我将JDateChooser用于正在开发的Java swing项目，因此可以用两种方式设置日期：最终用户或以编程方式设置日期。
因此，我在相应的类中定义了一个propertychangelistener（变量trig初始化为零，并跟踪监听了多少次属性更改）。
public class WriteEntry{
private int trig=0;
private Date currentDate = new Date();
public JDateChooser dateChooser = new JDateChooser();
public CustomDate selectedDate = DateConverter.convertDate(currentDate);
private static String filename = StorageSpace.currentpath+CurrentUser.getInstance().getUserName()+"\\"+
Integer.toString(selectedDate.getYear())+"\\"
+Integer.toString(selectedDate.getMonth())+"\\"+Integer.toString(selectedDate.getDay())+".txt";
private JLabel dayinfo = new JLabel("");
private JTextArea contentfield = new JTextArea("");
private PropertyChangeListener lis = new PropertyChangeListener(){
@Override
public void propertyChange(PropertyChangeEvent e) {
System.out.println("triggered "+trig++);
if(dateBoundary()) {
selectedDate = DateConverter.convertDate(dateChooser);
filename = StorageSpace.currentpath+CurrentUser.getInstance().getUserName()+"\\"+
Integer.toString(selectedDate.getYear())+"\\"
+Integer.toString(selectedDate.getMonth())+"\\"+Integer.toString(selectedDate.getDay())+".txt";
}
else {
updateDateChooser(selectedDate);
}
if(isAlreadyWritten())
{
try {
updateEditFields(selectedDate, "content");
} catch (IOException e1) {
e1.printStackTrace();
}
}
else
{
contentfield.setText("Start writing here");
dayinfo.setText("You are making entry for: "+ new SimpleDateFormat("dd/MM/yyyy").format(dateChooser.getDate()));
}
}
};
WriteEntry() //constructor
{
dateChooser.setDateFormatString("dd MM yyyy");
dateChooser.addPropertyChangeListener(lis);
updateEditFields(DateConverter.convertDate(currentDate), "Start");
}
}
这是dateBoundary（）的代码：
public static boolean dateBoundary() {
Object[] option = {"I get it","My Bad!"};
if(dateChooser.getDate().compareTo(currentDate)>0) {
JOptionPane.showOptionDialog(HomePage.getFrame(),"message1",
"",JOptionPane.DEFAULT_OPTION,JOptionPane.ERROR_MESSAGE,null,option,option[0]);
return false;
}
if(dateChooser.getDate().compareTo(DateConverter.convertfromCustom(CurrentUser.getInstance().getDob()))<0){
JOptionPane.showOptionDialog(HomePage.getFrame(),"message2",
"",JOptionPane.DEFAULT_OPTION,JOptionPane.ERROR_MESSAGE,null,option,option[0]);
return false;
}
return true;
}
isAlreadyWritten（）的代码：
public static boolean isAlreadyWritten() {
File f = new File(filename);
if(f.length()!=0)
{
Object[] option = {"Read","Edit"};
JOptionPane.showOptionDialog(HomePage.getFrame(),"You already updated diary for this day. Do you want to edit?",
"",JOptionPane.DEFAULT_OPTION,JOptionPane.INFORMATION_MESSAGE,null,option,option[0]);
return true;
}
else
return false;
}
updateDateChooser（）的代码：
public static void updateDateChooser(CustomDate date) {
dateChooser.removePropertyChangeListener(lis); //to stop it from getting triggered when date is set programatically
dateChooser.setDate(DateConverter.convertfromCustom(date));
dateChooser.addPropertyChangeListener(lis);
}
updateEditFields（）的代码：
public static void updateEditFields(CustomDate searchDate, String excontent) {
updateDateChooser(searchDate);
selectedDate = DateConverter.convertDate(dateChooser);
dayinfo.setText("You are editing entry for: "+ new SimpleDateFormat("dd/MM/yyyy").format(dateChooser.getDate()));
contentfield.setText(excontent);
}
现在，我的dateboundary函数正在按预期方式工作。每当选择一个大于当前日期的日期时，都会显示option对话框，并在单击后消失，并且datechooser设置为最后选择的日期，尽管propertychange方法被称为三次：
在对话框显示之前一次
对话框关闭后两次。
但是我的isAlreadyWritten（）不能按预期方式工作，而optiondialog被显示4次，而propertychange（）方法被调用了4次：
每次显示该对话框之前，请单击一次。
我想了解为什么即使以编程方式设置日期时，即使datechooser从侦听器中分离出来，propertychange仍被调用4次？
最佳答案
因此，我整理并运行了此摘要
import com.toedter.calendar.JDateChooser;
import java.awt.EventQueue;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.Date;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JDateChooser dateChooser = new JDateChooser();
dateChooser.addPropertyChangeListener(new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
System.out.println(evt.getPropertyName());
}
});
dateChooser.setDate(new Date());
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(dateChooser);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
}
我打开了日期选择器并选择了一个日期。程序输出...
date
ancestor
date
date
是我以编程方式设置日期吗
ancestor是否已添加到容器中是我选择日期选择器吗
我要选择一个日期吗
因此，如您所见，不仅您不仅收到大量“日期”属性更改的垃圾邮件，而且还获得了所有“其他”属性更改的信息😓
因此，您要做的第一件事就是将通知仅限制为“ date”属性，例如...
dateChooser.addPropertyChangeListener("date", new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
System.out.println(evt.getPropertyName());
}
});
这至少意味着您不会被所有无关的其他信息所困扰。
虽然您可以添加和删除侦听器，但由于我并不总是具有对侦听器的引用，因此我倾向于发现它很痛苦，相反，我倾向于使用状态标志来代替
private boolean manualDate = false;
//...
dateChooser.addPropertyChangeListener("date", new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
if (manualDate) {
return;
}
System.out.println(evt.getPropertyName());
}
});
manualDate = true;
dateChooser.setDate(new Date());
manualDate = false;
变化不大，但这仅意味着您现在只有两个事件通知。
相反，您应该将
oldValue与newValue的PropertyChangeEventJDateChooser dateChooser = new JDateChooser();
dateChooser.addPropertyChangeListener("date", new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
if (manualDate) {
return;
}
Date newDate = (Date) evt.getNewValue();
Date oldDate = (Date) evt.getOldValue();
if (newDate != null && oldDate != null) {
LocalDate newLD = LocalDate.ofInstant(newDate.toInstant(), ZoneId.systemDefault());
LocalDate oldLD = LocalDate.ofInstant(oldDate.toInstant(), ZoneId.systemDefault());
if (newLD.equals(oldLD)) {
return;
}
}
System.out.println(evt.getPropertyName());
}
});
现在，我们要进行一次变更活动。唯一的缺点是，当他们重新选择当前日期时，它不会告诉您。
更好的工作流程可能是完全忽略所有这些，而只是让用户可以按
JButton执行您需要执行的所有相关操作可运行的示例...
import com.toedter.calendar.JDateChooser;
import java.awt.EventQueue;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.time.LocalDate;
import java.time.ZoneId;
import java.util.Date;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
private boolean manualDate;
public Test() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JDateChooser dateChooser = new JDateChooser();
dateChooser.addPropertyChangeListener("date", new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
if (manualDate) {
return;
}
Date newDate = (Date) evt.getNewValue();
Date oldDate = (Date) evt.getOldValue();
if (newDate != null && oldDate != null) {
LocalDate newLD = LocalDate.ofInstant(newDate.toInstant(), ZoneId.systemDefault());
LocalDate oldLD = LocalDate.ofInstant(oldDate.toInstant(), ZoneId.systemDefault());
if (newLD.equals(oldLD)) {
return;
}
}
System.out.println(evt.getPropertyName());
}
});
manualDate = true;
dateChooser.setDate(new Date());
manualDate = false;
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(dateChooser);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
}