java - Android 使用 java nullpointerException 接口(interface)传递值

Question

我有一个寻呼机适配器如下

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);
}

}

这是我的联系人 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;
}

}

最后是界面

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

}

当我单击该项目时，它捕获 java.lang.nullpointerException我应该做什么才能让 MainPagerFragmentAdapter 在单击任何联系人 id 时获取 Id？

注意:ContactsFragment 是一个库项目，因此我使用接口(interface)在项目之间传递值

Answer 1

您的dataPasser为null。

将其初始化为实现该接口(interface)的非 null 对象，或者在尝试调用其方法之前检查 != null。