datefield.java

有关j2me的很好的例子可以研究一下

         */
        int timeSel = 0;

        /**
         * Traverse the clock
         *
         * @param action
         * @param top
         * @param bottom
         * @return int
         */
        int traverseClock(int action, int top, int bottom) {
            int hrInc = 1;

            switch (action) {
                case Canvas.LEFT:
                    if (timeSel == Calendar.MINUTE) {
                        timeSel = Calendar.HOUR;
                        return 0;
                    } else if (CLOCK_USES_AM_PM) {
                        if (timeSel == Calendar.AM_PM) {
                            timeSel = Calendar.MINUTE;
                        } else if (timeSel == Calendar.HOUR) {
                            timeSel = Calendar.AM_PM;
                        }
                        return 0;
                    }
                            return -1;

                case Canvas.RIGHT:
                    if (timeSel == Calendar.HOUR) {
                        timeSel = Calendar.MINUTE;
                        return 0;
                    } else if (CLOCK_USES_AM_PM) {
                        if (timeSel == Calendar.MINUTE) {
                            timeSel = Calendar.AM_PM;
                        } else if (timeSel == Calendar.AM_PM) {
                            timeSel = Calendar.HOUR;
                        }
                        return 0;
                    }
                    return -1;

                case Canvas.UP:
                    if (CLOCK_USES_AM_PM && (timeSel == Calendar.AM_PM)) {
                        hrInc = 12;
                    } else if (timeSel == Calendar.MINUTE) {
                        int m = calendar.get(Calendar.MINUTE);
                        if (m == 59) {
                            calendar.set(Calendar.MINUTE, 0);
                        } else {
                            calendar.set(Calendar.MINUTE, m + 1);
                            hrInc = 0;
                        }
                    }
                    calendar.set(Calendar.HOUR_OF_DAY,
                        (hrInc + calendar.get(Calendar.HOUR_OF_DAY)) % 24);
                    return 0;

                case Canvas.DOWN:
                    if (CLOCK_USES_AM_PM && (timeSel == Calendar.AM_PM)) {
                        hrInc = 12;
                    } else if (timeSel == Calendar.MINUTE) {
                        int m = calendar.get(Calendar.MINUTE);
                        if (m == 0) {
                            calendar.set(Calendar.MINUTE, 59);
                        } else {
                            calendar.set(Calendar.MINUTE, m - 1);
                            hrInc = 0;
                        }
                    }
                    hrInc = 24 - hrInc;
                    calendar.set(Calendar.HOUR_OF_DAY,
                        (hrInc + calendar.get(Calendar.HOUR_OF_DAY)) % 24);
                    return 0;
                }
            return -1;
        } // traverseClock()

        /**
         * Traverse the Date editor
         *
         * @param action
         * @param top
         * @param bottom
         * @return int
         */
        int traverseDate(int action, int top, int bottom) {
            int scrollHeight = 0;

            switch (action) {
                case Canvas.LEFT:
                    if (highlight == 1) {
                        return -1;
                    }
                    if (highlight > 1) {
                        highlight--;
                        if (calendar.get(Calendar.DAY_OF_WEEK) ==
                                Calendar.SUNDAY) {
                            int topOfHighlight = highlightY(false);
                            if (topOfHighlight < top) {
                                scrollHeight = top - topOfHighlight;
                            }
                        }
                        break;
                    }
                    int year  = calendar.get(Calendar.YEAR);
                    int month = calendar.get(Calendar.MONTH);
                    if (highlight == 0) {
                        if (month > Calendar.JANUARY) {
                            int day = calendar.get(Calendar.DATE);
                            lastDay = daysInMonth(month - 1, year);
                            if (day > lastDay) {
                                calendar.set(Calendar.DATE, lastDay);
                            }
                            calendar.set(Calendar.MONTH, month - 1);
                        } else {
                            lastDay = 31;
                            calendar.set(Calendar.MONTH, Calendar.DECEMBER);
                            calendar.set(Calendar.YEAR,  year - 1);
                        }
                    } else if (highlight == -1) {
                        calendar.set(Calendar.YEAR, year - 1);
                        lastDay = daysInMonth(month, year);
                    }
                    setDayOffset();
                    break;

                case Canvas.RIGHT:
                    if (highlight == lastDay) {
                        return -1;
                    }
                    if ((highlight > 0) && (highlight < lastDay)) {
                        highlight++;
                        if (calendar.get(Calendar.DAY_OF_WEEK) ==
                                Calendar.SATURDAY) {
                            int bottomOfHighlight = highlightY(true);
                            if (bottomOfHighlight > bottom) {
                                scrollHeight = bottomOfHighlight - bottom;
                            }
                        }
                        break;
                    }
                    year  = calendar.get(Calendar.YEAR);
                    month = calendar.get(Calendar.MONTH);
                    if (highlight == 0) {
                        if (month < Calendar.DECEMBER) {
                            int day = calendar.get(Calendar.DATE);
                            lastDay = daysInMonth(month + 1, year);
                            if (day > lastDay) {
                                calendar.set(Calendar.DATE, lastDay);
                            }
                            calendar.set(Calendar.MONTH, month + 1);
                        } else {
                            calendar.set(Calendar.MONTH, Calendar.JANUARY);
                            calendar.set(Calendar.YEAR, year + 1);
                        }
                    } else if (highlight == -1) {
                        calendar.set(Calendar.YEAR, year + 1);
                        lastDay = daysInMonth(month, year);
                    }
                    setDayOffset();
                    break;

                case Canvas.UP:
                    if (highlight == -1) {
                        return -1;
                    }
                    if (highlight == 0) {
                        highlight = -1;
                    } else if (highlight <= 7) {
                        highlight = 0;
                    } else {
                        highlight -= 7;
                    }
                    int topOfHighlight = highlightY(false);
                    if (topOfHighlight < top) {
                        scrollHeight = top - topOfHighlight;
                    }
                    break;

                case Canvas.DOWN:
                    if (highlight == lastDay) {
                        return -1;
                    }
                    if (highlight == -1) {
                        highlight = 0;
                    } else if (highlight == 0) {
                        highlight = 1;
                    } else if ((highlight + 7) < lastDay) {
                        highlight += 7;
                    } else if ((highlight + 7) > lastDay) {
                        highlight = lastDay;
                    }
                    int bottomOfHighlight = highlightY(true);
                    if (bottomOfHighlight > bottom) {
                        scrollHeight = bottomOfHighlight - bottom;
                    }
                    break;

                default:
                    return -1;
            }

            if (highlight > 0) {
                calendar.set(Calendar.DATE, highlight);
            }
                return scrollHeight;
        } // traverseDate()

        /**
         * The initial highlight
         */
        private int highlight;
        /**
         * The last day of the month
         */
        private int lastDay;
        /**
         * The day offset
         */
        private int dayOffset;

        /**
         * Utility method to calculate the number of days
         * in a month
         *
         * @param month  The month to use
         * @param year  The year the month occurs in
         * @return int  The number of days in the month
         */
        private int daysInMonth(int month, int year) {
            switch (month) {
                case Calendar.JANUARY:
                case Calendar.MARCH:
                case Calendar.MAY:
                case Calendar.JULY:
                case Calendar.AUGUST:
                case Calendar.OCTOBER:
                case Calendar.DECEMBER:
                    return 31;
                case Calendar.FEBRUARY:
                    if (((year % 400) == 0)
                        || (((year & 3) == 0) && ((year % 100) != 0))) {
                        return 29;
                    }
                    return 28;
                case Calendar.APRIL:
                case Calendar.JUNE:
                case Calendar.SEPTEMBER:
                case Calendar.NOVEMBER:
                default:
                    return 30;
            }
        }

        /**
         * The "large" Font
         */
        Font large   = Font.getFont(Font.FACE_SYSTEM,
                                    Font.STYLE_PLAIN,
                                    Font.SIZE_LARGE);

        /**
         * The "regular" font
         */
        Font regular = Font.getFont(Font.FACE_SYSTEM, 
                                    Font.STYLE_PLAIN, 
                                    Font.SIZE_SMALL);

        /**
         * The "bold" font
         */
        Font bold    = Font.getFont(Font.FACE_SYSTEM, 
                                    Font.STYLE_BOLD,
                                    Font.SIZE_SMALL);

        /**
         * Set the highlight
         *
         * @param addLineHeight
         * @return int
         */
        int highlightY(boolean addLineHeight) {
            if (highlight == -1) {
                return addLineHeight ? regular.getBaselinePosition() : 0;
            } else if (highlight == 0) {
                return regular.getBaselinePosition()
                    + (addLineHeight ? regular.getHeight() : 0);
            } else {
                int line = 1 + (highlight + dayOffset - 2) / 7;
                return (regular.getBaselinePosition() + 1) * line +
                       regular.getHeight() + 1 +
                       (addLineHeight ? regular.getBaselinePosition() +2 : 0);
            }
        }

        /**
         * Paint the Calendar
         *
         * @param g The Graphics context to paint to
         */
        void paintCalendar(Graphics g) {

            g.setColor(Display.ERASE_COLOR);
            g.fillRect(g.getClipX(), g.getClipY(), 
                       g.getClipWidth(), g.getClipHeight());

            boolean currentDateOnDisplay = false;
            int year      = calendar.get(Calendar.YEAR);
            int month     = calendar.get(Calendar.MONTH);
            int selection = calendar.get(Calendar.DATE);

            // check if currentDate is on display
            int currYear  = currentDate.get(Calendar.YEAR);
            int currMonth = currentDate.get(Calendar.MONTH);
            int currDate  = currentDate.get(Calendar.DATE);
            if ((currYear == year) && (currMonth == month)) {
                currentDateOnDisplay = true;
            }

            g.setFont(regular);
            int w = regular.stringWidth("0000");
            int h = regular.getBaselinePosition();
            g.translate(0, -1);

            if (highlight == -1) {
                g.setColor(Display.BG_H_COLOR);
                g.fillRect(((width - w) / 2) - 1, 1, w + 1, h);
                g.setColor(Display.FG_H_COLOR);
            } else {
                g.setColor(Display.FG_COLOR);
            }

            g.drawString("" + year, width / 2, 0,
                         Graphics.TOP | Graphics.HCENTER);
            g.drawImage(ARROW_LEFT, (width - w) / 2 - 2, h / 2,
                        Graphics.VCENTER | Graphics.RIGHT);
            g.drawImage(ARROW_RIGHT, (width + w) / 2 + 2, h / 2,
                        Graphics.VCENTER | Graphics.LEFT);

            g.translate(0, h + 1);
            w = regular.stringWidth(Resource.getString(MONTH_NAMES[month]));
            h = regular.getHeight();

            if (highlight == 0) {
                g.setColor(Display.BG_H_COLOR);
                g.fillRect(((width - w) / 2) - 1, 1, w + 2, h);
                g.setColor(Display.FG_H_COLOR);
            } else {
                g.setColor(Display.FG_COLOR);
            }

            g.setFont(regular);
            g.drawString(Resource.getString(MONTH_NAMES[month]), width / 2, 0,
                         Graphics.TOP | Graphics.HCENTER);
            g.drawImage(ARROW_LEFT, (width - w) / 2 - 2, h / 2,