Invalid cast when passing serializable object to activity

Question

I have a complex object (which includes further objects and hashmaps). All objects implement Serializable.

In the first activity I do:

public void secondActivity(MyObject o) {
    Intent intent = new Intent(this, SecondActivity.class);
    intent.putExtra("myobject", o);

    startActivity(intent);
    finish();
}

Then, in the second activity I'm doing:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Intent intent = getIntent();
    MyObject o = (MyObject)intent.getSerializableExtra("myobject");
}

But when casting I'm getting this exception:

java.lang.ClassCastException: java.util.ArrayList cannot be cast to myapp.MyObject

Is this the correct way to pass complex objects between activities? What am I missing?

Or should I implement singleton class?

Does `getIntent()` return the same intent to which `myobject` extra was added? — Chetan Kinger, Jun 20 '15 at 18:59
@ChetanKinger It should. There's no other place in the app where the secondactivity gets opened from. — Ivan-Mark Debono, Jun 21 '15 at 05:15

score 2 · Accepted Answer · edited May 23 '17 at 10:30

You are doing all fine, so I think that can be:

your are sending to secondActivity method an incorrect object (like ArrayList instead of correct MyObject)
Please look if you are using this key "myobject" in other part of the code and setting other object in putExtra.
verify MyObject class and look if some variable is an ArrayList and remove it (just to test)
your custom object not have "implements Serializable" like:

public class MyObject implements Serializable {

//variables and methods

}

So, I suggest that you verify this, and I think is better use Singleton class or Parcelable instead of Serializable, because Google says that is better acording to Good Practice. Please look this answer stackoverflow

I make some app and implement serializable, my custom object is:

public class Stores implements Serializable {
private static final long serialVersionUID = 1L;
public Integer id;
public String name;
public String store_hours;
public String telephone;
public String fax;
public String latitude;
public String longitude;

}

My firt Activity:

private void showDialog(Stores store)
    {
        Intent intent = new Intent(this,DisplayDialogActivity.class);
        intent.putExtra("Locations",store);
        startActivityForResult(intent, 0);
    }

And my second activity

Stores store = (Stores) getIntent().getSerializableExtra("Locations");

PD: I don't know speak english very well, so apologize for this.

score 0 · Answer 2 · answered Mar 25 '17 at 10:29

There are some general guidelines that why some objects are not serializable
It is too closely tied to native code (java.util.zip.Deflater).
The object's state depends on the internals of the virtual machine or the runtime environment and thus may change from run to run
(java.lang.Thread, java.io.InputStream, java.io.FileDescriptor,
java.awt.PrintJob).
The class is mostly a holder for static methods without any real internal state (java.beans.Beans, java.lang.Math).
The class is a nonstatic inner class. Serialization just doesn't work well with nonstatic inner classes. (Static inner classes have no problem being serialized.)
An alternate serialization format is preferred in a particular context. (XOM node classes are not serializable because the proper serialization format for XML is XML.)

Make sure your class is declared public

complete Reference . Java I/O 2nd Edition

Invalid cast when passing serializable object to activity

2 Answers2