向/从Android内存写入/读取任何对象

Question

I'm currently writing to methods to:

• read object from memory
• write object to memory

I tried to save a String object and read it again, yet my code didn't work.

This is my code:

public void writeObjectToMemory(String filename, Object object) {
        FileOutputStream fos;
        try {
            fos = game.openFileOutput(filename, Context.MODE_PRIVATE);
            ObjectOutputStream os = new ObjectOutputStream(fos);
            os.writeObject(object);
            os.close();
        } 
        catch (FileNotFoundException e) {
            e.printStackTrace();

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

        }

    }

    public void readObjectFromMemory(String filename, Object object) {
        FileInputStream fis;
        try {
            fis = game.openFileInput(filename);
            ObjectInputStream is = new ObjectInputStream(fis);
            object = is.readObject();
            is.close();
        } 
        catch (FileNotFoundException e) {
            e.printStackTrace();

        } 
        catch (StreamCorruptedException e) {
            e.printStackTrace();

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

        } 
        catch (ClassNotFoundException e) {
            e.printStackTrace();

        }

    }

Answer 1

You wrote :

public void readObjectFromMemory(String filename, Object object) {
    //...
    object = is.readObject();

But object is only a copy of the argument you passed to the function. You can change that copy inside the method (as you do), but this will have no effect on the actual parameter.

You have to return your object instead :

public Object readObjectFromMemory(String filename) {
    FileInputStream fis;
    Object obj;
    try {
        fis = game.openFileInput(filename);
        ObjectInputStream is = new ObjectInputStream(fis);
        obj = is.readObject();
        is.close();
    } 
    catch (...) {
        return null;
    }

    return obj;
}

Read this for more details : http://www.cs.utoronto.ca/~dianeh/tutorials/params/

Answer 2

Here's working code for anybody that is interested:

Note: When using the readObjectFromMemory(String filename, Object object) you will have to cast the returned object.

/**
     * <b><i>public void writeObjectToMemory(String filename, Object object)</i></b>
     * <br>
     * Since: API 1
     * <br>
     * <br>
     * Write a object to the phone's internal storage.
     * 
     * @param filename 
     * The name of the file you wish to write to.
     *
     *      
     */

    public void writeObjectToMemory(String filename, Object object) {
        FileOutputStream fos;
        try {
            fos = game.openFileOutput(filename, Context.MODE_PRIVATE);
            ObjectOutputStream os = new ObjectOutputStream(fos);
            os.writeObject(object);
            os.close();
            this.gameEngineLog.d(classTAG, "Object successfully written: " + filename);
        } 
        catch (FileNotFoundException e) {
            e.printStackTrace();
            this.gameEngineLog.d(classTAG, "Object couldn't be opened: " + filename);

        } 
        catch (IOException e) {
            e.printStackTrace();
            this.gameEngineLog.d(classTAG, "Object couldn't be opened: " + filename);

        }

    }

    /**
     * <b><i>public Object readObjectFromMemory(String filename, Object object)</i></b>
     * <br>
     * Since: API 1
     * <br>
     * <br>
     * Read a object from the phone's internal storage.
     * 
     * @param filename 
     * The name of the file you wish to read from.
     *
     *      
     */

    public Object readObjectFromMemory(String filename, Object object) {
        Object defautObject = null;
        FileInputStream fis;
        try {
            fis = game.openFileInput(filename);
            ObjectInputStream is = new ObjectInputStream(fis);
            defautObject = is.readObject();
            is.close();
            this.gameEngineLog.d(classTAG, "Object successfully read: " + filename);
        } 
        catch (FileNotFoundException e) {
            e.printStackTrace();
            this.gameEngineLog.d(classTAG, "Object couldn't be opened: " + filename);

        } 
        catch (StreamCorruptedException e) {
            e.printStackTrace();
            this.gameEngineLog.d(classTAG, "Object couldn't be opened: " + filename);

        } 
        catch (IOException e) {
            e.printStackTrace();
            this.gameEngineLog.d(classTAG, "Object couldn't be opened: " + filename);

        } 
        catch (ClassNotFoundException e) {
            e.printStackTrace();
            this.gameEngineLog.d(classTAG, "Object couldn't be opened: " + filename);

        }

        return defautObject;

    }