Question about serializing a Location subclass in order to write them to a file

As I understand things, in order to save an ArrayList of objects to a file using ObjectOutputStream, the Objects in the ArrayList need to implement Serializable.

I'm trying to save an ArrayList of Locations to a file, so I extend Location into a class that does that (and nothing else). So I have a class that looks like...

import java.io.Serializable;

import android.location.Location;

public class MyLocation extends Location implements Serializable{

/**
 * 
 */
private static final long serialVersionUID = 7599200646859829149L;

public MyLocation(Location l) {
    super(l);
    
}

} 

But now, in my location listener it crashes at

public void onLocationChanged(Location loc) {
        locat = (MyLocation)loc;

I suppose it doesn't like the typecasting? I dunno, I'm a little confused. Sorry if this is obvious, I haven't been doing this long.

The serialVersionUID line was generated by Eclipse using "add generated serial version ID"

Update:

Like I said before, I'm trying to read/write an arraylist of Locations to/from a file. When I write my data to a file, I don't get any exceptions, but I do get an exception when I try to read it. Basically I have a class that extends ArrayList (because I needed it to be parseable for Listview purposes...

public class开发者_如何学运维 LocationList extends ArrayList<MyLocation> implements Parcelable {


private static final long serialVersionUID = 1L;

it's a LocationList named waypoints that I write to a file. This seems to work fine (ie it doesn't throw an exception or crash)...

FileOutputStream fos;
    try {
        fos = context.openFileOutput(fileName, Context.MODE_PRIVATE);
        ObjectOutputStream os;
        os = new ObjectOutputStream(fos);
        os.writeObject(waypoints);   // <-- writeObject doesn't throw an exception.
        os.close();

but when I try to read that file, I get an IO exception...

FileInputStream fis;
    
    try {
        fis = context.openFileInput(fileName);
        ObjectInputStream is = new ObjectInputStream(fis);
        is.readObject();   // <--this is the line that throws an IO exception
        is.close();

This is probably a naive attempt at saving/loading a moderately complicated object. Any advice?

NOTE: I simplified it a bit. Originally the offending line was

waypoints = (LocationList) is.readObject(); 

but I was worried that I had a similar problem with the casting as above so i took it out temporarily. Anyway, readObject() throws an exception without the typecast there, so I guess that's not my current problem.

---

Is the location object that is passed to you a MyLocation instance? My guess would be no, since the system is providing it. Just because you extend a class doesn't mean you can cast from the super type. What you really want to do is:

   locat = new MyLocation(loc);