为决赛制作计算器,在更新 JLabel 时遇到困难。 当 Label 初始化时,它会很好地显示opNum
的起始值,但是每当调用该方法将数字添加到opNum
末尾时,它似乎不会更新。 我不确定它是否没有重新绘制,或者当我从按钮调用该方法时是否出了问题。我正在做一些愚蠢或糟糕的事情,或者两者兼而有之。 帮助?
JLabel和方法类:
import javax.swing.*;
import java.awt.*;
public class NumberText extends JPanel
{
private JLabel opNumLabel;
private String opNum;
private double storeNum = 0;
private boolean firstOp = true;
private char op;
private char sign = '+';
//Panel for Number
public NumberText()
{
//I heard that it could be an issue with the Label not having enough space, though this didnt help
opNumLabel = new JLabel ("1234567890111");
opNumLabel.setText(opNum);
add(opNumLabel);
setPreferredSize (new Dimension (150, 40));
setBackground (Color.white);
}
//Clears the current typed number
public void Clear ()
{
opNum = "";
opNumLabel.setText(opNum);
}
//Sets it back to conditions like the start of the program
public void ClearAll ()
{
opNum = "";
storeNum = 0;
firstOp = true;
opNumLabel.setText(opNum);
}
//for storing the operation
public void OpStore (char newOp)
{
op = newOp;
firstOp = false;
}
//for adding to the opNum
public void Edit (String button)
{
opNum = opNum + button;
opNumLabel.setText(opNum);
opNumLabel.repaint();
}
//for testing for the first Operation
public boolean IsFirstOp ()
{
return firstOp;
}
//for changing the sign
public void SignChange ()
{
if (sign == '+')
{
opNum = "-" + opNum;
opNumLabel.setText(opNum);
sign = '-';
}
else if (sign == '-')
{
opNum.replaceAll("-", "");
opNumLabel.setText(opNum);
sign = '+';
}
}
//for storing a number when an operation is pressed
public void StoreNum ()
{
storeNum = Double.parseDouble(opNum);
opNum = "";
}
//Math when an Operation is to be done
public void Operation()
{
double value = Double.parseDouble(opNum);
double total = 0;
switch(op)
{
case '+': total = storeNum + value;
break;
case '-': total = storeNum - value;
break;
case '/': total = storeNum / value;
break;
case '*': total = storeNum * value;
break;
case '%': total = storeNum % value;
break;
}
opNum = Double.toString(total);
opNumLabel.setText(opNum);
}
}
按钮示例:
public class Button1 extends JPanel
{
private JButton push;
private JLabel label;
public Button1 ()
{
push = new JButton ("1");
push.addActionListener (new ButtonListener());
add (push);
}
private class ButtonListener implements ActionListener
{
public void actionPerformed (ActionEvent event)
{
//to avoid non-static cant be ref by static
NumberText NumberText = new NumberText();
NumberText.Edit("1");
}
}
}
在actionPerformed(...)
中,您正在编辑NumberText.Edit("1")
一个新NumberText
,该不会添加到任何帧中。如果希望在 Edit(...)
方法中所做的更改生效,则需要获取对已显示NumberText
的引用。
下面是一个示例:
public static void main(String[] args) {
JFrame frame = new JFrame();
....
NumberText numberText = new NumberText();
Button1 button = new Button1(numberText);
JPanel pan = new JPanel();
pan.add(numberText);
pan.add(button);
frame.add(pan);
.....
}
public class Button1 extends JPanel {
private JButton push;
private JLabel label;
NumberText alreadyDisplayed;
public Button1 (NumberText alreadyDisplayed) {
this.alreadyDisplayed = alreadyDisplayed;
push = new JButton ("1");
push.addActionListener (new ButtonListener());
add(push);
}
private class ButtonListener implements ActionListener {
public void actionPerformed (ActionEvent event) {
alreadyDisplayed.Edit("1");
}
}
}