我有这个Java Swing应用程序，一个简单的计算器，我不知道如何不先添加操作。它允许我在插入数字之前添加操作，这对我来说是个大问题。谁能告诉我如何解决这个问题？
public class DetailsPanel extends JPanel{
private JTextField display;
private String buttonsLabel;
int labelCounter = 0;
private final GridBagLayout layout;
private final GridBagConstraints gc;
private JButton[] numberButton, oppButtons;
private String oppLabel[] = {"C","+/-","*","/","-","+","=",".","sqrt","sqr","min","max"}, lastOperator, lastNumber;
private Boolean operation = false, number = false, isSet = false, operatorExist = false, lastNumberExist = false;
//[0]=gridx,[1]=gridy,[2]=gridwidth,[3]=gridhewight
private final int[][] grid = new int[][] {
{0,6,2,1}, //0
{0,5,1,1}, //1
{1,5,1,1}, //2
{2,5,1,1}, //3
{0,4,1,1}, //4
{1,4,1,1}, //5
{2,4,1,1}, //6
{0,3,1,1}, //7
{1,3,1,1}, //8
{2,3,1,1} //9
};
private final int[][] grid2 = new int[][] {
/* C */{0,2,1,1},
/* +/- */{1,2,1,1},
/* * */{2,2,1,1},
/* / */{3,2,1,1},
/* - */{3,3,1,1},
/* + */{3,4,1,1},
/* = */{3,5,1,2},
/* . */{2,6,1,1},
/* sqrt */ {0,7,1,1},
/*sqr*/{1,7,1,1},
/*min*/{2,7,1,1},
/*max*/{3,7,1,1}
};
public DetailsPanel(){
//JOptionPane.showMessageDialog(null, 12.2 % 1 != 0);
Dimension size = getPreferredSize();
size.width = 224;
size.height = 324;
setPreferredSize(size);
//Dysplay
display = new JTextField("0");
display.setEditable(false);
display.setBackground(Color.WHITE);
//Set layout
layout = new GridBagLayout();
layout.columnWidths = new int[] {40,40,40,40};
layout.rowHeights = new int[] {40,40,40,40,40,40,40,40};
setLayout(layout);
gc = new GridBagConstraints();
//ADD Dysplay
gc.gridx = 0;
gc.gridy = 0;
gc.gridwidth = 4;
gc.gridheight = 2;
gc.fill = GridBagConstraints.BOTH;
add(display, gc);
numberButton = new JButton[10];
//Start adding buttons
for(int i = 0; i<numberButton.length;i++){
numberButton[i] = new JButton("" +i);
gc.gridx = grid[i][0];
gc.gridy = grid[i][1];
gc.gridwidth = grid[i][2];
gc.gridheight = grid[i][3];
gc.fill = GridBagConstraints.BOTH;
add(numberButton[i], gc);
}
oppButtons = new JButton[12];
for(int i = 0; i<oppLabel.length; i++){
oppButtons[i] = new JButton("" +oppLabel[i]);
gc.gridx = grid2[i][0];
gc.gridy = grid2[i][1];
gc.gridwidth = grid2[i][2];
gc.gridheight = grid2[i][3];
gc.fill = GridBagConstraints.BOTH;
add(oppButtons[i], gc);
}
//Action listener Object
HandlerClassNumbers handlerNumbers = new HandlerClassNumbers();
HandlerClassOpperations handlerOperations = new HandlerClassOpperations();
for (JButton numberButton1 : numberButton) {
numberButton1.addActionListener(handlerNumbers);
}
for(int i = 0; i<oppLabel.length; i++){
oppButtons[i].addActionListener(handlerOperations);
}
}//End of Details panel
//Action listener Classes start
public class HandlerClassNumbers implements ActionListener{
@Override
public void actionPerformed(ActionEvent e) {
if(!number){
addDysplay(e.getActionCommand(), operation);
}
}
}
public class HandlerClassOpperations implements ActionListener{
@Override
public void actionPerformed(ActionEvent e1) {
switch (e1.getActionCommand()) {
case "C":
delete();
break;
case "+/-":
display.setText(Double.toString(-1 * Double.parseDouble(display.getText())));
if(isInt()){
transformToInt();
}
break;
case ".":
addPoint();
break;
case "sqrt":
sqrt();
break;
case "sqr":
sqr();
break;
case "=":
if(operatorExist)
if(isNumeric(display.getText()))
switch (lastOperator) {
case "+":
plus();
reset();
break;
case "-":
minus();
reset();
break;
case "/":
div();
reset();
break;
case "*":
mul();
reset();
break;
case "max":
max();
reset();
break;
case "min":
min();
reset();
break;
}
else{
JOptionPane.showMessageDialog(null, "Numar introdus incorect!");
}
else{
JOptionPane.showMessageDialog(null, "Nu a-ti adaugat o operatie!");
}
/////////////////Action equal end///////////////////
break;
default:
if(!operatorExist){
lastOperator = e1.getActionCommand();
lastNumber = display.getText();
lastNumberExist = true;
operatorExist = true;
delete();
break;
}
}
}
}
//Program methods
public void addDysplay(String number, Boolean operation){
if(!isSet){
isSet = true;
display.setText(number);
}else{
display.setText(display.getText()+number);
}
}
public void delete(){
if(operatorExist){
display.setText(lastOperator);
}else
display.setText("0");
isSet = false;
}
public void reset(){
lastOperator = null;
lastNumber = null;
operatorExist = false;
lastNumberExist = false;
}
public void addPoint(){
String pattern = "^[-+]?\\d+\\.{0}\\d+$";
if(display.getText().matches(pattern)){
display.setText(display.getText()+".");
}else{
if(display.getText().length() == 1){
display.setText(display.getText()+".");
}
}
}
public Boolean isInt(){
Double disp = Double.parseDouble(display.getText());
return disp % 1 == 0;
}
public void transformToInt(){
Double disp = Double.parseDouble(display.getText());
display.setText(Integer.toString(disp.intValue()));
}
public static boolean isNumeric(String str){
return str.matches("-?\\d+(\\.\\d+)?"); //match a number with optional '-' and decimal.
}
////////////////////Operation methods////////////////////
public void plus(){
display.setText(Double.toString(Double.parseDouble(lastNumber)+Double.parseDouble(display.getText())));
if(isInt()){
transformToInt();
}
}
public void minus(){
display.setText(Double.toString(Double.parseDouble(lastNumber)-Double.parseDouble(display.getText())));
if(isInt()){
transformToInt();
}
}
public void mul(){
display.setText(Double.toString(Double.parseDouble(lastNumber)*Double.parseDouble(display.getText())));
if(isInt()){
transformToInt();
}
}
public void div(){
display.setText(Double.toString(Double.parseDouble(lastNumber)/Double.parseDouble(display.getText())));
if(isInt()){
transformToInt();
}
}
public void equal(){
if(isInt()){
transformToInt();
}
}
public void sqrt(){
if(Double.parseDouble(display.getText()) > 0)
display.setText(Double.toString(Math.sqrt(Double.parseDouble(display.getText()))));
else{
JOptionPane.showMessageDialog(null, "sqrt(" +display.getText() + ") impossible!");
delete();
}
if(isInt()){
transformToInt();
}
}
public void sqr(){
display.setText(Double.toString(Double.parseDouble(display.getText()) * Double.parseDouble(display.getText())));
if(isInt()){
transformToInt();
}
}
public void min(){
String disp = display.getText();
if(disp.compareTo(lastNumber) > 0){
display.setText(lastNumber);
}
if(isInt()){
transformToInt();
}
}
public void max(){
String disp = display.getText();
if(disp.compareTo(lastNumber) < 0){
display.setText(lastNumber);
}
if(isInt()){
transformToInt();
}
}
////////////////////Operation methods end/////////////////
}//Ends of DetailsPanel class