datefield.java

有关j2me的很好的例子可以研究一下

     * Utility method to return the cosine of an angle
     *
     * @param angle The angle to compute the cosine of
     * @return int The cosine of the angle
     */
    static int cos(int angle) {
        angle += 360000;
        angle %= 360;

        if (angle >= 270) {
            return TRIG_TABLE[360 - angle];
        } else if (angle >= 180) {
            return -TRIG_TABLE[angle - 180];
        } else if (angle >= 90) {
            return -TRIG_TABLE[180 - angle];
        } else {
            return TRIG_TABLE[angle];
        }
    }

    /**
     * Utility method to return the sin of an angle
     *
     * @param angle The angle to compute the sin of
     * @return int The sin of the angle
     */
    static int sin(int angle) {
        return cos(angle - 90);
    }

    // private

    /**
     * A utility method to do all the necessary height calculations
     * when content was changed.
     */
    private void contentChanged() {
        int deltaHeight = ((StringLayout)layouts[1]).setString(
                                  toString(mode == TIME ? TIME : DATE));
        if (mode == DATE_TIME) {
            deltaHeight += ((StringLayout)layouts[2]).setString(
                                  mode == DATE_TIME ? toString(TIME) : null);
        }
        height += deltaHeight;
        contentChanged(0, 0, deltaHeight);
    }

    /**
     * A utility method to return a numerical digit as two digits
     * if it is less than 10
     *
     * @param n The number to convert
     * @return String The String representing the number in two digits
     */
    private static String twoDigits(int n) {
        if (n == 0) {
            return "00";
        } else if (n < 10) {
            return "0" + n;
        } else {
            return "" + n;
        }
    }

    /**
     * The highlight of this DateField
     */
    private int highlight;
    /**
     * A flag indicating the initialization state of this DateField
     */
    private boolean initialized; // = false;
    /**
     * The mode of this DateField
     */
    private int mode;
    /**
     * The editor for this DateField
     */
    private EditScreen editor = null;
    /**
     * The height of this DateField
     */
    private int height;         //  = 0;
    /**
     * The last saved date.
     * This is used for making the last saved date bold.
     */
    private Calendar currentDate;
    /**
     * The image representing an up arrow
     */
    private static final Image ARROW_UP;
    /**
     * The image representing an down arrow
     */
    private static final Image ARROW_DOWN;
    /**
     * The image representing an left arrow
     */
    private static final Image ARROW_LEFT;
    /**
     * The image representing an right arrow
     */
    private static final Image ARROW_RIGHT;

    static {
        /**
         * The byte array to use for the up arrow
         */
        byte up_bytes[] = {
            (byte)0x89, (byte)0x50, (byte)0x4e, (byte)0x47,
            (byte)0x0d, (byte)0x0a, (byte)0x1a, (byte)0x0a,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x0d,
            (byte)0x49, (byte)0x48, (byte)0x44, (byte)0x52,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x07,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x04,
            (byte)0x08, (byte)0x02, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0xcd, (byte)0xa4, (byte)0xb2,
            (byte)0x2a, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x04, (byte)0x67, (byte)0x41, (byte)0x4d,
            (byte)0x41, (byte)0x00, (byte)0x00, (byte)0x58,
            (byte)0xc7, (byte)0xfc, (byte)0x47, (byte)0xe0,
            (byte)0x02, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x20, (byte)0x63, (byte)0x48, (byte)0x52,
            (byte)0x4d, (byte)0x00, (byte)0x00, (byte)0x7a,
            (byte)0x25, (byte)0x00, (byte)0x00, (byte)0x80,
            (byte)0x83, (byte)0x00, (byte)0x00, (byte)0xf9,
            (byte)0xff, (byte)0x00, (byte)0x00, (byte)0x80,
            (byte)0xe8, (byte)0x00, (byte)0x00, (byte)0x75,
            (byte)0x30, (byte)0x00, (byte)0x00, (byte)0xea,
            (byte)0x60, (byte)0x00, (byte)0x00, (byte)0x3a,
            (byte)0x97, (byte)0x00, (byte)0x00, (byte)0x17,
            (byte)0x6f, (byte)0x97, (byte)0xa9, (byte)0x99,
            (byte)0xd4, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x28, (byte)0x49, (byte)0x44, (byte)0x41,
            (byte)0x54, (byte)0x78, (byte)0x9c, (byte)0x62,
            (byte)0xf8, (byte)0x0f, (byte)0x03, (byte)0x0c,
            (byte)0x0c, (byte)0x0c, (byte)0x70, (byte)0x36,
            (byte)0x40, (byte)0x00, (byte)0x31, (byte)0xc0,
            (byte)0x85, (byte)0x20, (byte)0x00, (byte)0xc2,
            (byte)0x05, (byte)0x08, (byte)0x20, (byte)0x06,
            (byte)0x64, (byte)0x21, (byte)0xb8, (byte)0x04,
            (byte)0x40, (byte)0x00, (byte)0x31, (byte)0x60,
            (byte)0x05, (byte)0x00, (byte)0x01, (byte)0x06,
            (byte)0x00, (byte)0xbc, (byte)0x0c, (byte)0x23,
            (byte)0xdd, (byte)0x02, (byte)0x54, (byte)0x80,
            (byte)0xac, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0x49, (byte)0x45, (byte)0x4e,
            (byte)0x44, (byte)0xae, (byte)0x42, (byte)0x60,
            (byte)0x82,
        };

        /**
         * The byte array to use for the down arrow
         */
        byte down_bytes[] = {
            (byte)0x89, (byte)0x50, (byte)0x4e, (byte)0x47,
            (byte)0x0d, (byte)0x0a, (byte)0x1a, (byte)0x0a,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x0d,
            (byte)0x49, (byte)0x48, (byte)0x44, (byte)0x52,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x07,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x04,
            (byte)0x08, (byte)0x02, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0xcd, (byte)0xa4, (byte)0xb2,
            (byte)0x2a, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x04, (byte)0x67, (byte)0x41, (byte)0x4d,
            (byte)0x41, (byte)0x00, (byte)0x00, (byte)0x58,
            (byte)0xc7, (byte)0xfc, (byte)0x47, (byte)0xe0,
            (byte)0x02, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x20, (byte)0x63, (byte)0x48, (byte)0x52,
            (byte)0x4d, (byte)0x00, (byte)0x00, (byte)0x7a,
            (byte)0x25, (byte)0x00, (byte)0x00, (byte)0x80,
            (byte)0x83, (byte)0x00, (byte)0x00, (byte)0xf9,
            (byte)0xff, (byte)0x00, (byte)0x00, (byte)0x80,
            (byte)0xe8, (byte)0x00, (byte)0x00, (byte)0x75,
            (byte)0x30, (byte)0x00, (byte)0x00, (byte)0xea,
            (byte)0x60, (byte)0x00, (byte)0x00, (byte)0x3a,
            (byte)0x97, (byte)0x00, (byte)0x00, (byte)0x17,
            (byte)0x6f, (byte)0x97, (byte)0xa9, (byte)0x99,
            (byte)0xd4, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x26, (byte)0x49, (byte)0x44, (byte)0x41,
            (byte)0x54, (byte)0x78, (byte)0x9c, (byte)0x62,
            (byte)0x60, (byte)0xc0, (byte)0x06, (byte)0x00,
            (byte)0x02, (byte)0x88, (byte)0xe1, (byte)0xff,
            (byte)0xff, (byte)0xff, (byte)0x98, (byte)0x22,
            (byte)0x00, (byte)0x01, (byte)0x04, (byte)0xc2,
            (byte)0xc8, (byte)0x12, (byte)0x10, (byte)0x2e,
            (byte)0x40, (byte)0x00, (byte)0x41, (byte)0x29,
            (byte)0x88, (byte)0x04, (byte)0x9c, (byte)0x0d,
            (byte)0x10, (byte)0x60, (byte)0x00, (byte)0x98,
            (byte)0xe9, (byte)0x23, (byte)0xdd, (byte)0x30,
            (byte)0xaf, (byte)0x47, (byte)0x9e, (byte)0x00,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x49,
            (byte)0x45, (byte)0x4e, (byte)0x44, (byte)0xae,
            (byte)0x42, (byte)0x60, (byte)0x82,
        };

        /**
         * The byte array to use for the left arrow
         */
        byte left_bytes[] = {
            (byte)0x89, (byte)0x50, (byte)0x4e, (byte)0x47,
            (byte)0x0d, (byte)0x0a, (byte)0x1a, (byte)0x0a,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x0d,
            (byte)0x49, (byte)0x48, (byte)0x44, (byte)0x52,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x04,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x07,
            (byte)0x08, (byte)0x02, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0xa0, (byte)0x07, (byte)0x7b,
            (byte)0x87, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x04, (byte)0x67, (byte)0x41, (byte)0x4d,
            (byte)0x41, (byte)0x00, (byte)0x00, (byte)0x58,
            (byte)0xc7, (byte)0xfc, (byte)0x47, (byte)0xe0,
            (byte)0x02, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x20, (byte)0x63, (byte)0x48, (byte)0x52,
            (byte)0x4d, (byte)0x00, (byte)0x00, (byte)0x7a,
            (byte)0x25, (byte)0x00, (byte)0x00, (byte)0x80,
            (byte)0x83, (byte)0x00, (byte)0x00, (byte)0xf9,
            (byte)0xff, (byte)0x00, (byte)0x00, (byte)0x80,
            (byte)0xe8, (byte)0x00, (byte)0x00, (byte)0x75,
            (byte)0x30, (byte)0x00, (byte)0x00, (byte)0xea,
            (byte)0x60, (byte)0x00, (byte)0x00, (byte)0x3a,
            (byte)0x97, (byte)0x00, (byte)0x00, (byte)0x17,
            (byte)0x6f, (byte)0x97, (byte)0xa9, (byte)0x99,
            (byte)0xd4, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x32, (byte)0x49, (byte)0x44, (byte)0x41,
            (byte)0x54, (byte)0x78, (byte)0x9c, (byte)0x62,
            (byte)0xf8, (byte)0x0f, (byte)0x03, (byte)0x0c,
            (byte)0x0c, (byte)0x0c, (byte)0x00, (byte)0x01,
            (byte)0xc4, (byte)0x80, (byte)0x60, (byte)0x31,
            (byte)0x30, (byte)0x00, (byte)0x04, (byte)0x10,
            (byte)0x03, (byte)0x82, (byte)0xc5, (byte)0xc0,
            (byte)0x00, (byte)0x10, (byte)0x40, (byte)0x28,
            (byte)0x08, (byte)0x20, (byte)0x80, (byte)0x50,
            (byte)0x64, (byte)0x00, (byte)0x02, (byte)0x08,
            (byte)0x45, (byte)0x0f, (byte)0x40, (byte)0x00,
            (byte)0x31, (byte)0x20, (byte)0x9b, (byte)0x06,
            (byte)0x10, (byte)0x60, (byte)0x00, (byte)0xb9,
            (byte)0xf5, (byte)0x23, (byte)0xdd, (byte)0xb2,
            (byte)0x55, (byte)0x3d, (byte)0xf7, (byte)0x00,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x49,
            (byte)0x45, (byte)0x4e, (byte)0x44, (byte)0xae,
            (byte)0x42, (byte)0x60, (byte)0x82,
        };

        /**
         * The byte array to use for the right arrow
         */
        byte right_bytes[] = {
            (byte)0x89, (byte)0x50, (byte)0x4e, (byte)0x47,
            (byte)0x0d, (byte)0x0a, (byte)0x1a, (byte)0x0a,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x0d,
            (byte)0x49, (byte)0x48, (byte)0x44, (byte)0x52,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x04,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x07,
            (byte)0x08, (byte)0x02, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0xa0, (byte)0x07, (byte)0x7b,
            (byte)0x87, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x04, (byte)0x67, (byte)0x41, (byte)0x4d,
            (byte)0x41, (byte)0x00, (byte)0x00, (byte)0x58,
            (byte)0xc7, (byte)0xfc, (byte)0x47, (byte)0xe0,
            (byte)0x02, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x20, (byte)0x63, (byte)0x48, (byte)0x52,
            (byte)0x4d, (byte)0x00, (byte)0x00, (byte)0x7a,
            (byte)0x25, (byte)0x00, (byte)0x00, (byte)0x80,
            (byte)0x83, (byte)0x00, (byte)0x00, (byte)0xf9,
            (byte)0xff, (byte)0x00, (byte)0x00, (byte)0x80,
            (byte)0xe8, (byte)0x00, (byte)0x00, (byte)0x75,
            (byte)0x30, (byte)0x00, (byte)0x00, (byte)0xea,
            (byte)0x60, (byte)0x00, (byte)0x00, (byte)0x3a,
            (byte)0x97, (byte)0x00, (byte)0x00, (byte)0x17,
            (byte)0x6f, (byte)0x97, (byte)0xa9, (byte)0x99,
            (byte)0xd4, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x32, (byte)0x49, (byte)0x44, (byte)0x41,
            (byte)0x54, (byte)0x78, (byte)0x9c, (byte)0x62,
            (byte)0x60, (byte)0x60, (byte)0x60, (byte)0xf8,
            (byte)0x0f, (byte)0x03, (byte)0x00, (byte)0x01,
            (byte)0xc4, (byte)0x00, (byte)0x01, (byte)0x10,
            (byte)0x0e, (byte)0x40, (byte)0x00, (byte)0x31,
            (byte)0xc0, (byte)0x01, (byte)0x90, (byte)0x03,
            (byte)0x10, (byte)0x40, (byte)0x0c, (byte)0xc8,
            (byte)0x00, (byte)0x20, (byte)0x80, (byte)0x50,
            (byte)0x64, (byte)0x00, (byte)0x02, (byte)0x08,
            (byte)0x45, (byte)0x0f, (byte)0x40, (byte)0x00,
            (byte)0x21, (byte)0x58, (byte)0x40, (byte)0x00,
            (byte)0x10, (byte)0x60, (byte)0x00, (byte)0x06,
            (byte)0xa9, (byte)0x23, (byte)0xdd, (byte)0xcf,
            (byte)0x35, (byte)0x80, (byte)0x1e, (byte)0x00,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x49,
            (byte)0x45, (byte)0x4e, (byte)0x44, (byte)0xae,
            (byte)0x42, (byte)0x60, (byte)0x82,
        };

        ARROW_UP    = Image.createImage(up_bytes, 0, up_bytes.length);
        ARROW_DOWN  = Image.createImage(down_bytes, 0, down_bytes.length);
        ARROW_LEFT  = Image.createImage(left_bytes, 0, left_bytes.length);
        ARROW_RIGHT = Image.createImage(right_bytes, 0, right_bytes.length);
    }

    /**
     * The EditScreen class is a special editor for a DateField.
     * It can edit both date and time.
     */
    class EditScreen extends Screen implements CommandListener {
        /**
         * Flag to signal whether a select action transfers focus or not
         * (false by default)
         */
        private static final boolean SELECT_TRANSFERS_FOCUS = false;

        /**
         * Special command to go "back" from the editor to the DateField
         */
        Command Back = new Command(
            Resource.getString("Back"), Command.BACK, 0);
        /**
         * Special command to "ok" the changes done in the editor
         */
        Command OK   = new Command
            (Resource.getString("Save"), Command.OK, 1);

        /**
         * Flag to format am/pm string
         */
        private boolean ampmAfterTime = Resource.isAMPMafterTime();
        /**
         * The width and height of the editor
         */
        private int width, height;

        /**
         * Create a new EditScreen
         *
         * @param returnScreen The Screen to return to from the editor
         * @param field The DateField this EditScreen is editing
         */
        EditScreen(Screen returnScreen, DateField field) {
            super(field.getLabel());

            this.returnScreen = returnScreen;
            this.field = field;
            this.calendar = Calendar.getInstance();

            addCommand(OK);
            addCommand(Back);
            setCommandListener(this);
        }

        /**
         * Handle a command action
         *
         * @param cmd The Command to handle
         * @param s   The Displayable with the Command
         */
        public void commandAction(Command cmd, Displayable s) {
            Form form = null;
            Item item = null;