Question

如何在WhatsApp中滚动ListView时如何在应用中显示日期？
为清晰起见，请参见下图：

当我滚动ListView时，日期显示在列表上如果你仍然不明白我的问题，请打开你的WhatsApp，去任何一个组＆amp;开始滚动：您将看到旧文本显示的日期。

Answer 1

            Calendar cal = Calendar.getInstance();
            SimpleDateFormat sdf = new SimpleDateFormat("dd-MMM-yyyy");
            String strDate = sdf.format(cal.getTime());
            today = new String[user.length()];
            yesterday = new String[user.length()];
            earlier = new String[user.length()];
            int t_counter = 0;
            int y_counter = 0;
            int e_counter = 0;
            for (int i = 0; i < user.length(); i++) {
                JSONObject c = user.getJSONObject(i);
                post = c.getString(TAG_TEXT).toString();
                date = c.getString(TAG_DATE).toString();
                time = c.getString(TAG_TIME).toString();

                if (strDate.equals(c.getString(TAG_DATE.toString()))) {
                    if (t_counter == 0) {
                        TextView tv = getTextView(lp, "Today");
                        myLayout.addView(tv);
                        t_counter = t_counter + 1;
                    }
                    View msgView = generateChatView(post, time);
                    myLayout.addView(msgView);

                }
                try {
                    temp = sdf.parse(c.getString(TAG_DATE.toString()));
                    c_date = sdf.parse(strDate);
                } catch (ParseException e) {
                    e.printStackTrace();
                }
                if (c_date.getTime() - temp.getTime() == 86400000) {
                    if (y_counter == 0) {
                        TextView tv = getTextView(lp, "Yesterday");
                        myLayout.addView(tv);
                        ;
                        y_counter = y_counter + 1;
                    }
                    View msgView = generateChatView(post, time);
                    myLayout.addView(msgView);
                }
                if (c_date.getTime() - temp.getTime() > 86400000) {
                    if (e_counter == 0) {
                        TextView tv = getTextView(lp, "Earlier");
                        myLayout.addView(tv);
                        e_counter = e_counter + 1;
                    }
                    View msgView = generateChatView(post, time);
                    myLayout.addView(msgView);
                }

            }

Answer 2

要显示此屏幕截图的日期，可以使用

val firstVisiblePosition = layoutManager.findFirstVisibleItemPosition()
if (getDateFromFirebaseTime(messageArrayList[firstVisiblePosition].timestamp.toString().toLong()).isNotEmpty()) {
                tvDay.visibility = View.VISIBLE
                tvDay.text = getDateFromFirebaseTime(messageArrayList[firstVisiblePosition].timestamp.toString().toLong())
            } else {
                tvDay.visibility = View.GONE
            }

我在这里所做的是获取RecyclerView列表中第一个可见项的索引，然后从该索引中获取消息的时间戳，并使用函数{{1将其显示在 TextView tvDay }}

在ScrollListener的RecyclerView的this方法中添加了上面的代码

getDateFromFirebaseTime()

注意：在override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) { super.onScrolled(recyclerView, dx, dy) Log.d("scroll", "scrolling") //added here }可用的XML中添加了tvDay。 RecyclerView和RecyclerView是tvDay和RelativeLayout的子元素，它们被设置为tvDay，以使其居中。

如何在滚动ListView时显示类似Whatsapp的日期

2 个答案: