在cursor.getCount();处获得空指针异常在使用游标加载器执行ListView时适配器类如下
public class FriendsListCursorAdapter extends CursorAdapter {
private Cursor cursor;
final VROPreferenceManager preferenceManager = new VROPreferenceManager();
Context con;
public FriendsListCursorAdapter(Context context, Cursor c, boolean b) {
super(context,c,true);
cursor = c;
con=context;
}
public void addItems(Cursor newItems) {
if (0 == newItems.getCount()) {
return;
}
notifyDataSetChanged();
}
public int getCount() {
// TODO Auto-generated method stub
return cursor.getCount();
}
public Object getItem(int position) {
// TODO Auto-generated method stub
return position;
}
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public View newView(Context context, Cursor cursor, ViewGroup viewGroup) {
LayoutInflater inflater = LayoutInflater.from(context);
View view = inflater.inflate(R.layout.vro_contact_view, null);
bindView(view, context, cursor);
return view;
}
@Override
public void bindView(View view, Context context, Cursor cursor) {
TextView txtID = (TextView) view.findViewById(R.id.text_fname_lname);
txtID.setText(cursor.getString(cursor.getColumnIndex("first_name")));
// VROUser user =cursor.getColumnIndex("first_name");
// / ColCode
TextView txtCode = (TextView) view.findViewById(R.id.text_email);
txtCode.setText(cursor.getString(cursor.getColumnIndex("email")));
ImageView profilePic = (ImageView) view.findViewById(R.id.user_image);
cursor.getColumnIndex("user_profile_pic");
view.findViewById(R.id.ColCountry);
//txtCountry.setText(cursor.getString(cursor.getColumnIndex("Country")));
}
}
和游标加载器:
public class FindPeopleFragment extends BaseFragment implements LoaderCallbacks<Cursor> {
public FindPeopleFragment() {
}
private TextView advancedSearchOption;
private TextView saerchButton;
EndlessListView listUsers;
private EditText searchWord;
private EditText searchFirstName;
private EditText searchLastName;
private EditText searchEmail;
private EditText searchCountry;
private EditText searchState;
private int offset = 0;
private final int limit = 30;
private boolean mHaveMoreDataToLoad = true;
private VROAccountManager manager;
private ArrayList<VROUser> postsList = new ArrayList<>();
private View advanced;
private Cursor FriendsCursor;
// Cursor c;
private TextView description;
Object friend_name;
FriendsListCursorAdapter FRIEND_ADAPTER;
DatabaseHelper dh;
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
title = "My Friends";
// setSelection(0);
}
private View rootView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (rootView != null) {
((ViewGroup) rootView.getParent()).removeView(rootView);
return rootView;
}
rootView = inflater.inflate(R.layout.fragment_find_people, null);
getLoaderManager().initLoader(1, null, this);
progressBar = rootView.findViewById(R.id.progressBar);
saerchButton = (TextView) rootView.findViewById(R.id.button_search);
listUsers = (EndlessListView) rootView.findViewById(R.id.user_list);
searchWord = (EditText) rootView
.findViewById(R.id.editText_search_word);
searchFirstName = (EditText) rootView
.findViewById(R.id.editText_search_first_name);
searchLastName = (EditText) rootView
.findViewById(R.id.editText_search_last_name);
searchEmail = (EditText) rootView
.findViewById(R.id.editText_search_email);
searchCountry = (EditText) rootView
.findViewById(R.id.editText_search_country);
searchState = (EditText) rootView
.findViewById(R.id.editText_search_state);
advancedSearchOption = (TextView) rootView
.findViewById(R.id.advancedSearch);
advancedSearchOption.setVisibility(View.GONE);
manager = new VROAccountManager(getActivity());
advanced = rootView.findViewById(R.id.layout_advanced_search);
description = (TextView) rootView.findViewById(R.id.description);
description
.setText("You are friends with the following users. To find new friends or to view friends request sent or received use the menu on right");
FRIEND_ADAPTER = new FriendsListCursorAdapter(getActivity(),
FriendsCursor, true);
// loadMoreData();
saerchButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
listUsers.setAdapter(FRIEND_ADAPTER);
}
});
listUsers.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
friend_name=listUsers.getSelectedItem();
Toast.makeText(getActivity(), " "+friend_name, Toast.LENGTH_SHORT).show();
// Intent intent = new Intent(getActivity(), ProfileViewActivity.class);
// intent.putExtra("userId",(int)friend_name);
// getActivity().startActivity(intent);
}
});
return rootView;
}
private HashMap<String, String> data = new HashMap<>();
private final EndlessListView.OnLoadMoreListener loadMoreListener = new EndlessListView.OnLoadMoreListener() {
@Override
public boolean onLoadMore() {
if (true == mHaveMoreDataToLoad) {
//loadMoreData();
}
// else {
// Toast.makeText(getActivity(), "No more data to load",
// Toast.LENGTH_SHORT).show();
// }
return mHaveMoreDataToLoad;
}
@Override
public void onReachedTop(boolean isTop) {
// TODO Auto-generated method stub
}
};
private final Handler handler = new Handler();
private View progressBar;
@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
String[] projection = { FriendinfoTable.Cols.ID,FriendinfoTable.Cols.FIRST_NAME,
FriendinfoTable.Cols.LAST_NAME,FriendinfoTable.Cols.USER_NAME,FriendinfoTable.Cols.EMAIL,
FriendinfoTable.Cols.USER_PROFILE_PIC,FriendinfoTable.Cols.USER_TIMELINE_PIC,
FriendinfoTable.Cols.COUNTRY,FriendinfoTable.Cols.STATE,FriendinfoTable.Cols.CITY,
FriendinfoTable.Cols.ABOUT,FriendinfoTable.Cols.GENDER,FriendinfoTable.Cols.DATEOFBIRTH,
FriendinfoTable.Cols.FRIENDSHIP_STATUS,FriendinfoTable.Cols.QUICKBLOX_ID};
CursorLoader cursorLoader = new CursorLoader(getActivity(),
FriendinfoTable.CONTENT_URI, projection, null, null, null);
return cursorLoader;
}
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
FriendsCursor = data;
if (FRIEND_ADAPTER == null) {
FRIEND_ADAPTER = new FriendsListCursorAdapter(getActivity(),
FriendsCursor, true);
listUsers.setAdapter(FRIEND_ADAPTER);
} else {
FRIEND_ADAPTER.swapCursor(FriendsCursor);
}
}enter code here
@Override
public void onLoaderReset(Loader<Cursor> loader) {
}
}
无法找到问题，请通过加载器类，检查查询，请帮助我找到问题!
所以…在
行有一个NullPointerExceptionreturn cursor.getCount();
这仅仅意味着，cursor是null。cursor从何而来?它设置在哪里?我只看到构造函数:
public class FriendsListCursorAdapter extends CursorAdapter {
private Cursor cursor;
...
public FriendsListCursorAdapter(Context context, Cursor c, boolean b) {
super(context, c, true);
cursor = c;
con = context;
}
...
}
Cursor c提供实例。为了避免此类问题，您应该在构造函数中添加一个保护子句:
public FriendsListCursorAdapter(Context context, Cursor c, boolean b) {
super(context, c, true);
cursor = Objects.requireNonNull(c);
con = Objects.requireNonNull(context);
}
这将更早地抛出NPE(在构建时)，并将使您更进一步。您将看到这一行导致了这个NPE:
FRIEND_ADAPTER = new FriendsListCursorAdapter(getActivity(), FriendsCursor, true);
注意:这一行存在多次!
那么这里的问题是什么?显然FriendsCursor是null。顺便说一下:请坚持Java的命名约定，让你的变量以小写字母开头。
我没有看到任何FriendsCursor的初始化，所以这个实例变量仍然是null，这就是你的问题的原因。初始化这个变量(在正确的位置)。
您的cusror为空，因此它抛出空指针异常尝试处理游标nullpointerexception
public int getCount() {
// TODO Auto-generated method stub
//try using this
if(cursor==null)
return 0;
return cursor.getCount();
}