Java 图形不显示

Question

我一直在尝试显示游戏的图形，但面板上没有显示任何图形。

以下是我的代码。主类调用其他两个类的paint方法。

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;

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

public class Simulator extends JFrame implements KeyListener, Runnable, ActionListener {

    private final int WIDTH, HEIGHT;
    private Boolean right;
    private int xMotion;
    public Salt salt;
    public Player playR;
    Boolean running = false;
    private Thread thread;
    public static int score, highScore;
    private int saltSpeed;

    public Simulator(int width, int height) {
        JPanel panel = new JPanel();
        JFrame frame = new JFrame();
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        frame.setSize(width, height);
        panel.setBackground(Color.BLACK);
        frame.add(panel);

        playR = new Player();


        this.HEIGHT = height;
        this.WIDTH = width;
        int xCordSalt = (int) (Math.random() * 631);
        saltSpeed = 1;

        salt = new Salt(saltSpeed);
        right = true; 
        running = true;

    }


    public static void main(String[] args) {
        Simulator game = new Simulator(640, 480);

        game.start();
    }

    public void paintComponent(Graphics g)
    {


        salt.paint(g);
        playR.paint(g);



    }

    public void start() {

        running = true;
        thread = new Thread(this);
        thread.start();
        repaint();
        tick();
        run();


    }

    public void stop() {
        running = false;
        System.exit(0);
    }


    @Override
    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_D) {
            right = true;
        } else if (e.getKeyCode() == KeyEvent.VK_A) {
            right = false;

        }

    }

    public void tick() {
        salt.tick(this, playR);
        playR.tick();

    }

    @Override
    public void keyReleased(KeyEvent e) {


    }

    @Override
    public void keyTyped(KeyEvent e) {
        if(e.getKeyCode() == KeyEvent.VK_D)
        {
            playR.setDirection(true);
        }
        else if(e.getKeyCode() == KeyEvent.VK_A)
        {
            playR.setDirection(false);
        }

    }

    @Override
    public void run() {
        while (running) {
            tick();
            repaint();

            try {
                thread.sleep(7);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }



    public void incrementScore() {
        score++;

    }


    @Override
    public void actionPerformed(ActionEvent e) {
        repaint();
        tick();

    }

}

这是盐方法的代码:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.util.ArrayList;



public class Salt extends Rectangle{

    private final int WIDTH = 10;
    private final int HEIGHT = 10;
    public int xCordSalt, yCordSalt;
    private int speed;
    Rectangle boundBox;
    public Salt(int speedx)
    {

        xCordSalt = (int)Math.random()*641;
        yCordSalt = 0;
        speed = speedx;
        boundBox = new Rectangle(xCordSalt, yCordSalt, WIDTH, HEIGHT);
        boundBox.setBounds(xCordSalt, yCordSalt, WIDTH, HEIGHT);



    }

    public void tick(Simulator sim, Player playR)
    {
        boundBox.setBounds(xCordSalt, yCordSalt, WIDTH, HEIGHT);

        if(yCordSalt >= 480)
        {
            //sim.stop();
        }

        else if(checkCollision(playR))
        {
            sim.incrementScore();
            speed++;
            yCordSalt = -speed;

        }


        yCordSalt = yCordSalt + speed;


    }




    public boolean checkCollision(Player playR)
    {
        if(this.getBoundBox().intersects(playR.getBoundBox()))
        {
            return true;
        }
        return false;
    }

    public void paint(Graphics g) {
        g.setColor(Color.WHITE);
        g.fillRect(xCordSalt, yCordSalt, WIDTH, HEIGHT);
    }

    public Rectangle getBoundBox()
    {
        return boundBox;
    }

    public double getSpeed()
    {
        return speed;
    }


}

最后是方法player，它使用imageIcon类来显示图像:

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;

import javax.swing.ImageIcon;
import javax.swing.JPanel;

public class Player extends JPanel {
    private int xCord, yCord;
    public Rectangle boundBox;
    private static ImageIcon ryan;
    boolean isRight;

    public Player() {
        ryan = new ImageIcon("E:\ryan.png");
        xCord = 640/2;
        yCord = 460;
        boundBox = new Rectangle(xCord, yCord, 20, 20);


    }

    public static void main(String[] args) {

    }

    public void tick() {

    }

    public void setDirection(Boolean right)
    {
        if(right)
            isRight = true;
        else
            isRight = false;
    }


    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D)g;
        g2d.drawImage(ryan.getImage(), xCord, yCord, null);


    }

    public Rectangle getBoundBox()
    {
        return boundBox;
    }

}

现在其中一些不完整，但我不明白为什么它不显示任何图形。运行时，仅出现黑色框架/面板。我在每个类的tick()方法、每个类的paint()方法以及paintComponent()方法和start()方法中添加了一些打印语句。游戏将开始，运行每个类的tick方法，但会调用paintComponent()或任何paint()方法!

Answer 1

让我们从显而易见的开始......

public class Simulator extends JFrame ... {
    //...
    public void paintComponent(Graphics g) {

        salt.paint(g);
        playR.paint(g);

    }

JFrame 没有名为 paintComponent 的方法，因此您的 paintComponent 永远不会被调用，因此 salt > 和 playR 永远不会被绘制。

您可以通过将 @Override 添加到 paintComponent 来测试这一点，它会为您进行编译时健全性检查

public class Simulator extends JFrame ... {
    //...
    @Override
    public void paintComponent(Graphics g) {

        salt.paint(g);
        playR.paint(g);

    }

这将无法编译。

现在，您可以重写paint，但是 because , because , because , because , because ...我不会推荐它...

退后一步。 JFrame 真正负责什么？提供一个容器，您可以在其中添加 gui 并将其显示在屏幕上。您并没有真正向 JFrame 添加任何新功能，因此我不会将它用作您的“主要”组件，相反，我只是创建它的一个实例并添加任何组件你想使用它。

相反，我会从 JPanel 开始，并重写其 paintComponent 方法，并将所有自定义绘画放入其中。

然后，我将使用该组件作为核心逻辑和 Controller 的起点。

您甚至可以创建多个组件来充当菜单和选项 View 等内容，并使用 CardLayout 或 OverlayoutLayout 来显示它们。

我还建议您查看 How to Use Key Bindings而不是 KeyListener 当您使用它时，这将回答您的下一个问题。