Passing a list of objects between Activities

In Android, you can use Bundle to pass data between activities. There are many functions to pass Integer, String, etc. To pass an object, you will need to implement Parcelable interface and override some functions to serialize/de-serialize the object. Here is an example:

public class Category implements Parcelable {
private String category;
private ArrayList<Item> items;

public String getCategory() {
return category;
}

public void setCategory(String category) {
this.category = category;
}

public ArrayList<Item> getItems() {
return items;
}

public void setItems(ArrayList<Item> items) {
this.items = items;
}

public Category(){

}

public Category(String _category){
category = _category;
}

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

@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(category);
Bundle b = new Bundle();
b.putParcelableArrayList("items", items);
dest.writeBundle(b);

}

public static final Parcelable.Creator<Category> CREATOR = 
new Parcelable.Creator<Category>() { 
public Category createFromParcel(Parcel in) { 
Category category = new Category();
category.category = in.readString();
Bundle b = in.readBundle(Item.class.getClassLoader());        
category.items = b.getParcelableArrayList("items");

return category;
}

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

To pass an arraylist  of Category to another activity,

intent i = new Intent(_av.getContext(), ItemList.class);
Bundle b = new Bundle();
b.putParcelableArrayList("categories", categories);
b.putInt("index", _index);
i.putExtras(b);
startActivityForResult(i, ITEM_LIST);

To retrieve the data,

Bundle b = this.getIntent().getExtras();

ArrayList<Category> cats = b.getParcelableArrayList("categories");
int index = b.getInt("index");