Question

I am running into an issue where instantiating an Object from a Parcel is throwing a NullPointerException. My Class Contact implements Parcelable, contains a CREATOR, and all the hookups seem to work. A Contact object represents a contact in an Address book. The variables used are of types:

String firstName, lastName, note;
List<String> emails, phones;

The constructor initializes all the strings to “” and all the lists to empty lists. The writeToParcel and Contact(Parcel in) methods are shown below:

public void writeToParcel(Parcel out, int flags) {
    out.writeString(firstName);
    out.writeString(lastName);

    //If there are emails, write a 1 followed by the list. Otherwise, write a 0
    if (!emails.isEmpty())
    {
        out.writeInt(1);
        out.writeStringList(emails);
    }
    else
        out.writeInt(0);

    //If there are phone numbers, write a 1 followed by the list. Otherwise, write a 0
    if (!phones.isEmpty())
    {
        out.writeInt(1);
        out.writeStringList(phones);
    }
    else
        out.writeInt(0);
    out.writeString(note);
}

…

public Contact(Parcel in)
{
    firstName = in.readString();
    Log.i(TAG, firstName);
    lastName = in.readString();
    Log.i(TAG, lastName);
    int emailsExist = in.readInt();
    if (emailsExist == 1)
        in.readStringList(emails);
    else
        emails = new ArrayList<String>();
    int phonesExist = in.readInt();
    if (phonesExist == 1)
        in.readStringList(phones);//Line 80, where this app breaks
    else
        phones = new ArrayList<String>();
    note = in.readString();
}

The test I am currently working on provides a valid first and last name, one phone number, and a note. The relevant output I get when upacking this parcelable is as follows:

FATAL EXCEPTION: main
java.lang.RuntimeException: Failure delivering result ResultInfo...
...
Caused by: java.lang.NullPointerException
    at android.os.Parcel.readStringList(Parcel.java:1718)
    at com.mycompany.android.Contact.<init>(Contact.java:80) //This is the line marked above
    at com.mycompany.android.Contact$1.createFromParcel(Contact.java:40) //This is inside the CREATOR
    ...

What am I doing incorrectly? Can numbers not be written as String lists, or did I do something incorrectly?

Answer 1

I just poked around a few minutes more, and realized my mistake. The readStringList method cannot receive a null argument. My new Contact(Parcel in) method is as follows:

public Contact(Parcel in)
{
    firstName = in.readString();
    Log.i(TAG, firstName);
    lastName = in.readString();
    Log.i(TAG, lastName);
    int emailsExist = in.readInt();
    emails = new ArrayList<String>();
    if (emailsExist == 1)
        in.readStringList(emails);
    int phonesExist = in.readInt();
    phones = new ArrayList<String>();
    if (phonesExist == 1)
        in.readStringList(phones);          
    note = in.readString();
}