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如何使指向鼠标的线点？

我正在尝试在java中使一条线（Graphics2d）指向鼠标光标。它不是指向光标，而是指向相反的方向（如果光标在左侧，则线指向右侧，与 Y 轴相同）。这是我的代码：

import java.awt.Graphics;
import java.awt.Graphics2D;
public void paintChildren(Graphics g){
Graphics g2d2 = (Graphics)g;
int centerX = 16;
int centerY = 16;
deltaX = mouseX - centerX;
deltaY = mouseY - centerY;
double angle=Math.atan2(deltaY, deltaX);

g2d2.drawLine(16, 16, (int)Math.floor(deltaX + Math.cos(angle)), (int)Math.floor(deltaY + Math.sin(angle)));
}
4

1 回答 1

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好的，在您的应用程序屏幕上选择一个点。说，中心。将该点标记为锚点。

现在，将 a 添加MouseMotionListener到您的屏幕并在鼠标移动时查找。你需要这个点来画一条线。第一个点是锚点。
现在，repaint()每次鼠标移动时调用。

在 中paintComponent(Graphics g)，使用g.drawLine(anchorX,anchorY,mouseX,mouseY)来画线。由于paint()是 before 调用的repaint()，因此您需要为这 4 个变量赋予一些初始值。

SSCCE： 

    import java.awt.Color;
    import java.awt.Dimension;
    import java.awt.Graphics;
    import java.awt.Toolkit;
    import java.awt.event.MouseEvent;
    import java.awt.event.MouseMotionListener;

    import javax.swing.JFrame;
    import javax.swing.JPanel;
    import javax.swing.SwingUtilities;

    public class LineFollower extends JFrame{

        int anchorX = 0;
        int anchorY = 0;
        int mouseX = 0;
        int mouseY = 0;

        JPanel canvas = new JPanel(){

                @Override
                public Dimension getPreferredSize() {
                    return new Dimension(500, 500);
                }

                @Override
                public void paintComponent(Graphics g){
                        super.paintComponent();
                        g.setColor(Color.RED);
                        g.drawLine(anchorX, anchorY, mouseX, mouseY);
                }
        };

        public LineFollower(){
                anchorX = 500 / 2;
                anchorY = 500 / 2;

                this.getContentPane().add(canvas);
                this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                canvas.addMouseMotionListener(new MouseMotionListener(){
                        @Override
                        public void mouseDragged(MouseEvent e) {
                                mouseX = e.getX();
                                mouseY = e.getY();
                                repaint();
                        }

                        @Override
                        public void mouseMoved(MouseEvent e) {
                                mouseX = e.getX();
                                mouseY = e.getY();
                                repaint();
                        }
                });
                this.pack();
                //this.setSize(500,500);
                this.setVisible(true);
        }
        public static void main(String[] args) {
                SwingUtilities.invokeLater(new Runnable(){

                        @Override
                        public void run() {
                                new LineFollower();
                        }
                });
        }
}
于 2013-10-19T12:59:39.400 回答