JavaFX按鈕監聽器無法正常工作

Question

我正在創建一個簡單的計算器，它將在文本字段中輸入的兩個值相加，然後在按下按鈕時將總和顯示在第三個文本字段中。然而，當我按下按鈕什麼都沒有發生，我不知道什麼是錯的。我沒有收到任何錯誤消息，程序編譯按鈕只是沒有做任何事情。

import javafx.application.*; 
import javafx.geometry.*; 
import javafx.scene.*; 
import javafx.stage.*; 
import javafx.scene.layout.*; 
import javafx.scene.control.*; 
import javafx.event.*; 


public class Calculator extends Application{ 

private TextField sumField; 
private TextField firstVField; 
private TextField secondVField; 

public void start(Stage myStage){ 
    myStage.setTitle("Simple Calculator"); 

    GridPane rootNode = new GridPane(); 
    rootNode.setPadding(new Insets(30)); 
    rootNode.setHgap(5); 
    rootNode.setVgap(5); 

    Scene myScene = new Scene(rootNode, 350,250); 

    Label firstVLabel = new Label("First Value:"); 
    Label secondVLabel = new Label("Second Value:"); 
    Label sumLabel = new Label("Sum:"); 


    TextField firstVField = new TextField(); 
    TextField secondVField = new TextField(); 
    TextField sumField = new TextField(); 


    sumField.setEditable(false); 

    Button calculate = new Button("Calculate"); 

    rootNode.add(firstVLabel, 0, 0); 
    rootNode.add(firstVField, 1, 0); 
    rootNode.add(secondVLabel, 0, 1); 
    rootNode.add(secondVField, 1, 1); 
    rootNode.add(sumLabel, 0, 2); 
    rootNode.add(sumField, 1, 2); 
    rootNode.add(calculate, 1, 3); 

    myStage.setScene(myScene); 
    myStage.setResizable(false); 
    myStage.show(); 

} 

class ButtonHandler implements EventHandler<ActionEvent>{ 

    public void handle(ActionEvent e) { 
     int sum = (int)firstVField.getText() + (int)secondVField.getText(); 
     sumField.setText(Integer.toString(sum)); 

    } 
} 

public static void main(String [] args){ 
    launch(args); 
} 

} 

Answer 1

你忘了你的連接到ButtonHandler的calculate按鈕

calculate.setOnAction(new ButtonHandler());