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Android Build a Self-Destructing Message Android App Relating Users in Parse.com Displaying Our List of Friends

Posted by Evgeny Goldin
Evgeny Goldin
Courses Plus Student 3,090 Points

My app crashes with an NullPointerException where I call getActionBar().setDisplayHomeAsUpEnabled(true);

Tried to google it, and all I've found was referring to ActionBarActivity.

2 Answers

Kristian Terziev
Kristian Terziev
28,449 Points
Kristian Terziev
Kristian Terziev
28,449 Points

We can't do much without your code included.

Evgeny Goldin
PLUS
Evgeny Goldin
Courses Plus Student 3,090 Points
Evgeny Goldin
Evgeny Goldin
Courses Plus Student 3,090 Points

private static final String TAG = EditFriendActivity.class.getSimpleName(); protected List<ParseUser> mParseUsers; protected ParseRelation<ParseUser> mFriendsRelations; protected ParseUser mCurrentUser;

@Override
protected void onCreate(Bundle savedInstanceState) {
    requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_edit_friend);
    getListView().setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);

// getActionBar().setDisplayHomeAsUpEnabled(true); // At this point it would crash }

@Override
protected void onResume() {
    super.onResume();

    mCurrentUser = ParseUser.getCurrentUser();
    mFriendsRelations = mCurrentUser.getRelation(ParseConstants.KEY_FRIENDS_RELATION);

    setProgressBarIndeterminateVisibility(true);

    ParseQuery<ParseUser> query = ParseUser.getQuery();
    query.orderByAscending(ParseConstants.KEY_USERNAME);
    query.setLimit(1000);
    query.findInBackground(new FindCallback<ParseUser>() {
        @Override
        public void done(List<ParseUser> parseUsers, ParseException e) {
            setProgressBarIndeterminateVisibility(true);
            if(e == null) {
                //Success
                mParseUsers = parseUsers;
                String[] usernames = new String[mParseUsers.size()];
                int i = 0;
                for (ParseUser user : mParseUsers) {
                    usernames[i] = user.getUsername();
                    i++;
                }
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(EditFriendActivity.this, android.R.layout.simple_list_item_checked, usernames);
                setListAdapter(adapter);

                addFriendCheckmarks();
            } else {
                Log.e(TAG, e.getMessage());

                AlertDialog.Builder builder = new AlertDialog.Builder(EditFriendActivity.this);
                builder.setTitle(getString(R.string.error_title));
                builder.setMessage(e.getMessage());
                builder.setPositiveButton(android.R.string.ok, null);
                builder.show();
            }

        }
    });
}

private void addFriendCheckmarks() {
    mFriendsRelations.getQuery().findInBackground(new FindCallback<ParseUser>() {
        @Override
        public void done(List<ParseUser> parseUsers, ParseException e) {
            if(e == null) {
                //List returned
                for (int i = 0; i < mParseUsers.size(); i++) {
                    ParseUser user = mParseUsers.get(i);
                    for (ParseUser contact : parseUsers) {
                        if(contact.getObjectId().equals(user.getObjectId())) {
                            getListView().setItemChecked(i, true);
                        }
                    }
                }
            } else {
                Log.e(TAG, e.getMessage());
            }
        }
    });
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    super.onListItemClick(l, v, position, id);
    if(getListView().isItemChecked(position)){
        //Add friend
        mFriendsRelations.add(mParseUsers.get(position));
    } else {
        mFriendsRelations.remove(mParseUsers.get(position));
    }
    mCurrentUser.saveInBackground(new SaveCallback() {
        @Override
        public void done(ParseException e) {

// Log.e(TAG, e.getMessage()); } }); }

Kristian Terziev
Kristian Terziev
28,449 Points

I doubt you'll get any help before learning how to post READABLE code in the comments. Use the search bar in the Forum section and see where it takes you!