Thread: Gregorian Calendar - Problems

Hello... I am working on a project for my intro to Java class and I am stuck. We have to design a functioning calendar, and I am using GregorianCalendar to pull my Current Day, Month, Year, etc. For some reason the month is off by 1 month though (6 instead of 7). Also, I would much rather return the name of the month (July instead of 6) but I can't seem to figure it out. Lastly, I can't seem to get the number of days to fall on the buttons in the proper place. I know I'm asking a lot, but this assignment is really hard, and I'm trying to get as much help as I can because I am stuck...

Here is my code...

public class Calendar extends JFrame {
 
	public Calendar() {
		this.setSize(640,480);
		this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
		this.setVisible(true);
		this.setTitle("Calendar");
 
		JPanel borderPanel = new JPanel();
		borderPanel.setLayout(new BorderLayout());
		getContentPane().add(borderPanel);
 
		// Initialize GregorianCalendar
		GregorianCalendar cal = new GregorianCalendar();
		int currYear = cal.get(GregorianCalendar.YEAR);
		int currDOM = cal.get(GregorianCalendar.DAY_OF_MONTH);
		int currMnth = cal.get(GregorianCalendar.MONTH);
		int nod, som;
		nod = cal.getActualMaximum(GregorianCalendar.DAY_OF_MONTH); //Number of Days
		som = cal.get(GregorianCalendar.DAY_OF_WEEK); // Start of the Month
 
		// Button Layout
		final int ROWS = 6;
		final int COLS = 7;
		JButton[][] days;
		JPanel calendar = new JPanel();
		calendar.setLayout(new GridLayout(6,7));
		days = new JButton[ROWS][COLS];
		for(int row = 0; row < ROWS; row++) {
			for(int col = 0; col < COLS; col++) {
				days[row][col] = new JButton("");
				calendar.add(days[row][col]);
			}
		}
 
		// Add Some Number to the Buttons
		int[] tableMonth = {31,28,31,30,31,30,31,31,30,31,30,31};
		int startDay = som;
		int daysInMonth = tableMonth[currMnth];
		for(int i = 0; i < daysInMonth; i++){
			days[(startDay + i)/7][(startDay + i) % 7].setText("" + (i + 1));
		}
		borderPanel.add(calendar, BorderLayout.CENTER);
 
		// North Panel - Current Month / Prev & Next Button
		JPanel month = new JPanel();	
		month.add(new JButton("Previous"));
		month.add(new JButton("The Month is: " + currMnth));
		month.add(new JButton("Next"));
		borderPanel.add(month, BorderLayout.NORTH);
 
		// West Panel - Current Date
		JPanel year = new JPanel();
		year.add(new JButton("The Year is: " + currYear ));
		borderPanel.add(year, BorderLayout.SOUTH);
 
		// South Panel - Current Year
		JPanel today = new JPanel();
		today.add(new JButton("Today is: " + currMnth + "/" + currDOM + "/" + currYear));
		borderPanel.add(today, BorderLayout.WEST);
 
	}
	public static void main(String[] args) {
		new Calendar();
	}
}

Thank you so much for any help!

What do you mean exactly by that?

The days of the month don't fall on the proper blocks. For example, July first was a Sunday, but it is falling on Tuesday. I think something is wrong with my for loop, but I can't see it.

Thanks so much! I got the month to return with July instead of 6 thanks to the switch. I am not quite getting the calendar to fill in properly, I tried the DAY_OF_WEEK_IN_MONTH but it didn't help, or I did it wrong. I swear this stuff is way to hard for a 100 level intro to Java, but I gotta get it done, lol... Thanks again!

Okay... so I've got everything working in terms of populating the buttons with the calendar. I am trying to setup the ActionListener for the prev and next buttons and I can't get it to work... well, its working, if I hit the button and do a println it updates the month +1 or -1 in my console, but the calendar itself is not refreshing. So, any ideas would be greatly appreciated!!!

public class Calendar extends JFrame {
 
	static JButton btnNext, btnPrev;
	static int currYear, currDOM, currentMonth;
 
	public Calendar() {
		this.setSize(800,600);
		this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
		this.setVisible(true);
		this.setTitle("Calendar");
 
 
		JPanel borderPanel = new JPanel();
		borderPanel.setLayout(new BorderLayout());
		getContentPane().add(borderPanel);
 
		// Initialize GregorianCalendar
		GregorianCalendar cal = new GregorianCalendar();
		int currYear = cal.get(GregorianCalendar.YEAR);
		int currDOM = cal.get(GregorianCalendar.DAY_OF_MONTH);
		int currMnth = cal.get(GregorianCalendar.MONTH);
		currentMonth = currMnth;
		String StringMnth = "";
			switch(currMnth) {
			case 0: StringMnth = "January"; break;
			case 1: StringMnth = "February"; break;
			case 2: StringMnth = "March"; break;
			case 3: StringMnth = "April"; break;
			case 4: StringMnth = "May"; break;
			case 5: StringMnth = "June"; break;
			case 6: StringMnth = "July"; break;
			case 7: StringMnth = "August"; break;
			case 8: StringMnth = "September"; break;
			case 9: StringMnth = "October"; break;
			case 10: StringMnth = "November"; break;
			case 11: StringMnth = "December"; break;
		}
		int nod, som;
		cal.set(GregorianCalendar.DATE, 1);
		nod = cal.getActualMaximum(GregorianCalendar.DAY_OF_MONTH); //Number of Days
		som = (cal.get(GregorianCalendar.DAY_OF_WEEK) - GregorianCalendar.SUNDAY + 7)%7; // Start of the Month
 
		// Button Layout
		final int ROWS = 6;
		final int COLS = 7;
		JButton[][] days;
		JPanel calendar = new JPanel();
		calendar.setLayout(new GridLayout(6,7));
		days = new JButton[ROWS][COLS];
		for(int row = 0; row < ROWS; row++) {
			for(int col = 0; col < COLS; col++) {
				days[row][col] = new JButton("");
				calendar.add(days[row][col]);
			}
		}
 
		// Add Some Number to the Buttons
		int[] tableMonth = {31,28,31,30,31,30,31,31,30,31,30,31};
		int startDay = som;
		int daysInMonth = tableMonth[currMnth];
		for(int i = 0; i < daysInMonth; i++){
			days[(startDay + i)/7][(startDay + i) % 7].setText("" + (i + 1));
		}
		borderPanel.add(calendar, BorderLayout.CENTER);
 
		// North Panel - Current Month / Prev & Next Button
		btnNext = new JButton(">>");
		btnPrev = new JButton("<<");
		JPanel month = new JPanel();	
		month.add(btnPrev);
		month.add(new JLabel(StringMnth));
		month.add(btnNext);
		borderPanel.add(month, BorderLayout.NORTH);
 
		//Listeners
		btnPrev.addActionListener(new btnPrev_Action());
		btnNext.addActionListener(new btnNext_Action());
 
		// West Panel - Current Date
		JPanel year = new JPanel();
		year.add(new JButton("The Year is: " + currYear ));
		borderPanel.add(year, BorderLayout.SOUTH);
 
		// South Panel - Current Year
		JPanel today = new JPanel();
		today.add(new JButton("Today is: " + StringMnth + " " + currDOM + ", " + currYear));
		borderPanel.add(today, BorderLayout.WEST);
 
	}
 
	static class btnNext_Action implements ActionListener{
		public void actionPerformed (ActionEvent e){
			currentMonth += 1;
			System.out.print(currentMonth);
		}
	}
 
	static class btnPrev_Action implements ActionListener{
		public void actionPerformed (ActionEvent e){
			currentMonth -= 1;
			System.out.print(currentMonth);
		}
	}
	public static void main(String[] args) {
		new Calendar();
	}
}

Anyone? I am stuck on the ActionListener... I can't seem to figure this out and it's driving me nuts!