！
警告：前面有很多代码。
所以我有一个任务，我觉得我已经很接近要开始工作了。它编译并显示按钮。
问题：当我按下按钮时，没有数字出来。
这是我的指示：
设计并实现一个显示数字键的程序-
手机上可能出现的键盘。在键盘按钮上方，
显示一个标签，其中显示了被拾取的数字。到
键盘按钮的右侧，包括另一个按钮以清除
显示。使用边框布局来管理整个演示文稿，
以及用于管理键盘按钮的网格布局。放置边框
围绕键盘按钮进行可视化分组，并带有边框
在显示器周围。
悬崖：基本上是制作一个GUI，让您可以像电话一样打入数字。
这是我的代码的样子。我有一个驱动程序文件，以及一个大多数实际程序在其中的文件：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Phonekeypadpanel extends JPanel
{
private JLabel tnum;
private JPanel pad, clr,title;
private JButton one,two,three,four,five,six,seven,eight,nine,zero,clear,aster,pound;
private String num;
public Phonekeypadpanel ()
{
//KEYPAD YO
JPanel pad = new JPanel(new GridLayout(4,3));
setBackground (Color.red);
setLayout (new BorderLayout());
one=new JButton ("1");
two=new JButton ("2");
three=new JButton ("3");
four=new JButton ("4");
five=new JButton ("5");
six=new JButton ("6");
seven=new JButton ("7");
eight=new JButton ("8");
nine=new JButton ("9");
aster=new JButton ("*");
zero=new JButton ("0");
pound=new JButton ("#");
pad.add(one);
pad.add(two);
pad.add(three);
pad.add(four);
pad.add(five);
pad.add(six);
pad.add(seven);
pad.add(eight);
pad.add(nine);
pad.add(aster);
pad.add(zero);
pad.add(pound);
one.addActionListener(new ButtonListener());
two.addActionListener(new ButtonListener());
three.addActionListener(new ButtonListener());
four.addActionListener(new ButtonListener());
five.addActionListener(new ButtonListener());
six.addActionListener(new ButtonListener());
seven.addActionListener(new ButtonListener());
eight.addActionListener(new ButtonListener());
nine.addActionListener(new ButtonListener());
aster.addActionListener(new ButtonListener());
zero.addActionListener(new ButtonListener());
pound.addActionListener(new ButtonListener());
//And here is the clear button.
JPanel clr = new JPanel();
clear= new JButton("CLR");
clr.add(clear);
clear.addActionListener(new ButtonListener());
//The buttons get added to a border layout here.
add(pad,BorderLayout.CENTER);
add(clr,BorderLayout.EAST);
//display code where pushed buttons will be seen.
num = "";
tnum = new JLabel();
tnum.setText(num);
add(tnum,BorderLayout.NORTH);
}
// Here we have the code for what to do when buttons are pressed.
private class ButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
if (event.getSource()==("1"))
{
num = "1" + num;
tnum.setText("Telephone number: " + num);
}else
if(event.getSource()==("2"))
{
num = "2" + num;
tnum.setText("Telephone number: " + num);
}else
if (event.getSource()==("3"))
{
num = "3" + num;
tnum.setText("Telephone number: " + num);
}else
if (event.getSource()==("4"))
{
num = "4" + num;
tnum.setText("Telephone number: " + num);
}else
if (event.getSource()==("5"))
{
num = "5" + num;
tnum.setText("Telephone number: " + num);
}else
if (event.getSource()==("6"))
{
num = "6" + num;
tnum.setText("Telephone number: " + num);
}else
if (event.getSource()==("7"))
{
num = "7" + num;
tnum.setText("Telephone number: " + num);;
}else
if (event.getSource()==("8"))
{
num = "8" + num;
tnum.setText("Telephone number: " + num);
}else
if (event.getSource()==("9"))
{
num = "9" + num;
tnum.setText("Telephone number: " + num);
}else
if (event.getSource()==("*"))
{
num = "*" + num;
tnum.setText("Telephone number: " + num);
}else
if (event.getSource()==("0"))
{
num = "0" + num;
tnum.setText("Telephone number: " + num);
}else
if (event.getSource()==("#"))
{
num = "#" + num;
tnum.setText("Telephone number: " + num);
}
else
if (event.getSource()==("CLR"))
{
num = "";
tnum.setText("Telephone number: " + num);
}
}
}
}
您并不需要真正看一下，但这是我的驱动程序文件：
import java.awt.*;
import javax.swing.*;
public class Phonekeypad
{
public static void main(String[] args)
{
JFrame frame = new JFrame("Phone Keypad");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new Phonekeypadpanel());
frame.pack();
frame.setVisible(true);
}
}
最佳答案
在类tnum和构造函数中都声明了变量num和Phonekeypadpanel。当您尝试为它们分配值时，最终只会更改驻留在构造函数中的本地副本，而不会更改类变量。将行String num = "";更改为num = "";，并将JLabel tnum = new JLabel();更改为tnum = new JLabel();。
最后，将每个"one"，"two"等替换为"1"，"2"等。因为将System.out.println(event.getActionCommand());放在actionPerformed的顶部时，您会看到输出是标签的标签。按钮。