问题是Logger未使用Logger.getLogger(class_name.class.getName())
方法初始化。
你可以看到下面的代码。我标记了导致异常的行。
我必须注意,我尝试过没有静态setLevel
阻止。
// File that contains logger
public class Experience {
private final static Experience INSTANCE = new Experience();
private final static Logger LOGGER = Logger.getLogger(Experience.class.getName());
private MainFrame main_frame;
static {
LOGGER.setLevel(Level.SEVERE);
}
public static Experience getInstance()
{
return INSTANCE;
}
private Experience()
{
try
{
FileHandler fh = new FileHandler(System.getProperty("user.dir") + "/log.txt");
fh.setFormatter(new XPLogFormatter());
LOGGER.addHandler(fh); // NULLPOINTEREXCEPION HERE
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
// Just a loader
public class Loader
{
public static void main(String args[])
{
JFrame.setDefaultLookAndFeelDecorated(true);
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
MainFrame main_frame = new MainFrame();
}
});
}
}
// Stripped down version of main frame
public class MainFrame extends JFrame
{
private Experience XP;
public MainFrame()
{
super();
XP = Experience.getInstance(this);
}
}
// Modified formatter
public class XPLogFormatter extends Formatter
{
@Override
public String format(LogRecord record)
{
StringBuffer buf = new StringBuffer(1000);
buf.append(formatMessage(record));
return buf.toString();
}
}
您能否告诉我究竟是什么导致了这个错误?
答案 0 :(得分:8)
问题是这两个静态变量初始值设定项是按文本顺序执行的:
private final static Experience INSTANCE = new Experience();
public final static Logger LOGGER = Logger.getLogger(Experience.class.getName());
所以当第一行调用构造函数时,包括:
LOGGER.addHandler(fh);
... LOGGER
仍为空。
最简单的修复只是颠倒声明的顺序......但另一个更清晰的替代方法是在静态初始化器中完成所有操作:
private final static Experience INSTANCE;
public final static Logger LOGGER;
static {
LOGGER = Logger.getLogger(Experience.class.getName());
LOGGER.setLevel(Level.SEVERE);
INSTANCE = new Experience();
}
(出于兴趣,您真的希望记录器公开吗?)
答案 1 :(得分:0)
因为您从未定义过名为“Experience”的Logger。当您调用getLogger(String)时,它会查找具有该名称的已定义记录器。尝试使用Logger.getLogger(Experience.class),它可以让你获得体验的记录器