java - JTextField 要求我在进行正确更新之前再次给予它焦点

Question

在我的项目中，我有一个用于输入日期的JTextField。我有一个InputVerifier来确保输入正确的信息并对其进行一些处理。我需要的一件事是从输入的日期中获取DAY_OF_WEEK。我这样做是用

Calendar calTest = Calendar.getInstance();
calTest.setTime(primer);
int day = calTest.get(Calendar.DAY_OF_WEEK);

然后我将其打印到屏幕上，无论输入什么日期，显示的数字都是4，但是当我单击该字段并单击返回而不进行更改时，正确的数字是打印到屏幕上。我不明白这是为什么？特别是当字段失去焦点后立即正确打印字符串形式的日期时。 下面是发生这种情况的方法:

private void updatePrimer(String dateString) {
    Calendar calTest = Calendar.getInstance();
    calTest.setTime(primer);
    int day = calTest.get(Calendar.DAY_OF_WEEK);
    try {
        primer = simpleFormat.parse(dateString);
    } catch (ParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    System.out.println(day);
    shortString = shortFormat.format(primer);
    System.out.println(shortString);
    labelTrip = true;
    stringTrip = dateString;
    updateLabels(labelTrip, stringTrip);
}

这是一个小的可运行程序，我基本上将其用作沙箱: 编辑这只是我在实现主程序之前一直使用的“沙箱”程序，以便我可以测试基本功能。我需要的最终结果是让 JTextField 接收一个字符串，然后将其格式化为 MM/dd/yyyy 格式的日期。使用此日期，JLabel 将更新为相同的日期，但格式为 MM/dd。此外，旁边的 JLabel 将更新为前一个日期减去一天的日期，然后对剩余的 JLabel 进行相同的处理。颜色的变化用于帮助我可视化程序的操作顺序。文本区域只是让我点击一些东西来改变焦点。该按钮仅打印 JTextField

中输入的日期

重要的是，这里的问题是为什么在 updatePrimer(String dateString) 中，只有在 JTextField 第二次获得焦点时才正确打印正确的星期几

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.swing.InputVerifier;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.MaskFormatter;


public class Hello implements ActionListener{
    private JFrame frame = new JFrame();
    private JPanel panel = new JPanel();
    private Date endingDate = new Date();
    private Date primer = new Date();
    private String endingString = null;
    private SimpleDateFormat simpleFormat = new SimpleDateFormat("MM/dd/yyyy");
    private SimpleDateFormat shortFormat = new SimpleDateFormat("MM/dd");
    private JFormattedTextField weekEndingData = null;

    private JLabel dateData[] = new JLabel[3]; 
    private JTextArea ta = new JTextArea(20, 10);
    private JButton b = new JButton("click");
    private String shortString = null;
    private boolean labelTrip = false;
    private String stringTrip = null;
    private Calendar cal = Calendar.getInstance();
    private Color blank = Color.LIGHT_GRAY;

    public Hello() {
        b.addActionListener(this);

        weekEndingData = createFormattedTextField();
        simpleFormat.setLenient(false); 

        panel.add(weekEndingData);
        for (int i=0; i<3; i++){
            dateData[i] = new JLabel("12/34");
            dateData[i].setForeground(blank);
            panel.add(dateData[i]);
        }

        panel.add(ta);
        panel.add(b);

        frame.add(panel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);

    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable(){
            public void run(){
                new Hello();    
            }
        });

        System.out.println("Hello, World");
    }

    private JFormattedTextField createFormattedTextField() {
        JFormattedTextField formattedField = null;
        try {
            MaskFormatter dateMask = new MaskFormatter("##/##/####");
            formattedField = new JFormattedTextField(dateMask);
        } catch (ParseException ex) {
            Logger.getLogger(Hello.class.getName()).log(Level.SEVERE, null, ex);
        }
        formattedField.setColumns(10);
        formattedField.setInputVerifier(getInputVerifier());
        return formattedField;
    }

    private InputVerifier getInputVerifier() {
        InputVerifier verifier = new InputVerifier() {

            @Override
            public boolean verify(JComponent input) {
                JFormattedTextField field = (JFormattedTextField) input;
                String text = field.getText();
                return isValidDate(text);
            }

            @Override
            public boolean shouldYieldFocus(JComponent input) {
                boolean valid = verify(input);
                if (!valid) {
                    JOptionPane.showMessageDialog(null, "Please enter a valid date in format dd/mm/yyyy");
                    weekEndingData.setText("");
                }
                return valid;
            }

        };
        return verifier;
    }

    public boolean isValidDate(String dateString) {
        if (dateString.equals("  /  /    ")){
            resetLabels();
            return true; //returns true in order to allow user to accidentally click field and still yield focus 
        }
        else{
            try {
                simpleFormat.parse(dateString);
                updatePrimer(dateString);
                return true;
            } catch (ParseException ex) {
                resetLabels();
                return false;
            }

        }
    }

    private void updatePrimer(String dateString) {
        Calendar calTest = Calendar.getInstance();
        calTest.setTime(primer);
        int day = calTest.get(Calendar.DAY_OF_WEEK);
        try {
            primer = simpleFormat.parse(dateString);
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println(day);
        shortString = shortFormat.format(primer);
        System.out.println(shortString);
        labelTrip = true;
        stringTrip = dateString;
        updateLabels(labelTrip, stringTrip);
    }

    private void resetLabels() {
        weekEndingData.setValue(null);
        labelTrip = false;
        updateLabels(labelTrip, stringTrip);
    }

    private void updateLabels(boolean trip, String date) {
        boolean validUpdate = trip;
        if (validUpdate == false){
            for (int i = 0; i < 3; i++){
                dateData[i].setText("12/34");
                dateData[i].setForeground(blank);
            }
        }
        else if (validUpdate == true){
            try {
                cal.setTime(simpleFormat.parse(date));
            } catch (ParseException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            int day = -1;
            for (int i = 0; i < 3; i++){
                cal.add(Calendar.DATE, day);
                dateData[i].setText(shortFormat.format(cal.getTime()));
                dateData[i].setForeground(Color.GREEN);
            }

        }
    }

    public void actionPerformed(ActionEvent e) {
        /*System.out.println("Action performed");
        System.out.println(formattedField);
        endingDate = (Date) formattedField.getValue();

        System.out.println(endingDate);
        endingString = format.format(endingDate);
        System.out.println(endingString);*/
        System.out.println(weekEndingData.getText());

    }

}

Answer 1

打印出我的代码并通过程序跟踪我的数据后，我发现了我的问题。

在

private void updatePrimer(String dateString) {
    Calendar calTest = Calendar.getInstance();
    calTest.setTime(primer);
    int day = calTest.get(Calendar.DAY_OF_WEEK);
    try {
        primer = simpleFormat.parse(dateString);
    } catch (ParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    System.out.println(day);
    shortString = shortFormat.format(primer);
    System.out.println(shortString);
    labelTrip = true;
    stringTrip = dateString;
    updateLabels(labelTrip, stringTrip);
}

行:

calTest.setTime(primer);
int day = calTest.get(Calendar.DAY_OF_WEEK);

需要移动到 primer = simpleFormat.parse(dateString); try-catch block 之后。我的问题是我在设置日期之前设置了时间。