如何使 JLabel 变得可拖动？

Question

伙计们，我想知道是否有办法让这个 arrow 可以只用 X 轴拖动。我这里用的是null layout，这个arrow是加在jframe里的jlabel。这是更多信息的图像。提前谢谢你。

(在解决这个问题之前，我已经编辑了它以显示我的一些代码。这里显示的代码只是关于 ImageIcon、JLabel 和一些部分JFrame)

public class Level03 extends JFrame implements ActionListener, MouseListener, WindowListener {
// These are the Global Variables of the Level03 Class
ImageIcon slide = new ImageIcon("slide to unlock.png");
    ImageIcon slideButton = new ImageIcon("arrow icon.png");
    JLabel slideLabel = new JLabel(slide);
    JLabel slideArrow = new JLabel(slideButton);

Level03 (){ // This is the constructor
        // This is just setting the bounds of the arrow on the JFrame
        slideLabel.setBounds(100,350, 400,50);
        slideArrow.setBounds(117,350,50,50); // slideArrow is the JLabel with the ImageIcon that looks like an arrow.
        slideArrow.addMouseListener(this);
        mainFrame.add(slideArrow);
        mainFrame.add(slideLabel);
}

注意！！！我还从 implements ActionListener, MouseListener, WindowListener

下面获得了这些覆盖

@Override
    public void actionPerformed(ActionEvent e){}

@Override
    public void mouseClicked(MouseEvent e) {}

    @Override
    public void mousePressed(MouseEvent e) {}

    @Override
    public void mouseReleased(MouseEvent e) {}

    @Override
    public void mouseEntered(MouseEvent e) {}

    @Override
    public void mouseExited(MouseEvent e) {}

Answer 1

用 JLabel 做这种事情并非不可能，只是很复杂。

就个人而言，我很想只使用自定义绘制的路线，因为它可以让您进行所有控制。

例如...

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.Image;
import java.awt.Insets;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.RoundRectangle2D;
import java.io.IOException;
import java.time.Duration;
import java.time.Instant;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.border.EmptyBorder;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    JFrame frame = new JFrame();
                    frame.add(new TestPane());
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (IOException ex) {
                    Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() throws IOException {
            setBorder(new EmptyBorder(32, 32, 32, 32));
            setLayout(new GridBagLayout());
            add(new SlideToUnlock());
        }

    }

    public class SlideToUnlock extends JPanel {

        private String text;
        private Image indicatorImage;
        private Rectangle indicatorBounds;

        private Integer clickXOffset; // I can make it null and then ignore it
        private Integer dragX; // The x position of the drag

        public SlideToUnlock() throws IOException {
            indicatorImage = ImageIO.read(getClass().getResource("/images/ArrowRight.png"));
            setText("Slide to unlock");

            MouseAdapter mouseAdapter = new MouseAdapter() {
                @Override
                public void mousePressed(MouseEvent e) {
                    resetTimer();

                    Rectangle bounds = getIndiciatorImageBounds();
                    if (bounds.contains(e.getPoint())) {
                        clickXOffset = e.getPoint().x - bounds.x;
                    } else {
                        clickXOffset = null;
                    }
                    dragX = null;
                    repaint();
                }

                @Override
                public void mouseReleased(MouseEvent e) {
                    invalidate();
                    repaint();
                }

                @Override
                public void mouseDragged(MouseEvent e) {
                    dragX = e.getPoint().x;
                    if (didReachTheOtherSide()) {
                        // Notifiy some kind of observer
                    }
                    repaint();
                }
            };

            addMouseListener(mouseAdapter);
            addMouseMotionListener(mouseAdapter);
        }

        @Override
        public Dimension getPreferredSize() {
            FontMetrics fm = getFontMetrics(getFont());
            Image indicatorImage = getIndicatorImage();
            Insets insets = getInsets();

            int imageWidth = 0;
            int imageHeight = 0;

            if (indicatorImage != null) {
                imageWidth = indicatorImage.getWidth(this);
                imageHeight = indicatorImage.getHeight(this);
            }

            int height = Math.max(fm.getHeight(), imageHeight)
                    + 1 // Border
                    + 8; // Inner track

            int width = 1 + 8 + fm.stringWidth(getText()) + imageWidth;

            width += insets.left + insets.right;
            height += insets.top + insets.top;

            return new Dimension(width, height);
        }

        @Override
        public void invalidate() {
            super.invalidate();
            indicatorBounds = null;
            clickXOffset = null;
            dragX = null;
        }

        @Override
        public void revalidate() {
            super.revalidate();
            indicatorBounds = null;
            clickXOffset = null;
            dragX = null;
        }

        protected boolean didReachTheOtherSide() {
            Rectangle bounds = getIndiciatorImageBounds();

            return bounds.x + bounds.width >= getWidth() - 1;
        }

        protected Rectangle getIndiciatorImageBounds() {
            if (getParent() == null) {
                return null;
            }

            if (dragX == null && indicatorBounds != null) {
                return indicatorBounds;
            }

            Image indicatorImage = getIndicatorImage();
            int indicatorX = 1;
            int indicatorY = (getHeight() - indicatorImage.getHeight(this)) / 2;
            indicatorBounds = new Rectangle(indicatorX, indicatorY, indicatorImage.getWidth(this), indicatorImage.getHeight(this));

            if (dragX != null) {
                indicatorBounds.x = (indicatorBounds.x - clickXOffset) + dragX;

                if (indicatorBounds.x + indicatorBounds.width > (getWidth() - 1)) {
                    indicatorBounds.x = getWidth() - indicatorBounds.width - 1;
                } else if (indicatorBounds.x < 1) {
                    indicatorBounds.x = 1;
                }
            }

            return indicatorBounds;
        }

        public String getText() {
            return text;
        }

        public void setText(String text) {
            this.text = text;
        }

        public Image getIndicatorImage() {
            return indicatorImage;
        }

        public void setIndicatorImage(Image indicatorImage) {
            this.indicatorImage = indicatorImage;
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();

            int cornerRadius = 16;

            paintText(g2d);
            paintOverlay(g2d);
            paintIndicator(g2d);

            g2d.setColor(getForeground());
            g2d.draw(new RoundRectangle2D.Double(0, 0, getWidth() - 1, getHeight() - 1, cornerRadius, cornerRadius));

            g2d.dispose();
        }

        protected void paintOverlay(Graphics2D g) {
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(getBackground());
            Rectangle bounds = getIndiciatorImageBounds();
            g2d.fillRect(1, 1, bounds.x + bounds.width, getHeight() - 2);
            g2d.dispose();
        }

        protected void paintText(Graphics2D g) {
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(getForeground());
            FontMetrics fm = g2d.getFontMetrics();
            String text = getText();
            int xPos = getWidth() - 1 - 4 - fm.stringWidth(text);
            int yPos = ((getHeight() - fm.getHeight()) / 2) + fm.getAscent();
            g2d.drawString(text, xPos, yPos);
            g2d.dispose();
        }

        protected void paintIndicator(Graphics2D g) {
            Graphics2D g2d = (Graphics2D) g.create();
            Rectangle bounds = getIndiciatorImageBounds();

            g2d.translate(bounds.x, bounds.y);
            Image indicatorImage = getIndicatorImage();
            g2d.drawImage(indicatorImage, 0, 0, this);
            g2d.dispose();
        }

    }
}

好的，所以，“有效”，它完成了工作，但它缺少一些东西......反弹！当用户松开滑动控件时，它应该为反弹设置动画！

（我打赌你很抱歉你现在问了）

啊，这样更好，是小细节造就了

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.Image;
import java.awt.Insets;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.RoundRectangle2D;
import java.io.IOException;
import java.time.Duration;
import java.time.Instant;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.border.EmptyBorder;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    JFrame frame = new JFrame();
                    frame.add(new TestPane());
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (IOException ex) {
                    Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() throws IOException {
            setBorder(new EmptyBorder(32, 32, 32, 32));
            setLayout(new GridBagLayout());
            add(new SlideToUnlock());
        }

    }

    public class SlideToUnlock extends JPanel {

        private String text;
        private Image indicatorImage;
        private Rectangle indicatorBounds;

        private Integer clickXOffset; // I can make it null and then ignore it
        private Integer dragX; // The x position of the drag

        private Timer reboundTimer;

        public SlideToUnlock() throws IOException {
            indicatorImage = ImageIO.read(getClass().getResource("/images/ArrowRight.png"));
            setText("Slide to unlock");

            MouseAdapter mouseAdapter = new MouseAdapter() {
                @Override
                public void mousePressed(MouseEvent e) {
                    resetReboundTimer();

                    Rectangle bounds = getIndiciatorImageBounds();
                    if (bounds.contains(e.getPoint())) {
                        clickXOffset = e.getPoint().x - bounds.x;
                    } else {
                        clickXOffset = null;
                    }
                    dragX = null;
                    repaint();
                }

                @Override
                public void mouseReleased(MouseEvent e) {
                    startReboundTimer();
                }

                @Override
                public void mouseDragged(MouseEvent e) {
                    dragX = e.getPoint().x;
                    if (didReachTheOtherSide()) {
                        // Notifiy some kind of observer
                    }
                    repaint();
                }
            };

            addMouseListener(mouseAdapter);
            addMouseMotionListener(mouseAdapter);
        }

        protected void resetReboundTimer() {
            if (reboundTimer == null) {
                return;
            }
            reboundTimer.stop();
            reboundTimer = null;
        }

        protected void startReboundTimer() {
            resetReboundTimer();
            Rectangle bounds = getIndiciatorImageBounds();

            clickXOffset = 0;
            dragX = bounds.x + (bounds.width / 2);

            int lowerRange = 1 + (bounds.width / 2);
            int upperRange = getWidth() - 1 - (bounds.width / 2);

            int fullRange = upperRange - lowerRange;
            int currentRange = (bounds.x + (bounds.width / 2)) - lowerRange;
            double progressRange = currentRange / (double) fullRange;
            Duration fullDuration = Duration.ofMillis(250);
            Duration desiredDuration = Duration.ofMillis((long) (fullDuration.toMillis() * progressRange));

            int remainingRange = (int) (fullRange * progressRange);

            reboundTimer = new Timer(5, new ActionListener() {
                private Instant startTime = null;

                @Override
                public void actionPerformed(ActionEvent e) {
                    if (startTime == null) {
                        startTime = Instant.now();
                    }
                    Duration runTime = Duration.between(startTime, Instant.now());
                    double runTimeProgress = runTime.toMillis() / (double) desiredDuration.toMillis();
                    if (runTimeProgress >= 1.0) {
                        resetReboundTimer();
                        invalidate();
                    } else {
                        dragX = (int) (remainingRange * (1.0 - runTimeProgress));
                    }

                    repaint();
                }
            });
            reboundTimer.setInitialDelay(0);
            reboundTimer.start();
        }

        @Override
        public Dimension getPreferredSize() {
            FontMetrics fm = getFontMetrics(getFont());
            Image indicatorImage = getIndicatorImage();
            Insets insets = getInsets();

            int imageWidth = 0;
            int imageHeight = 0;

            if (indicatorImage != null) {
                imageWidth = indicatorImage.getWidth(this);
                imageHeight = indicatorImage.getHeight(this);
            }

            int height = Math.max(fm.getHeight(), imageHeight)
                    + 1 // Border
                    + 8; // Inner track

            int width = 1 + 8 + fm.stringWidth(getText()) + imageWidth;

            width += insets.left + insets.right;
            height += insets.top + insets.top;

            return new Dimension(width, height);
        }

        @Override
        public void invalidate() {
            super.invalidate();
            indicatorBounds = null;
            clickXOffset = null;
            dragX = null;
        }

        @Override
        public void revalidate() {
            super.revalidate();
            indicatorBounds = null;
            clickXOffset = null;
            dragX = null;
        }

        protected boolean didReachTheOtherSide() {
            Rectangle bounds = getIndiciatorImageBounds();

            return bounds.x + bounds.width >= getWidth() - 1;
        }

        protected Rectangle getIndiciatorImageBounds() {
            if (getParent() == null) {
                return null;
            }

            if (dragX == null && indicatorBounds != null) {
                return indicatorBounds;
            }

            Image indicatorImage = getIndicatorImage();
            int indicatorX = 1;
            int indicatorY = (getHeight() - indicatorImage.getHeight(this)) / 2;
            indicatorBounds = new Rectangle(indicatorX, indicatorY, indicatorImage.getWidth(this), indicatorImage.getHeight(this));

            if (dragX != null) {
                indicatorBounds.x = (indicatorBounds.x - clickXOffset) + dragX;

                if (indicatorBounds.x + indicatorBounds.width > (getWidth() - 1)) {
                    indicatorBounds.x = getWidth() - indicatorBounds.width - 1;
                } else if (indicatorBounds.x < 1) {
                    indicatorBounds.x = 1;
                }
            }

            return indicatorBounds;
        }

        public String getText() {
            return text;
        }

        public void setText(String text) {
            this.text = text;
        }

        public Image getIndicatorImage() {
            return indicatorImage;
        }

        public void setIndicatorImage(Image indicatorImage) {
            this.indicatorImage = indicatorImage;
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();

            int cornerRadius = 16;

            paintText(g2d);
            paintOverlay(g2d);
            paintIndicator(g2d);

            g2d.setColor(getForeground());
            g2d.draw(new RoundRectangle2D.Double(0, 0, getWidth() - 1, getHeight() - 1, cornerRadius, cornerRadius));

            g2d.dispose();
        }

        protected void paintOverlay(Graphics2D g) {
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(getBackground());
            Rectangle bounds = getIndiciatorImageBounds();
            g2d.fillRect(1, 1, bounds.x + bounds.width, getHeight() - 2);
            g2d.dispose();
        }

        protected void paintText(Graphics2D g) {
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(getForeground());
            FontMetrics fm = g2d.getFontMetrics();
            String text = getText();
            int xPos = getWidth() - 1 - 4 - fm.stringWidth(text);
            int yPos = ((getHeight() - fm.getHeight()) / 2) + fm.getAscent();
            g2d.drawString(text, xPos, yPos);
            g2d.dispose();
        }

        protected void paintIndicator(Graphics2D g) {
            Graphics2D g2d = (Graphics2D) g.create();
            Rectangle bounds = getIndiciatorImageBounds();

            g2d.translate(bounds.x, bounds.y);
            Image indicatorImage = getIndicatorImage();
            g2d.drawImage(indicatorImage, 0, 0, this);
            g2d.dispose();
        }

    }
}

现在，使用标签执行此操作将遵循非常相似的过程，唯一的补充是，您必须自己管理标签大小和位置（因为大多数布局管理器不允许您这样做）

以下是通过 MouseMotionListener

拖动标签的一些示例

JLabel is not moving properly using mouse motion listener, Why?
How to prevent JLabel positions from resetting?
JLabels, that store ImageIcons, are returned back to original location when the mouse is clicked in the panel
How to make draggable components with ImageIcon

现在，在您的情况下，您并不真正关心 y 位置，因此它可以相对于容器（或轨道）保持居中，您只需要更新 x 根据点击偏移量和当前拖动位置的位置。复杂的情况是您需要监视标签的拖动，但要将移动的位置转换为父容器。可行，但这是一个额外的并发症

有了`JLabel`

基本工作流程是一样的，只是现在您需要管理标签的组件状态（实际上是标签，因为我假设您还想要一些文本）。

这是一个允许您拖动标签的基本示例，其核心工作流程与前面的示例基本相同，但它增加了管理组件大小和位置的开销嗯

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    JFrame frame = new JFrame();
                    frame.add(new TestPane());
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (IOException ex) {
                    Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() throws IOException {
            setBorder(new EmptyBorder(32, 32, 32, 32));
            setLayout(new GridBagLayout());
            add(new SlideToUnlock());
        }

    }

    public class SlideToUnlock extends JPanel {

        private JLabel indicatorLabel;
        private JPanel overLayPane;
        private JLabel textLabel;

        private Integer clickXOffset;
        private Integer dragX;

        public SlideToUnlock() throws IOException {
            setLayout(null);
            setBorder(new LineBorder(getForeground(), 1, true));
            indicatorLabel = new JLabel(new ImageIcon(ImageIO.read(getClass().getResource("/images/ArrowRight.png"))));
            indicatorLabel.setBounds(1, 1, indicatorLabel.getPreferredSize().width, indicatorLabel.getPreferredSize().height);
            add(indicatorLabel);

            overLayPane = new JPanel();
            add(overLayPane);

            textLabel = new JLabel("Slide to unlock");
            textLabel.setBounds(1, 1, textLabel.getPreferredSize().width, textLabel.getPreferredSize().height);
            add(textLabel);

            MouseAdapter mouseAdapter = new MouseAdapter() {

                protected void resetDrag() {
                    clickXOffset = null;
                    dragX = null;
                }

                @Override
                public void mousePressed(MouseEvent e) {
                    Point point = e.getPoint();
                    Point localPoint = SwingUtilities.convertPoint(SlideToUnlock.this, point, indicatorLabel);
                    if (indicatorLabel.getBounds().contains(localPoint)) {
                        clickXOffset = point.x - indicatorLabel.getBounds().x;
                    } else {
                        resetDrag();
                    }
                }

                @Override
                public void mouseReleased(MouseEvent e) {
                    resetDrag();
                    doLayout();
                    repaint();
                }

                @Override
                public void mouseDragged(MouseEvent e) {
                    dragX = e.getPoint().x;
                    doLayout();
                    repaint();
                }
            };

            addMouseListener(mouseAdapter);
            addMouseMotionListener(mouseAdapter);
        }

        @Override
        public void doLayout() {
            Dimension preferredSize = indicatorLabel.getPreferredSize();
            int xPos = 1;
            if (dragX != null) {
                xPos = (1 - clickXOffset) + dragX;

                if (xPos + preferredSize.width > (getWidth() - 1)) {
                    xPos = getWidth() - preferredSize.width - 1;
                } else if (xPos < 1) {
                    xPos = 1;
                }
            }
            indicatorLabel.setBounds(xPos, 1, indicatorLabel.getPreferredSize().width, getHeight() - 2);
            overLayPane.setBounds(1, 1, indicatorLabel.getX() + indicatorLabel.getWidth() - 1, getHeight() - 2);
            textLabel.setBounds(getWidth() - textLabel.getPreferredSize().width - 4, 1, textLabel.getPreferredSize().width, getHeight() - 2);
        }

        @Override
        public Dimension getPreferredSize() {

            Dimension preferredSize = indicatorLabel.getPreferredSize();
            preferredSize.width = preferredSize.width * 4;

            int height = Math.max(indicatorLabel.getPreferredSize().height, textLabel.getPreferredSize().height);
            int width = indicatorLabel.getPreferredSize().width + 4 + textLabel.getPreferredSize().width + 4 + 1;

            Insets insets = getInsets();

            width += insets.left + insets.right;
            height += insets.top + insets.bottom;

            return new Dimension(width, height);
        }

    }
}

这是一个快速的“hack”。您需要提供附加功能来更改文本、支持更改背景颜色并在更改时更新状态

如何使 JLabel 变得可拖动？

How to make a JLabel became dragable?

java

swing

jlabel

有了JLabel

有了`JLabel`