java - 如何在 Java Swing 中命名坐标（点）

Question

我正在使用 java swing 设计一个界面。有一个画布供用户绘制形状（圆形、三角形、正方形等）。当用户绘制形状时，我想按字母顺序命名形状中的每个点。我知道如何获取坐标，但如何命名这些点？

Answer 1

这是一种方法。您使用Character.toString(char)和使用'A'+offset从字母表中获取任何字符。

请参阅这个绘制多边形的小型演示示例。

• 单击即可创建多边形的顶点
• 双击存储当前多边形并开始创建新多边形
• 右键单击清除当前多边形并开始一个新多边形。

旁注：文本的定位不智能，因此有时会与多边形的线重叠。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Polygon;
import java.awt.event.MouseAdapter;
import java.util.ArrayList;
import java.util.List;

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

public class TestNaming {

    private static final int PANEL_WIDTH = 600;
    private static final int PANEL_HEIGHT = 600;

    public static class Drawing extends JPanel {

        private static final Font FONT = new Font("Arial", Font.PLAIN, 12);

        private List<Polygon> polygons = new ArrayList<Polygon>();

        private Polygon currentPolygon = new Polygon();

        private MouseAdapter mouseListener = new MouseAdapter() {
            @Override
            public void mouseClicked(java.awt.event.MouseEvent e) {
                if (SwingUtilities.isLeftMouseButton(e)) {
                    if (e.getClickCount() == 1) {
                        addPoint(e.getX(), e.getY());
                    } else if (e.getClickCount() == 2) {
                        createPolygon();
                    }
                } else if (SwingUtilities.isRightMouseButton(e)) {
                    clearCurrentPolygon();
                }
            }

        };

        public Drawing() {
            addMouseListener(mouseListener);
        }

        protected void addPoint(int x, int y) {
            currentPolygon.addPoint(x, y);
            repaint();
        }

        protected void clearCurrentPolygon() {
            currentPolygon = new Polygon();
            repaint();
        }

        protected void createPolygon() {
            if (currentPolygon.npoints > 2) {
                polygons.add(currentPolygon);
            }
            clearCurrentPolygon();
            repaint();
        }

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

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.RED);
            g.setFont(FONT);
            for (Polygon polygon : polygons) {
                drawPolygon(g, polygon);
            }
            g.setColor(Color.GREEN);
            drawPolygon(g, currentPolygon);
        }

        private void drawPolygon(Graphics g, Polygon polygon) {
            if (polygon.npoints < 3) {
                if (polygon.npoints == 1) {
                    g.fillOval(polygon.xpoints[0] - 2, polygon.ypoints[0] - 2, 4, 4);
                    drawNthPoint(g, polygon, 0);
                } else if (polygon.npoints == 2) {
                    g.drawLine(polygon.xpoints[0], polygon.ypoints[0], polygon.xpoints[1], polygon.ypoints[1]);
                    drawNthPoint(g, polygon, 0);
                    drawNthPoint(g, polygon, 1);
                }
            } else {
                g.drawPolygon(polygon);
                for (int i = 0; i < polygon.npoints; i++) {
                    drawNthPoint(g, polygon, i);
                }
            }
        }

        private void drawNthPoint(Graphics g, Polygon polygon, int nth) {
            // Only works 26 times!
            String name = Character.toString((char) ('A' + nth));
            int x = polygon.xpoints[nth];
            int height = g.getFontMetrics().getHeight();
            int y = polygon.ypoints[nth] < height ? polygon.ypoints[nth] + height : polygon.ypoints[nth];
            g.drawString(name, x, y);
        }

    }

    protected static void initUI() {
        JFrame frame = new JFrame("test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new Drawing());
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                initUI();
            }
        });
    }
}

Answer 2

如果我对您的理解正确，您想按字母顺序标记坐标（如 A、B、C、D）

既然你说你已经知道坐标了......使用JLabel：

JLabel A_label = new JLabel("A");
JLabel B_label = new JLabel("B");

A_label.setLocation(shape1_x, shape1_y);
B_label.setLocation(shape2_x, shape2_y);