Java JTextField actionListener不工作

Question

我正在用JButtons和JTextFields制作一个程序。ActionListener适用于JButton，但不适用于JTextFields。

    public class Gui extends JFrame {

private JButton Subject[] = new JButton[8];
private String SubjNames[] = {"Length", "Mass", "Currency", "Temperature", "Time", "Speed", "Data", "Cooking"};
private JButton Length1[] = new JButton[8];
private JButton Length2[] = new JButton[8];
private String LengNames[] = {"inches", "feet", "yards", "miles", "millimeters", "centimeters", "meters", "kilometers"};
private JTextField convertedFrom;
private JTextField amountFrom;
private JTextField convertedTo;
private JTextField amountTo;
private String from;
private String CTo;
private String ATo;
private int SubjectLocX = 40;
private int SubjectLocY = 50;
private int Length1LocX = 40;
private int Length1LocY = 150;
private int Length2LocX = 330;
private int Length2LocY = 150;
private int t = 0;

public Gui (){

    super("Converter");
    setLayout(null);

    System.out.println("yes");

    for (int i = 0; i<8; i++) {
    Subject[i] = new JButton(SubjNames[i]);
    Subject[i].setLocation(SubjectLocX,SubjectLocY);
    Subject[i].setSize(200,50);
    add(Subject[i]);
    if (i < 3) {
        SubjectLocX = 40;
        SubjectLocY += 100;
    } else if (i == 3) {
        SubjectLocX = 330;
        SubjectLocY = 50;
    } else if (i > 3) {
        SubjectLocY += 100;
        }
    }

    HandlerClass handler = new HandlerClass();

    for (int i = 0; i<8; i++) {
    Subject[i].addActionListener(handler);
    }


    for (int i = 0; i<8; i++) {
    Length1[i] = new JButton(LengNames[i]);
    Length2[i] = new JButton(LengNames[i]);
    }
    convertedFrom = new JTextField(from, 20);
    convertedTo = new JTextField(CTo, 20);
    amountFrom = new JTextField("amount", 20);
    amountFrom.addActionListener(handler);
    amountTo = new JTextField(ATo, 20);

    for (int i = 0; i<8; i++) {
        Length1[i].addActionListener(handler);
        Length2[i].addActionListener(handler);
        }

    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(600,500);
    setLocation(400,200);
    setVisible(true);
}

public void Step2() {

    for (int i = 0; i<8; i++) {
        remove(Subject[i]);
    }
    for (int i = 0; i<8; i++) {
        remove(Length1[i]);
        remove(Length2[i]);
    }
    remove(convertedFrom);
    remove(convertedTo);
    remove(amountFrom);
    remove(amountTo);

    HandlerClass handler = new HandlerClass();

    convertedFrom = new JTextField(from, 20);
    convertedFrom.setEditable(false);
    convertedFrom.setLocation(40,50);
    convertedFrom.setSize(200,30);
    add(convertedFrom);

    convertedTo = new JTextField(CTo, 20);
    convertedTo.setEditable(false);
    convertedTo.setLocation(330,50);
    convertedTo.setSize(200,30);
    add(convertedTo);

    amountFrom = new JTextField("amount", 20);
    amountFrom.setLocation(40,100);
    amountFrom.setSize(200,30);
    add(amountFrom);

    amountTo = new JTextField(ATo, 20);
    amountTo.setEditable(false);
    amountTo.setLocation(330,100);
    amountTo.setSize(200,30);
    add(amountTo);

    Length1LocX = 40;
    Length1LocY = 150;
    Length2LocX = 330;
    Length2LocY = 150;

    for (int i = 0; i<8; i++) {
        Length1[i].setLocation(Length1LocX, Length1LocY);
        Length1[i].setSize(90, 50);
        add(Length1[i]);
        if (i < 3) {
            Length1LocX = 40;
            Length1LocY += 100;
        } else if (i == 3) {
            Length1LocX = 150;
            Length1LocY = 150;
        } else if (i > 3) {
            Length1LocY += 100;
            }
        Length2[i].setLocation(Length2LocX, Length2LocY);
        Length2[i].setSize(90, 50);
        add(Length2[i]);
        if (i < 3) {
            Length2LocX = 330;
            Length2LocY += 100;
        } else if (i == 3) {
            Length2LocX = 440;
            Length2LocY = 150;
        } else if (i > 3) {
            Length2LocY += 100;
            }
    } 
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(600,600);
    setLocation(400,200);
    setVisible(true);
}
private class HandlerClass implements ActionListener {
    public void actionPerformed(ActionEvent event) {
        System.out.println("bruhhh");
        if (event.getSource() == amountFrom) {
            System.out.println("works");
        }
        for (int i = 0; i<8; i++) {
            if (event.getSource() == Length1[i]) {
                from = event.getActionCommand();
            }
            if (event.getSource() == Length2[i]) {
                CTo = event.getActionCommand();
            }
        }

        Step2();
    }
}
}

在我的Gui构造函数的中间，创建了“金额来自”TextField，然后我添加了一个actionListener。然后，在ActionHandler类的底部，我查找它的事件。但是，当我运行程序（单击“长度”）然后更改文本字段中的金额并按回车键时，我没有得到控制台打印（它被认为是在文本字段操作发生时将“工作”打印到控制台）。所有其他JButtactionListeners都可以工作，但这个text field actionListener不起作用。

Answer 1

在构造函数中，将ActionListener添加到JTextField中。

amountFrom = new JTextField("amount", 20);
amountFrom.addActionListener(handler);

但是在您的方法Step2（）中，您创建了一个JTextField的新实例，并且没有向其添加侦听器。

amountFrom = new JTextField("amount", 20);
amountFrom.setLocation(40,100);
amountFrom.setSize(200,30);
add(amountFrom);

注意：请查看布局管理器并考虑使用它们。https://docs.oracle.com/javase/tutorial/uiswing/layout/visual.html