我刚开始学习java GUI，正如标题所说，我遇到了getActionCommand的问题。它是微波模拟。当倒计时正在运行且用户按下停止时，它会将计时器重置为0（或空字符串）。 CountF是JLabel，而startB是JButton。任何帮助将不胜感激
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Countdown extends JFrame implements ActionListener
{
private JLabel countF;
private JButton oneB;
private JButton twoB;
private JButton threeB;
private JButton fourB;
private JButton fiveB;
private JButton sixB;
private JButton sevenB;
private JButton eightB;
private JButton nineB;
private JButton zeroB;
private JButton startB;
private JButton openB;
private int cookingSeconds;
private int time;
public static void main(String[] args)
{
Countdown demoGui = new Countdown( );
demoGui.setVisible(true);
}
public Countdown()
{
super("Microwave");
this.setSize(700, 400);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLayout(new GridLayout(1,2));
add(new JLabel("Food to be heated"));
JPanel rightP = new JPanel();
add(rightP);
rightP.setLayout(new BorderLayout());
JPanel textP = new JPanel();
textP.setPreferredSize(new Dimension(300, 50));
textP.setBackground(Color.WHITE);
countF = new JLabel();
textP.add(countF);
rightP.add(textP, BorderLayout.NORTH);
JPanel tempP = new JPanel();
rightP.add(tempP, BorderLayout.CENTER);
tempP.setLayout(new GridLayout(4,3));
oneB = new JButton("1");
tempP.add(oneB);
twoB = new JButton("2");
tempP.add(twoB);
threeB = new JButton("3");
tempP.add(threeB);
fourB = new JButton("4");
tempP.add(fourB);
fiveB = new JButton("5");
tempP.add(fiveB);
sixB = new JButton("6");
tempP.add(sixB);
sevenB = new JButton("7");
tempP.add(sevenB);
eightB = new JButton("8");
tempP.add(eightB);
nineB = new JButton("9");
tempP.add(nineB);
zeroB = new JButton("0");
tempP.add(zeroB);
startB = new JButton("Start");
tempP.add(startB);
openB = new JButton("Open");
tempP.add(openB);
startB.addActionListener(this);
openB.addActionListener(this);
oneB.addActionListener(this);
twoB.addActionListener(this);
threeB.addActionListener(this);
fourB.addActionListener(this);
fiveB.addActionListener(this);
sixB.addActionListener(this);
sevenB.addActionListener(this);
eightB.addActionListener(this);
nineB.addActionListener(this);
zeroB.addActionListener(this);
}
public void setCountDownLabelText(String text)
{
countF.setText(text);
}
public void setOpenBEnable()
{
openB.setEnabled(true);
oneB.setEnabled(true);
twoB.setEnabled(true);
threeB.setEnabled(true);
fourB.setEnabled(true);
fiveB.setEnabled(true);
sixB.setEnabled(true);
sevenB.setEnabled(true);
eightB.setEnabled(true);
nineB.setEnabled(true);
zeroB.setEnabled(true);
}
//you need to add the event handling for 1, 2, ...9, 0 buttons to calculate the cookingSeconds.
public void actionPerformed(ActionEvent e)
{
if(e.getSource() == startB)
{
time = Integer.parseInt(countF.getText());
cookingSeconds = time;
new CountDownTimer(this, cookingSeconds).start();
startB.setText("Stop");
openB.setEnabled(false);
oneB.setEnabled(false);
twoB.setEnabled(false);
threeB.setEnabled(false);
fourB.setEnabled(false);
fiveB.setEnabled(false);
sixB.setEnabled(false);
sevenB.setEnabled(false);
eightB.setEnabled(false);
nineB.setEnabled(false);
zeroB.setEnabled(false);
if(e.getActionCommand().equals("Stop"))
{
// this is not working
countF.setText("");
}
}
else if (e.getSource() == openB)
{
countF.setText("");
}
else if (e.getSource() == oneB)
{
countF.setText(countF.getText() + "1");
}
else if (e.getSource() == twoB)
{
countF.setText(countF.getText() + "2");
}
else if (e.getSource() == threeB)
{
countF.setText(countF.getText() + "3");
}
else if (e.getSource() == fourB)
{
countF.setText(countF.getText() + "4");
}
else if (e.getSource() == fiveB)
{
countF.setText(countF.getText() + "5");
}
else if (e.getSource() == sixB)
{
countF.setText(countF.getText() + "6");
}
else if (e.getSource() == sevenB)
{
countF.setText(countF.getText() + "7");
}
else if (e.getSource() == eightB)
{
countF.setText(countF.getText() + "8");
}
else if (e.getSource() == nineB)
{
countF.setText(countF.getText() + "9");
}
else if (e.getSource() == zeroB)
{
countF.setText(countF.getText() + "0");
}
}
}
答案 0 :(得分：2)
当您从事件中获取ActionCommand时，您必须从Button获得值{em>旧值，因为您在{{1}内设置文本阻止你在这一点上需要if。
setActionCommand答案 1 :(得分：1)
我无法分辨为什么你的代码在没有猜测的情况下无法正常工作，但无论如何都在这里 - 也许你从未将actionCommand设置为“Stop”。如果是这样，那么if块将永远不会运行。请注意，如果您通过setText(...)设置JButton的文本，则不会自动设置actionCommand。
如果这没有帮助，请考虑花点时间创建并发布minimal example program，以便我们完全理解您的问题，而不必猜测。
我的猜测是正确的 - 你从未设置按钮的actionCommand，因为我没有看到在任何地方调用setActionCommand（...）。
我自己，我给每组独特的按钮都有自己的ActionListeners或Actions，并让他们处理这类事情，而不是拥有一个“交换机”类型的监听器。例如，......
import java.awt.event.*;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class StartStopActionTest {
public static void main(String[] args) {
Action startStopAction = new StartStopAction("Start", KeyEvent.VK_S, "Stop", KeyEvent.VK_S);
JButton startStopButton = new JButton(startStopAction);
JPanel panel = new JPanel();
panel.add(startStopButton);
JOptionPane.showMessageDialog(null, panel);
}
}
class StartStopAction extends AbstractAction {
private String startText;
private int startMnemonic;
private String stopText;
private int stopMnemonic;
public StartStopAction(String startText, int startMnemonic, String stopText,
int stopMnemonic) {
super(startText);
putValue(MNEMONIC_KEY, startMnemonic);
this.startText = startText;
this.startMnemonic = startMnemonic;
this.stopText = stopText;
this.stopMnemonic = stopMnemonic;
}
@Override
public void actionPerformed(ActionEvent e) {
if (getValue(NAME).equals(startText)) {
putValue(NAME, stopText);
putValue(MNEMONIC_KEY, stopMnemonic);
// start action code here
} else {
putValue(NAME, startText);
putValue(MNEMONIC_KEY, startMnemonic);
// stop action code here
}
}
}