实现保存和恢复对象属性状态的最佳方法

Question

What is the best way to implement save and restore / push and pop object attribute state? Like glPushMatrix() and glPopMatrix()?

For example:

obj.v1 = false;
obj.v2 = 0;
obj.v3 = "init";

obj.save();
obj.v1 = true;
obj.v2 = 2;
obj.v3 = "foo"
/* Do something... */

obj.restore();
/* Now v1 = false, v2 = 0, v3 = "init" again */

Answer 1

To save to a file: Make your class serializable

package com.yourpackage.name;
import java.io.Serializable;

public class myClass implements Serializable {
    public enum counterType {
        count_down,
        count_up
    }
    public int myIntValue= 0;
}

If you get the warning 'The Serializable class X does not declare a static final serialVersionUID field of type long', you can solve this by adding a value for serialVersionUID, eg:

private static final long serialVersionUID = 1234567890abcdefg;

Declare your variable as you always do (eg in your main activity):

myClass myClassVariable = new myClass();
myClassVariable.myIntValue = 99;

Now you can save the data to a file, using:

try
{
   FileOutputStream myFileOutputStream = new FileOutputStream(getFilesDir() + "file_name.ser");
   ObjectOutputStream myObjectOutputStream = new ObjectOutputStream(myFileOutputStream);
   myObjectOutputStream.writeObject(myClassVariable);
   myObjectOutputStream.close();
}
catch (Exception e)
{
    Log.e("Error when saving to file.",Log.getStackTraceString(e)); 
}

To load your data again:

try
{
    FileInputStream myFileInputStream = new FileInputStream(getFilesDir() + "file_name.ser");
    ObjectInputStream myObjectInputStream = new ObjectInputStream(myFileInputStream);
    readClassVariable = (myClass) myObjectInputStream.readObject(); 
    myObjectInputStream.close();
}
catch (Exception e)
{
    Log.e("Error when loading from file.",Log.getStackTraceString(e));
}

readClassVariable now contains your saved class, eg readClassVariable.myIntValue is equal to 99

Hope it helps. Comments welcome :)

PS I need the rep, so don't forget to accept answer if you like it!

Answer 2

To save to RAM:

You can simply copy it to another class variable.

However note that when you use the equal sign only the REFERENCE is copied (you are still working with the same variable):

myClass1 = myClass2

In this case, the easiest is to make a new class and copy the parameters individually for all parameters:

myClass1.myIntValue = myClass2.myIntValue

This way you copy the value and not a reference to the (same) variable.