Android Parcelable write / read String List null object reference

Question

I'm trying to read a List of Strings and I keep having the following error:

with the following Parcelable class:

import java.util.List;

import android.os.Parcel;
import android.os.Parcelable;

public class ActivePolicies implements Parcelable {

    private List<String> activePolicies;

    public ActivePolicies(List<String> activePolicies) {
        this.activePolicies = activePolicies;
    }

    public List<String> getActivePolicies(){
        return activePolicies;
    }

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

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeStringList(activePolicies);
    }

    public static final Parcelable.Creator<ActivePolicies> CREATOR = new Parcelable.Creator<ActivePolicies>() {
        @Override
        public ActivePolicies createFromParcel(Parcel in) {

            try {
                return new ActivePolicies(in.createStringArrayList());
            } catch (Exception e) {
                e.printStackTrace();
                return null;
            }
        }
        @Override
        public ActivePolicies[] newArray(int size) {
            return new ActivePolicies[size];
        }
    };

}

It keeps giving me the exception on createFromParcel(), but I can't figure out why.
It seems a simple parcelable, but when I'm debugging at readStringList() from the Parcel class, the list is null.
But when I evaluate the value in createStringArrayList() before it's returning, the list is there with the expected values.

score 0 · Answer 1 · answered Oct 13 '16 at 01:12

0

you need to create constructor that accept Parcel

public ActivePolicies(Parcel in) {
    in.readStringList(activePolicies);
}

answered Oct 13 '16 at 01:12

hakim

3,819
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OneCricketeer · Answer 2 · 2016-10-13T02:03:06.443

0

in.createStringArrayList()? Why are you creating a new String list when you want to construct your object?

Use this method.

Parcel.readStringList(List<String> list)

Read into the given List items String objects that were written with writeStringList(List) at the current dataPosition().

Recommended: implement a constructor that accepts a Parcel, then, optionally a readFromParcel method.

public class ActivePolicies implements Parcelable {

    private List<String> activePolicies;

    public ActivePolicies() {
        activePolicies = new ArrayList<String>();
    }

    public ActivePolicies(Parcel in) {
        this();
        readFromParcel(in);
    }

   private void readFromParcel(Parcel in) {
      in.readStringList(activePolicies);
   }

In the creator.

return new ActivePolicies(in);

edited Oct 13 '16 at 02:03

answered Oct 13 '16 at 01:12

OneCricketeer

179,855
19
132
245

You are right. I want to construct the object. Even though using what you said, it still not working unfortunately. I'm using exactly what you said and added a set method for the List. So I can give a value to it. But still with null... – fvcpinheiro Oct 13 '16 at 01:46
Not sure what to tell you, but you do need `readStringList` at some point – OneCricketeer Oct 13 '16 at 01:52
One app is calling a remote method from another which returns ActivePolicies. This remote application has the list value and so I return new ActivePolicies(list). Even though, it's keep messing with null when readStringList is called. – fvcpinheiro Oct 13 '16 at 02:01
Then it sounds like the list is already null when you did `dest.writeStringList(activePolicies);` – OneCricketeer Oct 13 '16 at 02:02
Actually, try the update – OneCricketeer Oct 13 '16 at 02:03
I guess maybe I can't define a interface method in AIDL without input as I'm doing: interface IReferenceMonitorService { ActivePolicies requestActivePolicies(); } – fvcpinheiro Oct 13 '16 at 02:04
it's not null when writing... – fvcpinheiro Oct 13 '16 at 02:04
AIDL or an interface isn't a problem. I think you need actually initialize the list. – OneCricketeer Oct 13 '16 at 02:06
That's why I had a constructor in first place... The list is initialized when writeToParcel is called and still not working. – fvcpinheiro Oct 13 '16 at 02:13
And I need a setMethod for list. Look: http://imgur.com/LrHCPlZ – fvcpinheiro Oct 13 '16 at 02:16
I need to define an AIDL method with a parcelable input. – fvcpinheiro Oct 13 '16 at 02:22
I think I need, I can't edit last comment (or I don't know how). Gotta test that... – fvcpinheiro Oct 13 '16 at 02:24
Your stacktrace in the image seems to hint that the list is null at `readStringList`. Have you done `activePolicies = new ArrayList()`, or not? – OneCricketeer Oct 13 '16 at 02:27
Yes I did. http://imgur.com/a/2RqEg, On the right there is the remote application method implementation and below the remote caller. – fvcpinheiro Oct 13 '16 at 02:33
You didn't call `this()` in the constructor that accepts the parcel – OneCricketeer Oct 13 '16 at 02:34
Still not working even with this(). – fvcpinheiro Oct 13 '16 at 02:37
It's initialized but doesn't have the value. http://imgur.com/a/HVOAT – fvcpinheiro Oct 13 '16 at 02:39
At that line, no, it won't have any data yet. That method copies the strings from the parcel into the empty list – OneCricketeer Oct 13 '16 at 02:40
`readInt()` returns 0, so nothing is read – fvcpinheiro Oct 13 '16 at 02:46

Android Parcelable write / read String List null object reference

2 Answers2