我正在尝试使两类Java计算器正常工作（Java的新手），但到目前为止，我还没有成功。下面概述了这两个类，calcFrame用于接口，而calEngine应该进行实际的计算，但是我无法让他们互相交谈。我非常感谢您提供的任何帮助。谢谢。
CalcFrame代码：
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
import java.awt.event.*;
/**
*A Class that operates as the framework for a calculator.
*No calculations are performed in this section
*/
public class CalcFrame implements ActionListener {
private CalcEngine calc;
private JFrame frame;
private JTextField display;
private JLabel status;
/**
* Constructor for objects of class GridLayoutExample
*/
public CalcFrame()
{
makeFrame();
//calc = engine;
}
/**
* This allows you to quit the calculator.
*/
// Alows the class to quit.
private void quit()
{
System.exit(0);
}
// Calls the dialog frame with the information about the project.
private void showAbout()
{
JOptionPane.showMessageDialog(frame,
"Group Project",
"About Calculator Group Project",
JOptionPane.INFORMATION_MESSAGE);
}
private void makeFrame()
{
frame = new JFrame("Group Project Calculator");
makeMenuBar(frame);
JPanel contentPane = (JPanel)frame.getContentPane();
contentPane.setLayout(new BorderLayout(8, 8));
contentPane.setBorder(new EmptyBorder( 10, 10, 10, 10));
/**
* Insert a text field
*/
display = new JTextField();
contentPane.add(display, BorderLayout.NORTH);
//Container contentPane = frame.getContentPane();
contentPane.setLayout(new GridLayout(4, 4));
JPanel buttonPanel = new JPanel(new GridLayout(4, 4));
contentPane.add(new JButton("1"));
contentPane.add(new JButton("2"));
contentPane.add(new JButton("3"));
contentPane.add(new JButton("4"));
contentPane.add(new JButton("5"));
contentPane.add(new JButton("6"));
contentPane.add(new JButton("7"));
contentPane.add(new JButton("8"));
contentPane.add(new JButton("9"));
contentPane.add(new JButton("0"));
contentPane.add(new JButton("+"));
contentPane.add(new JButton("-"));
contentPane.add(new JButton("/"));
contentPane.add(new JButton("*"));
contentPane.add(new JButton("="));
contentPane.add(new JButton("C"));
contentPane.add(buttonPanel, BorderLayout.CENTER);
//status = new JLabel(calc.getAuthor());
//contentPane.add(status, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
}
/**
* Create the main frame's menu bar.
* The frame that the menu bar should be added to.
*/
private void makeMenuBar(JFrame frame)
{
final int SHORTCUT_MASK =
Toolkit.getDefaultToolkit().getMenuShortcutKeyMask();
JMenuBar menubar = new JMenuBar();
frame.setJMenuBar(menubar);
JMenu menu;
JMenuItem item;
// create the File menu
menu = new JMenu("File");
menubar.add(menu);
// create the Quit menu with a shortcut "Q" key.
item = new JMenuItem("Quit");
item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Q, SHORTCUT_MASK));
item.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) { quit(); }
});
menu.add(item);
// Adds an about menu.
menu = new JMenu("About");
menubar.add(menu);
// Displays
item = new JMenuItem("Calculator Project");
item.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) { showAbout(); }
});
menu.add(item);
}
/**
* An interface action has been performed.
* Find out what it was and handle it.
* @param event The event that has occured.
*/
public void actionPerformed(ActionEvent event)
{
String command = event.getActionCommand();
if(command.equals("0") ||
command.equals("1") ||
command.equals("2") ||
command.equals("3") ||
command.equals("4") ||
command.equals("5") ||
command.equals("6") ||
command.equals("7") ||
command.equals("8") ||
command.equals("9")) {
int number = Integer.parseInt(command);
calc.numberPressed(number);
}
else if(command.equals("+")) {
calc.plus();
}
else if(command.equals("-")) {
calc.minus();
}
else if(command.equals("=")) {
calc.equals();
}
else if(command.equals("C")) {
calc.clear();
}
else if(command.equals("?")) {
}
// else unknown command.
redisplay();
}
/**
* Update the interface display to show the current value of the
* calculator.
*/
private void redisplay()
{
display.setText("" + calc.getDisplayValue());
}
/**
* Toggle the info display in the calculator's status area between the
* author and version information.
*/
}
CalcEngine：
public class CalcEngine
{
// The calculator's state is maintained in three fields:
// buildingDisplayValue, haveLeftOperand, and lastOperator.
// The current value (to be) shown in the display.
private int displayValue;
// The value of an existing left operand.
private int leftOperand;
/**
* Create a CalcEngine.
*/
public CalcEngine()
{
clear();
}
public int getDisplayValue()
{
return displayValue;
}
/**
* A number button was pressed.
* Either start a new operand, or incorporate this number as
* the least significant digit of an existing one.
* @param number The number pressed on the calculator.
*/
public void numberPressed(int number)
{
if(buildingDisplayValue) {
// Incorporate this digit.
displayValue = displayValue*10 + number;
}
else {
// Start building a new number.
displayValue = number;
buildingDisplayValue = true;
}
}
/**
* The 'plus' button was pressed.
*/
public void plus()
{
applyOperator('+');
}
/**
* The 'minus' button was pressed.
*/
public void minus()
{
applyOperator('-');
}
/**
* The '=' button was pressed.
*/
public void equals()
{
// This should completes the building of a second operand,
// so ensure that we really have a left operand, an operator
// and a right operand.
if(haveLeftOperand &&
lastOperator != '?' &&
buildingDisplayValue) {
calculateResult();
lastOperator = '?';
buildingDisplayValue = false;
}
else {
keySequenceError();
}
}
/**
* The 'C' (clear) button was pressed.
* Reset everything to a starting state.
*/
public void clear()
{
lastOperator = '?';
haveLeftOperand = false;
buildingDisplayValue = false;
displayValue = 0;
}
/**
* @return The title of this calculation engine.
*/
public String getTitle()
{
return "Java Calculator";
}
/**
* @return The author of this engine.
*/
public String getAuthor()
{
return "David J. Barnes and Michael Kolling";
}
/**
* @return The version number of this engine.
*/
public String getVersion()
{
return "Version 1.0";
}
/**
* Combine leftOperand, lastOperator, and the
* current display value.
* The result becomes both the leftOperand and
* the new display value.
*/
private void calculateResult()
{
switch(lastOperator) {
case '+':
displayValue = leftOperand + displayValue;
haveLeftOperand = true;
leftOperand = displayValue;
break;
case '-':
displayValue = leftOperand - displayValue;
haveLeftOperand = true;
leftOperand = displayValue;
break;
default:
keySequenceError();
break;
}
}
/**
* Apply an operator.
* @param operator The operator to apply.
*/
private void applyOperator(char operator)
{
// If we are not in the process of building a new operand
// then it is an error, unless we have just calculated a
// result using '='.
if(!buildingDisplayValue &&
!(haveLeftOperand && lastOperator == '?')) {
keySequenceError();
return;
}
if(lastOperator != '?') {
// First apply the previous operator.
calculateResult();
}
else {
// The displayValue now becomes the left operand of this
// new operator.
haveLeftOperand = true;
leftOperand = displayValue;
}
lastOperator = operator;
buildingDisplayValue = false;
}
/**
* Report an error in the sequence of keys that was pressed.
*/
private void keySequenceError()
{
System.out.println("A key sequence error has occurred.");
// Reset everything.
clear();
}
}
最佳答案
“引擎”未初始化”
public CalcFrame() {
makeFrame();
calc = new CalcEngine();
}
和：
您应该在按钮上附加一个侦听器，以便在单击按钮时调用actionPerformed（）
JButton button = new JButton("1");
button.addActionListener(this);
contentPane.add(button);
应该为每个按钮完成此操作，因此最好首先将按钮放在列表中：
JPanel buttonPanel = new JPanel(new GridLayout(4, 4));
List<JButton> buttons = new ArrayList<JButton>();
buttons.add(new JButton("1"));
buttons.add(new JButton("2"));
buttons.add(new JButton("3"));
buttons.add(new JButton("4"));
buttons.add(new JButton("5"));
buttons.add(new JButton("6"));
buttons.add(new JButton("7"));
buttons.add(new JButton("8"));
buttons.add(new JButton("9"));
buttons.add(new JButton("0"));
buttons.add(new JButton("+"));
buttons.add(new JButton("-"));
buttons.add(new JButton("/"));
buttons.add(new JButton("*"));
buttons.add(new JButton("="));
buttons.add(new JButton("C"));
for(JButton button : buttons){
buttonPanel.add(button);
button.addActionListener(this);
}
contentPane.add(buttonPanel, BorderLayout.CENTER);
顺便说一句，您缺少
} else if (command.equals("*")) {部分关于java - '简单'2类Java计算器不接受输入或进行计算，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/2470793/