Java根据鼠标点击绘制三个形状？

Question

我是 Java 绘图新手，在使用鼠标监听器事件时遇到了一些问题。我想做的是在单击时绘制一个点，然后在单击时绘制一条从该点延伸的线，最后单击时的最后一个点连接起来形成一个三角形。到目前为止，我只是致力于让点和线发挥作用。我认为我现在的方式已经很接近了；在顶角绘制一个圆圈，而不是用户单击的位置，但单击时会从圆圈所在的位置绘制一条线。尝试使用 boolean 值来决定何时应该绘制某些内容，但没有成功。感谢您的帮助。

主类

package TriangleDraw;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class TriangleDrawMain {

    public static void main(String[] args) {
        //create a frame or window

       JFrame frame = new JFrame();
       //set window size
       frame.setSize(500, 500);
       //set the title
       frame.setTitle("Triangle Draw");
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

       //add panel to frame and make it visible
       MouseComponent component = new MouseComponent();
       frame.add(component);
       frame.setVisible(true);

    }
}

绘画课

package TriangleDraw;
import java.util.*;
import java.awt.*;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
import javax.swing.*;
import java.awt.geom.*;

public class MouseComponent extends JPanel implements MouseListener{
        boolean drawPoint = true;
        boolean drawLine = false;
        boolean drawTriangle = false;

    public MouseComponent(){
        super();
        pointX = 0;
        pointY = 0;   
        oldX = 0;
        oldY = 0;
        addMouseListener(this);
    }

    int pointX, pointY, oldX,oldY;

        @Override
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        if(drawPoint == true){
        g.drawOval(pointX,pointY,10,10);
        drawPoint = false;
        drawLine = true;
        oldX = pointX;
        oldY = pointY;
        }
        if(drawLine == true){
            g.drawLine(pointX, pointY, oldX, oldY);
        }


    }

    public void mouseClicked(MouseEvent mouse){

        pointX = mouse.getX();
        pointY = mouse.getY();

        repaint();
    }
    public void mouseEntered(MouseEvent mouse){ }   
    public void mouseExited(MouseEvent mouse){ }
    public void mousePressed(MouseEvent mouse){ }
    public void mouseReleased(MouseEvent mouse){ }
}

Answer 1

我不会改变paintComponent中的状态，你不知道什么时候会调用它(你分配oldX和oldY的地方)。我建议创建两个 Point 对象，并在每个其他 mouseClicked 事件中在这两个点对象之间切换。

如果在 mouseClicked 之间多次调用 PaintComponent，则最终将 oldX 和 OldY 等于 pointX 和 pointY。