設定Shell的透明度

publicc void setAlpha(int alpha)
alpha範圍為0~255

從eclipse3.4開始支援此方法

/**
 * Sets the receiver's alpha value which must be
 * between 0 (transparent) and 255 (opaque).
 * <p>
 * This operation requires the operating system's advanced
 * widgets subsystem which may not be available on some
 * platforms.
 * </p>
 * @param alpha the alpha value
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.4
 */
public void setAlpha (int alpha) {
 checkWidget ();
 if (!OS.IsWinCE && OS.WIN32_VERSION >= OS.VERSION (5, 1)) {
  alpha &= 0xFF;
  int bits = OS.GetWindowLong (handle, OS.GWL_EXSTYLE);
  if (alpha == 0xFF) {
   OS.SetWindowLong (handle, OS.GWL_EXSTYLE, bits & ~OS.WS_EX_LAYERED);
   int flags = OS.RDW_ERASE | OS.RDW_INVALIDATE | OS.RDW_FRAME | OS.RDW_ALLCHILDREN;
   OS.RedrawWindow (handle, null, 0, flags);
  } else {
   OS.SetWindowLong (handle, OS.GWL_EXSTYLE, bits | OS.WS_EX_LAYERED);
   OS.SetLayeredWindowAttributes (handle, 0, (byte)alpha, OS.LWA_ALPHA);
  }
 }
}