choicegroup.java

有关j2me的很好的例子可以研究一下

    private void checkFlag(boolean[] flag) {
        if (flag == null) {
            throw new NullPointerException();
        }

        if (flag.length < numOfEls) {
            throw new IllegalArgumentException();
        }
    }

    /**
     * Image to represent an unselected checkbox
     */
    private static final Image CKBX_OFF_IMG;
    /**
     * Image to represent a selected checkbox
     */
    private static final Image CKBX_ON_IMG;
    /**
     * Width of a checkbox image (both selected and unselected)
     */
    private static final int CKBX_WIDTH = 10;
    /**
     * Image to represent an unselected radio button
     */
    private static final Image RD_OFF_IMG;
    /**
     * Image to represent a selected radio button
     */
    private static final Image RD_ON_IMG;
    /**
     * Width of a radio button image (both selected and unselected)
     */
    private static final int RD_WIDTH = 11;

    static {
        /**
         * Byte array used to create an unselected checkbox
         */
        byte ckbx_off[] = {
            (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)0x0a,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x0b,
            (byte)0x02, (byte)0x03, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0x3b, (byte)0x00, (byte)0xf4,
            (byte)0x8b, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x06, (byte)0x50, (byte)0x4c, (byte)0x54,
            (byte)0x45, (byte)0xff, (byte)0xff, (byte)0xff,
            (byte)0xbb, (byte)0xbb, (byte)0xbb, (byte)0xc7,
            (byte)0x4b, (byte)0xdf, (byte)0xf8, (byte)0x00,
            (byte)0x00, (byte)0x00, (byte)0x1e, (byte)0x49,
            (byte)0x44, (byte)0x41, (byte)0x54, (byte)0x78,
            (byte)0xda, (byte)0x63, (byte)0x60, (byte)0x60,
            (byte)0x60, (byte)0x60, (byte)0x0c, (byte)0x65,
            (byte)0xf8, (byte)0xcd, (byte)0xe0, (byte)0xc0,
            (byte)0x20, (byte)0xc0, (byte)0xc4, (byte)0xc0,
            (byte)0xc0, (byte)0x80, (byte)0x0b, (byte)0x33,
            (byte)0x86, (byte)0x32, (byte)0xfc, (byte)0x06,
            (byte)0x00, (byte)0x3f, (byte)0x74, (byte)0x03,
            (byte)0x01, (byte)0x35, (byte)0x94, (byte)0x27,
            (byte)0xe6, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0x49, (byte)0x45, (byte)0x4e,
            (byte)0x44, (byte)0xae, (byte)0x42, (byte)0x60,
            (byte)0x82,
        };

        /**
         * Byte array used to create a selected checkbox
         */
        byte ckbx_on[] = {
            (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)0x0a,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x0b,
            (byte)0x02, (byte)0x03, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0x3b, (byte)0x00, (byte)0xf4,
            (byte)0x8b, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x0c, (byte)0x50, (byte)0x4c, (byte)0x54,
            (byte)0x45, (byte)0xff, (byte)0xff, (byte)0xff,
            (byte)0xbb, (byte)0xbb, (byte)0xbb, (byte)0x6a,
            (byte)0x6a, (byte)0x6a, (byte)0x02, (byte)0x02,
            (byte)0x02, (byte)0x6a, (byte)0x99, (byte)0x0e,
            (byte)0xd1, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x35, (byte)0x49, (byte)0x44, (byte)0x41,
            (byte)0x54, (byte)0x78, (byte)0xda, (byte)0x63,
            (byte)0x60, (byte)0x60, (byte)0x7c, (byte)0xc0,
            (byte)0xf0, (byte)0xff, (byte)0xb3, (byte)0x03,
            (byte)0xd3, (byte)0x41, (byte)0x91, (byte)0x0f,
            (byte)0x4c, (byte)0x0c, (byte)0x6c, (byte)0x0c,
            (byte)0x4c, (byte)0x0c, (byte)0xfc, (byte)0x0c,
            (byte)0x4c, (byte)0x0c, (byte)0x12, (byte)0x0c,
            (byte)0x4c, (byte)0xbc, (byte)0x7f, (byte)0x18,
            (byte)0x98, (byte)0x7e, (byte)0x2d, (byte)0x60,
            (byte)0x60, (byte)0xf9, (byte)0xf5, (byte)0x93,
            (byte)0x81, (byte)0xe9, (byte)0xbf, (byte)0x03,
            (byte)0x03, (byte)0xe3, (byte)0x7f, (byte)0x86,
            (byte)0x8f, (byte)0x00, (byte)0x05, (byte)0x25,
            (byte)0x0c, (byte)0xde, (byte)0x01, (byte)0x9d,
            (byte)0xad, (byte)0x64, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0x00, (byte)0x49, (byte)0x45,
            (byte)0x4e, (byte)0x44, (byte)0xae, (byte)0x42,
            (byte)0x60, (byte)0x82,
        };

        /**
         * Byte array used to create an unselected radio button
         */
        byte rad_off[] = {
            (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)0x0b,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x0b,
            (byte)0x02, (byte)0x03, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0xd4, (byte)0xc2, (byte)0x9f,
            (byte)0xb5, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x09, (byte)0x50, (byte)0x4c, (byte)0x54,
            (byte)0x45, (byte)0xff, (byte)0xff, (byte)0xff,
            (byte)0xbb, (byte)0xbb, (byte)0xbb, (byte)0x6a,
            (byte)0x6a, (byte)0x6a, (byte)0xd4, (byte)0x0d,
            (byte)0xff, (byte)0xe8, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0x2a, (byte)0x49, (byte)0x44,
            (byte)0x41, (byte)0x54, (byte)0x78, (byte)0xda,
            (byte)0x63, (byte)0x60, (byte)0x5a, (byte)0xc5,
            (byte)0xc0, (byte)0x20, (byte)0xc1, (byte)0x30,
            (byte)0x81, (byte)0x41, (byte)0x81, (byte)0x41,
            (byte)0x81, (byte)0x29, (byte)0x81, (byte)0xe1,
            (byte)0x05, (byte)0x13, (byte)0x03, (byte)0x03,
            (byte)0x03, (byte)0x32, (byte)0x66, (byte)0x50,
            (byte)0x60, (byte)0x50, (byte)0x60, (byte)0xfa,
            (byte)0xc1, (byte)0x50, (byte)0xc0, (byte)0xc0,
            (byte)0xb4, (byte)0x8a, (byte)0x01, (byte)0x00,
            (byte)0x71, (byte)0x18, (byte)0x05, (byte)0x3d,
            (byte)0x49, (byte)0xbc, (byte)0x9c, (byte)0x62,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x49, (byte)0x45, (byte)0x4e, (byte)0x44,
            (byte)0xae, (byte)0x42, (byte)0x60, (byte)0x82,
        };

        /**
         * Byte array used to create a selected radio button
         */
        byte rad_on[] = {
            (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)0x0b,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x0b,
            (byte)0x02, (byte)0x03, (byte)0x00, (byte)0x00,
            (byte)0x00, (byte)0xd4, (byte)0xc2, (byte)0x9f,
            (byte)0xb5, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x0c, (byte)0x50, (byte)0x4c, (byte)0x54,
            (byte)0x45, (byte)0xff, (byte)0xff, (byte)0xff,
            (byte)0xbb, (byte)0xbb, (byte)0xbb, (byte)0x6a,
            (byte)0x6a, (byte)0x6a, (byte)0x02, (byte)0x02,
            (byte)0x02, (byte)0x6a, (byte)0x99, (byte)0x0e,
            (byte)0xd1, (byte)0x00, (byte)0x00, (byte)0x00,
            (byte)0x32, (byte)0x49, (byte)0x44, (byte)0x41,
            (byte)0x54, (byte)0x78, (byte)0xda, (byte)0x05,
            (byte)0xc1, (byte)0x41, (byte)0x0d, (byte)0x00,
            (byte)0x20, (byte)0x0c, (byte)0x04, (byte)0xc1,
            (byte)0xed, (byte)0xf5, (byte)0x8b, (byte)0x01,
            (byte)0x12, (byte)0x44, (byte)0x9c, (byte)0x0a,
            (byte)0x34, (byte)0x13, (byte)0x5e, (byte)0x48,
            (byte)0x40, (byte)0x11, (byte)0x65, (byte)0x86,
            (byte)0x2c, (byte)0xd4, (byte)0xe3, (byte)0x62,
            (byte)0xcc, (byte)0x59, (byte)0x4d, (byte)0x9a,
            (byte)0x28, (byte)0x02, (byte)0x55, (byte)0xa1,
            (byte)0xb7, (byte)0xc1, (byte)0x98, (byte)0xc1,
            (byte)0x25, (byte)0x8b, (byte)0x0f, (byte)0xd8,
            (byte)0x77, (byte)0x0a, (byte)0x29, (byte)0x4e,
            (byte)0x1a, (byte)0xb1, (byte)0x3b, (byte)0x00,
            (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x49,
            (byte)0x45, (byte)0x4e, (byte)0x44, (byte)0xae,
            (byte)0x42, (byte)0x60, (byte)0x82,
        };

        CKBX_OFF_IMG = Image.createImage(ckbx_off, 0, ckbx_off.length);
        CKBX_ON_IMG  = Image.createImage(ckbx_on, 0, ckbx_on.length);
        RD_OFF_IMG   = Image.createImage(rad_off, 0, rad_off.length);
        RD_ON_IMG    = Image.createImage(rad_on, 0, rad_on.length);
    }

    /**
     * This class handles the layout for a choice group item, which consists
     * of an image (optionally) and a string. When the image is less the half
     * the display width, the string appears on the same line as the image.
     * When the image is more than half the display width, the string appears
     * below the image, indented by 3 white spaces.
     *
     * This class extends the StringLayout class to allow the superclass to
     * handle the string layout.
     */
    class IaSLayout extends StringLayout {
        /**
         * Image of the element
         */
        private Image img;
        /**
         * Height and width of the image of the element
         */
        private int imgHeight, imgWidth;

        /**
         * This is the total height and width of the item. This is different
         * from the sum of the image and string height and width, because
         * depending on the width of the image, they could be side-by-side,
         * or on-top of each other.
         */
        private int layoutedHeight, layoutedWidth;

        /**
         * Construct a new IaSLayout
         *
         * @param str The string part of the element
         * @param img The image part of the element
         * @param font The Font used to render the string of the element
         * @param offset The offset of the text from the image of the element
         */
        IaSLayout(String str, Image img, Font font, boolean offset) {
            super(str, font);

            this.img = img;
            if (img != null) {
                imgHeight = img.getHeight();
                // pad the image with same spaces before the string
                imgWidth  = img.getWidth() + 2;
            }
            setOffset(offset);
        }

        /**
         * Get the image for this element
         *
         * @return Image The image to render for this element
         */
        Image getImage() {
            return img;
        }

        /**
         * Get the width of this element
         *
         * @return int  The width of this element
         */
        public int getWidth() {
            return layoutedWidth;
        }

        /**
         * Set the allowable width for this element
         *
         * @param w The allowable width for this element
         * @return int  The height required to display this element
         *              given the allowable width
         */
        public int setWidth(int w) {
            if ((layoutedWidth == w) || (w < 0)) {
                return layoutedHeight;
            }

            layoutedWidth = w;

            if (imgWidth > (w / 2)) {
                // height of the item is the sum of the image and 
                // string heights if the image is too wide.
                layoutedHeight = super.setWidth(w - offsetWidth) + imgHeight;
            } else {
                // return the taller of the image or the text
                int superHeight = super.setWidth(w - imgWidth);
                layoutedHeight = imgHeight;
                if (superHeight > layoutedHeight) {
                    layoutedHeight = superHeight;
                }
            }

            return layoutedHeight;
        }

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

        /**
         * Paint this element
         *
         * @param g The Graphics context to paint to
         * @param eraseBgrnd    A flag to erase the background before painting
         * @param inverted  A flag to signal the element should be painted in
         *                  inverted colors
         */
        public void paint(Graphics g,
                          boolean eraseBgrnd, boolean inverted) {
            // clear the background
            if (eraseBgrnd) {
                g.setColor(inverted ?
                    Display.BG_H_COLOR : Display.ERASE_COLOR);
                g.fillRect(0, 0, layoutedWidth, layoutedHeight);
            }

            if (img != null) {
                // center the image vertically in a line, only
                // when the image is less than a line height, and there is
                // only one line of text.
                if (imgWidth < (Display.WIDTH / 2) &&
                        layoutedHeight <= lineHeight) {
                    g.drawImage(img, 0, lineHeight / 2,
                                Graphics.VCENTER | Graphics.LEFT);
                } else {
                    g.drawImage(img, 0, 0, Graphics.TOP | Graphics.LEFT);
                }
            }

            // depending on the width of the image, the string appears to the
            // right or below (and indented) of the image.
            int tx = 0;
            int ty = 0;
            if (imgWidth > (Display.WIDTH / 2)) {
                ty = imgHeight;
                tx = offsetWidth;
            } else {
                tx = imgWidth;
            }
            g.translate(tx, ty);
            super.paint(g, false, inverted);
            g.translate(-tx, -ty);
        }
    } // end of IaStringLayout
}