paintComponent没有在整个JPanel中绘制

Question

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    this.setBackground(Color.LIGHT_GRAY);
    g.setColor(Color.black);
    g.fillRect(xpos, ypos, width, height);
}

public Snake() {
        setLayout(new BorderLayout());
        addKeyListener(l);
        segment = new Segment(100, 100, Segment.Dir.RIGHT);
        segment.setPreferredSize(new Dimension(500,500));
        add(segment, BorderLayout.CENTER);
        timer.start();
        setVisible(true);
        pack();
        setTitle("Snake");
        setResizable(false);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
    }

import java.awt.*;
import javax.swing.*;

public class Segment extends JPanel {

private int width = 10;
private int height = 10;
private int xpos, ypos;
private Dir dir;

public enum Dir {
    LEFT, RIGHT, UP, DOWN;
}

public Segment() {
    xpos = 0;
    ypos = 0;
    dir = Dir.RIGHT;
}

public Segment(int x, int y, Dir d) {
    xpos = x;
    ypos = y;
    dir = d;
}

public Dir getDir() {
    return dir;
}
public void setDir(Dir d) {
    dir = d;
}
public void setX(int x) {
    xpos = x;
    repaint();
}
public void setY(int y) {
    ypos = y;
    repaint();
}
public int getX() {
    return xpos;
}
public int getY() {
    return ypos;
}

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    this.setBackground(Color.LIGHT_GRAY);
    g.setColor(Color.black);
    g.fillRect(xpos, ypos, width, height);
}
}

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

public class Snake extends JFrame implements ActionListener {

Segment segment;
Timer timer = new Timer(50, this);

public Snake() {
    setLayout(new BorderLayout());
    setSize(500,500);
    segment = new Segment(100, 100, Segment.Dir.RIGHT);
    segment.setPreferredSize(new Dimension(getWidth(),getHeight()));
    add(segment, BorderLayout.CENTER);
    timer.start();
    setVisible(true);
    setTitle("Snake");
    setResizable(false);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
}

    public void actionPerformed(ActionEvent e) {
    if (e.getSource() == timer) {
            segment.setX((segment.getX() + 4 + getWidth())%getWidth());
    }
}

public static void main(String[] arg) {
    new Snake();
}

}

Answer 1

不要重写Segment类的getX（）和getY（）。

这些是所有Swing组件的方法。它们获取组件在父容器中的当前位置。

使用不同的方法名称来控制画蛇的位置。由于变量名是xpo，ypo可能使用getXPos（）和getYPos（）。