创建在插入每个点后更新的多边形

Question

我对一个学校项目有问题，在该项目中，我创建一个多边形，当我插入时，在插入每个点后指出多边形更新。

例如

，我的程序：

我想要的结果：

我理解的是，要使结果看起来像结果，请删除Point3和Point1之间的链接，而新的链接将在Point4和Point1之间。如果这是解决方案，我不知道该添加到我的代码中进行修复。

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

public class ShapesByMouseDrag3 extends JFrame {

    private static final int FW = 800;
    private static final int FH = 600;

    private Point p1;
    private Point p2;

    private int x;
    private int y;

    ArrayList<Integer> alX = new ArrayList<>();
    ArrayList<Integer> alY = new ArrayList<>();

    JRadioButton lineRB = new JRadioButton("Line");
    JRadioButton rectRB = new JRadioButton("Rectangle");
    JRadioButton Ellipse = new JRadioButton("Ellipse");
    JRadioButton PolygonRB = new JRadioButton("Polygon");

    public static void main(String[] args) {
        new ShapesByMouseDrag3();
    }

    public ShapesByMouseDrag3() {
        setSize(FW, FH);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setTitle("Draw Graphics Objects by Mouse Drag");
        setLocationRelativeTo(null);

        setLayout(new BorderLayout());

        PaintPanel paintPanelObj = new PaintPanel(FW, FH);

        JPanel chooseShapePanel = new JPanel();
        chooseShapePanel.setBackground(Color.WHITE);
        chooseShapePanel.setLayout(new GridLayout(4, 1));

        chooseShapePanel.setBorder(BorderFactory.createTitledBorder(
                BorderFactory.createEtchedBorder(), "Shapes"));

        //Create the radio buttons.
        //Create a button group and add buttons
        ButtonGroup bgroup = new ButtonGroup();
        bgroup.add(lineRB);
        bgroup.add(rectRB);
        bgroup.add(Ellipse);
        bgroup.add(PolygonRB);

        // add buttons to chooseShapePanel panel
        chooseShapePanel.add(lineRB);
        chooseShapePanel.add(rectRB);
        chooseShapePanel.add(Ellipse);
        chooseShapePanel.add(PolygonRB);
        add(paintPanelObj, BorderLayout.CENTER);
        add(chooseShapePanel, BorderLayout.WEST);
        setVisible(true);
        pack();
    }

    private class PaintPanel extends JPanel {

        private int PW; // panel-width
        private int PH; // panel-height

        Collection<Shape> shapeList = new ArrayList<Shape>();
        Collection<Shape> shapeListR = new ArrayList<Shape>();

        public PaintPanel(int W, int H) {
            PW = W;
            PH = H;
            setPreferredSize(new Dimension(PW, PH)); // set width & height of panel 
            setBorder(BorderFactory.createTitledBorder(
                    BorderFactory.createEtchedBorder(), "Canvas"));

            addMouseListener(new MouseClickListener());
        }

        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D) g;

            g2.setStroke(new BasicStroke(2f));
            g2.setColor(Color.blue);

            if (lineRB.isSelected()) {
                makeLine();
            } else if (rectRB.isSelected()) {
                makeRectangle();
            } else if (Ellipse.isSelected()) {
                makeEllipse();
            } else if (PolygonRB.isSelected()) {
                makePolygon();
            }

            // draw all the shapes stored in the collection
            Iterator itr = shapeList.iterator();
            while (itr.hasNext()) {
                g2.draw((Shape) itr.next());
            }

            // reset
            p1 = null;
            p2 = null;

        }

        public void makeLine() {
            if (p1 != null && p2 != null) {
                shapeList.add(new Line2D.Double(p1.x, p1.y, p2.x, p2.y));
            }
        }

        public void makeRectangle() {
            double RectangleX = Math.min(p1.x, p2.x);
            double RectangleY = Math.min(p1.y, p2.y);
            double RectangleW = Math.abs(p1.x - p2.x);
            double RectangleH = Math.abs(p1.y - p2.y);
            if (p1 != null && p2 != null) {
                shapeList.add(new Rectangle2D.Double(RectangleX, RectangleY, RectangleW, RectangleH));
            }
        }

        public void makeEllipse() {
            double EllipseX = Math.min(p1.x, p2.x);
            double EllipseY = Math.min(p1.y, p2.y);
            double EllipseW = Math.abs(p1.x - p2.x);
            double EllipseH = Math.abs(p1.y - p2.y);
            if (p1 != null && p2 != null) {
                shapeList.add(new Ellipse2D.Double(EllipseX, EllipseY, EllipseW, EllipseH));
            }
        }

        public void makePolygon() {

            int[] xArray = new int[alX.size()];
            int[] yArray = new int[alY.size()];
            for (int i = 0; i < alX.size(); i++) {
                xArray[i] = alX.get(i);
                yArray[i] = alY.get(i);

            }
            if (p1 != null && p2 != null) {
                shapeList.add(new Polygon(xArray, yArray, xArray.length));
            }

        }

        private class MouseClickListener extends MouseAdapter {

            public void mousePressed(MouseEvent event) {
                p1 = new Point(event.getX(), event.getY());
                alX.add(p1.x);
                alY.add(p1.y);
            }

            public void mouseEntered(MouseEvent event) {
                alX.clear();
                alY.clear();
            }

            public void mouseReleased(MouseEvent event) {
                p2 = new Point(event.getX(), event.getY());
                alX.add(p2.x);
                alY.add(p2.y);
                repaint();
            }
        }
    }
}

Answer 1

不要使用 paintComponent 来构建形状，这不是 paintComponent 的用途。

当您以更简单的方式向 Path2D 添加新点时，我会使用 Path2D （而不是 Polygon）。

下面是一个简单的示例，它使用两个 Path2D 实例来跟踪形状。第一个是“开放”路径，我们不断向其添加点，第二个是第一个路径的“封闭”副本。这是故意的，就好像每次单击后关闭形状一样，它只会绘制从第一个单击点延伸的线。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Line2D;
import java.awt.geom.Path2D;
import javax.swing.JFrame;
import javax.swing.JPanel;

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

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private Path2D polygon = null;
        // Give some guidence
        private Point lastClickPoint = null;
        private Point currentMousePoint = null;

        public TestPane() {
            MouseAdapter ma = new MouseAdapter() {
                // This is the "acutal" shape been draw
                // This allows us to "close" the polygon
                // without it breaking the underlying shape
                private Path2D mouseShape = null;

                @Override
                public void mouseClicked(MouseEvent e) {
                    if (mouseShape == null) {
                        mouseShape = new Path2D.Double();
                        mouseShape.moveTo(e.getX(), e.getY());
                    } else {
                        mouseShape.lineTo(e.getX(), e.getY());
                    }
                    polygon = new Path2D.Double();
                    polygon.append(mouseShape, true);
                    polygon.closePath();
                    lastClickPoint = e.getPoint();
                    repaint();
                }

                @Override
                public void mouseMoved(MouseEvent e) {
                    currentMousePoint = e.getPoint();
                    repaint();
                }
            };

            addMouseListener(ma);
            addMouseMotionListener(ma);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 400);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(Color.BLACK);
            if (polygon != null) {
                g2d.draw(polygon);
            }
            if (lastClickPoint != null && currentMousePoint != null) {
                g2d.setColor(Color.GRAY);
                g2d.draw(new Line2D.Double(lastClickPoint, currentMousePoint));
            }
            g2d.dispose();
        }

    }
}

这是一个重点示例，仅解决一个问题，您将需要修改代码以适应它。我将在每次单击鼠标时确定您要尝试创建的形状类型并创建一个可以绘制的“中间”，直到用户“提交”更改，此时将添加形状到 List，但这就是我