一个关于paintComponent的小细节问题

喜欢ヅ旅行 2022-08-27 03:28 213阅读 0赞

import java.awt.*;
    import javax.swing.*;
    
    public class TestPolyline extends JFrame {
        public TestPolyline() {
            add(new PolylinePanel());
        }
        public static void main(String[] args) {
            TestPolyline frame = new TestPolyline();
            frame.setTitle("TestPolyline");
            frame.setSize(300,200);
            frame.setLocationRelativeTo(null);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);
        }
        
        static class PolylinePanel extends JPanel {
            private Polygon p = new Polygon();
            
            public PolylinePanel() {
                
            }
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                p.addPoint(getWidth() / 2, getHeight() / 2);
                p.addPoint(50, 50);
                g.drawPolyline(p.xpoints, p.ypoints, p.npoints);
                g.drawString("" + (p.xpoints).length, 50, 50);
            }
        }
    }

import java.awt.*;
    import javax.swing.*;
    
    public class TestPolyline extends JFrame {
        public TestPolyline() {
            add(new PolylinePanel());
        }
        public static void main(String[] args) {
            TestPolyline frame = new TestPolyline();
            frame.setTitle("TestPolyline");
            frame.setSize(300,200);
            frame.setLocationRelativeTo(null);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);
        }
        
        static class PolylinePanel extends JPanel {
            private Polygon p = new Polygon();
            
            public PolylinePanel() {
                p.addPoint(getWidth() / 2, getHeight() / 2);
                p.addPoint(50, 50);
            }
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                g.drawPolyline(p.xpoints, p.ypoints, p.npoints);
                g.drawString("" + (p.xpoints).length, 50, 50);
            }
        }
    }