java - 抛硬币程序

Question

我尝试编写一个抛硬币的程序(先显示正面图像，然后显示反面图像)，但在运行该问题时试图查看硬币图像时遇到了问题；只会显示一个空白屏幕。不知道是jpg图片保存方式不当，还是代码出错。在再次编写显示头部图像和不显示尾部图像的程序之前，我还遇到了一个错误。

CoinTest.java 运行投币器，Coin.java 是该程序的类。

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

public class CoinTest extends JPanel
implements ActionListener
{
  private Coin coin;

  public CoinTest ()
{
Image heads = (new ImageIcon("quarter-coin-head.jpg")).getImage();
Image tails = (new ImageIcon("Indiana-quarter.jpg")).getImage();
coin = new Coin(heads, tails);

Timer clock = new Timer(2000, this);
clock.start();
}

public void paintComponent(Graphics g)
{
super.paintComponent(g);

int x = getWidth() / 2;
int y = getHeight() / 2;
coin.draw(g, x, y);
}

 public void actionPerformed(ActionEvent e)
   {
    coin.flip();
    repaint();
   }

public static void main(String[] args)
{
JFrame w = new JFrame("Flipping coin");
w.setSize(300, 300);
w.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    CoinTest panel = new CoinTest();
    panel.setBackground(Color.WHITE);
    Container c = w.getContentPane();
    c.add(panel);

    w.setVisible(true);
  }
}

现在是实际的 Coin 类。

import java.awt.Image;
import java.awt.Graphics;

public class Coin
{
private Image heads;
private Image tails;
private int side = 1;

public Coin(Image h, Image t)
{
    heads = h;
    tails = t;
}

//flips the coin
public void flip()
{
    if (side == 1)
        side = 0;
    else
        side = 1;
}

//draws the appropriate side of the coin - centered  in the JFrame
public void draw(Graphics g, int x, int y)
{
    if (side == 1)
    g.drawImage(heads, heads.getWidth(null)/3, heads.getHeight(null)/3, null);
    else 
    g.drawImage(heads, tails.getWidth(null)/3, tails.getHeight(null)/3, null);
}
}

Answer 1

首先，确保两张图片都位于正确的加载位置。

其次，你这里有一个错字:

if (side == 1)
  g.drawImage(heads, heads.getWidth(null)/3, heads.getHeight(null)/3, null);
else 
  g.drawImage(heads, tails.getWidth(null)/3, tails.getHeight(null)/3, null);
              ^^^^

应该是尾部...