//设置一个按钮为一个图片，不要border

        ImageIcon searchIcon = ImageToolkit.loadImageIcon(/search.png");

            ImageIcon searchHoverIcon = ImageToolkit.loadImageIcon("/search_hover.png");

            ImageIcon searchPressIcon = ImageToolkit.loadImageIcon("/search_press.png");

            searchBtn = new JButton(searchIcon);

            searchBtn.setRolloverEnabled(true);

            searchBtn.setRolloverIcon(searchHoverIcon);

            searchBtn.setPressedIcon(searchPressIcon);

             searchBtn.setBorderPainted(false);

             searchBtn.setContentAreaFilled(false);

            searchBtn.setFocusable(false);

            searchBtn.setRequestFocusEnabled(false);

            searchBtn.setPreferredSize(new Dimension(18, 18));

            searchBtn.setOpaque(false);

            searchBtn.addActionListener(new ActionListener() {

                @Override

                public void actionPerformed(ActionEvent e) {

                    enterPressed();

                }

            });