CODEWITHSUNDEEP
javaandroidinterfaceandroid-library
Then
Then

Reputation: 1

Android passing value with interface java nullpointerexception

I having a pager adapter as following

public class MainPagerFragmentAdapter extends FragmentPagerAdapter implements IdInterface {

ContactsFragment contactSearch;

public MainPagerFragmentAdapter(FragmentManager fragmentManager) {
    super(fragmentManager);
}

@Override
public Fragment getItem(int position) {

    switch (position) {
    case 0:
        if (contactSearch == null)
            contactSearch = new ContactsFragment();
        return contactSearch;
    }

    return null;
}

public void onRawIdAcquired(long arg0) {
    Log.d("LOG","id=" + arg0);
}

}

this is my contacts fragment

public class ContactsFragment extends Fragment implements
    LoaderManager.LoaderCallbacks<Cursor> {
private long rawId;
private SimpleCursorAdapter mAdapter;

public static final String ARG_ID = "RAWID";
public static final String SORT_KEY_PRIMARY = "sort_key";
public static final Uri URI = ContactsContract.Data.CONTENT_URI;

public static final String[] PROJECTION = new String[] {
        ContactsContract.Data._ID, ContactsContract.Data.RAW_CONTACT_ID};

public static final String SELECTION = ContactsContract.Data.MIMETYPE
        + " = ? ";

public static final List<String> ARGS;
static {
    ARGS = new ArrayList<String>();
    ARGS.add(ContactsContract.CommonDataKinds.Organization.CONTENT_ITEM_TYPE);
}

private ListView mContactList;
private View mContactFragmentView;
private TextView noResultText;
private Button searchOnlineBtn;

IdInterface dataPasser;

public ContactsFragment() {
    dataPasser = (IdInterface) null;
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    super.onCreateView(inflater, container, savedInstanceState);
    mContactFragmentView = inflater.inflate(R.layout.fragment_contacts,
            container, false);

    mContactList = (ListView) mContactFragmentView
            .findViewById(R.id.contacts_list);

    String[] fromColumns = { SORT_KEY_PRIMARY };
    int[] toViews = { R.id.contactName };
    mAdapter = new ContactsCursorAdapter(getActivity(),
            R.layout.contact_list_item, null, fromColumns, toViews);
    mContactList.setAdapter(mAdapter);

    mContactList.setOnItemClickListener(new OnItemClickListener() {

        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {

            Cursor cursor = (Cursor) parent.getAdapter().getItem(position);

            rawId = cursor.getLong(cursor
                    .getColumnIndex(ContactsContract.Data.RAW_CONTACT_ID));

            Bundle params = new Bundle();
            params.putLong(ARG_ID, rawId);
            ContactsFragment fragobj = new ContactsFragment();
            fragobj.setArguments(params);
            Log.v("", "fragobj=" + params);

            try {
                dataPasser.onRawIdAcquired(rawId);
            } catch (Exception e) {
                Log.v("", "error=" + e);
            }

        }

    });
    getLoaderManager().initLoader(0, null, this);
    return mContactFragmentView;
}

}

and lastly Interface

public interface IdInterface {
public void onRawIdAcquired(long rawId);

}

when i click on the item, it catches java.lang.nullpointerexception What i should do in order to let the MainPagerFragmentAdapter to obtain the Id when any of the contact id being clicked?

Noted: ContactsFragment is a library project, thus i am using interface to passing value among project

Upvotes: 0

Views: 1361

Answers (4)

Then
Then

Reputation: 1

Finally got it solved, initialize the dataPasser as following in the Fragment

@Override
public void onAttach(Activity activity){
  super.onAttach(activity);
  context = getActivity();
  dataPasser =(IdInterface)context;
}

The Interface should implements on MainActivity which call the FragmentAdapter instead of the FragmentAdapter.

Upvotes: 0

John Doe
John Doe

Reputation: 146

In yourreturn getItem Function you are always returning null unless you ask for position 0 Then you return a ContactsFragment.

This function is called on item click so I guess this is where you'll find your problem.

public Fragment getItem(int position) {

switch (position) {
case 0:
    if (contactSearch == null)
        contactSearch = new ContactsFragment();
    return contactSearch;
}

return null;  <--- should be the problem

}

You should fix this function to actually return a fragment. According to the other answers I'd suggest to have a closer look on your code. Looks like there are some more obvious problems.

To initialize your dataPasser you should first implement it as its a interface. Try by replacing 

dataPasser = (IdInterface) null;

with

dataPasser = new IdInterface {
    public void onRawIdAcquired(long rawId){
        //your code
    }
};

Or create a new class implementing this interface and instantiate it here instead.

Upvotes: 0

Kevin Cruijssen
Kevin Cruijssen

Reputation: 9326

In your constructor you put dataPasser to null:

IdInterface dataPasser;

public ContactsFragment() {
    dataPasser = (IdInterface) null; // <- Here
}

But I don't see code where you initialize it, so dataPasser.onRawIdAcquired(rawId); causes a NullPointerException because your dataPasser is null.

Either initialize the dataPasser somewhere, or if it's already supposed to do this and it isn't for some reason, use this instead:

if(dataPasser != null)
    dataPasser.onRawIdAcquired(rawId);

Upvotes: 0

laalto
laalto

Reputation: 152787

Your dataPasser is null.

Either initialize it to a non-null object that implements the interface, or check for != null before trying to call a method on it.

Upvotes: 1

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