Transfer Custom object array from one activity to another

Question

I created a class called CardView. CardView object has 1 property: int number

I want to trasfer arrayList of CardView Objects from MainActivity to MainActivity2 I tried to do it but when I printed getNumber of the first(or any) object it returns 0 instead of the number I set in new Cardview(int number).

here is the code:

MainActivity onCreate():

List<CardView> list = new ArrayList<>();
    list.add(new CardView(10));
    list.add(new CardView(11));
    list.add(new CardView(12));
    Intent mIntent = new Intent(this, MainActivity2.class);
    mIntent.putParcelableArrayListExtra("Data", (ArrayList<? extends Parcelable>) list);
    startActivity(mIntent);

MainActivity2 onCreate():

List list;
    list = getIntent().getExtras().getParcelableArrayList("Data");
    Toast.makeText(this, ((CardView)list.get(0)).getNumber()+"", Toast.LENGTH_SHORT).show();

CardView Class:

public class CardView implements Parcelable {
    int number;
    public CardView(int number){
        this.number = number;
    }

    public int getNumber() {
        return number;
    }

    protected CardView(Parcel in) {
    }

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

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

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

    @Override
    public void writeToParcel(Parcel parcel, int i) {
    }
}

Yeldar Nurpeissov · Accepted Answer · 2020-12-19 18:40:56Z

1

Try this:

protected CardView(Parcel in) {
    number = in.readInt();
}

@Override public void writeToParcel(Parcel parcel, int i) {    
    parcel.writeInt(number); 
}

By default the value of uninitialized int variable will be 0, so initial value of number is 0. With this constructor number receive from parcel.

edited Dec 19, 2020 at 18:40

answered Dec 19, 2020 at 15:42

Yeldar Nurpeissov

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3 Comments

Yaniv Over a year ago

Because of this line the app crash onCreate() of the second Activity

Yeldar Nurpeissov Over a year ago

@Override public void writeToParcel(Parcel parcel, int i) { parcel.writeInt(number); }

Yaniv Over a year ago

I already understood it but really, Thank you! Please edit your answer so I can mark it as the correct answer

Son Truong · Accepted Answer · 2020-12-20 09:19:23Z

0

I figured it out with this video: https://www.youtube.com/watch?v=WBbsvqSu0is&ab_channel=CodinginFlow

I should add the following code to CardView class.

protected CardView(Parcel in) {
    number = in.readInt();
}

@Override
public void writeToParcel(Parcel parcel, int i) {
    parcel.writeInt(number);
}

edited Dec 20, 2020 at 9:19

Son Truong

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answered Dec 19, 2020 at 16:15

Yaniv

1352 silver badges11 bronze badges

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