Question

JFrame中怎么添加背景图片，输入框的大小怎么修改

我用eclipse编写的
如图，1、怎么添加背景图片
2、输入框这么大不太好看，怎么调整大小啊，还有两个输入框之间的间距能调吗
3、按钮之间的间距能修改吗

Answer 1

import java.awt.*;
import java.awt.image.*;
import javax.swing.*;
import javax.imageio.ImageIO;

public class LoginExample {
    public static void main(final String... args) {
        EventQueue.invokeLater(new Runnable(){
                @Override public void run(){
                    try {
                        final XPanel container = new XPanel(ImageIO.read(LoginExample.class.getResource("/images/background.jpg")));
                        final JPanel panel = new JPanel();
                        final GroupLayout layout = new GroupLayout(panel);
                        container.setLayout(new BorderLayout());
                        panel.setLayout(layout);
                        panel.setOpaque(false);
                        layout.setAutoCreateGaps(true);
                        layout.setAutoCreateContainerGaps(true);

                        final JLabel name = new JLabel("用户名");
                        final JLabel pass = new JLabel("密码");
                        final JTextField name_field = new JTextField(12);
                        final JPasswordField pass_field = new JPasswordField(12);
                        name_field.setOpaque(false);
                        pass_field.setOpaque(false);

                        GroupLayout.SequentialGroup hGroup = layout.createSequentialGroup();

                        hGroup.addGroup(layout.createParallelGroup(GroupLayout.Alignment.TRAILING).
                                        addComponent(name).addComponent(pass));
                        hGroup.addGroup(layout.createParallelGroup().
                                        addComponent(name_field).addComponent(pass_field));
                        layout.setHorizontalGroup(hGroup);

                        GroupLayout.SequentialGroup vGroup = layout.createSequentialGroup();

                        vGroup.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE).
                                        addComponent(name).addComponent(name_field));
                        vGroup.addGroup(layout.createParallelGroup(GroupLayout.Alignment.BASELINE).
                                        addComponent(pass).addComponent(pass_field));
                        layout.setVerticalGroup(vGroup);

                        final JFrame frame = new JFrame("Login");
                        container.add(new JLabel("**欢迎您登录**", JLabel.CENTER), BorderLayout.PAGE_START);
                        container.add(panel);
                        frame.setContentPane(container);
                        frame.pack();
                        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                        frame.setVisible(true);
                    } catch (Exception e) {
                    }
                }
            });
    }
    public static class XPanel extends JPanel {
        private BufferedImage background;
        public XPanel(BufferedImage background) {
            this.background = background;
        }

        @Override public void paintComponent(Graphics g) {
            BufferedImage bufimg = new BufferedImage(getWidth(),getHeight(), BufferedImage.TYPE_INT_ARGB);

            Graphics2D g2 = bufimg.createGraphics();
            // restore the foreground color in case the superclass needs it
            g2.setColor(g.getColor());
            super.paintComponent(g2);
            // do an alpha composite
            Graphics2D gx = (Graphics2D) g;
            gx.drawImage(background,0,0,null);
            gx.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER,0.8f));
            gx.drawImage(bufimg,0,0,null);
        }
    }
}

Answer 2

如果你对布局十分在行的话，可以用绝对布局，就是用setLayout(null)设置空布局，然后用setLocation(int x, int y)和setSize(int width, int height)或setBounds(int x, int y, int width, int height)设置位置大小。

Answer 3

看看用的是哪个布局。界面不是太复杂，不使用布局，绝对bounds定位，还方便

背景在paintComponent事件，绘一张图片

追问

能不能说的具体点，才接触java，不是太懂呢

能不能说的具体点，才接触java，不是太懂呢