Question

I need a way to save an ArrayList of objects. I have browsed similar issues in the site and I (seem 😉 to have implemented what I found, but I get two problems:

1. If I define the class as Serializable and put the constructor, it crashes at launch
2. Otherwise, It does not save the array

Can you please help? I am developing code for a volunteer’s project and I am stuck…

Thank you a lot in advance.

My application has the following defined class: Globals (file Globals.java)

---

public class Globals extends Application implements Serializable {  

    private int position=-1;
    private ArrayList<RaccoltaPunti> raccoltePuntiList = new ArrayList<RaccoltaPunti>();
    public static final long serialVersionUID = 1L;
    /** constructor - seem required by Serializable, but creating it crashes app */
    public Globals(int position, ArrayList<RaccoltaPunti> raccoltePuntiList) {
        this.position = position;
        this.raccoltePuntiList = raccoltePuntiList;
    }
     // {getters and setters…}

    public void saveData(){

        String filename = getResources().getString(R.string.GLB_filename);
        String fileWithPath = this.getFilesDir().getPath().toString()+"/"+filename;
        Toast.makeText(this, "Salvataggio testo..."+ fileWithPath, Toast.LENGTH_LONG).show();
        try {
            FileOutputStream fos = new FileOutputStream(fileWithPath);
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(this.raccoltePuntiList);    
            oos.close();
            Toast.makeText(Globals.this, "DatiSalvati ", Toast.LENGTH_SHORT).show();
        } catch (IOException e) {
            Log.e("FileSave", "CDM - IOException", e);
            Toast.makeText(this, "Errore saving file", Toast.LENGTH_LONG).show();
        }
    }
}

The class referenced is: RaccoltaPunti.java

public class RaccoltaPunti {

    private String nomeRaccolta;
    private String nomePromoter;
    private String numeroTessera;
    private Long puntiPusseduti;
    private String dataScadenzaPunti;
    private String sitoWeb;
    private String sitoWebUsername;

        // constructor, getters and setters…….
}

---

Answer 1

The problem seems resolved (now the file is successfully saved without errors and by manually opening it it seems to contain all the info).
Thank you to you all.

I summarise the solution for the benefit of any other future reader with the same issue.

The problem was resolved by making the class RaccoltaPunti Serializable, as per following code fragment:

    import java.io.Serializable;
    ...

    public class RaccoltaPunti implements Serializable {
    ...

I noted that RaccoltaPunti had already a constructor with parameters:

    public  RaccoltaPunti(
        String nomeRaccolta,
        String nomePromoter,
        String numeroTessera,
        Long puntiPusseduti,
        String dataScadenzaPunti,
        String sitoWeb,
        String sitoWebUsername) {

For reference, the error reported in the log was referring to the line of code:

    oos.writeObject(this.raccoltePuntiList);    

Regarding the constructor for the Globals class, my experiments showed that everything is working by just commenting it out. I did not try all possible combinations (i.e. with or without parameters): I just removed it.

Thank you all who helped.