法
自定义组件解决方案 另一种在结构上更接近原始版本的方法是将
AlertController
替换为
Alert.fxml(注意对根元素的更改,并且fx:controller
已被删除):
AlertController.java:
package controller;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.stage.Stage;
import java.io.IOException;
public class AlertController extends AnchorPane {
Stage window;
@FXML
public Label alertLabel;
@FXML
Button alertButton;
public AlertController() {
window = new Stage();
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("../view/Alert.fxml"));
loader.setController(this);
loader.setRoot(this);
loader.load();
Scene scene = new Scene(this);
window.setScene(scene);
window.setTitle("Alert");
} catch (IOException e) {
e.printStackTrace();
}
}
public void displayAlert() {
window.show();
}
public void setAlertLabel(String str) {
alertLabel.setText(str);
}
@FXML
public void onAlertButtonClicked() {
window.close();
}
}
现在,您的主控制器可以如下所示:
package controller;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
public class MainController {
AlertController alertController = new AlertController();
@FXML
public Label mainLabel;
@FXML
public TextField mainTextField;
@FXML
public Button mainButton;
@FXML
public void onMainButtonClicked() {
alertController.displayAlert();
alertController.setAlertLabel("Hello from MainController!");
}
}
我现在明白了。非常感谢:DI仍然在{AlertController constructor}部分出错<代码>公共AlertController(){window=new Stage();尝试{FXMLLoader=new FXMLLoader(getClass().getResource(“../view/Alert.fxml”);loader.setController(此);loader.setRoot(此);loader.load();场景=新场景(此);window.setScene(场景);window.setTitle(“Alert”);}catch(IOException e){e.printStackTrace();}}我现在明白了。非常感谢:DI仍然在{AlertController constructor}部分出错<代码>公共AlertController(){window=new Stage();尝试{FXMLLoader=new FXMLLoader(getClass().getResource(“../view/Alert.fxml”);loader.setController(此);loader.setRoot(此);loader.load();场景=新场景(此);window.setScene(场景);window.setTitle(“警报”);}捕获(IOException e){e.printStackTrace();}}