Question

我在阅读一些文件时遇到了一些问题。我正在制作游戏，并决定为地图制作自己的文件类型。我制作了一个特殊的应用程序来制作这些地图文件。一旦我实例化了一个地图，我就可以选择调用readFile（String path）来将地图设置为保存的地图。我知道我必须以相同的顺序读取和写入流，一切顺利，直到我添加了关于读取和写入byte [] []的语句。我无法弄清楚为什么我得到这个异常以及如何仍然读取一个byte [] []。这是我的班级。

public class Map implements Serializable{

    String savePath;
    int boxWidth;
    int boxHeight;
    int mapWidth;
    int mapHeight;
    BufferedImage map;
    byte[][] encoded;
    LinkedList<BufferedImage> tileSet = new LinkedList<BufferedImage>();

    Map(int boxWidth, int boxHeight, int mapWidth, int mapHeight){
        map = new BufferedImage(boxWidth * mapWidth, boxHeight * mapHeight, BufferedImage.TYPE_INT_RGB);
        Graphics g = map.createGraphics();
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, map.getWidth(), map.getHeight());
        g.dispose();
        this.boxHeight = boxHeight;
        this.boxWidth = boxWidth;
        this.mapHeight = mapHeight;
        this.mapWidth = mapWidth;
        initEncode();
    }

    Map(){
        map = new BufferedImage(1, 1, BufferedImage.TYPE_INT_ARGB);
        this.boxHeight = 0;
        this.boxWidth = 0;
        this.mapHeight = 0;
        this.mapWidth = 0;
        initEncode();
    }

    void initEncode(){
        int width = 2 * mapWidth + 1;
        int height = 2 * mapHeight + 1;
        encoded = new byte[width][height];
        for(int i = 0; i < width; i++){
            for(int j = 0; j < height; j++){
                encoded[i][j] = 0;
            }
        }
    }

    void setMapTile(int i, int j, byte index){
        encoded[2 * i + 1][2 * j + 1] = index;
    }

    void setMapWall(int i, int j, byte index){
        encoded[2 * i][2 * i] = index;
    }

    void addToTileset(Tile tile){
        tileSet.add(tile.tile);
        writeFile(savePath);
    }

    //writing to file with path - boolean is for whether it went successfully or not
    boolean writeFile(String path){
        savePath = path;
        try{
            OutputStream file = new FileOutputStream(path);
            OutputStream buffer = new BufferedOutputStream(file);
            ObjectOutputStream output = new ObjectOutputStream(buffer);

            writeObject(output);

            output.close();
            buffer.close();
            file.close();
        }catch(IOException ex){
            System.err.println("Could not Write to file: " + path + "\nError caused by: " + ex);
            return false;
        }
        return true;
    }

    //reading from file with path - boolean is for whether it went successfully or not
    boolean readFile(String path){
        savePath = path;
        try{
            InputStream file = new FileInputStream(path);
            InputStream buffer = new BufferedInputStream(file);
            ObjectInputStream in = new ObjectInputStream(buffer);

            readObject(in);
            initEncode();

            file.close();
            buffer.close();
            in.close();
        }catch(IOException ex){
            System.err.println("Could not read from file: " + path + "\nError caused by: " + ex + "\n");
            ex.printStackTrace();
            return false;
        }catch(ClassNotFoundException e){
            System.err.println("Could not read from file: " + path + "\nError caused by: " + e + "\n");
            e.printStackTrace();
        }
        return true;
    }

    private void writeObject(ObjectOutputStream out) throws IOException {
        out.writeInt(boxHeight);
        out.writeInt(boxWidth);
        out.writeInt(mapHeight);
        out.writeInt(mapWidth);

        ImageIO.write(map, "png", out);
        out.writeObject(encoded);

        out.writeInt(tileSet.size());
        for(BufferedImage b: tileSet){
            ImageIO.write(b, "png", out);
         }
    }

    public void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException{
        boxHeight = in.readInt();
        boxWidth = in.readInt();
        mapHeight = in.readInt();
        mapWidth = in.readInt();

        map = ImageIO.read(in);
        encoded = (byte[][]) in.readObject();

        int tileSetSize = in.readInt();
        for(int i = 0; i < tileSetSize; i++){
            tileSet.add(ImageIO.read(in));
        }
    }
}

是否有某些原因导致我的（byte [] []）readObject（）行抛出OptionalDataException，我如何仍然读/写我的byte [] []。

编辑：感谢您的回答Abhinav Kumar。我忽略了这一点，但是当我修复代码时，它仍然在同一行上给了我同样的错误。（该课程现已修好）。

Answer 1

您必须以与您在流中编写的相同顺序和相同格式读取InputStream，否则您将获得OptionalDataException

您已按以下顺序在OutputStream中写入数据： -

        ImageIO.write(map, "png", out);
        out.writeInt(2 * mapWidth + 1);
        out.writeObject(encoded);

您正按顺序阅读信息流： -

        map = ImageIO.read(in);
        encoded = (byte[][]) in.readObject();

在阅读地图后阅读int。正确的代码是： -

 public void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException{
        boxHeight = in.readInt();
        boxWidth = in.readInt();
        mapHeight = in.readInt();
        mapWidth = in.readInt();
        map = ImageIO.read(in);
        in.readInt();// you read this int and assign it to the object as you wish
        encoded = (byte[][]) in.readObject();
        int tileSetSize = in.readInt();
        for(int i = 0; i < tileSetSize; i++){
            tileSet.add(ImageIO.read(in));
        }
    }

使用readObject获取byte [] []给出OptionalDataException

1 个答案: