单击鼠标添加图像？ Java 小程序

Question

当鼠标点击时，如何在鼠标坐标上添加图像？我看过这个：Adding Images on Mouse Click to JPanel

但我不明白，我想在小程序中点击鼠标添加它

请不要说，"Learn some basic java first! and provide me with a link to some oracle docs"，我只是无法从那些东西中获得任何信息。

代码：

> `import java.applet.Applet;
    import java.awt.Graphics;
    import java.awt.event.MouseEvent;
    import java.awt.event.MouseListener;
    import java.awt.image.BufferedImage;
    import java.io.IOException;
`import java.net.URL;

import javax.imageio.ImageIO;

public class SHR extends Applet implements MouseListener{

    int a;
    int b;

    @Override
    public void mouseClicked(MouseEvent e) {
        a = e.getX();
        b = e.getY();

        paint(null, a, b);/this is the part i am having trouble with
    }

    @Override
    public void mouseEntered(MouseEvent arg0) {

    }

    @Override
    public void mouseExited(MouseEvent arg0) {

    }

    @Override
    public void mousePressed(MouseEvent arg0) {

    }

    @Override
    public void mouseReleased(MouseEvent arg0) {

    }

    public void paint(Graphics g, int x, int y){
        BufferedImage photo = null;
          try 
          {
             URL u = new URL(getCodeBase(),"SilverHandRecruit.png");
             photo = ImageIO.read(u);
          }   
          catch (IOException e) 
          {
             g.drawString("Problem reading the file", 100, 100);
          }

          g.drawImage(photo,x, y, 10, 30, null);
    }



}
`

问题是，我不知道应该用什么替换 "null" 才能让它工作

谢谢

Answer 1

先看看 Painting in AWT and Swing and Performing Custom Painting 以了解绘画在 AWT/Swing 中的工作原理。

然后，查看 2D Graphics 了解有关如何使用 Graphics class 绘画的更多详细信息。

这是一个非常基本的示例，它加载单个图像，每次单击面板时，都会将其移动到该点。

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class DrawImage {

    public static void main(String[] args) {
        new DrawImage();
    }

    public DrawImage() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage image;
        private Point drawPoint;

        public TestPane() {
            try {
                image = ImageIO.read(getClass().getResource("/SmallPony.png"));
                addMouseListener(new MouseAdapter() {

                    @Override
                    public void mouseClicked(MouseEvent e) {
                        drawPoint = new Point(e.getPoint());
                        repaint();
                    }

                });
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            if (drawPoint != null) {
                g2d.drawImage(image, drawPoint.x, drawPoint.y, this);
            }
            g2d.dispose();
        }

    }

}

单击鼠标添加图像？ Java 小程序

Add image on mouse click? Java applet

java

swing

applet