Question

我有一个Swing计划。我无法将整个主类保存到文件中。

public class GreenHouseMain extends JFrame implements ActionListener,
        MouseListener, Runnable, WindowListener, KeyListener, Serializable
{
//.....other components
static GreenHouseMain ghMain;
}
public static void main(String[] args)
    {
        ghMain = new GreenHouseMain();
    }

public void startEvents()
    {
        suspended = false;
        terminate = false;
        jbStart.setEnabled(false);
        worker = new Thread(new Runnable()
        {
            public void run()
            {
                try
                {
                    //Other Code
                } catch (ControllerException e)
                {
                    try
                    {
                        Date now = new Date();
                        String log = "";
                        PrintWriter out = new PrintWriter(new BufferedWriter(
                                new FileWriter("error.log")));
                        if (e.getMessage() == "Unknown Windows Malfuction")
                        {
                            log = "ErrorCode=1, WindowMalfunction," + now;
                        } else
                        {
                            log = "ErrorCode=2, PowerOut," + now;
                        }
                        out.println(log);
                        jTextArea.append(log + "\n");
                        out.close();
                        out.flush();

                        ObjectOutputStream output = new ObjectOutputStream(
                                new FileOutputStream("dump.out"));
                //It failed in here, says "java.lang.NullPointerException
                        output.writeObject(GreenHouseMain.ghMain);

                        output.flush();


                    } catch (IOException ex)
                    {
                        System.out.println(ex.getMessage());
                    }
                }
            }
        });
        worker.start();

    }

你应该知道几件事： 1.所有类都已实现Serializable接口 2.程序中有几个线程（不知道是否是异常的原因 3.我已经使用序列化了一个对象来提交大约相同的代码，但是在控制台应用程序中。不知道为什么它在这里失败。

at javax.swing.plaf.basic.BasicScrollPaneUI.paint（Unknown Source）在javax.swing.plaf.ComponentUI.update（未知来源）在javax.swing.JComponent.paintComponent（未知来源）在javax.swing.JComponent.paint（未知来源）在javax.swing.JComponent.paintToOffscreen（未知来源）在javax.swing.RepaintManager $ PaintManager.paintDoubleBuffered（未知来源）在javax.swing.RepaintManager $ PaintManager.paint（未知来源）在javax.swing.RepaintManager.paint（未知来源）在javax.swing.JComponent._paintImmediately（未知来源）在javax.swing.JComponent.paintImmediately（未知来源）在javax.swing.RepaintManager.paintDirtyRegions（未知来源）在javax.swing.RepaintManager.paintDirtyRegions（未知来源）在javax.swing.RepaintManager.seqPaintDirtyRegions（未知来源） at javax.swing.SystemEventQueueUtilities $ ComponentWorkRequest.run（Unknown Source） at java.awt.event.InvocationEvent.dispatch（Unknown Source） at java.awt.EventQueue.dispatchEvent（Unknown Source） at java.awt.EventDispatchThread.pumpOneEventForFilters（Unknown Source） at java.awt.EventDispatchThread.pumpEventsForFilter（Unknown Source） at java.awt.EventDispatchThread.pumpEventsForHierarchy（Unknown Source） at java.awt.EventDispatchThread.pumpEvents（Unknown Source） at java.awt.EventDispatchThread.pumpEvents（Unknown Source）在java.awt.EventDispatchThread.run（未知来源）

Answer 1

此

                } catch (IOException ex) {
                    System.out.println(ex.getMessage());
                }

应该是：

                } catch (IOException ex)  {
                    ex.printStackTrace();
                }

这将为您提供更多更好的信息，最重要的是发生NullPointerException的确切行以及到达该行的位置。如果这不能解决问题的原因，请在调试器中启动程序并在该行上放置断点。

Java可序列化对象到文件

1 个答案: