单击按钮时，将图像放置在随机网格点上

Question

我正在使用Java和Window builder我在jframe上用jlabels创建了一个4x4网格（每个网格点都是不同的jlabel）。我还有一个叫btnPlace的按钮。我想做的是在点击按钮时，在一个随机的网格点上出现一个图像。该图像文件名为red.png，它是一个红色圆圈。图像可以出现在除网格点编号1以外的任何网格点。
有点像这样：https://i.stack.imgur.com/bBn6D.png

这是我的代码：

public class grid {
public static void main (String[] args) 
{ 
    JFrame grid =new JFrame();
    grid.setDefaultCloseOperation 
    (JFrame.EXIT_ON_CLOSE); 
    JPanel set = new JPanel();      
    set.setBounds(10, 11, 307, 287);
    grid.getContentPane().add(set);
    set.setLayout(new GridLayout(4, 4, 0, 0));
    JLabel a = new JLabel("");
    set.add(a);
    JLabel b = new JLabel("");      
    set.add(b);
    JLabel c = new JLabel("");      
    set.add(c);
    ^^ this repeats up to JLabel p. just to save time.
    JButton btnPlace = new JButton("Place");        
    grid.getContentPane().add(btnPlace);
    grid.setVisible(true); 
}   }

Answer 1

下面是一个完整的工作示例：

按下按钮，它将在随机选择的JLabel 上绘制图像

package stackoverflow;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class DummyColor {
    private JFrame frame;
    private JLabel[] labels = new JLabel[4];
    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    DummyColor window = new DummyColor();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }
    /**
     * Create the application.
     */
    public DummyColor() {
        initialize();
    }
    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setResizable(false);
        frame.setBounds(100, 100, 657, 527);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);
        JLabel lbl1 = new JLabel("First BOX");
        lbl1.setBounds(10, 11, 273, 194);
        frame.getContentPane().add(lbl1);
        JLabel label = new JLabel("Second BOX");
        label.setBounds(336, 11, 273, 194);
        frame.getContentPane().add(label);
        JLabel label_1 = new JLabel("Third  BOX");
        label_1.setBounds(10, 251, 273, 194);
        frame.getContentPane().add(label_1);
        JLabel label_2 = new JLabel("Fourth BOX");
        label_2.setBounds(347, 251, 273, 194);
        frame.getContentPane().add(label_2);
        labels[0] = lbl1;
        labels[1] = label;
        labels[2] = label_1;
        labels[3] = label_2;
        JButton btnPick = new JButton("Place");
        btnPick.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                ImageIcon imageIcon = new ImageIcon(DummyColor.class.getResource("/red.jpg"));
                int randInt = randInt(1, 4);
                System.out.println(randInt);
                for (int i = 0; i < labels.length; i++) {
                    JLabel jLabel = labels[i];
                    if (i == randInt - 1) {
                        jLabel.setIcon(imageIcon);
                    } else {
                        jLabel.setIcon(null);
                    }
                }
            }
        });
        btnPick.setBounds(10, 439, 57, 23);
        frame.getContentPane().add(btnPick);
    }
    private static int randInt(int min, int max) {
        // Usually this can be a field rather than a method variable
        Random rand = new Random();
        // nextInt is normally exclusive of the top value,
        // so add 1 to make it inclusive
        int randomNum = rand.nextInt((max - min) + 1) + min;
        return randomNum;
    }
}

Answer 2

我会创建一个自定义的JPanel并添加一个MouseListener。每当点击面板时，就会在面板上点击的点上绘制一幅图像

public class grid{
    public static void main(String[] args){
        JFrame frame = new JFrame();
        frame.add(new MyPanel());
    }
}
class MyPanel extends JPanel{
    Point p;
    BufferedImage img;
    addMouseListener(new MouseAdapter(){
        public void mouseClicked(MouseEvent e){
            p = e.getLocationOnScreen();
            repaint();
        }
    });
    @Override
    protected void paintComponent(Graphics g){
        super.paintComponent(g);
        try{
            img = ImageIO.read("someImage.png");
        }catch(Exception e){e.printStackTrace();}
        g.drawImage(img, p.getX(), p.getY(), width, height, this);
    }
}