java - 如何拖动对象

Question

我想拖动一个框，我希望我的鼠标光标位于我在拖动矩形时单击矩形的位置。我尝试了这段代码，当我尝试拖动时遇到了一堆错误。

import objectdraw.*;

import java.awt.*;

public class TouchWindow extends WindowController
{

    private FilledRect a;
    private boolean b;
    private Location c;
    private int x;
    private int y;
    public void begin()
    {
        b=false;
        a=new FilledRect(0,0,50,50,canvas);
    }
    public void onMouseClick(Location pt)
    {
        if(a.contains(pt))
        {
        b=true;
        pt=c;
        }
    }
    public void onMouseDrag(Location pt2)
    {
        if(b==true)
        {
        x=(int)c.getX()-(int)pt2.getX();
        y=(int)c.getY()-(int)pt2.getY();
        a.move(x,y);
        }
    }
}

Answer 1

嗯，这里有一个例子，虽然不是小程序，但它可以非常简单地移植。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class ShapeMover {

    public ShapeMover() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setTitle("Shape Mover");

        initComponents(frame);

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

    public static void main(String s[]) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new ShapeMover();
            }
        });

    }

    private void initComponents(JFrame frame) {
        frame.getContentPane().add(new DragPanel());
    }
}

class DragPanel extends JPanel {

    Rectangle rect = new Rectangle(0, 0, 100, 50);
    int preX, preY;
    boolean isFirstTime = true;
    Rectangle area;
    boolean pressOut = false;
    private Dimension dim = new Dimension(400, 300);

    public DragPanel() {
        setBackground(Color.white);
        addMouseMotionListener(new MyMouseAdapter());
        addMouseListener(new MyMouseAdapter());
    }

    @Override
    public Dimension getPreferredSize() {
        return dim;
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        Graphics2D g2d = (Graphics2D) g;
        if (isFirstTime) {
            area = new Rectangle(dim);
            rect.setLocation(50, 50);
            isFirstTime = false;
        }

        g2d.setColor(Color.black);
        g2d.fill(rect);
    }

    boolean checkRect() {
        if (area == null) {
            return false;
        }

        if (area.contains(rect.x, rect.y, rect.getWidth(), rect.getHeight())) {
            return true;
        }

        int new_x = rect.x;
        int new_y = rect.y;

        if ((rect.x + rect.getWidth()) > area.getWidth()) {
            new_x = (int) area.getWidth() - (int) (rect.getWidth() - 1);
        }
        if (rect.x < 0) {
            new_x = -1;
        }
        if ((rect.y + rect.getHeight()) > area.getHeight()) {
            new_y = (int) area.getHeight() - (int) (rect.getHeight() - 1);
        }
        if (rect.y < 0) {
            new_y = -1;
        }
        rect.setLocation(new_x, new_y);
        return false;
    }

    private class MyMouseAdapter extends MouseAdapter {

        @Override
        public void mousePressed(MouseEvent e) {
            preX = rect.x - e.getX();
            preY = rect.y - e.getY();

            if (rect.contains(e.getX(), e.getY())) {
                updateLocation(e);
            } else {
                pressOut = true;
            }
        }

        @Override
        public void mouseDragged(MouseEvent e) {
            if (!pressOut) {
                updateLocation(e);
            } else {
            }
        }

        @Override
        public void mouseReleased(MouseEvent e) {
            if (rect.contains(e.getX(), e.getY())) {
                updateLocation(e);
            } else {
                pressOut = false;
            }
        }

        public void updateLocation(MouseEvent e) {
            rect.setLocation(preX + e.getX(), preY + e.getY());
            checkRect();

            repaint();
        }
    }
}