所以我尝试在 JFrame 周围单击并拖动 JLabel。以下代码允许在屏幕上的任何一点按下/拖动鼠标时在屏幕上移动 JLabel，但我不确定如何添加第二个 ActionListener 来检查鼠标是否单击标签，假设是解决方案。

我想在屏幕上有多个 JLabel，以便移动的唯一标签是鼠标单击并正在拖动的标签。

谢谢。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

@SuppressWarnings("serial")
public class test extends JFrame implements MouseMotionListener {

private JPanel panel = new JPanel(null);    
private JLabel dragLabel = new JLabel("drag test");
private int mouseX = 200;
private int mouseY = 200;

public test() {
    this.add(panel);
    panel.setBackground(Color.WHITE);
    panel.add(dragLabel);
    dragLabel.setForeground(Color.RED);
    dragLabel.setBounds(mouseX, mouseY, 100, 50);
    panel.addMouseMotionListener(this);
}

@Override
public void mouseDragged(MouseEvent e) {
    mouseX = e.getX();
    mouseY = e.getY();
    dragLabel.setBounds(mouseX, mouseY, 100, 50);
}

@Override
public void mouseMoved(MouseEvent e) {}

public static void main(String[] args) {
    test frame = new test();
    frame.setVisible(true);
    frame.setSize(600, 400);
    frame.setResizable(false);
    frame.setLocationRelativeTo(null);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

最佳答案

另一种方法是将 JLabel 添加到 JLayeredPane 或 JLayeredPane 持有的 JPanel，并添加 MouseAdapter 作为 JLayeredPane 的 MouseListener 和 MouseMotionListener。然后在单击标签时，将其移动到 JLayeredPane 的 JLayeredPane.DRAG_LAYER 以便它移动到其他所有内容之上，然后将 JLabel 放置在鼠标释放时最合适的级别上。例如，我发现在棋盘上移动棋子时效果很好，并且您想确保在拖动时移动的棋子显示在所有其他棋子之上。

补充:您可能已经离开了这个线程，但如果您回来，或者为了其他人的利益，我想通过发布示例来阐明使用 JLayeredPane 的意思。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class DragLabelOnLayeredPane extends JLayeredPane {
    public static final int WIDTH = 680;
    public static final int HEIGHT = 480;
    private static final int GRID_ROWS = 8;
    private static final int GRID_COLS = 6;
    private static final int GAP = 3;
    private static final Dimension LAYERED_PANE_SIZE = new Dimension(WIDTH, HEIGHT);
    private static final Dimension LABEL_SIZE = new Dimension(60, 40);
    private GridLayout gridlayout = new GridLayout(GRID_ROWS, GRID_COLS, GAP, GAP);
    private JPanel backingPanel = new JPanel(gridlayout);
    private JPanel[][] panelGrid = new JPanel[GRID_ROWS][GRID_COLS];
    private JLabel redLabel = new JLabel("Red", SwingConstants.CENTER);
    private JLabel blueLabel = new JLabel("Blue", SwingConstants.CENTER);

    public DragLabelOnLayeredPane() {
        backingPanel.setSize(LAYERED_PANE_SIZE);
        backingPanel.setLocation(2 * GAP, 2 * GAP);
        backingPanel.setBackground(Color.black);
        for (int row = 0; row < GRID_ROWS; row++) {
            for (int col = 0; col < GRID_COLS; col++) {
                panelGrid[row][col] = new JPanel(new GridBagLayout());
                backingPanel.add(panelGrid[row][col]);
            }
        }

        redLabel.setOpaque(true);
        redLabel.setBackground(Color.red.brighter().brighter());
        redLabel.setPreferredSize(LABEL_SIZE);
        panelGrid[4][3].add(redLabel);

        blueLabel.setOpaque(true);
        blueLabel.setBackground(Color.blue.brighter().brighter());
        blueLabel.setPreferredSize(LABEL_SIZE);
        panelGrid[1][1].add(blueLabel);

        backingPanel.setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
        setPreferredSize(LAYERED_PANE_SIZE);
        add(backingPanel, JLayeredPane.DEFAULT_LAYER);
        MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
        addMouseListener(myMouseAdapter);
        addMouseMotionListener(myMouseAdapter);
    }

    private class MyMouseAdapter extends MouseAdapter {
        private JLabel dragLabel = null;
        private int dragLabelWidthDiv2;
        private int dragLabelHeightDiv2;
        private JPanel clickedPanel = null;

        @Override
        public void mousePressed(MouseEvent me) {
            clickedPanel = (JPanel) backingPanel.getComponentAt(me.getPoint());
            Component[] components = clickedPanel.getComponents();
            if (components.length == 0) {
                return;
            }
            // if we click on jpanel that holds a jlabel
            if (components[0] instanceof JLabel) {

                // remove label from panel
                dragLabel = (JLabel) components[0];
                clickedPanel.remove(dragLabel);
                clickedPanel.revalidate();
                clickedPanel.repaint();

                dragLabelWidthDiv2 = dragLabel.getWidth() / 2;
                dragLabelHeightDiv2 = dragLabel.getHeight() / 2;

                int x = me.getPoint().x - dragLabelWidthDiv2;
                int y = me.getPoint().y - dragLabelHeightDiv2;
                dragLabel.setLocation(x, y);
                add(dragLabel, JLayeredPane.DRAG_LAYER);
                repaint();
            }
        }

        @Override
        public void mouseDragged(MouseEvent me) {
            if (dragLabel == null) {
                return;
            }
            int x = me.getPoint().x - dragLabelWidthDiv2;
            int y = me.getPoint().y - dragLabelHeightDiv2;
            dragLabel.setLocation(x, y);
            repaint();
        }

        @Override
        public void mouseReleased(MouseEvent me) {
            if (dragLabel == null) {
                return;
            }
            remove(dragLabel); // remove dragLabel for drag layer of JLayeredPane
            JPanel droppedPanel = (JPanel) backingPanel.getComponentAt(me.getPoint());
            if (droppedPanel == null) {
                // if off the grid, return label to home
                clickedPanel.add(dragLabel);
                clickedPanel.revalidate();
            } else {
                int r = -1;
                int c = -1;
                searchPanelGrid: for (int row = 0; row < panelGrid.length; row++) {
                    for (int col = 0; col < panelGrid[row].length; col++) {
                        if (panelGrid[row][col] == droppedPanel) {
                            r = row;
                            c = col;
                            break searchPanelGrid;
                        }
                    }
                }

                if (r == -1 || c == -1) {
                    // if off the grid, return label to home
                    clickedPanel.add(dragLabel);
                    clickedPanel.revalidate();
                } else {
                    droppedPanel.add(dragLabel);
                    droppedPanel.revalidate();
                }
            }

            repaint();
            dragLabel = null;
        }
    }

    private static void createAndShowUI() {
        JFrame frame = new JFrame("DragLabelOnLayeredPane");
        frame.getContentPane().add(new DragLabelOnLayeredPane());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                createAndShowUI();
            }
        });
    }
}

如有任何问题、需要澄清或更正，请随时发表。

关于java - 在屏幕上拖动一个 jlabel，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/4893265/