Question

I’m trying to pass a java.util.Stack object from an Activity to another in an android app.

The way I do it is to use the fact that the Stack class implements the Serializable interface and pass the object via an Intent object.

The strange thing is that when I use getSerializableExtra(...) in my other Activity, the class of the object has changed from Stack to ArrayList.

I did not find anything about that on the internet.
Do you have any idea of the reason it behaves like that ?

Thanks

Here is a simple code that reproduce the thing (I tried on android 2.3.3 and 4.0.3):

Class A:

package my.test;

import java.util.Stack;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;

public class A extends Activity {

    Stack<Integer> stack;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        stack = new Stack<Integer>();
        stack.push(42);
        stack.push(7);

        Log.i("Class of stack in A (1)",stack.getClass().getName());

        Intent i = new Intent(this,B.class);
        i.putExtra("stack", stack);

        Log.i("Class of stack in A (2)",i.getSerializableExtra("stack").getClass().getName());

        startActivity(i);

    }
}

Class B:

package my.test;

import java.io.Serializable;
import java.util.Stack;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;

public class B extends Activity {
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Intent i = getIntent();
        Serializable s = i.getSerializableExtra("stack");

        Log.i("class of stack in B",s.getClass().getName());

        Stack<Integer> stack = (Stack<Integer>) s;
    }
}

Output of Log.i(...):

04-20 15:36:56.596: I/Class of stack in A (1)(748): java.util.Stack
04-20 15:36:56.596: I/Class of stack in A (2)(748): java.util.Stack
04-20 15:36:56.736: I/class of stack in B(748): java.util.ArrayList

Answer 1

Thanks Aidanc. It seems that it’s triggering exactly this bug : http://code.google.com/p/android/issues/detail?id=3847