Java Jpanel以及paintComponent的显示问题

Question

我想实现QQ消息这种气泡框，然后我首先写了一个类 A ，包含JFrame,然后在JFrame中写了JPanel, 然后我又写了一个类 B 继承Jpanel，从类A向类B传递Jpanel和输入框中的信息，在B类中，我重写了paintComponent(Graphics g )这个方法，画了一个框，但是在调用类A时，无法显示，应该如何解决这个问题呢？

package chat;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FileDialog;
import java.awt.Font;
import java.awt.GraphicsEnvironment;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.ImageFilter;
import java.io.File;
import java.io.FilenameFilter;
import java.net.Socket;
import java.util.List;

import javax.swing.BorderFactory;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JColorChooser;
import javax.swing.JComboBox;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JMenuItem;
import javax.swing.JPopupMenu;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.ScrollPaneConstants;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.border.Border;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.filechooser.FileView;

import message_show.Messageshow;
import toast.Toast;
import toast.ToastStatus;

public class ChatFrame extends JFrame {
    private static final long serialVersionUID = -8945833334986986964L;

    /**
     * 服务器窗体宽度
     */
    public static final Integer FRAME_WIDTH = 750;
    
    /**
     * 服务器窗体高度
     */
    public static final Integer FRAME_HEIGHT = 800;
    
    //接收框
    public JPanel acceptPane;

    Socket socket;
    
    ChatFrame chatFrame;
    private Color roverBorderColor = Color.gray;

    public ChatFrame() {
        
        chatFrame = this;
//        this.socket = socket;
        
        
        this.setTitle("我的电脑");
        setSize(FRAME_WIDTH, FRAME_HEIGHT);
        //窗体不可扩大
        setResizable(false);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //获取屏幕
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        int width = screenSize.width;
        int height = screenSize.height;
        //屏幕居中处理
        setLocation((width-FRAME_WIDTH)/2, (height-FRAME_HEIGHT)/2);
        
        //加载窗体的背景图片
        ImageIcon imageIcon = new ImageIcon("src/image/beijing.jpg");
        //创建一个标签并将图片添加进去
        JLabel frameBg = new JLabel(imageIcon);
        //设置图片的位置和大小
        frameBg.setBounds(0, 0, FRAME_WIDTH, FRAME_HEIGHT);
        this.add(frameBg);
        

        // 接收框
        acceptPane = new JPanel();
        acceptPane.setLayout(null);
        acceptPane.setOpaque(false);//设置透明
//        acceptPane.setFont(new Font("宋体", 0, 16));
        
        // 设置接收框滚动条
        JScrollPane scoPaneOne = new JScrollPane(acceptPane);
        scoPaneOne.setSize(750, 498);
//        scoPaneOne.setBounds(0, 20, 750, 498);
        //设置背景透明
        scoPaneOne.setOpaque(false);
        scoPaneOne.getViewport().setOpaque(false);
        scoPaneOne.setVerticalScrollBarPolicy(   
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
        frameBg.add(scoPaneOne);
        
        //添加图片符号点击功能
        //发送照片功能
        JButton picbut=new JButton();

        picbut.setBorder(null);
        ImageIcon picIcon = new ImageIcon("src/image/picture.png");
        picbut.setIcon(picIcon);
        picbut.setBounds(20, 530, picIcon.getIconWidth(), picIcon.getIconHeight());
        picbut.setContentAreaFilled(false);
        picbut.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e){
                
                FileDialog fileDialog = new FileDialog(new JFrame(),"选择照片", FileDialog.LOAD);
                fileDialog.setFile("*.jpg;*.png;*.jpeg;*.gif");
                fileDialog.setDirectory("Home");
                fileDialog.setMultipleMode(true);    //实现多选
                fileDialog.setVisible(true);
//                String pathString = fileDialog.getDirectory() + fileDialog.getFile();
                fileDialog.setMultipleMode(true);    //实现多选
                fileDialog.setVisible(true);
                File[] picfile = fileDialog.getFiles();
                String pathString = fileDialog.getDirectory();
                System.out.println(picfile.length);
                System.out.println(pathString);

            }
            });
        frameBg.add(picbut);    
        
        //发送视频功能
                JButton vdobut=new JButton();
                vdobut.setBorder(null);
                ImageIcon setIcon = new ImageIcon("src/image/vedio.png");
                vdobut.setIcon(setIcon);
                vdobut.setBounds(100, 530, setIcon.getIconWidth(), setIcon.getIconHeight());
                vdobut.setContentAreaFilled(false); 
                vdobut.addActionListener(new ActionListener() {
                    
                    @Override
                    public void actionPerformed(ActionEvent e){
                         JFileChooser vedioflc = new JFileChooser();
                         vedioflc.setToolTipText("选择视频");
                         FileNameExtensionFilter ff = new FileNameExtensionFilter("视频文件(mp4)", "mp4");
                         vedioflc.setFileFilter(ff);
                         vedioflc.showOpenDialog(null);
                    }
                    });
                frameBg.add(vdobut);
                
                
                //设置功能
                JButton setbut=new JButton();
                setbut.setBorder(null);
                ImageIcon settIcon = new ImageIcon("src/image/setting.png");
                setbut.setIcon(settIcon);
                setbut.setBounds(180, 530, settIcon.getIconWidth(), settIcon.getIconHeight());
                setbut.setContentAreaFilled(false); 
                setbut.addActionListener(new ActionListener() {
                    
                    @Override
                    public void actionPerformed(ActionEvent e){
                    }
                    });
                frameBg.add(setbut);
        
        
        
        // 输入框
        JTextPane sendPane = new JTextPane();
        sendPane.setOpaque(false);
        sendPane.setFont(new Font("宋体", 1, 20));
        JScrollPane scoPane = new JScrollPane(sendPane);// 设置滚动条
        scoPane.setBounds(0, 570, 750, 130);
        scoPane.setOpaque(false);
        scoPane.getViewport().setOpaque(false);
        scoPane.setBorder(null); 
        frameBg.add(scoPane);
        

        
        /*
         * 发送按钮
         */
        JButton send = new JButton("发 送");
        send.setBounds(610, 720, 125, 25);
        send.addActionListener(new ActionListener() {
            
            @Override
            public void actionPerformed(ActionEvent e) {
                String message=sendPane.getText();
                new Messageshow(acceptPane,scoPaneOne,true,message);
            }
        });
        frameBg.add(send);
        
        
        setVisible(true);
    }

    public static void main(String[] args) {

         new ChatFrame();

          }
    }

package message_show;

import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.SimpleAttributeSet;

import entity.UColor;

public class Messageshow  extends JPanel{
    
    public static int nowHeight=5;
    static final int maxWIDTH = 500;
    static final int initHEIGHT = 65;
    private static final Graphics Graphics = null;
    ImageIcon comimage = new ImageIcon("src/image/computer.png");
    JTextPane contentcontain = new JTextPane();
    JPanel midpanel;
    int height = initHEIGHT;
    Messageshow Messageshow;
    int realwidth;
    boolean self;
    Graphics g;
    /*
     * 将消息包装显示
     */

       public Messageshow(JPanel chatpanel, JScrollPane jsp,boolean isself, String content) {
        
           self = isself;
           JLabel comheadlabel = new JLabel(comimage);
//         this.setOpaque(false);
           contentcontain.setFont(new Font("宋体", 1, 20));   //设置框内的字体
           contentcontain.setOpaque(false);
           contentcontain.setEditable(false);
           SimpleAttributeSet set = new SimpleAttributeSet();
           Document doc = contentcontain.getStyledDocument();
           FontMetrics fm = contentcontain.getFontMetrics(contentcontain.getFont());// 得到JTextPane
           int cnt = 0; // 的当前字体尺寸
           int paneWidth = contentcontain.getWidth();// 面板的宽度
           int fontheight = fm.getHeight();
           int allmaxwidth = 0;
//将文本信息传入文本框
           try {
               for (int i = 0; i < content.length(); ++i) {
                   if (content.charAt(i) == '\n' || (cnt += fm.charWidth(content.charAt(i))) >= maxWIDTH) {// 当属出字符的宽度大于面板的宽度时换行，也就是达到JTextPane不会出现水平的滚动条
                       System.out.println(cnt);
                       allmaxwidth=Math.max(allmaxwidth, cnt);
                       cnt = 0;
                       doc.insertString(doc.getLength(), "\n", set);
                       height += fontheight;
                       continue;
                   }
                   doc.insertString(doc.getLength(), String.valueOf(content.charAt(i)), set);
               }
               if (height == initHEIGHT) {
                   realwidth = cnt + 5;
               } else {
                   realwidth = allmaxwidth+5;
               }
               // 就是将JTextPane中的插入符的位置移动到文本的末端！
           } catch (BadLocationException e) {
               // TODO Auto-generated catch block
               e.printStackTrace();
           }

           nowHeight += height + 5;
           contentcontain.setDocument(doc);
//判断是谁发出
           if (isself) {
               comheadlabel.setBounds(655, nowHeight-50, comimage.getIconHeight(), comimage.getIconWidth());
               contentcontain.setBounds(650 - realwidth - comimage.getIconHeight(), nowHeight-40, realwidth + 5, height - 25);
           } else {
               comheadlabel.setBounds(5, 5, comimage.getIconHeight(), comimage.getIconWidth());
               contentcontain.setBounds(75, 20, realwidth + 5, height - 25);
               
          }
           
           chatpanel.setPreferredSize(new Dimension(500,nowHeight));
           jsp.doLayout();
           jsp.getViewport().setViewPosition(new Point(0, jsp.getVerticalScrollBar().getMaximum()));
           chatpanel.add(comheadlabel);
           chatpanel.add(contentcontain);      //将文本消息和头像框添加至面板
           chatpanel.updateUI();
           chatpanel.revalidate();
           chatpanel.repaint();
           
       }
    
    
    /*
     * 制作消息框
     */
       @Override
    public void  paintComponent(Graphics g) {
        
        Graphics2D g2D = (Graphics2D) g;
        System.out.println("到这一步了");
        g2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        int xPoints[] = new int[3];
        int yPoints[] = new int[3];
        if (self) {
            g2D.setColor(UColor.CharBubbleColor_blue);
            g2D.fillRoundRect(760 - realwidth - comimage.getIconHeight() - 35 - 5, 20 - 5, realwidth + 5 + 5,
                    height - 25 + 5, 10, 10);
            // 绘制圆角消息气泡边框
            g2D.setColor(UColor.CharBubbleColor_blue);
            g2D.drawRoundRect(760 - realwidth - comimage.getIconHeight() - 35 - 5, 20 - 5, realwidth + 5 + 5,
                    height - 25 + 5, 10, 10);

            xPoints[0] = (760 - realwidth - comimage.getIconHeight() - 35 - 5) + (realwidth + 5 + 5);
            yPoints[0] = 20;
            xPoints[1] = xPoints[0] + 8;
            yPoints[1] = 20;
            xPoints[2] = xPoints[0];
            yPoints[2] = 20 + 6;
            g2D.setColor(UColor.CharBubbleColor_blue);
            g2D.fillPolygon(xPoints, yPoints, 3);
            g2D.setColor(UColor.CharBubbleColor_blue);
            g2D.drawPolyline(xPoints, yPoints, 3);
            g2D.setColor(UColor.CharBubbleColor_blue);
            g2D.drawLine(xPoints[0], yPoints[0] + 1, xPoints[2], yPoints[2] - 1);
        } else {
            g2D.setColor(UColor.CharBubbleColor_orange);
            g2D.fillRoundRect(75 - 5, 20 - 5, realwidth + 5 + 5, height - 25 + 5, 10, 10);
            // 绘制圆角消息气泡边框
            g2D.setColor(UColor.CharBubbleColor_orange);
            g2D.drawRoundRect(75 - 5, 20 - 5, realwidth + 5 + 5, height - 25 + 5, 10, 10);

            xPoints[0] = 75 - 5;
            yPoints[0] = 20;
            xPoints[1] = xPoints[0] - 8;
            yPoints[1] = 20;
            xPoints[2] = xPoints[0];
            yPoints[2] = 20 + 6;

           g2D.setColor(UColor.CharBubbleColor_orange);
           g2D.fillPolygon(xPoints, yPoints, 3);
           g2D.setColor(UColor.CharBubbleColor_orange);
           g2D.drawPolyline(xPoints, yPoints, 3);
           g2D.setColor(UColor.CharBubbleColor_orange);
           g2D.drawLine(xPoints[0], yPoints[0] + 1, xPoints[2], yPoints[2] - 1);
       }

   }
    
    
    
    
    /*
     * 获取当时时间
     */
    static String getTime() {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        return sdf.format(new Date());
    }

}

Answer 1

其实只要重写paint方法即可，需要重画时调用repaint方法，会自动触发paint方法。