我知道类似的问题在javascript中被问及并回答但是我在Java中有一项任务，涉及显示单个/多个位置的时间（从列表中选择）。
我有一定数量的内置，如下面的代码所示。但是，当我选择多个位置时，我陷入困境，唯一的“滴答”时钟是所选的最后一个时钟，其他时钟只是在它们被创建时冻结。
有人可以查看下面的代码，看看他们是否可以给我一些指导？
由于
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ListSelectionModel;
import javax.swing.Timer;
public class AssignmentV1 implements ActionListener/* ,ListSelectionListener */
{
private String[] cities;
private JButton addBtn;
private JButton minusBtn;
private JList cityList;
private JPanel right;
private JPanel displayArea;
private JPanel[] clockDisplay;
private long currentTime;
private long cityTime;
private int hourDiff;
private String cityName;
private String timeInFormat;
private JLabel time;
private JPanel topRight;
private ArrayList<String> cityNamesList;
private ArrayList<Long> cityTimes;
public AssignmentV1() {
JFrame appWin = new JFrame("World Time");
appWin.setSize(400, 400);
appWin.setLocationRelativeTo(null);
appWin.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Font preferredFont = new Font("OCR A EXTENDED", Font.BOLD, 50);
Container contentPane = appWin.getContentPane();
displayArea = new JPanel();
displayArea.setLayout(new GridLayout(1, 2));
JPanel left = new JPanel();
left.setLayout(new GridLayout(2, 1));
JPanel topLeft = new JPanel();
topLeft.setLayout(new FlowLayout(FlowLayout.CENTER));
// adding of +/- buttons to display
addBtn = new JButton();
addBtn.setText("+");
addBtn.addActionListener(this);
topLeft.add(addBtn);
minusBtn = new JButton();
minusBtn.setText("-");
minusBtn.addActionListener(this);
topLeft.add(minusBtn);
left.add(topLeft);
// adding of list of cities to a scrollpane to add to display
JPanel bottomLeft = new JPanel();
setUpCities();
cityList = new JList(cities);
cityList.setSelectedIndex(0);
cityList.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
JScrollPane scrollableList = new JScrollPane(cityList);
bottomLeft.add(scrollableList);
left.add(bottomLeft);
right = new JPanel();
topRight = new JPanel();
clockDisplay = new JPanel[1];
topRight.setLayout(new GridLayout(clockDisplay.length, 1));
for (int i = 0; i < clockDisplay.length; i++) {
clockDisplay[i] = new JPanel();
cityName = cities[0].substring(0, cities[0].indexOf(","));
hourDiff = Integer.parseInt(cities[0].substring(cities[0].indexOf(",") + 1));
currentTime = System.currentTimeMillis();
cityTime = System.currentTimeMillis() + (1000 * 60 * 60 * hourDiff);
clockDisplay[i].setBorder(BorderFactory.createTitledBorder(cityName));
time = new JLabel();
time.setOpaque(true);
timeInFormat = textAsTime(cityTime);
time.setText(timeInFormat);
clockDisplay[i].add(time);
topRight.add(clockDisplay[i]);
}
right.add(topRight);
displayArea.add(left);
displayArea.add(right);
contentPane.add(displayArea);
Timer t = new Timer(1000, this);
t.start();
appWin.setVisible(true);
}
public void actionPerformed(ActionEvent e) {
cityTime = tick(cityTime);
timeInFormat = textAsTime(cityTime);
time.setText(timeInFormat);
cityNamesList = new ArrayList<String>();
cityTimes = new ArrayList<Long>();
Object[] obj = cityList.getSelectedValues();
Object source = e.getSource();
if (source == addBtn) {
topRight.removeAll();
right.setLayout(new GridLayout(obj.length, 1));
clockDisplay = new JPanel[obj.length];
topRight.setLayout(new GridLayout(obj.length, 1));
ArrayList<String> cityNamesList = new ArrayList<String>();
ArrayList<Long> cityTimes = new ArrayList<Long>();
for (int i = 0; i < obj.length; i++) {
String temp = (String) obj[i];
clockDisplay[i] = new JPanel();
cityName = temp.substring(0, temp.indexOf(","));
cityNamesList.add(cityName);
hourDiff = Integer.parseInt(temp.substring(temp.indexOf(",") + 1));
currentTime = System.currentTimeMillis();
cityTime = System.currentTimeMillis() + (1000 * 60 * 60 * hourDiff);
cityTimes.add(cityTime);
tick(cityTime);
clockDisplay[i].setBorder(BorderFactory.createTitledBorder(cityName));
time = new JLabel();
time.setOpaque(true);
timeInFormat = textAsTime(cityTime);
time.setText(timeInFormat);
clockDisplay[i].add(time);
topRight.add(clockDisplay[i]);
}
right.add(topRight);
}
}
public void setUpCities() {
cities = new String[] { "Accra,0", "Addis Abada,+3", "Adelaide,+11", "Algiers,-1",
"Almaty,+6", "Amman,+3", "Amsterdam,+1", "Anadyr,+12", "Anchorage,-8", "Ankara,+2",
"London,0", "Paris,+1" };
}
public String textAsTime(long currentTime) {
long second = (currentTime / 1000) % 60;
long minute = (currentTime / (1000 * 60)) % 60;
long hour = (currentTime / (1000 * 60 * 60)) % 24;
return String.format("%02d:%02d:%02d", hour, minute, second);
}
public static void main(String[] args) {
new AssignmentV1();
}
public long tick(long cityTime) {
cityTime = cityTime + 1000;
return cityTime;
}
}
答案 0 :(得分：0)
看看actionPerformed（），那里有一些问题。您需要以允许您在for循环中添加更多内容的方式设置时钟JLabel，并且每次定时器触发时仍然引用已经生成的JLabel。目前，每次添加新时钟时，您只是覆盖单个“时间”JLabel的值，这实际上无法在先前的标签上调用setText（）（或其他任何内容）。
此外，一旦完成此更改，请确保记住迭代所有时钟并更新它们各自的时间。