如何从内部重新绘制面板

Question

所以我有一个使用边框布局的日历 GUI。有一个带有月份和年份组合框的标题（北）。当我在月份组合框中选择一个项目时，例如六月，它将更新日历并重新绘制中心（中心有 42 个 JButton）。中心是一个装满按钮的 JPanel。这些按钮很难显示当天的事件（尽可能多地列出信息）。

我的问题是重新绘制面板并拉伸框架。当我拉伸框架时，由于某种原因，中心面板会重复。当我调用 revalidate 时，它​​会继续重复。

import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;

public class cPan extends JPanel implements ChangeListener
{
String date;
public HashMap<String, ArrayList<Event>> haM;
DataModel data;
JButton dayB;
MyCalendar cal;

public cPan(MyCalendar c, HashMap<String, ArrayList<Event>> hm, DataModel d)
{
    haM = hm;
    data = d;
    cal = c;
}

public void paintComponent(Graphics g) {
    super.paintComponent(g);
    int year = cal.get(Calendar.YEAR);
    int month = cal.get(Calendar.MONTH);
    System.out.println(month);
    int day = cal.get(Calendar.DAY_OF_MONTH);
    int daysInMonth = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
    Calendar calForDay = Calendar.getInstance();
    calForDay.set(Calendar.DATE, day);
    calForDay.set(Calendar.MONTH, month);
    calForDay.set(Calendar.YEAR, year);
    calForDay.set(Calendar.DAY_OF_MONTH, 1);
    Date firstDayOfMonth = calForDay.getTime();
    int counter = 0;
    SimpleDateFormat sdf = new SimpleDateFormat("EEEE");
    String fDOM = sdf.format(firstDayOfMonth);

    //print empty buttons
    if(fDOM.equalsIgnoreCase("SUNDAY")) {counter = 1;}
    if(fDOM.equalsIgnoreCase("MONDAY")) {counter = 2;}
    if(fDOM.equalsIgnoreCase("TUESDAY")) {counter = 3;}
    if(fDOM.equalsIgnoreCase("WEDNESDAY")) {counter = 4;}
    if(fDOM.equalsIgnoreCase("THURSDAY")) {counter = 5;}
    if(fDOM.equalsIgnoreCase("FRIDAY")) {counter = 6;}
    if(fDOM.equalsIgnoreCase("SATURDAY")) {counter = 7;}
    setLayout(new GridLayout(7,7));
    DAYS[] arrOfDays = DAYS.values();
    for(DAYS s : arrOfDays)
    {
        dayB = new JButton(s.name());
        dayB.setBackground(new Color(255, 204, 153 , 255));
        add(dayB);
    }
    for (int j = 1; j < counter; j++)
    {
        dayB.setBackground(new Color(255, 229, 204, 255));
        dayB = new JButton("");
        add(dayB);
    }
    //print day buttons
    for(int i = 1; i <= daysInMonth; i++)
    {
        String dayNum = String.valueOf(i);
        String monthNum = String.valueOf(month + 1);
        String yearNum = String.valueOf(year);
        String dayNum2 = dayNum;
        if(dayNum.length() == 1)
        {
            dayNum2 = "0" + dayNum;
        }
        if(String.valueOf(month).length() == 1)
        {
            monthNum = "0" + monthNum;
        }
        date = yearNum + monthNum + dayNum2;

        dayB = new JButton(dayNum);
        if(i == day)
        {
            dayB.setBackground(new Color(153, 255, 153, 255));
        }
        else if(haM.containsKey(date))
        {
            dayB.setBackground(new Color(255, 255, 153, 255));
        }
        else
        {
            dayB.setBackground(new Color(255, 229, 204, 255));
        }
        dayB.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                DayFrame dayF = new DayFrame(date, haM);
            }
        });
        add(dayB);
        counter++;
    }
    //print empty buttons
    for(int i = counter; i <= 42; i++)
    {
        dayB = new JButton("");
        dayB.setBackground(new Color(255, 229, 204, 255));
        add(dayB);
    }
}

public void stateChanged(ChangeEvent e) {
    System.out.println("Something is going on in statechange");
    cal.set(Calendar.MONTH, 10); // only did this to test it out
    cPan.this.revalidate();
    cPan.this.repaint();
}
}

Answer 1

您的paintComponent 方法正在做许多它不应该做的事情，例如创建和放置组件。它应该只绘画和绘画。

我建议您将组件放入类的构造函数内的 GUI 中，然后再次使用 paintComponent 进行绘画，仅此而已。如果要显示日历，请考虑将每天显示为 JPanel，该 JPanel 包含在使用 GridLayout 的 JPanel 中。 DayPanel 可以在其自己的类中以重构信息。

另外，你应该重命名你的类，因为按照惯例，类名应该以大写字母开头，所以像 CalendarPanel 这样的名字会更好。