javafx 事件处理程序返回错误我不完全理解

Question

我对Javafx还很陌生，正在努力理解我遇到的错误。创建事件处理程序时，程序将返回错误：错误：(56，94(java:->预期值。

Main.java

package sample;
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("sample.fxml"));
primaryStage.setTitle("Credit Card Input");
primaryStage.setScene(new Scene(root, 300, 275));
primaryStage.show();
}

public static void main(String[] args) {
launch(args);
}
}
Controller.java
package sample;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.scene.control.TextField;
import javafx.scene.input.KeyEvent;

public class Controller{
@FXML
TextField creditCardNo;
@FXML
TextField expDate;
@FXML
TextField ccvInput ;
@FXML
String imageOutput = new String("default.png");

public String ccvCheck(Object ccvInput){
String ccInput = this.ccvInput.getText();
char[] intArray = ccInput.toCharArray();
StringBuilder doubleDigitCheck = new StringBuilder();
doubleDigitCheck.append(intArray[0]).append(intArray[1]);
String str = new String(doubleDigitCheck);
int checkValue = Integer.parseInt(String.valueOf(intArray[0]));
String str2 = ccInput.substring(0,1);
if (str.matches("34")) {
return imageOutput = new String("amex.png");
}
if (str.matches("35")) {
return this.imageOutput = new String("jcb.png");
}
if (str.matches("37")) {
return this.imageOutput = new String("amex.png");
}
if (str2.matches("4")) {
return this.imageOutput = new String("visa.png");
}
if (str2.matches("5")) {
return this.imageOutput = new String("mastercard.png");
} else return this.imageOutput = new String("default.png");
}
public TextField getCcvInput() {
return ccvInput;
}
EventHandler<? super KeyEvent> eventHandler= ccvInput.setOnKeyReleased(eventHandler -> ()   { ccvCheck(ccvInput); });
//TODO:Set event handler to run checkValue and link to ccvInput

}

sample.fxml

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import javafx.scene.image.*?>
<?import javafx.scene.layout.*?>
<GridPane prefHeight="119.0" prefWidth="321.0" xmlns="http://javafx.com/javafx/10.0.2-internal" xmlns:fx="http://javafx.com/fxml/1">
<columnConstraints>
<ColumnConstraints />
<ColumnConstraints maxWidth="160.5" minWidth="160.5" prefWidth="160.5" />
<ColumnConstraints maxWidth="0.0" minWidth="0.0" prefWidth="0.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints />
<RowConstraints minHeight="10.0" prefHeight="10.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="10.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="10.0" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<TextField fx:id="creditCardNo" GridPane.rowIndex="1" />
<TextField fx:id="expDate" GridPane.columnIndex="1" GridPane.rowIndex="1" />
<TextField fx:id="ccvInput" onAction="#eventHandler" GridPane.rowIndex="3"/>
<ImageView fx:id="imageOutput" fitHeight="72.0" fitWidth="105.0" opacity="0.0" pickOnBounds="true" preserveRatio="true" GridPane.columnIndex="1" GridPane.rowIndex="3">
<image>
<Image url="@../../visa.png" />
</image></ImageView>
<Label text="Credit Card Number" />
<Label text="Exp Date" GridPane.columnIndex="1" />
<Label text="CCV" GridPane.rowIndex="2" />
</children>
</GridPane>

我正在尝试设置事件处理程序，以便当用户将数字输入CVV字段(TextField-ccvInput(时，会选择一个图像。目前收到的错误，据我所知。它们的语法是正确的。如有任何帮助，我们将不胜感激。

Answer 1

这不是创建EventHandler的正确方法。您可以使用lambda直接在setOnKeyReleased()方法中定义EventHandler：

ccvInput.setOnKeyReleased(event -> {
ccvCheck(ccvInput.getText());
});

然而，您的代码可能会遇到许多其他问题，您可能需要重新思考您的结构和流程。