为什么我无法在jpanel中添加按钮和渲染按钮，它们重叠

Question

这是我的Pong游戏主类的代码，它工作正常，直到我添加指令按钮。当我添加指令按钮时，屏幕不再显示按钮以外的任何其他内容。

package pongg; 
import java.awt.BasicStroke; 
import java.awt.Color; 
import java.awt.Font; 
import java.awt.Graphics; 
import java.awt.Graphics2D; 
//import java.awt.RenderingHints; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

import java.awt.event.KeyEvent; 
import java.awt.event.KeyListener; 


import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.Timer; 

public class Pong extends JFrame implements ActionListener, KeyListener{ 
    public static Pong pong; 
    int width =700, height = 700; 
    public Renderer renderer; 
    public Paddle player1; 
    public Paddle player2; 
    public Ball ball; 
    JButton rules = new JButton ("INSTRUCTIONS"); 


    public boolean comp = false; //ai 
    public boolean w, s, up, down; // so many booleans so that when u press two keys they dont interfere w each other 
    public int gameStatus = 0; // 1 = paused, 0= stop, 2=play 

    public Pong(){ 
    Timer timer = new Timer(20, this); 
    JFrame jframe = new JFrame("PONG"); 
    renderer = new Renderer(); 
    jframe.setSize(width +15, height+35); 
    jframe.setVisible(true); 
    jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    jframe.add(renderer); 


    jframe.addKeyListener (this); 

    timer.start(); 

    if (gameStatus ==0){ 
     rules.setSize(200,100); 
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     jframe.add(rules); 
     setVisible(true); 
    } 

    } 

    private void add(JButton rules2) { 


    } 

    public void start(){ 

    gameStatus =2; 
    player1 = new Paddle(1); 
    player2 = new Paddle (2); 
    ball = new Ball(this); 
    } 

    public void update(){ 
    if (w){ 
    player1.move(true); // up is true and down is false 
    } 

    if (s){ 
    player1.move(false); 
    } 

    if (up){ 
    player2.move(true); 
    } 

    if (down){ 
    player2.move(false); 
    } 

    ball.update(player1, player2); 
    } 


    public void render (Graphics2D g){ 

    g.setColor (Color.ORANGE); 
    g.fillRect(0,0, width, height); 
    //g.setRenderingHint (RenderingHints.KEY_ANTIALISING, RenderingHint.VALUE_ANTIALIAS_ON); 

    if (gameStatus ==0){ 

    g.setColor(Color.BLACK); 
    g.setFont(new Font("Arial", Font.PLAIN, 40)); 
    g.drawString ("WELCOME TO PONG TWIST!", width/10, 100); 

    g.setFont(new Font("Arial", Font.PLAIN, 20)); 
    g.drawString ("Press Space to Play", width/2 -150, height/2 - 50); 
    g.drawString ("Press Shift to Play with Computer", width/2 -200, height/2); 


    } 

    if (gameStatus ==2 || gameStatus ==1){ 

    g.setColor(Color.WHITE); 
    g.setStroke(new BasicStroke (5f)); // make it thicker 
    g.drawLine(width/2, 0, width/2, height); // FIX MAYBE 


    player1.render (g); 
    player2.render(g); 
    ball.render(g); 
    } 
    if (gameStatus ==1){ 
    g.setColor(Color.WHITE); 

    g.drawString ("PAUSED", width/2 -105, height /2 - 105); 
    } 
    } 

Answer 1

其中一个可能的问题是布局不正确。您可以尝试前添加rules.setLayout(null)：

rules.setSize(200, 100); 
jframe.add(rules); 
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

此外，您还可以有更多的解释here：