英文:
How to call a method in another controller when multiforming with JavaFX?
问题
以下是翻译好的内容：
我想创建一个包含两个表单的项目，但是当我试图从第一个控制器调用第二个控制器中的一个方法时，出现了问题。为了简单起见，我已经创建了一个最小可重现示例。两个控制器分别如下：
第一个控制器：
package sample;import javafx.fxml.FXML;import javafx.fxml.FXMLLoader;import javafx.scene.Parent;import javafx.scene.Scene;import javafx.scene.control.Button;import javafx.event.ActionEvent;import javafx.stage.Stage;public class Controller {@FXML Button btnNew;public void switchHandler(ActionEvent evt) {try {launch(Main.getStage(), "sample2.fxml", "");Controller2 cont = new Controller2();cont.text();} catch (Exception e) {e.printStackTrace();}}private void launch(Stage primaryStage, String form, String title) throws Exception {Parent root = FXMLLoader.load(getClass().getResource(form));primaryStage.setTitle(title);primaryStage.setScene(new Scene(root, 600, 400));primaryStage.show();}}
第二个控制器：
package sample;import javafx.fxml.FXML;import javafx.scene.control.TextField;public class Controller2 {@FXMLTextField txt;public void text() {txt.setText("Hello World"); // 此行出错}}
两个表单如下：
第一个表单：
<?xml version="1.0" encoding="UTF-8"?><?import javafx.scene.control.*?><?import java.lang.*?><?import javafx.scene.layout.*?><?import javafx.geometry.Insets?><?import javafx.scene.layout.GridPane?><?import javafx.scene.control.Button?><?import javafx.scene.control.Label?><AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller"><children><Button fx:id="btnNew" onAction="#switchHandler" layoutX="213.0" layoutY="145.0" mnemonicParsing="false" text="Button" /></children></AnchorPane>
第二个表单：
<?xml version="1.0" encoding="UTF-8"?><?import java.lang.*?><?import java.util.*?><?import javafx.scene.*?><?import javafx.scene.control.*?><?import javafx.scene.layout.*?><AnchorPane prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller2"><children><TextField fx:id="txt" layoutX="151.0" layoutY="156.0" /></children></AnchorPane>
txt.setText("Hello World"); 这行代码会产生一个 NullPointerException。有人能告诉我为什么以及如何解决这个问题吗？
英文:
I want to create a project with two forms, but now there's a problem when I try to call a method in the second controller from the first controller. I've created a minimal reproducible example for simplicity. The two controllers are as follows:
package sample;import javafx.fxml.FXML;import javafx.fxml.FXMLLoader;import javafx.scene.Parent;import javafx.scene.Scene;import javafx.scene.control.Button;import javafx.event.ActionEvent;import javafx.stage.Stage;public class Controller {@FXML Button btnNew;public void switchHandler (ActionEvent evt) {try {launch(Main.getStage(), "sample2.fxml", "");Controller2 cont = new Controller2();cont.text();} catch (Exception e) {e.printStackTrace();}}private void launch(Stage primaryStage, String form, String title) throws Exception {Parent root = FXMLLoader.load(getClass().getResource(form));primaryStage.setTitle(title);primaryStage.setScene(new Scene(root, 600, 400));primaryStage.show();}}
And the second controller:
package sample;import javafx.fxml.FXML;import javafx.scene.control.TextField;public class Controller2 {@FXMLTextField txt;public void text() {txt.setText("Hello World"); //this line goes wrong}}
The forms are as follows:
<?xml version="1.0" encoding="UTF-8"?><?import javafx.scene.control.*?><?import java.lang.*?><?import javafx.scene.layout.*?><?import javafx.geometry.Insets?><?import javafx.scene.layout.GridPane?><?import javafx.scene.control.Button?><?import javafx.scene.control.Label?><AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller"><children><Button fx:id="btnNew" onAction="#switchHandler" layoutX="213.0" layoutY="145.0" mnemonicParsing="false" text="Button" /></children></AnchorPane>
And the second form:
<?xml version="1.0" encoding="UTF-8"?><?import java.lang.*?><?import java.util.*?><?import javafx.scene.*?><?import javafx.scene.control.*?><?import javafx.scene.layout.*?><AnchorPane prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller2"><children><TextField fx:id="txt" layoutX="151.0" layoutY="156.0" /></children></AnchorPane>
The line txt.setText("Hello World"); produces a NullPointerException. Can someone tell me why and how to fix this problem?
答案1
得分: 1
一个小样例供您参考。只需将其替换为您的类名。
您应该像这样进行操作：
FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("/sample2.fxml"));Parent root = fxmlLoader.load();MyController controller = fxmlLoader.getController();... //显示场景等。controller.text();
英文:
A small sample for you. Just replace with your classes.
You should do something like that:
FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("/sample2.fxml"));Parent root = fxmlLoader.load();MyController controller = fxmlLoader.getController();... //show scene etc.controller.text();
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