写入和读取多个对象到文件

Question

我正在为Android设计一个手写应用程序。

class LogInfo每当用户按下Enter键时，我都希望将信息（）写入日志文件。

之后，我想读取存储的信息。

这是我的类的一部分，带有自定义的write方法：

public class LogInfo implements Serializable {

private static final long serialVersionUID = -5777674941129067422L;

public static List<Point[][]> strokes;
public static List<byte[]> codes;

// Only write and read methods shown

private void writeObject(ObjectOutputStream stream) throws IOException
{
    stream.defaultWriteObject();
    stream.writeInt(strokes.size());
    Point[][] pointsArray = null;
    for (int i = 0; i < strokes.size(); i++)
    {
        pointsArray = ((Point[][])strokes.get(i));
        stream.writeInt(pointsArray.length);
        for (int j = 0; j < pointsArray.length; j++)
        {
            stream.writeInt(pointsArray[j].length);
            for (int k = 0; k < pointsArray[j].length; k++)
            {
                stream.writeInt(pointsArray[j][k].x);
                stream.writeInt(pointsArray[j][k].y);
                //stream.writeObject(elementData[i]);
            }
        }
    }

    int size = codes.size();
    stream.writeInt(size);
    for (int i = 0; i < size; i++)
    {
        stream.write(codes.get(i));
    }
}

这是读取方法：

private void readObject(java.io.ObjectInputStream stream)
    {
        stream.defaultReadObject();
        int strokesSize = stream.readInt();
        for (int i = 0; i < strokesSize; i++)
        {
            int arrayXSize = stream.readInt();
            Point[][] points = new Point[arrayXSize][];
            for (int j = 0; j < arrayXSize; j++)
            {
                int arrayYSize = stream.readInt();
                points[j] = new Point[arrayYSize];
                for (int k = 0; k < arrayYSize; k++)
                    points[j][k] = new Point(stream.readInt(), stream.readInt());
            }
            strokes.add(points);
        }

        int codesSize = stream.readInt();
        for (int i = 0; i < codesSize; i++)
        {
            byte[] buffer = new byte[3];
            stream.read(buffer, 0, 3);
            codes.add(buffer);
        }
    }

当我在文件中仅保存一个对象时，它会很好地工作。当我尝试节省更多时，阅读不起作用（抛出StreamCorruptedException）。
它在while循环中仅读取一个对象！

在主类中，我仅使用两种简单的方法：

// WRITE TO FILE
logInfo.writeLog();

// READ FROM FILE
ArrayList<LogInfo> logInfoArrayList = logInfo.readLog();

定义为：

public void writeLog()
{
    File file = new File (Environment.getExternalStorageDirectory().getAbsolutePath(), "data.log");
    FileOutputStream fos;
    try {
        fos = new FileOutputStream(file, true);
        //fos = openFileOutput(Environment.getExternalStorageDirectory().getAbsolutePath() + "/data.log", Context.MODE_APPEND);
        ObjectOutputStream os = new ObjectOutputStream(fos);
        os.writeObject(this);
        os.close(); 
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public ArrayList<LogInfo> readLog()
{
    ArrayList<LogInfo> logInfoArray = new ArrayList<LogInfo>();

    try{
        File file = new File (Environment.getExternalStorageDirectory().getAbsolutePath(), "data.log");
        FileInputStream fis  = new FileInputStream(file);
        ObjectInputStream reader = new ObjectInputStream(fis);

        LogInfo tempLogInfo = new LogInfo();
        while((tempLogInfo = (LogInfo)reader.readObject()) != null)
            logInfoArray.add(tempLogInfo);
        reader.close();
    } catch (Exception e) {
     //TODO Auto-generated catch block
     e.printStackTrace();
    }

    return logInfoArray;
}

请求的更新：

//We use this class to not write a header in a file that already exist
class MyObjectOutputStream extends ObjectOutputStream {

    public MyObjectOutputStream(OutputStream os) throws IOException {
        super(os);
      }

    @Override
    protected void writeStreamHeader() {}
}

Answer 1

1. 您不能附加到使用创建的现有文件中ObjectOutputStream，至少要费劲。关于扩展ObjectOutputStream和覆盖该writeStreamHeader()方法有一个技巧，以便不要第二次写入流头，但是我不赞成这样做。您应该真正重写整个文件，也许将其重写为列表。

2. 您不需要所有这些代码。只需make strokes和codesnon-static和non-transient，就完全摆脱readObject()和writeObject()方法。