Android:lossing data when pass arraylist of arraylists from activity to activty

Question

i could to pass an arraylist from activity A to Activity B Successfully. AS Shown below :

At activity A :

            Intent intent = new Intent(Activity_A.this, Activity_B.class);
            intent.putParcelableArrayListExtra("albums", (ArrayList<? extends Parcelable>) albums);
            startActivity(intent);

The Model Album is implemented as below:

 public class Album implements Parcelable
 {
    public ArrayList<Song> Songs = new ArrayList<Song>();
    public int id;
    public String album_name;
    public String pic;



  public static final Creator<Album> CREATOR = new Creator<Album>()
  {
    @Override
    public Album createFromParcel(Parcel in)
    {
        return new Album(in);
    }

    @Override
    public Album[] newArray(int size)
    {
        return new Album[size];
    }
};

  @Override
  public int describeContents()
 {
    return 0;
 }

@Override
public void writeToParcel(Parcel parcel, int i)
{
    parcel.writeInt(id);
    parcel.writeString(album_name);
    parcel.writeString(pic);
}
 }

As Shown the album contain of arraylist of songs and another data

Here is the implementation of Song Model:

    public class Song implements Parcelable
    {

      public int id;
      public String file_name;
      public String file_url;
      public String pic_url;
      public int Album_id;


       public static final Creator<Song> CREATOR = new Creator<Song>()
     {
      @Override
      public Song createFromParcel(Parcel in)
      {
        return new Song(in);
      }

    @Override
    public Song[] newArray(int size)
    {
        return new Song[size];
    }
  };


@Override
public int describeContents()
{
    return 0;
}

@Override
public void writeToParcel(Parcel parcel, int i)
{
    parcel.writeInt(id);
    parcel.writeString(file_name);
    parcel.writeString(file_url);
    parcel.writeString(pic_url);
    parcel.writeInt(Album_id);

  }
  }


      }

And to get data passed at At activity B :

    Bundle bundle = getIntent().getExtras();
    ArrayList<Album> albums = bundle.getParcelableArrayList("albums");

The problem here is that Data is passed successfully From Activity A to Activity B But The list of songs is null with size zero for every album although i checked in activity A that every album has list of songs

Answer 1

Your songs list is empty because you didn't save it to Parcel in writeToParcel(Parcel, int) method in Album class.

Your writeToParcel(Parcel, int) method should look like this:

@Override
public void writeToParcel(Parcel dest, int flags) {
    dest.writeTypedList(this.Songs);
    dest.writeInt(this.id);
    dest.writeString(this.album_name);
    dest.writeString(this.pic);
}

And Album(Parcel) like this:

protected Album(Parcel in) {
    this.Songs = in.createTypedArrayList(Song.CREATOR);
    this.id = in.readInt();
    this.album_name = in.readString();
    this.pic = in.readString();
}