我希望能够在 Java Swing 中使拖动组件发生碰撞

Question

我尝试让 JPanel 组件可以从我观看的 YT 视频中拖动，问题是即使我的鼠标没有直接位于面板上方，它也会拖动面板。我还尝试在网上查找如何设置拖动的界限，但我找不到任何内容。我想知道是否有人有解决方案。

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;

public class DragPanel extends JPanel {

    ImageIcon image = new ImageIcon("A:\\Aseprite\\Saves\\Blue Log.png");
    Point imageCorner;
    Point prePt;

    DragPanel() {

        imageCorner = new Point(0,0);
        ClickListener clickListener = new ClickListener();
        DragListener dragListener = new DragListener();
        this.addMouseListener(clickListener);
        this.addMouseMotionListener(dragListener);
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        image.paintIcon(this, g,(int)imageCorner.getX(),(int)imageCorner.getY());
    }

    private class ClickListener extends MouseAdapter {

        public void mousePressed(MouseEvent e) {
            prePt = e.getPoint();
        }
    }

    private class DragListener extends MouseMotionAdapter {

        public void mouseDragged(MouseEvent e) {
            Point currentPt = e.getPoint();

            imageCorner.translate(((int)(currentPt.getX() - prePt.getX())), (int)(currentPt.getY() - prePt.getY()));
            prePt = currentPt;
            repaint();
        }
    }
}

Answer 1

Oracle 有一个有用的教程，使用 Swing 创建 GUI。 跳过使用 NetBeans IDE 学习 Swing 部分。

问题中发布的代码创建了一个

JPanel

。  为了使代码可以运行，我添加了一些代码。

这是我创建的 GUI 的图像。

我在网上找到了一张图片。 我添加了一个

JFrame

 来固定 

JPanel

。

修改了

mousePressed

方法以检查按下的点是否在图像的边界内。  修改了

mouseDragged

方法来检查按下的点是否有效。

这是完整的可运行代码。

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class DragPanelExample implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new DragPanelExample());
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("DragPanel Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.add(new DragPanel(), BorderLayout.CENTER);

        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public class DragPanel extends JPanel {

        private static final long serialVersionUID = 1L;

        ImageIcon image;
        Point imageCorner;
        Point prePt;

        public DragPanel() {
            this.imageCorner = new Point(0, 0);
            this.image = getImage("https://www.wallpaperflare.com/static/"
                    + "454/537/313/wood-texture-blue-tree-wallpaper.jpg");
            this.setPreferredSize(new Dimension(960, 540));

            ClickListener clickListener = new ClickListener();
            DragListener dragListener = new DragListener();
            this.addMouseListener(clickListener);
            this.addMouseMotionListener(dragListener);
        }

        private ImageIcon getImage(String urlString) {
            try {
                @SuppressWarnings("deprecation")
                URL url = new URL(urlString);
                Image image = ImageIO.read(url);
                Image smallImage = image.getScaledInstance(192, 108,
                        Image.SCALE_SMOOTH);
                return new ImageIcon(smallImage);
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            image.paintIcon(this, g, (int) imageCorner.getX(),
                    (int) imageCorner.getY());
        }

        private class ClickListener extends MouseAdapter {

            @Override
            public void mousePressed(MouseEvent e) {
                Point currentPt = e.getPoint();
                if (currentPt.x <= (imageCorner.x + image.getIconWidth())
                        && (currentPt.x >= imageCorner.x)
                        && (currentPt.y <= (imageCorner.y + image.getIconHeight())
                        && (currentPt.y >= imageCorner.y))) {
                    prePt = e.getPoint();
                } else {
                    prePt = null;
                }
                
            }
        }

        private class DragListener extends MouseMotionAdapter {

            @Override
            public void mouseDragged(MouseEvent e) {
                if (prePt != null) {
                    Point currentPt = e.getPoint();
                    imageCorner.translate(
                            ((int) (currentPt.getX() - prePt.getX())),
                            (int) (currentPt.getY() - prePt.getY()));
                    prePt = currentPt;
                    repaint();
                }
            }
        }
    }

}