Java JTextField actionListener不起作用

Question

我正在使用JButtons和JTextFields制作一个程序。 ActionListeners适用于JButtons，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构造的中间，“amountFrom”文本字段创建，然后我添加一个ActionListener。然后，在ActionHandler类的底部，我查找它的事件。但是，当我运行程序（点击'长度'），然后更改金额从文本字段并按回车，我没有得到一个控制台打印（它是假设打印“作品”的控制台时，textField操作发生）。 所有其他的Jbutton actionlisteners都可以工作，但是这个textfield actionListener不起作用。

Answer 1

在您的构造函数中，将ActionListener添加到您的JTextField中。

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

但在你的方法Step2()您创建一个JTextField的新实例，并且不添加一个侦听它。

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

注： 请看看布局管理器，并考虑使用它们。 https://docs.oracle.com/javase/tutorial/uiswing/layout/visual.html