在面板内绘制图像

我有一个带两个按钮的面板。 我正在尝试在面板中插入图像，我想在单击按钮后在图像内部绘制线条。 我使用了下面的代码，但这似乎不起作用。

public class Try_Panel extends JFrame { // start attributes private JPanel jPanel1 = new JPanel(null, true); private JButton jButton1 = new JButton(); private JButton jButton2 = new JButton(); // end attributes public Try_Panel(String title) { // Frame-Init super(title); setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); int frameWidth = 300; int frameHeight = 300; setSize(frameWidth, frameHeight); Dimension d = Toolkit.getDefaultToolkit().getScreenSize(); int x = (d.width - getSize().width) / 2; int y = (d.height - getSize().height) / 2; setLocation(x, y); setResizable(false); Container cp = getContentPane(); cp.setLayout(null); // start components jPanel1.setBounds(48, 24, 209, 145); jPanel1.setOpaque(false); cp.add(jPanel1); jButton1.setBounds(88, 208, 75, 25); jButton1.setText("jButton1"); jButton1.setMargin(new Insets(2, 2, 2, 2)); jButton1.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent evt) { jButton1_ActionPerformed(evt); } }); cp.add(jButton1); jButton2.setBounds(184, 208, 75, 25); jButton2.setText("jButton2"); jButton2.setMargin(new Insets(2, 2, 2, 2)); jButton2.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent evt) { jButton2_ActionPerformed(evt); } }); cp.add(jButton2); // end components setVisible(true); } // end of public Try_Panel // start methods public void jButton1_ActionPerformed(ActionEvent evt) { BufferedImage image=new BufferedImage(jPanel1.getWidth(), jPanel1.getHeight(), BufferedImage.TYPE_3BYTE_BGR); JLabel l=new JLabel(new ImageIcon(image)); Graphics graphics = image.getGraphics(); Graphics2D g = (Graphics2D) graphics; g.fillRect(0, 0, image.getWidth(), image.getHeight()); g.setColor(Color.BLUE); g.drawLine(0, 0, 300, 400); jPanel1.add(l); } // end of jButton1_ActionPerformed public void jButton2_ActionPerformed(ActionEvent evt) { // TODO add your code here } // end of jButton2_ActionPerformed // end methods public static void main(String[] args) { new Try_Panel("Try_Panel"); } // end of main } // end of class Try_Panel 

最大的问题是我的其他课程中使用的代码相同。

Answer 1

在更新后，尝试将image包装在ImageIcon 。 此外，在完成渲染到图形上下文时，还应调用Graphics#dispose 。

 public void jButton1_ActionPerformed(ActionEvent evt) { BufferedImage image=new BufferedImage(jPanel1.getWidth(), jPanel1.getHeight(), BufferedImage.TYPE_3BYTE_BGR); Graphics2D g = image.createGraphics(); g.fillRect(0, 0, image.getWidth(), image.getHeight()); g.setColor(Color.BLUE); g.drawLine(0, 0, 300, 400); g.dispose(); JLabel l=new JLabel(new ImageIcon(image)); jPanel1.add(l); } 

您还应该依赖布局管理器，而不是自己尝试，它只会让您的生活更轻松。

就个人而言，我认为直接绘制到自定义组件（如JPanel会更容易。 查看执行自定义绘画了解更多详情

用例子更新

基本上，我把你的例子改为

1. 使用布局管理器
2. 在EDT的上下文中加载UI
3. revalidate jPanel1

 public class BadLabel extends JFrame { // start attributes private JPanel jPanel1 = new JPanel(new BorderLayout(), true); private JButton jButton1 = new JButton(); private JButton jButton2 = new JButton(); // end attributes public BadLabel(String title) { // Frame-Init super(title); setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); int frameWidth = 300; int frameHeight = 300; setSize(frameWidth, frameHeight); Dimension d = Toolkit.getDefaultToolkit().getScreenSize(); int x = (d.width - getSize().width) / 2; int y = (d.height - getSize().height) / 2; setLocation(x, y); // setResizable(false); Container cp = getContentPane(); // cp.setLayout(null); // start components // jPanel1.setBounds(48, 24, 209, 145); jPanel1.setOpaque(true); jPanel1.setBackground(Color.RED); cp.add(jPanel1); JPanel buttons = new JPanel(); // jButton1.setBounds(88, 208, 75, 25); jButton1.setText("jButton1"); jButton1.setMargin(new Insets(2, 2, 2, 2)); jButton1.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent evt) { jButton1_ActionPerformed(evt); } }); buttons.add(jButton1); // jButton2.setBounds(184, 208, 75, 25); jButton2.setText("jButton2"); jButton2.setMargin(new Insets(2, 2, 2, 2)); jButton2.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent evt) { jButton2_ActionPerformed(evt); } }); buttons.add(jButton2); // end components cp.add(buttons, BorderLayout.SOUTH); setVisible(true); } // end of public BadLabel // start methods public void jButton1_ActionPerformed(ActionEvent evt) { BufferedImage image = new BufferedImage(jPanel1.getWidth(), jPanel1.getHeight(), BufferedImage.TYPE_3BYTE_BGR); Graphics2D g = image.createGraphics(); g.fillRect(0, 0, image.getWidth(), image.getHeight()); g.setColor(Color.BLUE); g.drawLine(0, 0, 300, 400); g.dispose(); JLabel l = new JLabel(new ImageIcon(image)); l.setBorder(new LineBorder(Color.BLUE)); jPanel1.add(l); jPanel1.revalidate(); } // end of jButton1_ActionPerformed public void jButton2_ActionPerformed(ActionEvent evt) { // TODO add your code here } // end of jButton2_ActionPerformed // end methods public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (Exception exp) { } new BadLabel("BadLabel"); } }); } // end of main } // end of class BadLabel} 

Answer 2

像这样的东西：

 import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.awt.image.BufferedImage; import javax.swing.border.EmptyBorder; public class Try_Panel { // start attributes private JButton jButton1 = new JButton("jButton1"); private JButton jButton2 = new JButton("jButton2"); private JLabel imageView; BufferedImage image; int x = 300; int y = 50; // end attributes public Component getGui() { JPanel gui = new JPanel(new BorderLayout(5, 5)); gui.setBorder(new EmptyBorder(3, 3, 3, 3)); image = new BufferedImage(300, 100, BufferedImage.TYPE_INT_RGB); imageView = new JLabel(new ImageIcon(image)); gui.add(imageView, BorderLayout.CENTER); JPanel buttons = new JPanel(new FlowLayout(FlowLayout.CENTER, 15, 15)); gui.add(buttons, BorderLayout.PAGE_END); jButton1.setMargin(new Insets(2, 2, 2, 2)); jButton1.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent evt) { jButton1_ActionPerformed(evt); } }); buttons.add(jButton1); jButton2.setMargin(new Insets(2, 2, 2, 2)); jButton2.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent evt) { jButton2_ActionPerformed(evt); } }); buttons.add(jButton2); // end components return gui; } public static void main(String[] args) { Runnable r = new Runnable() { public void run() { // Frame-Init JFrame f = new JFrame("Try Panel"); f.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); f.setLocationByPlatform(true); Container cp = f.getContentPane(); cp.setLayout(new BorderLayout(3, 3)); Try_Panel tp = new Try_Panel(); cp.add(tp.getGui()); f.pack(); f.setMinimumSize(f.getSize()); f.setVisible(true); } }; SwingUtilities.invokeLater(r); } // end of public Try_Panel // start methods public void jButton1_ActionPerformed(ActionEvent evt) { Graphics graphics = image.getGraphics(); Graphics2D g = (Graphics2D) graphics; g.setColor(Color.RED); g.drawLine(0, 0, x, y); x -= 4; y += 2; g.dispose(); imageView.repaint(); } // end of jButton1_ActionPerformed public void jButton2_ActionPerformed(ActionEvent evt) { // TODO add your code here } // end of jButton2_ActionPerformed } // end of class Try_Panel