Android：空对象参考

Question

我正在尝试提供一个联系人列表，每个联系人都有一个QuickContactBadge 。 当我尝试添加QuickContactBadge ，我的应用程序崩溃程序和logcat在调用getColumnIndex();时在mCursor上mCursor空对象引用getColumnIndex(); 。 我在做什么错，此代码可以正确实现QuickContactBadge吗？

private CursorAdapter mAdapter;
private Cursor mCursor;
private String currentQuery;
private int mIdColumn;
private int mLookupKeyColumn;
private Uri mContactUri;
private QuickContactBadge mBadge;
private static final String[] PROJECTION = {
        Contacts._ID,
        Contacts.DISPLAY_NAME_PRIMARY,
        Contacts.LOOKUP_KEY,
        Contacts.PHOTO_THUMBNAIL_URI,
        Contacts.HAS_PHONE_NUMBER
};
private static final String[] FROM = { Contacts.DISPLAY_NAME_PRIMARY };
private static final int[] TO = { R.id.contact_text };
private static final String SELECTION = "(" + Contacts.IN_VISIBLE_GROUP +
        " = 1) AND (" + Contacts.HAS_PHONE_NUMBER + " != 0 )";


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    mCursor = null;
    mAdapter = new SimpleCursorAdapter(getActivity(), R.layout.contacts_list_item, mCursor, FROM, TO, 0);

    mBadge = (QuickContactBadge) getActivity().findViewById(R.id.badge);
    mIdColumn = mCursor.getColumnIndex(Contacts._ID);
    mLookupKeyColumn = mCursor.getColumnIndex(Contacts.LOOKUP_KEY);
    mContactUri =
            Contacts.getLookupUri(
                    mCursor.getLong(mIdColumn),
                    mCursor.getString(mLookupKeyColumn)
            );
    mBadge.assignContactUri(mContactUri);
}

Answer 1

mCursor = null;
mAdapter = new SimpleCursorAdapter(getActivity(), R.layout.contacts_list_item, mCursor, FROM, TO, 0);

mBadge = (QuickContactBadge) getActivity().findViewById(R.id.badge);
mIdColumn = mCursor.getColumnIndex(Contacts._ID);

在此处检查第一行和最后一行...您的mCursor为空，并且您正在对其调用getColumnIndex（）。