当我按下一个键时没有调用 keyPressed() 方法？
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【中文标题】当我按下一个键时没有调用 keyPressed() 方法？【英文标题】：The keyPressed() method isn't being called when I press a key? 【发布时间】：2018-07-16 15:29:29 【问题描述】：我的程序只是一个简单的计算器，出于某种原因，每当我按下键盘上的某个键时，都不会调用 keyPressed() 方法。我已经完成了 System.out.println() 以测试它是否被调用，但事实并非如此。请帮忙
import java.awt.*;
import java.awt.event.*;
import javax.swing.JOptionPane;
public class FullCalculator extends Frame implements ActionListener,KeyListener
private Button btn0, btn1, btn2, btn3, btn4, btn5, btn6, btn7, btn8, btn9,
btnAdd, btnSub, btnMul, btnDiv, btnEquals, btnDot, btnC, btnCE, btnRand,
btnBack;
private Label lbl1, lbl2, black;
private float temp, temp2;
private String operator, tempS;
public FullCalculator (String s)
super (s);
init();
this.addKeyListener(this);
this.setFocusable(true);
this.requestFocus(true);
setLayout(null);
public void init()
Font f = new Font ("Courier", Font.BOLD, 13);
btn0 = new Button ("0");
btn0.setBounds(6, 285, 70, 70);
btn0.addActionListener(this);
btn0.setFont (f);
btn1 = new Button ("1");
btn1.setBounds(6, 215, 70, 70);
btn1.addActionListener(this);
btn1.setFont (f);
btn2 = new Button ("2");
btn2.setBounds(76, 215, 70, 70);
btn2.addActionListener(this);
btn2.setFont (f);
btn3 = new Button ("3");
btn3.setBounds(146, 215, 70, 70);
btn3.addActionListener(this);
btn3.setFont (f);
btn4 = new Button ("4");
btn4.setBounds(6, 145, 70, 70);
btn4.addActionListener(this);
btn4.setFont (f);
btn5 = new Button ("5");
btn5.setBounds(76, 145, 70, 70);
btn5.addActionListener(this);
btn5.setFont (f);
btn6 = new Button ("6");
btn6.setBounds(146, 145, 70, 70);
btn6.addActionListener(this);
btn6.setFont (f);
btn7 = new Button ("7");
btn7.setBounds(6, 75, 70, 70);
btn7.addActionListener(this);
btn7.setFont (f);
btn8 = new Button ("8");
btn8.setBounds(76, 75, 70, 70);
btn8.addActionListener(this);
btn8.setFont (f);
btn9 = new Button ("9");
btn9.setBounds(146, 75, 70, 70);
btn9.addActionListener(this);
btn9.setFont (f);
btnAdd = new Button ("+");
btnAdd.setBounds(216, 75, 70, 70);
btnAdd.addActionListener(this);
btnAdd.setFont (f);
btnSub = new Button ("-");
btnSub.setBounds(216, 145, 70, 70);
btnSub.addActionListener(this);
btnSub.setFont (f);
btnMul = new Button ("*");
btnMul.setBounds(216, 215, 70, 70);
btnMul.addActionListener(this);
btnMul.setFont (f);
btnDiv = new Button ("/");
btnDiv.setBounds(146, 285, 70, 70);
btnDiv.addActionListener(this);
btnDiv.setFont (f);
btnEquals = new Button ("=");
btnEquals.setBounds(216, 285, 70, 70);
btnEquals.addActionListener(this);
btnEquals.setFont (f);
btnDot = new Button (".");
btnDot.setBounds (76, 285, 70, 70);
btnDot.addActionListener(this);
btnDot.setFont (f);
btnC = new Button ("C");
btnC.setBounds (76, 355, 70, 70);
btnC.addActionListener(this);
btnC.setFont (f);
btnCE = new Button ("CE");
btnCE.setBounds (146, 355, 70, 70);
btnCE.addActionListener(this);
btnCE.setFont (f);
btnRand = new Button ("RandNum");
btnRand.setBounds (6, 355, 70, 70);
btnRand.addActionListener(this);
btnRand.setFont (f);
btnBack = new Button ("<==");
btnBack.setBounds (216, 355, 70, 70);
btnBack.addActionListener (this);
btnBack.setFont (f);
lbl1 = new Label ("", Label.RIGHT);
lbl1.setBounds (9, 52, 274, 22);
lbl1.setBackground (Color.WHITE);
lbl1.setFont (new Font ("Courier", Font.BOLD, 20));
lbl2 = new Label ("", Label.RIGHT);
lbl2.setBounds (9, 32, 274, 20);
lbl2.setBackground (Color.WHITE);
lbl2.setFont (new Font ("Monospaced", Font.PLAIN, 12));
black = new Label ("");
black.setBounds (6, 30, 280, 50);
black.setBackground (Color.BLACK);
add(btn0);
add(btn1);
add(btn2);
add(btn3);
add(btn4);
add(btn5);
add(btn6);
add(btn7);
add(btn8);
add(btn9);
add(btnAdd);
add(btnSub);
add(btnMul);
add(btnDiv);
add(btnEquals);
add(btnDot);
add(btnC);
add(btnCE);
add(btnRand);
add(btnBack);
add(lbl1);
add(lbl2);
add(black);
addWindowListener(new WindowAdapter()
public void windowClosing(WindowEvent we)
System.exit(0);
);
@Override
public void actionPerformed(ActionEvent e)
try
if (e.getSource()==btn0)
setLabel("0");
else if (e.getSource()==btn1)
setLabel("1");
else if (e.getSource()==btn2)
setLabel("2");
else if (e.getSource()==btn3)
setLabel("3");
else if (e.getSource()==btn4)
setLabel("4");
else if (e.getSource()==btn5)
setLabel("5");
else if (e.getSource()==btn6)
setLabel("6");
else if (e.getSource()==btn7)
setLabel("7");
else if (e.getSource()==btn8)
setLabel("8");
else if (e.getSource()==btn9)
setLabel("9");
else if (e.getSource()==btnAdd)
temp = Float.parseFloat(lbl1.getText());
operator = "+";
lbl2.setText(lbl1.getText()+"+");
lbl1.setText("");
else if (e.getSource()==btnSub)
temp = Float.parseFloat(lbl1.getText());
operator = "-";
lbl2.setText(lbl1.getText()+"-");
lbl1.setText("");
else if (e.getSource()==btnMul)
temp = Float.parseFloat(lbl1.getText());
operator = "*";
lbl2.setText(lbl1.getText()+"*");
lbl1.setText("");
else if (e.getSource()==btnDiv)
temp = Float.parseFloat(lbl1.getText());
operator = "/";
lbl2.setText(lbl1.getText()+"/");
lbl1.setText("");
else if (e.getSource()==btnEquals)
temp2 = Float.parseFloat(lbl1.getText());
switch (operator)
case "+": lbl1.setText("" + (temp+temp2)); break;
case "-": lbl1.setText("" + (temp-temp2)); break;
case "*": lbl1.setText("" + (temp*temp2)); break;
case "/": lbl1.setText("" + (temp/temp2)); break;
else if (e.getSource()==btnDot)
setLabel(".");
else if (e.getSource()==btnC)
lbl1.setText("");
lbl2.setText("");
else if (e.getSource()==btnCE)
lbl1.setText("");
else if (e.getSource()==btnRand)
lbl1.setText(""+(int)(Math.random()*100)+1);
else if (e.getSource()==btnBack)
tempS = lbl1.getText();
lbl1.setText((lbl1.getText().substring(0, tempS.length() - 1)));
catch (Exception ex)
JOptionPane.showMessageDialog (null, "Error " + ex.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
@Override
public void keyPressed(KeyEvent e)
if (e.getKeyCode()==(KeyEvent.VK_0|KeyEvent.VK_NUMPAD0))
setLabel("0");
else if (e.getKeyCode()==(KeyEvent.VK_1|KeyEvent.VK_NUMPAD1))
setLabel("1");
else if (e.getKeyCode()==(KeyEvent.VK_2|KeyEvent.VK_NUMPAD2))
setLabel("2");
else if (e.getKeyCode()==(KeyEvent.VK_3|KeyEvent.VK_NUMPAD3))
setLabel("3");
else if (e.getKeyCode()==(KeyEvent.VK_4|KeyEvent.VK_NUMPAD4))
setLabel("4");
else if (e.getKeyCode()==(KeyEvent.VK_5|KeyEvent.VK_NUMPAD5))
setLabel("5");
else if (e.getKeyCode()==(KeyEvent.VK_6|KeyEvent.VK_NUMPAD6))
setLabel("6");
else if (e.getKeyCode()==(KeyEvent.VK_7|KeyEvent.VK_NUMPAD7))
setLabel("7");
else if (e.getKeyCode()==(KeyEvent.VK_8|KeyEvent.VK_NUMPAD8))
setLabel("8");
else if (e.getKeyCode()==(KeyEvent.VK_9|KeyEvent.VK_NUMPAD9))
setLabel("9");
else if (e.getKeyCode()==KeyEvent.VK_PLUS)
temp = Float.parseFloat(lbl1.getText());
operator = "+";
lbl2.setText(lbl1.getText()+"+");
lbl1.setText("");
else if (e.getKeyCode()==KeyEvent.VK_MINUS)
temp = Float.parseFloat(lbl1.getText());
operator = "-";
lbl2.setText(lbl1.getText()+"-");
lbl1.setText("");
else if (e.getKeyCode()==KeyEvent.VK_ASTERISK)
temp = Float.parseFloat(lbl1.getText());
operator = "*";
lbl2.setText(lbl1.getText()+"*");
lbl1.setText("");
else if (e.getKeyCode()==KeyEvent.VK_SLASH)
temp = Float.parseFloat(lbl1.getText());
operator = "/";
lbl2.setText(lbl1.getText()+"/");
lbl1.setText("");
else if (e.getKeyCode()==KeyEvent.VK_PERIOD)
setLabel(".");
@Override
public void keyReleased(KeyEvent e)
@Override
public void keyTyped(KeyEvent e)
public void setLabel(String key)
lbl1.setText(lbl1.getText()+key);
我也试过不使用 setFocus(true) 和 requestFocus(true)
【问题讨论】：
为什么你有一个也是 KeyListener 的 Frame？您应该避免创建“一体化”类。 Pipe (|) operator in Java的可能重复 请阅读欺骗问题以了解此e.getKeyCode()==(KeyEvent.VK_6|KeyEvent.VK_NUMPAD6) 并不意味着“VK_6 或 VK_NUMPAD0”。
请将代码格式化为代码，并仅提供最小示例。 (MCVE)
另外，您的 KeyListener 被分配给 Frame，而不是 Labels。
【参考方案1】：
您遇到的第一个问题是Unresponsive KeyListener for JFrame.
考虑将 keylistener 注册到相关组件。
然后，正如@Tom 也指出的那样，例如KeyEvent.VK_0|KeyEvent.VK_NUMPAD0 在整数 值KeyEvent.VK_0 和KeyEvent.VK_NUMPAD0 之间执行按位OR 运算。
还有
if (e.getKeyCode()==(KeyEvent.VK_0|KeyEvent.VK_NUMPAD0))
变成
if (e.getKeyCode()==<result of the above bitwise OR operation>)
用例如替换你的条件
if ((e.getKeyCode()==KeyEvent.VK_0) || (e.getKeyCode()==KeyEvent.VK_NUMPAD0))
获得预期的行为。
还要注意双管道||，这样可以防止在左侧部分为真时评估右侧部分。
参照。 Pipe (|) operator in Java
【讨论】：
请注意，在这种情况下，VK_0=48 和 VK_NUMPAD0=96、48|96=112 和 VK_F1=112。因此，在尝试检查 0 时，它实际上与 F1 匹配。 虽然有趣，但不要在代码中使用数字，使用 KeyEvent.VK_ 常量
我很感谢您的回复，但使用 ||它没有工作，出现以下错误；
二元运算符“||”的操作数类型错误第一种：int；第二种：int;
当我完全删除 OR 时，它确实有效，所以无论如何 ;)
现在，由于某种原因，出现了另一个问题......每当我输入任何数字时，它都会将计算器显示设置为“00”而不是“0”......请帮助；/跨度>
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