datefield.java

有关j2me的很好的例子可以研究一下

        if (hour >= 12) {
            return ((minute == 0) && (hour == 12)) ? "noon" : "PM";
        } else {
            return ((minute == 0) && (hour == 00)) ? "mid." : "AM";
        }
    }

    /**
     * Get the day of the week text given a Calendar
     *
     * @param calendar The Calendar object to retrieve the date from
     * @return String The day of the week text based on the date in the
     *                  calendar
     */
    static String dayOfWeekString(Calendar calendar) {
        String str;
        switch (calendar.get(Calendar.DAY_OF_WEEK)) {
        case Calendar.SUNDAY:    str = "Sun"; break;
        case Calendar.MONDAY:    str = "Mon"; break;
        case Calendar.TUESDAY:   str = "Tue"; break;
        case Calendar.WEDNESDAY: str = "Wed"; break;
        case Calendar.THURSDAY:  str = "Thu"; break;
        case Calendar.FRIDAY:    str = "Fri"; break;
        case Calendar.SATURDAY:  str = "Sat"; break;
        default: 
            str = Integer.toString(calendar.get(Calendar.DAY_OF_WEEK));
        }
        return str;
    }

    /**
     * Translate the mode of a DateField into a readable string
     *
     * @param mode The mode to translate
     * @return String A human readable string representing the mode of the
     *              DateField
     */
    String toString(int mode) {
        if (mode == DATE) {
            if (!initialized) {
                    return Resource.getString("<date>");
            }

            return Resource.getDateString(
                dayOfWeekString(currentDate),
                twoDigits(currentDate.get(Calendar.DATE)),
                MONTH_NAMES[currentDate.get(Calendar.MONTH)].substring(0, 3),
                Integer.toString(currentDate.get(Calendar.YEAR)));

        } else if (mode == TIME) {
            if (!initialized) {
                    return Resource.getString("<time>");
            }

            if (CLOCK_USES_AM_PM) {
                return Resource.getTimeString(
                    twoDigits(currentDate.get(Calendar.HOUR)),
                    twoDigits(currentDate.get(Calendar.MINUTE)),
                    twoDigits(currentDate.get(Calendar.SECOND)),
                    ampmString(currentDate));
            } else {
                return Resource.getTimeString(
                    twoDigits(currentDate.get(Calendar.HOUR_OF_DAY)),
                    twoDigits(currentDate.get(Calendar.MINUTE)),
                    twoDigits(currentDate.get(Calendar.SECOND)),
                    null);
            }
        } else {
            if (!initialized) {
                    return Resource.getString("<date/time>");
            }

            return Resource.getDateTimeString(
                dayOfWeekString(currentDate),
                twoDigits(currentDate.get(Calendar.DATE)),
                MONTH_NAMES[currentDate.get(Calendar.MONTH)].substring(0, 3),
                Integer.toString(currentDate.get(Calendar.YEAR)),
                twoDigits(currentDate.get(Calendar.HOUR_OF_DAY)),
                twoDigits(currentDate.get(Calendar.MINUTE)),
                twoDigits(currentDate.get(Calendar.SECOND)),
                ampmString(currentDate));
        }
    }

    /**
     * Get the height of this DateField
     *
     * @return int  The height of this DateField
     */
    int getHeight() {
        return height;
    }

    /**
     * Set the allowable width of this DateField
     *
     * @param width The allowable width of this DateField
     * @return int The height of this DateField based on the
     *              allowable width
     */
    int setWidth(int width) {
        height = 0;
        if (layouts != null) {
            for (int i = 0; i < layouts.length; i++) {
                if (layouts[i] != null) {
                    height += layouts[i].setWidth(width);
                }
            }
        }
        return height;
    }

    /**
     * Initialize the highlight of this DateField
     *
     * @param vpY
     * @param vpH
     * @return int Always returns 0;
     */
    int initHilight(int vpY, int vpH) {
        // Label has focus only if it is taller than the viewPort
        if (layouts[0].getHeight() > vpH) {
            highlight = 0;
        } else {
            highlight = 1;
        }
        return 0;
    }

    /**
     * Perform a selection on this DateField
     *
     * @return boolean Always returns false
     */
    boolean select() {
        Screen returnScreen = getOwner();

        if (editor == null) {
            editor = new EditScreen(returnScreen, this);
        }

        switch (mode) {
        case DATE:
            if (!initialized) {
                currentDate.set(Calendar.HOUR, 0);
                currentDate.set(Calendar.MINUTE, 0);
                currentDate.set(Calendar.SECOND, 0);
                currentDate.set(Calendar.MILLISECOND, 0);
            }
            editor.setDateTime(currentDate.getTime(), DATE);
            break;

        case TIME:
            editor.setDateTime(initialized ? currentDate.getTime() : EPOCH,
                               TIME);
            break;

        case DATE_TIME:
            editor.setDateTime(currentDate.getTime(),
                               (highlight < 2) ? DATE : TIME);
        }

        editor.layoutChanged();

        returnScreen.currentDisplay.setCurrent(editor);

        return false;
    }

    /**
     * Traverse this DateField
     *
     * @param dir
     * @param top
     * @param bottom
     * @param traversingIn
     * @param allowTraverseOut
     * @return int
     */
    int traverse(int dir, int top, int bottom, 
                 boolean traversingIn,  boolean allowTraverseOut) {

        int s = Form.traverse(dir == Canvas.DOWN, top, bottom, 
                              getHeight(), Screen.CONTENT_HEIGHT,
                              traversingIn, takesFocus());

        int labelHeight = layouts[0].getHeight();

        // NOTE: We assume that each Date and Time are
        // represented each by one line

        // Traversing into this item (focus of that item was set to false)
        if (traversingIn) {
            if (dir == Canvas.DOWN) {
                highlight = labelHeight > (bottom - top) ? 0 : 1;
            } else {
                highlight = (mode == DATE_TIME ? 2 : 1);
            }
            return s;
        }

        // Item already has focus (further traversal)
        if (dir == Canvas.DOWN) {
            if (highlight == 0) { // currently label is shown
                // after scrolling by height = s is done
                // portion of Date or Time (depending on the mode)
                // will be displayed and it should be highlighted
                if (labelHeight < bottom + s) {
                    highlight = 1;
                }
            } else if (highlight == 1) { // currently first field has focus
                int endOfField = labelHeight + layouts[1].getHeight();
                // possibly only portion of this field was shown
                if (endOfField > bottom) {
                    s = endOfField - bottom;
                } else if (mode == DATE_TIME) {
                    highlight = 2;
                    // possibly no scrolling is needed to transfer focus
                    if (s < 0) {
                        s = 0;
                    }
                }
            }
        } else {
            if (highlight == 2) {
                highlight = 1;
                // possibly no scrolling is needed to transfer focus
                if (s < 0 || (top < labelHeight)) {
                    s = 0;
                }
            } else if (highlight == 1) {
                // after scrolling by height = s is done
                // only label will be displayed
                if (bottom - s < labelHeight) {
                    highlight = 0;
                }
            }
        }

        if (s == 0 && highlight != 0) {
            repaint(0, labelHeight, Display.WIDTH, height - labelHeight);
        }
        return s;
    }

    /**
     * Static zero epoch Date - used as a default value for
     * uninitialized DateFields with TIME mode.
     */
    static final java.util.Date EPOCH = new java.util.Date(0);

    // REMIND: Needs to be localized?
    /**
     * Static array holding the names of the 12 months
     */
    static final String MONTH_NAMES[] = {
        "January", "February", "March",     "April",   "May",      "June",
        "July",    "August",   "September", "October", "November", "December"
    };

    /**
     * table of trigonometric functions, in 16.16 fixed point
     */
    static final int TRIG_TABLE[] = {
        65535, // cos 0
        65525, // cos 1
        65495, // cos 2
        65445, // cos 3
        65375, // cos 4
        65285, // cos 5
        65175, // cos 6
        65046, // cos 7
        64897, // cos 8
        64728, // cos 9
        64539, // cos 10
        64330, // cos 11
        64102, // cos 12
        63855, // cos 13
        63588, // cos 14
        63301, // cos 15
        62996, // cos 16
        62671, // cos 17
        62327, // cos 18
        61964, // cos 19
        61582, // cos 20
        61182, // cos 21
        60762, // cos 22
        60325, // cos 23
        59869, // cos 24
        59394, // cos 25
        58902, // cos 26
        58392, // cos 27
        57863, // cos 28
        57318, // cos 29
        56754, // cos 30
        56174, // cos 31
        55576, // cos 32
        54962, // cos 33
        54330, // cos 34
        53683, // cos 35
        53018, // cos 36
        52338, // cos 37
        51642, // cos 38
        50930, // cos 39
        50202, // cos 40
        49459, // cos 41
        48701, // cos 42
        47929, // cos 43
        47141, // cos 44
        46340, // cos 45
        45524, // cos 46
        44694, // cos 47
        43851, // cos 48
        42994, // cos 49
        42125, // cos 50
        41242, // cos 51
        40347, // cos 52
        39439, // cos 53
        38520, // cos 54
        37589, // cos 55
        36646, // cos 56
        35692, // cos 57
        34728, // cos 58
        33753, // cos 59
        32767, // cos 60
        31771, // cos 61
        30766, // cos 62
        29752, // cos 63
        28728, // cos 64
        27696, // cos 65
        26655, // cos 66
        25606, // cos 67
        24549, // cos 68
        23485, // cos 69
        22414, // cos 70
        21336, // cos 71
        20251, // cos 72
        19160, // cos 73
        18063, // cos 74
        16961, // cos 75
        15854, // cos 76
        14742, // cos 77
        13625, // cos 78
        12504, // cos 79
        11380, // cos 80
        10251, // cos 81
        9120,  // cos 82
        7986,  // cos 83
        6850,  // cos 84
        5711,  // cos 85
        4571,  // cos 86
        3429,  // cos 87
        2287,  // cos 88
        1143,  // cos 89
        0      // cos 90
    };

    /**