如何在用戶滾動時顯示或隱藏日期文本視圖，就像whatsappchatandroidKotlin

嘿，我正在開發聊天應用程式。我從

如何實作其他功能。

1.由于我的串列太大，如何對我的日期進行分類以有效地顯示每天對話之間的日期。我剛剛添加了示例

2.如何在用戶滾動聊天時顯示日期滾動效果，就像whatsapp有昨天、今天和其他日期格式一樣。

3.在上面的串列示例中，添加了一個屬性，這意味著在群聊中添加了某人。在 whatsapp XYZ 中使用群組邀請鏈接加入。

我正在添加 whatsapp 的螢屏截圖

uj5u.com熱心網友回復：

盡管目前還不清楚是什么，你的意思是“這不是我的解決方案的作業”，我不知道這個問題是一個崩潰或空串列或...但檢查方法項的邏輯areItemsTheSame和areContentsTheSame是錯誤的：該方法areItemsTheSame用于檢查舊專案的身份是否等于新專案的身份。并且該方法areContentsTheSame用于檢查2項中的值是否相等

所以areContentsTheSame你只需要檢查id專案，因為其他東西是專案的值，你寫的東西areContentsTheSame沒有意義，因為你只是檢查專案的參考。所以把它改成這樣：

   private val MESSAGE_COMPARATOR = object : DiffUtil.ItemCallback<MM>() {
        override fun areItemsTheSame(oldItem: MM, newItem: MM): Boolean {
            return oldItem.id == newItem.id
        }

        override fun areContentsTheSame(oldItem: MM, newItem: MM): Boolean {
   return ((oldItem.added == newItem.added)
                    && (oldItem.addedTime == newItem.addedTime)
                    && (oldItem.sentAt == newItem.sentAt)
                    && (oldItem.text == newItem.text))            }

    }

uj5u.com熱心網友回復：

的持有人在哪里TimingViewHolder？

override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        if (holder is IncomingViewHolder) {
            holder.bindItem(getItem(position))
        } else if (holder is OutGoingViewHolder) {
            holder.bindItem(getItem(position))
        }
    }

[更新]

如何對我的日期進行分類以顯示每天對話之間的日期效率低下，因為我的串列太大了。

你想把對話UI做成這樣嗎？

如果是，您可以嘗試這種方法，為了清楚地解釋，我需要更改您的代碼。

資料類MessageEntry// 它來自服務器，它是原始資料

資料類Message// 它來自 MessageEntry

data class MessageEntry(
    val id: String? = null,
    val text: String? = null,
    val time: String? = null,
    val type: String? = null,
    val name: String? = null
)

確保類 Message 中沒有可為空的欄位

data class Message(
    val id: String,
    val text: String,
    val time: Date, // SDK's class
    val type: String, // It's better to use enum
    val name: String
)

//Raw data from Server
val mutableRawList = mutableListOf<MessageEntry>(
            MessageEntry(id = "1", text = "avc", time = "2021-10-08T15:34:00", type = "outgoing"),
            MessageEntry(id = "2", text = "dsds", time = "2021-10-08T15:36:00", type = "incoming"),
            MessageEntry(id = "3", type = "added", time = "2021-10-08T00:00:00", name = "ABC"),
            MessageEntry(id = "4", type = "added", time = "2021-10-07T15:50:00", name = "XYZ"),
            MessageEntry(id = "5", text = "asvc", time = "2021-10-07T15:46:00", type = "outgoing"),
            MessageEntry(id = "6", text = "asvc", time = "2021-10-07T15:46:00", type = "incoming"),
            MessageEntry(id = "6", text = "asvc", time = "2021-10-06T12:34:00", type = "outgoing"),
            MessageEntry(id = "8", text = "asvc", time = "2021-10-06T12:50:00", type = "incoming"),
            MessageEntry(id = "9", type = "added", time = "2021-10-06T12:46:00", name = "DEF")
        )

//I ignore the changing, MessageEntry.toMessage(), for an instance.
val mutableMessageList = mutableListOf<Message>(
            Message(id = "1", text = "avc", time = Date(2021-10-08T15:34:00), type = "outgoing"),
            Message(id = "2", text = "dsds", time = Date(2021-10-08T15:36:00), type = "incoming"),
            Message(id = "3", type = "added", time = Date(2021-10-08T00:00:00), name = "ABC"),
            Message(id = "4", type = "added", time = Date(2021-10-07T15:50:00), name = "XYZ"),
            Message(id = "5", text = "asvc", time = Date(2021-10-07T15:46:00), type = "outgoing"),
            Message(id = "6", text = "asvc", time = Date(2021-10-07T15:46:00), type = "incoming"),
            Message(id = "6", text = "asvc", time = Date(2021-10-06T12:34:00), type = "outgoing"),
            Message(id = "8", text = "asvc", time = Date(2021-10-06T12:50:00), type = "incoming"),
            Message(id = "9", type = "added", time = Date(2021-10-06T12:46:00), name = "DEF")
        )


private var lastMessageDate: Date? = null
...
val adapter = ConversationAdapter()
binding.conversationRecyclerView.adapter = adapter

// Need to change raw list MessageEntry to Message
// TODO, maybe you should change the related code of xxxAdapter, xxxViewHolder...

adapter.submitList(mutableMessageList.toFlatMessageItems)

有什么方法 toFlatMessageItems()

//Rebuild the message list from TreeMap<Date, List<Message>>
private fun MutableList<Message>.toFlatMessageItems() =
        mutableListOf<Message>().apply {
            val messageByDate = this@toFlatMessageItems.splitByDate()
            for (time in messageByDate.keys) {
                if (time != lastMessageDate) {
                    val dateHeaderItem = time.toMessage()
                    add(dateHeaderItem)                   
                }
                for (message in messageByDate.getValue(date)) {
                    val messageItem = message
                    add(messageItem)
                }
            }
            lastMessageDate = messageByDate.keys.lastOrNull()
        }

方法是什么splitByDate：

//Split the data by Date
private fun List<Message>.splitByDate() =
        TreeMap<Date, List<Message>>(Collections.reverseOrder()).apply {
            for (message in this@splitByDate) {
                val date = Message.time.noTime() // need you implement noTime() extension function, only the (year, month, day)
                var value = this[date] as MutableList<Message>?
                if (value == null) {
                    value = mutableListOf()
                    this[date] = value
                }

                value.add(message)
            }
        }

Kotlin 擴展函式

1. Change MessageEntry to Message

MessageEntry.toMessage() = Message(
    id = id ?: "", // or add an extension fuction to set empty string
    text = text ?: "",
    time = time.toDate(), // extension function from time string to Date, for spliting date
    type = type ?: "",
    name = name ?: ""
)

2. time(String or Long) to Date

String/Long.toDate(): Date {
 //TODO change string/long time format to Date
}

3. Date.noTime()

Date.toDate(): Date {
 //TODO, only year, month, day
}

4. Date.toMessage()

Date.toMessage() = Message(
    id = "",
    text = "",
    time = time, // the type of time is Date
    type = "added",
    name = ""
)

Note:

1. I didn't test it, just show you an idea.
2. Using MutableList or List, it's up to you.
3. Some extension functions need you to finish them.

標籤：安卓 科特林 安卓布局 android-recyclerview 安卓适配器

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