我尝试着创造一款战舰游戏,但是我并没有成功地在JPanel
中添加JButton
s而使用循环。我可以一个一个地添加,但不能在for
循环中添加。
我没有得到任何错误,只有在编译;
"Exception in thread "main" java.lang.NullPointerException
at Allo.<init>(Allo.java:38)
at Allo.main(Allo.java:55)"
代码如下:
import javax.swing.JFrame;
import java.awt.GridLayout;
import javax.swing.JPanel;
import javax.swing.SpringLayout;
import java.awt.Color;
import javax.swing.JButton;
public class Allo {
JFrame fenetre = new JFrame();
static JButton[][] bouton;
public Allo(int width, int height) {
fenetre.setSize(800, 500);
fenetre.setResizable(false);
SpringLayout springLayout = new SpringLayout();
fenetre.getContentPane().setLayout(springLayout);
JPanel panel = new JPanel();
panel.setBackground(Color.DARK_GRAY);
fenetre.getContentPane().add(panel);
SpringLayout sl_panel = new SpringLayout();
panel.setLayout(sl_panel);
for (int r = 0; r < 16; r++)
{
for (int c = 0; c < 8; c++)
{
bouton[r][c] = new JButton("("+r+","+c+")");
panel.add(bouton[r][c]);
//fenetre.getContentPane().add(bouton[r][c]);
}
}
fenetre.setVisible(true);
}
public static void main(String[] args) {
// TODO Auto-generated method stub
new Allo(16,8);
}
}
还没有初始化按钮数组,所以下面这行会抛出异常:
bouton[r][c] = new JButton("("+r+","+c+")");
您的代码缺少以下行:
bouton = new JButton[16][8];