我在计算器上找不到代码0 * 2 = 2或0/2 = 2的解决方案
我在calculate（）中有问题。当我按0-2或0 * 2或0/2时打开计算器时，总是得出我在零之前输入的数字。如果我不这样做，否则我打开计算器时不编码第一个数字。在编程方面，请帮我一个新手。
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.Toolkit;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.SwingConstants;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JLabel;
import javax.swing.border.Border;
import javax.swing.border.LineBorder;
public class Calculator{
private JFrame frame;
private JButton btnX;
private JButton button_1, button;
private JButton button_2;
private JLabel label;
private JLabel label2;
private JButton button_3;
private JButton button_4;
private JButton button_5;
private JButton button_6;
private JButton button_7;
private JButton button_8;
private JButton button_9, button_15;
private JButton button_11, button_14;
private JButton button_12, button_16;
private JButton button_13, button_17;
private JButton button_22;
private Double result = 0.0;
private Double inverse;
private Double squareRoot;
private Double square;
private Double percent;
private boolean newin = true;
private String arg = "";
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Calculator window = new Calculator();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public Calculator() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
ImageIcon image = new ImageIcon("D:/Programming/MyApps/src/1440353685_MB__calculator.png");
frame = new JFrame();
KeyListener l = new KeyListener() {
@Override
public void keyPressed(KeyEvent e) {
switch (e.getKeyCode()) {
case KeyEvent.VK_0 :
case KeyEvent.VK_NUMPAD0 : button_9.doClick();
break;
case KeyEvent.VK_NUMPAD1 :
case KeyEvent.VK_1 : button.doClick();
break;
case KeyEvent.VK_2 :
case KeyEvent.VK_NUMPAD2 : button_1.doClick();
break;
case KeyEvent.VK_3 :
case KeyEvent.VK_NUMPAD3 : button_2.doClick();
break;
case KeyEvent.VK_4 :
case KeyEvent.VK_NUMPAD4 : button_3.doClick();
break;
case KeyEvent.VK_5 :
case KeyEvent.VK_NUMPAD5 : button_4.doClick();
break;
case KeyEvent.VK_6 :
case KeyEvent.VK_NUMPAD6 : button_5.doClick();
break;
case KeyEvent.VK_7 :
case KeyEvent.VK_NUMPAD7 : button_6.doClick();
break;
case KeyEvent.VK_8 : if (e.isShiftDown()) button_14.doClick();
else button_7.doClick();
break;
case KeyEvent.VK_NUMPAD8 : button_7.doClick();
break;
case KeyEvent.VK_9 :
case KeyEvent.VK_NUMPAD9 : button_8.doClick();
break;
case KeyEvent.VK_PERIOD :
case KeyEvent.VK_DECIMAL : button_13.doClick();
break;
case KeyEvent.VK_EQUALS : if(e.isShiftDown()) button_12.doClick();
else button_17.doClick();
break;
case KeyEvent.VK_ENTER : button_17.doClick();
break;
case KeyEvent.VK_MINUS :
case KeyEvent.VK_SUBTRACT : button_11.doClick();
break;
case KeyEvent.VK_C : button_16.doClick();
break;
case KeyEvent.VK_ADD : button_12.doClick();
break;
case KeyEvent.VK_MULTIPLY : button_14.doClick();
break;
case KeyEvent.VK_DIVIDE :
case KeyEvent.VK_SLASH : button_15.doClick();
break;
case KeyEvent.VK_BACK_SPACE : btnX.doClick();
break;
case KeyEvent.VK_AMPERSAND : button_22.doClick();
}
}
@Override
public void keyReleased(KeyEvent e) {
}
@Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
};
frame.setResizable(false);
frame.setBounds(100, 100, 289, 452);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setTitle("Calculator");
frame.addKeyListener(l);
frame.setIconImage(image.getImage());
frame.getContentPane().setLayout(null);
Border border = LineBorder.createGrayLineBorder();
button = new JButton("1");
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if (label.getText().length() == 22) {
Toolkit.getDefaultToolkit().beep();
return;
}
if (label.getText().equals("0") || newin) label.setText("");
label.setText(label.getText() + "1");
newin = false;
}
});
button.setBounds(10, 68, 47, 34);
button.setFocusable(false);
button.setContentAreaFilled(false);
frame.getContentPane().add(button);
btnX = new JButton("<X");
btnX.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (label.getText().length() > 0 && !label.getText().equals("0")) {
label.setText(label.getText().substring(0, label.getText().length()-1));
}
if (label.getText().length() == 0) label.setText("0");
}
});
btnX.setBounds(224, 68, 49, 34);
btnX.setFocusable(false);
btnX.setToolTipText("Press \"Backspace\" instead");
btnX.setContentAreaFilled(false);
frame.getContentPane().add(btnX);
button_1 = new JButton("2");
button_1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (label.getText().length() == 22) {
Toolkit.getDefaultToolkit().beep();
return;
}
if (label.getText().equals("0") || newin) label.setText("");
label.setText(label.getText() + "2");
newin = false;
}
});
button_1.setBounds(59, 68, 47, 34);
button_1.setFocusable(false);
button_1.setContentAreaFilled(false);
frame.getContentPane().add(button_1);
button_2 = new JButton("3");
button_2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (label.getText().length() == 22) {
Toolkit.getDefaultToolkit().beep();
return;
}
if (label.getText().equals("0") || newin) label.setText("");
label.setText(label.getText() + "3");
newin = false;
}
});
button_2.setBounds(108, 68, 47, 34);
button_2.setFocusable(false);
button_2.setContentAreaFilled(false);
frame.getContentPane().add(button_2);
label2 = new JLabel("");
label2.setBounds(10, 15, 260, 14);
label2.setOpaque(true);
label2.setBackground(Color.WHITE);
label2.setFont(new Font("Arial", Font.BOLD, 10));
label2.setHorizontalAlignment(SwingConstants.RIGHT);
label = new JLabel("0");
label.setHorizontalAlignment(SwingConstants.RIGHT);
label.setVerticalAlignment(SwingConstants.BOTTOM);
label.setOpaque(true);
label.setBackground(Color.white);
label.setBorder(border);
label.setLayout(new BorderLayout());
label.setFont(new Font("Arial", Font.BOLD, 20));
label.add(label2, BorderLayout.PAGE_START);
label.setBounds(10, 11, 265, 42);
frame.getContentPane().add(label);
button_3 = new JButton("4");
button_3.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if (label.getText().length() == 22) {
Toolkit.getDefaultToolkit().beep();
return;
}
if (label.getText().equals("0")) label.setText("");
label.setText(label.getText() + "4");
newin = false;
}
});
button_3.setBounds(10, 113, 47, 34);
button_3.setFocusable(false);
button_3.setContentAreaFilled(false);
frame.getContentPane().add(button_3);
button_4 = new JButton("5");
button_4.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (label.getText().length() == 22) {
Toolkit.getDefaultToolkit().beep();
return;
}
if (label.getText().equals("0") || newin) label.setText("");
label.setText(label.getText() + "5");
newin = false;
}
});
button_4.setBounds(59, 113, 47, 34);
button_4.setFocusable(false);
button_4.setContentAreaFilled(false);
frame.getContentPane().add(button_4);
button_5 = new JButton("6");
button_5.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (label.getText().length() == 22) {
Toolkit.getDefaultToolkit().beep();
return;
}
if (label.getText().equals("0") || newin) label.setText("");
label.setText(label.getText() + "6");
newin = false;
}
});
button_5.setBounds(108, 113, 47, 34);
button_5.setFocusable(false);
button_5.setContentAreaFilled(false);
frame.getContentPane().add(button_5);
button_6 = new JButton("7");
button_6.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (label.getText().length() == 22) {
Toolkit.getDefaultToolkit().beep();
return;
}
if (label.getText().equals("0") || newin) label.setText("");
label.setText(label.getText() + "7");
newin = false;
}
});
button_6.setBounds(10, 160, 47, 34);
button_6.setFocusable(false);
button_6.setContentAreaFilled(false);
frame.getContentPane().add(button_6);
button_7 = new JButton("8");
button_7.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (label.getText().length() == 22) {
Toolkit.getDefaultToolkit().beep();
return;
}
if (label.getText().equals("0") || newin) label.setText("");
label.setText(label.getText() + "8");
newin = false;
}
});
button_7.setBounds(59, 160, 47, 34);
button_7.setFocusable(false);
button_7.setContentAreaFilled(false);
frame.getContentPane().add(button_7);
button_8 = new JButton("9");
button_8.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (label.getText().length() == 22) {
Toolkit.getDefaultToolkit().beep();
return;
}
if (label.getText().equals("0") || newin) label.setText("");
label.setText(label.getText() + "9");
newin = false;
}
});
button_8.setBounds(108, 160, 47, 34);
button_8.setFocusable(false);
button_8.setContentAreaFilled(false);
frame.getContentPane().add(button_8);
button_9 = new JButton("0");
button_9.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (label.getText().length() == 22) {
Toolkit.getDefaultToolkit().beep();
return;
}
if (label.getText().equals("0") || newin) label.setText("");
label.setText(label.getText() + "0");
newin = false;
}
});
button_9.setFocusable(false);
button_9.setContentAreaFilled(false);
button_9.setBounds(59, 205, 47, 34);
frame.getContentPane().add(button_9);
JButton button_10 = new JButton("±");
button_10.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if (label.getText().equals("0")) return;
if (label.getText().substring(0, 1).equals("-")) label.setText(label.getText().substring(1));
else label.setText("-" + label.getText());
}
});
button_10.setFocusable(false);
button_10.setContentAreaFilled(false);
button_10.setBounds(165, 68, 49, 34);
frame.getContentPane().add(button_10);
button_11 = new JButton("-");
button_11.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (newin && !label2.getText().equals("")) {
String in = reverseString(label2.getText());
in = in.substring(1);
in = "-" + in;
label2.setText("");
label2.setText(reverseString(in));
arg = "-";
} else {
label2.setText(label2.getText() + " " + label.getText() + " -");
calculate();
arg = "-";
label.setText(removeZeros(result));
newin = true;
}
}
});
button_11.setFocusable(false);
button_11.setContentAreaFilled(false);
button_11.setBounds(165, 113, 49, 34);
frame.getContentPane().add(button_11);
button_12 = new JButton("+");
button_12.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (newin && !label2.getText().equals("")) {
String in = reverseString(label2.getText());
in = in.substring(1);
in = "+" + in;
label2.setText("");
label2.setText(reverseString(in));
arg = "+";
} else {
label2.setText(label2.getText() + " " + label.getText() + " +");
calculate();
arg = "+";
label.setText(removeZeros(result));
newin = true;
}
}
});
button_12.setFocusable(false);
button_12.setContentAreaFilled(false);
button_12.setBounds(165, 157, 49, 82);
frame.getContentPane().add(button_12);
button_13 = new JButton(".");
button_13.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
for (int i = 0; i < label.getText().length(); i++) {
char a = label.getText().charAt(i);
if (a == '.') return;
}
label.setText(label.getText() + ".");
}
});
button_13.setFocusable(false);
button_13.setContentAreaFilled(false);
button_13.setBounds(108, 205, 47, 34);
frame.getContentPane().add(button_13);
button_14 = new JButton("x");
button_14.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if (newin && !label2.getText().equals("")) {
String in = reverseString(label2.getText());
in = in.substring(1);
in = "x" + in;
label2.setText("");
label2.setText(reverseString(in));
arg = "*";
} else {
label2.setText(label2.getText() + " " + label.getText() + " x");
calculate();
arg = "*";
label.setText(removeZeros(result));
newin = true;
}
}
});
button_14.setFocusable(false);
button_14.setContentAreaFilled(false);
button_14.setBounds(224, 160, 49, 34);
frame.getContentPane().add(button_14);
button_15 = new JButton("/");
button_15.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if (newin && !label2.getText().equals("")) {
String in = reverseString(label2.getText());
in = in.substring(1);
in = "/" + in;
label2.setText("");
label2.setText(reverseString(in));
arg = "/";
} else {
label2.setText(label2.getText() + " " +
removeZeros(Double.valueOf(label.getText())) + " /");
calculate();
arg = "/";
label.setText(removeZeros(result));
newin = true;
}
}
});
button_15.setFocusable(false);
button_15.setContentAreaFilled(false);
button_15.setBounds(224, 205, 49, 34);
frame.getContentPane().add(button_15);
button_16 = new JButton("C");
button_16.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
label.setText("0");
label2.setText("");
result = 0.0;
arg = "";
newin = false;
}
});
button_16.setFocusable(false);
button_16.setToolTipText("Press \"C\" instead");
button_16.setContentAreaFilled(false);
button_16.setBounds(224, 113, 49, 34);
frame.getContentPane().add(button_16);
button_17 = new JButton("=");
button_17.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
calculate();
label.setText(removeZeros(result));
label2.setText("");
arg = "";
newin = true;
result = 0.0;
}
});
button_17.setFocusable(false);
button_17.setContentAreaFilled(false);
button_17.setBounds(10, 205, 47, 34);
frame.getContentPane().add(button_17);
button_22 = new JButton("1/x");
button_22.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
label2.setText(("reciproc"+ "("+label.getText()+")"));
inverse = 1/Double.parseDouble(label.getText());
label.setText(removeZeros(inverse));
}
});
button_22.setFocusable(false);
button_22.setContentAreaFilled(false);
button_22.setBounds(76, 270, 63, 60);
frame.getContentPane().add(button_22);
}
private void calculate() {
if (result == 0) {
result = Double.valueOf(label.getText());
return;
}
switch (arg) {
case "+" : result += Double.parseDouble(label.getText());
break;
case "-" : result -= Double.parseDouble(label.getText());
break;
case "*" : result *= Double.valueOf(label.getText());
break;
case "/" : result /= Double.valueOf(label.getText());
break;
}
}
private String removeZeros(Double n) {
String in = String.valueOf(n);
while (in.indexOf(".") != -1) {
if (in.substring(in.length() - 1).equals("0") ||
in.substring(in.length() - 1).equals("."))
in = in.substring(0, in.length() - 1);
else break;
}
return in;
}
private String reverseString(String input) {
String output = "";
for (int i = input.length() - 1; i > -1; i--) {
output += input.charAt(i);
}
return output;
}
}
问题来源：Stack Overflow
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-
问题在于，当您输入零然后再进行任何操作然后输入操作数时，您的“结果”变量为零，因此“ calculate（）”会像未输入任何内容一样对待这种情况，只需设置“结果”到新操作数，而不是执行“ 0（操作）（操作数）”。
如果添加一个新的布尔变量“ isClear”（最初设置为true），则可以解决该问题。每次按下按钮进行某些操作时，都将此变量设置为false。在您的calculate（）方法中，替换
if (result == 0) { result = Double.valueOf(label.getText()); return; }与
if (isClear) { result = Double.valueOf(label.getText()); return; }当您按“ C”按钮清除输入时，还应将“ isClear”设置为true。
回答来源：Stack Overflow
2020-03-24 16:45:32赞同 展开评论 打赏
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