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我正在一个小程序中构建一个小游戏。每当我尝试运行它,我得到就行了以下错误 buttons[i][k] = new ActiveSquare(k);
填充二维数组时出现空指针异常
错误:
java.lang.NullPointerException
at com.proj3.renee.ClickAid.<init>(ClickAid.java:21)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at java.lang.Class.newInstance(Class.java:379)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:795)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:724)
at sun.applet.AppletPanel.run(AppletPanel.java:380)
at java.lang.Thread.run(Thread.java:745)
我类似的答案,newInstance0发出读了,我已经检查,以确保ActiveSquare内的类正在工作,但我仍然不能解决问题。任何建议或进一步阅读将不胜感激。 这里的代码和构造函数的第一位(我可以发布更多,如果需要):
public class ClickAid extends Applet implements ActionListener {
ActiveSquare[][] buttons;
private static final long serialVersionUID = 1L;
public ClickAid() {
setLayout(new GridLayout(0, 2, 5, 5));
JPanel panel = new JPanel();
add(panel);
for (int i = 0; i < 4; ++i){//default = 4
for (int k = 0; k < 6; ++k){
buttons[i][k] = new ActiveSquare(k); //this is where the error is
panel.add(buttons[i][k].buttonaspect);
buttons[i][k].buttonaspect.addActionListener(this);
}
}
}
看起来你只是想'ActiveSquare [] []按钮=新的ActiveSquare [4] [6];' –