Question

我正在尝试反转ListView，以便首先显示最新的项目。我已经看到了修改getItem（）方法的结果，但是这需要我向下滚动并向上滚动以查看新项目。有没有办法让项目出现在列表的顶部而不需要滚动？

 public class ListAdapter extends ArrayAdapter<Comments> {

    Firebase BaseRef = new Firebase(FIREBASE_URL);
    Firebase PollsRef = mBaseRef.child(POLLS_LABEL);
    Firebase UpdateRef = mPollsRef.child(mCurrentDateString).child(String.valueOf(mPollIndex + 1));
    Firebase CommentsRef = mUpdateRef.child(COMMENTS_LABEL);
    int pollCommentCount;


    public ListAdapter(Context context, int textViewResourceId) {
        super(context, textViewResourceId);
    }

    public ListAdapter(Context context, int resource, List<Comments> items) {
        super(context, resource, items);
    }


    @Override
    public int getCount() {
        CommentsRef.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                pollCommentCount = (int) dataSnapshot.getChildrenCount();
                Log.v("POLL_COMMENT_COUNT", "The poll comment count is " + pollCommentCount);
            }

            @Override
            public void onCancelled(FirebaseError firebaseError) {

            }
        });
        return pollCommentCount;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View v = convertView;

        if (v == null) {
            LayoutInflater vi;
            vi = LayoutInflater.from(getContext());
            v = vi.inflate(R.layout.individual_comment, null);
        }

        Comments p = getItem(position);

        if (p != null) {
            TextView userID = (TextView) v.findViewById(R.id.user_ID);
            TextView userComment = (TextView) v.findViewById(R.id.user_comment);

            if (userID != null) {
                userID.setText(p.getUserID());
            }

            if (userComment != null) {
                userComment.setText(p.getUserComment());
            }
        }


        return v;
    }

}

Answer 1

您可以在创建适配器之前对Comment列表进行排序。通过这种方式，它们已经按照您希望它们的顺序排列。我不知道Comment对象包含哪些变量可以让您知道它何时被修改，但假设它是一个日期，您可以像这样对列表进行排序：

Collections.sort(commentsList, new Comparator<Comment>() {
    public int compare(Comment c1, Comment c2) {
        return c1.getDate().compareTo(c2.getDate());
    }
});

您也可以使用Collections.reverse(commentList)

简单地撤消列表

Answer 2

调用<?php if(isset($_POST['query'])) { //connect to database include 'connect.php'; //retrieve the query $query = $_POST['query']; //search database for all similar items $sql = mysql_query("SELECT * FROM ( SELECT customer_id, customer_name, address, street, phone_1, phone_2, phone_3, phone_4, CONCAT(customer_name, ' ', address, ' ', street, ' ', phone_1, ' ', phone_2, ' ', phone_3, ' ', phone_4) as `mysearch` FROM customers) base WHERE `mysearch` LIKE '%{$query}%' ORDER BY customer_name ASC, street ASC, address ASC "); $array = array(); while ($row = mysql_fetch_assoc($sql)) { $array[] = $row['customer_name'] . " " . $row['address'] . " " . $row['street'] . " " . $row['phone_1']. " " . $row['phone_2']. " " . $row['phone_4']. " " . $row['phone_3']." id#" . $row['customer_id']; } //return JSON array echo json_encode($array); } ?>应该更新列表。

Answer 3

我意识到.add（）方法实际上是在特定索引处插入项目。如果我总是向索引（0）添加新项目，那么这些项目将自然地以相反的顺序出现。

我认为Google会更直观地使用Android代码并允许使用insert（）方法，但index（o）中的add（）方法可以达到目的：

mUpdateRef.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            setImage(dataSnapshot);
            setQuestion(dataSnapshot);
            createInitialCommentIDArray(dataSnapshot);
            mNumberOfCommentsAtPoll = (int) dataSnapshot.child(COMMENTS_LABEL).getChildrenCount();
            for (int i = 0; i < mNumberOfCommentsAtPoll; i++) {
                String commentID = (String) dataSnapshot.child(COMMENTS_LABEL).child(mCommentIDArrayList.get(i)).child("COMMENT").getValue();
                Log.v("COMMENT_ID", "The comment ID is " + commentID);
                String userID = (String) dataSnapshot.child(COMMENTS_LABEL).child(mCommentIDArrayList.get(i)).child("USER_ID").getValue();
                Log.v("USER_ID", "The user ID is " + userID);
                mCommentArrayList.add(0 , new Comments(mUserAvatar, userID, commentID));
                mCommentAdapter.notifyDataSetChanged();
            }

        }

在不滚动的情况下反转ListView顺序和显示

3 个答案: