}
    else if (e.getActionCommand() == "修改書籍") {
      BookModify BookModifyFrame = new BookModify();
      Dimension FrameSize = BookModifyFrame.getPreferredSize();
      Dimension MainFrameSize = getSize();
      Point loc = getLocation();
      BookModifyFrame.setLocation( (MainFrameSize.width - FrameSize.width) / 2 +
                                  loc.x,
                                  (MainFrameSize.height - FrameSize.height) / 2 +
                                  loc.y);
      BookModifyFrame.pack();
      BookModifyFrame.show();
    }
    else if (e.getActionCommand() == "刪除書籍") {
      BookDelete BookDeleteFrame = new BookDelete();
      Dimension FrameSize = BookDeleteFrame.getPreferredSize();
      Dimension MainFrameSize = getSize();
      Point loc = getLocation();
      BookDeleteFrame.setLocation( (MainFrameSize.width - FrameSize.width) / 2 +
                                  loc.x,
                                  (MainFrameSize.height - FrameSize.height) / 2 +
                                  loc.y);
      BookDeleteFrame.pack();
      BookDeleteFrame.show();
    }
    else if (e.getActionCommand() == "書籍出借") {
      BorrowBook BorrowBookFrame = new BorrowBook();
      Dimension FrameSize = BorrowBookFrame.getPreferredSize();
      Dimension MainFrameSize = getSize();
      Point loc = getLocation();
      BorrowBookFrame.setLocation( (MainFrameSize.width - FrameSize.width) / 2 +
                                  loc.x,
                                  (MainFrameSize.height - FrameSize.height) / 2 +
                                  loc.y);
      BorrowBookFrame.pack();
      BorrowBookFrame.show();
    }
    else if (e.getActionCommand() == "出借信息修改") {
      BorrowInfo BorrowInfoFrame = new BorrowInfo();
      Dimension FrameSize = BorrowInfoFrame.getPreferredSize();
      Dimension MainFrameSize = getSize();
      Point loc = getLocation();
      BorrowInfoFrame.setLocation( (MainFrameSize.width - FrameSize.width) / 2 +
                                  loc.x,
                                  (MainFrameSize.height - FrameSize.height) / 2 +
                                  loc.y);
      BorrowInfoFrame.pack();
      BorrowInfoFrame.show();
    }
    else if (e.getActionCommand() == "書籍還入") {
      ReturnBook ReturnBookFrame = new ReturnBook();
      Dimension FrameSize = ReturnBookFrame.getPreferredSize();
      Dimension MainFrameSize = getSize();
      Point loc = getLocation();
      ReturnBookFrame.setLocation( (MainFrameSize.width - FrameSize.width) / 2 +
                                  loc.x,
                                  (MainFrameSize.height - FrameSize.height) / 2 +
                                  loc.y);
      ReturnBookFrame.pack();
      ReturnBookFrame.show();
    }
    else if (e.getActionCommand() == "書籍還入信息修改") {
      ReturnInfo ReturnInfoFrame = new ReturnInfo();
      Dimension FrameSize = ReturnInfoFrame.getPreferredSize();
      Dimension MainFrameSize = getSize();
      Point loc = getLocation();
      ReturnInfoFrame.setLocation( (MainFrameSize.width - FrameSize.width) / 2 +
                                  loc.x,
                                  (MainFrameSize.height - FrameSize.height) / 2 +
                                  loc.y);
      ReturnInfoFrame.pack();
      ReturnInfoFrame.show();
    }
    else if (e.getActionCommand() == "書籍列表") {
      BookList BookListFrame = new BookList();
      Dimension FrameSize = BookListFrame.getPreferredSize();
      Dimension MainFrameSize = getSize();
      Point loc = getLocation();
      BookListFrame.setLocation( (MainFrameSize.width - FrameSize.width) / 2 +
                                loc.x,
                                (MainFrameSize.height - FrameSize.height) / 2 +
                                loc.y);
      BookListFrame.pack();
      BookListFrame.show();
    }
    else if (e.getActionCommand() == "借閱情況表") {
      BorrowBookList BorrowBookListFrame = new BorrowBookList();
      Dimension FrameSize = BorrowBookListFrame.getPreferredSize();
      Dimension MainFrameSize = getSize();
      Point loc = getLocation();
      BorrowBookListFrame.setLocation( (MainFrameSize.width - FrameSize.width) /
                                      2 + loc.x,
                                      (MainFrameSize.height - FrameSize.height) /
                                      2 + loc.y);
      BorrowBookListFrame.pack();
      BorrowBookListFrame.show();
    }
    else if (e.getActionCommand() == "用戶列表") {
      UserList UserListFrame = new UserList();
      Dimension FrameSize = UserListFrame.getPreferredSize();
      Dimension MainFrameSize = getSize();
      Point loc = getLocation();
      UserListFrame.setLocation( (MainFrameSize.width - FrameSize.width) / 2 +
                                loc.x,
                                (MainFrameSize.height - FrameSize.height) / 2 +
                                loc.y);
      UserListFrame.pack();
      UserListFrame.show();
    }
    else if (e.getActionCommand() == "關于") {
      AboutFrame aboutFrame = new AboutFrame();
      Dimension FrameSize = aboutFrame.getPreferredSize();
      Dimension MainFrameSize = getSize();
      Point loc = getLocation();
      aboutFrame.setLocation( (MainFrameSize.width - FrameSize.width) / 2 +
                                loc.x,
                                (MainFrameSize.height - FrameSize.height) / 2 +
                                loc.y);
      aboutFrame.pack();
      aboutFrame.show();
    }
    else if (e.getActionCommand() == "退出") {
      this.dispose();
      System.exit(0);
    }
  }

  //--設置登錄用戶的權限--
  public void setEnable(String powerType) {
    if (powerType.trim().equals("系統管理員")) {
      UserMGRMenu.setEnabled(true);
      BookMGRMenu.setEnabled(true);
      BorrowBookMenu.setEnabled(true);
      ReturnBookMenu.setEnabled(true);
      InfoBrowseMenu.setEnabled(true);
      UserListMenuItem.setEnabled(true);
    }
    else if (powerType.trim().equals("書籍管理員")) {
      UserMGRMenu.setEnabled(false);
      BookMGRMenu.setEnabled(true);
      BorrowBookMenu.setEnabled(false);
      ReturnBookMenu.setEnabled(false);
      InfoBrowseMenu.setEnabled(true);
      UserListMenuItem.setEnabled(false);

    }
    else if (powerType.trim().equals("借閱管理員")) {
      UserMGRMenu.setEnabled(false);
      BookMGRMenu.setEnabled(false);
      BorrowBookMenu.setEnabled(true);
      ReturnBookMenu.setEnabled(true);
      InfoBrowseMenu.setEnabled(true);
      UserListMenuItem.setEnabled(false);
    }
    else if (powerType.trim().equals("else")) {
      UserMGRMenu.setEnabled(false);
      BookMGRMenu.setEnabled(false);
      BorrowBookMenu.setEnabled(false);
      ReturnBookMenu.setEnabled(false);
      InfoBrowseMenu.setEnabled(false);
    }
  }

  public static void main(String args[]) {
    try {
      UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    }
    catch (Exception e) {
      e.printStackTrace();
    }

    MainWindow mainFrame = new MainWindow();
    mainFrame.setSize(400,300);
    //mainFrame.addWindowListener(new MyWindowListener());
    Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
    mainFrame.setLocation( (d.width - mainFrame.getSize().width) / 2,
                      (d.height - mainFrame.getSize().height) / 2);
    mainFrame.show();
  }
}