我可以更新列表视图但如何？ [英] I can update the listview but how?

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问题描述

我有一个列表，并linkedhashmap.I我在主类的顶部以下行定义：

 列表＆LT;会话与GT; conversationsList =新的ArrayList＆LT;会话与GT;（）;
LinkedHashMap的＆LT;弦乐，会话与GT; conversationsMap =新的LinkedHashMap＆LT;弦乐，会话与GT;（）;

在的onCreate（）我从数据库将数据传输到HashMap的，然后转移映射值到ArrayList和我使用此ArrayList的适配器视图与下面几行：

  conversationsMap = _db.getAllConversations（）;
conversationsList =新的ArrayList＆LT;会话与GT;（conversationsMap.values​​（））;
conversationsAdapter =新ConversationsAdapter（这一点，conversationsList）;

但有件事我不understand.I可以更新这些行名单：

  conversationsMap.get（ROOM_NAME）.increaseUnread（）;
（（ConversationsAdapter）conversationsAdapter）.updateConversations（conversationsList）;

它的工作，但我没有更新 conversationsList 为什么这工作，我不明白？我刚刚更新 conversationsMap 不是 conversationsList 。任何人都可以，为什么这是工作向我解释？

在数据库处理程序 getAllConversations 方法：

 公共LinkedHashMap的＆LT;弦乐，会话与GT; getAllConversations（）{
    清单＆LT;会话与GT; conversationsList =新的ArrayList＆LT;会话与GT;（）;
    最终的LinkedHashMap＆LT;弦乐，会话与GT;对话=新的LinkedHashMap＆LT;弦乐，会话与GT;（）;
    字符串selectQuery =SELECT * FROM+ TABLE_CONVERSATIONS +ORDER BY ID ASC;        SQLiteDatabase分贝= this.getWritableDatabase（）;
        光标光标= db.rawQuery（selectQuery，NULL）;
        如果（cursor.moveToFirst（））{
            做{
                交谈交谈=新的对话（）;
                Conversation.setId（的Integer.parseInt（cursor.getString（0）））;
                Conversation.setSender（cursor.getString（1））;
                Conversation.setTo（cursor.getString（2））;
                Conversation.setName（cursor.getString（3））;
                Conversation.setBio（cursor.getString（4））;
                Conversation.setPicture（cursor.getString（5））;
                Conversation.setTime（的Integer.parseInt（cursor.getString（6）））;
                Conversation.setUnread（的Integer.parseInt（cursor.getString（7）））;
                conversations.put（cursor.getString（2），对话）;
            }而（cursor.moveToNext（））;
        }
        cursor.close（）;
        回到对话;
}

和这是会话类：

 类对话
{
    串发件人，于姓名，生物，图片;
    整数ID，时间，未读;
    公共会话（）{    }
    公共会话（INT ID，字符串发件人，字符串，字符串名称，生物字符串，字符串的画面，诠释时间，INT读）{
        this.sender =发送;
        this.to =到;
        this.id = ID;
        this.name =名称;
        this.bio =生物;
        this.picture =图片;
        this.time =时间;
        this.unread =未读;
    }    公共无效setSender（字符串发送）{
        this.sender =发送;
    }
    公共无效setTo（字符串）{
        this.to =到;
    }
    公共无效SETID（INT ID）{
        this.id = ID;
    }
    公共无效的setTime（INT时间）{
        this.time =时间;
    }
    公共无效setUnread（INT读）{
        this.unread =未读;
    }
    公共无效increaseUnread（）{
        this.unread ++;
    }
    公共无效setname可以（字符串名称）{
        this.name =名称;
    }
    公共无效setBio（字符串生物）{
        this.bio =生物;
    }
    公共无效setPicture（字符串图片）{
        this.picture =图片;
    }    公共字符串getSender（）{
        返回this.sender;
    }
    公共字符串会过（）{
        返回this.to;
    }
    公众诠释的getId（）{
        返回this.id;
    }
    公众诠释的getTime（）{
        返回this.time;
    }
    公众诠释getUnread（）{
        返回this.unread;
    }
    公共字符串的getName（）{
        返回this.name;
    }
    公共字符串getBio（）{
        返回this.bio;
    }
    公共字符串Getpicture中（）{
        返回this.picture;
    }
}


解决方案

你熟悉 notifyDataSetChanged（）和 notifyDataSetInvalidated（）在适配器的方法呢？数据集的每一个变化，这是用来在列表/方格被绘制后，你应该 updateConversations（conversationsList）之后调用这两个方法（可能是第一个）之一;

也：行新的ArrayList＆LT;会话＆GT;（conversationsMap.values​​（））; 应该做你的地图值的浅拷贝，检查的 //stackoverflow.com/questions/689370/java-collections-copy-list-i-dont-understand\">this堆栈线程获取更多信息。

I have a list and linkedhashmap.I am defining with following lines in top of main class:

List<Conversation> conversationsList=new ArrayList<Conversation>();
LinkedHashMap<String, Conversation> conversationsMap=new LinkedHashMap<String, Conversation>();

In onCreate() I am transferring data from db to hashmap then transferring map values to arraylist and I am using this arraylist in adapterview with following lines:

conversationsMap=_db.getAllConversations();
conversationsList=new ArrayList<Conversation>(conversationsMap.values());
conversationsAdapter=new ConversationsAdapter(this,conversationsList);

But there is something I don't understand.I can update the list with these lines:

conversationsMap.get(room_name).increaseUnread();
((ConversationsAdapter) conversationsAdapter).updateConversations(conversationsList);

It's working but I didn't update conversationsList why this is working I don't understand ? I just updated conversationsMap not the conversationsList. Can anyone explain to me why this is working ?

In db handler getAllConversations method:

public LinkedHashMap<String, Conversation> getAllConversations() {
    List<Conversation> conversationsList=new ArrayList<Conversation>();
    final LinkedHashMap<String, Conversation> conversations = new LinkedHashMap<String, Conversation>();
    String selectQuery = "SELECT * FROM " + TABLE_CONVERSATIONS+" order by id asc";

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        if (cursor.moveToFirst()) {
            do {
                Conversation Conversation = new Conversation();
                Conversation.setId(Integer.parseInt(cursor.getString(0)));
                Conversation.setSender(cursor.getString(1));
                Conversation.setTo(cursor.getString(2));
                Conversation.setName(cursor.getString(3));
                Conversation.setBio(cursor.getString(4));
                Conversation.setPicture(cursor.getString(5));
                Conversation.setTime(Integer.parseInt(cursor.getString(6)));
                Conversation.setUnread(Integer.parseInt(cursor.getString(7)));          
                conversations.put(cursor.getString(2),Conversation);
            } while (cursor.moveToNext());
        }
        cursor.close();
        return conversations;
}

And this is the Conversation class:

class Conversation
{
    String sender,to,name,bio,picture;
    Integer id,time,unread;
    public Conversation() {

    }
    public Conversation (int id,String sender,String to,String name,String bio,String picture,int time,int unread) {
        this.sender=sender;
        this.to=to;
        this.id=id;
        this.name=name;
        this.bio=bio;
        this.picture=picture;
        this.time=time;
        this.unread=unread;
    }

    public void setSender(String sender) {
        this.sender=sender;
    }
    public void setTo(String to) {
        this.to=to;
    }
    public void setId(int id) {
        this.id=id;
    }
    public void setTime(int time) {
        this.time=time;
    }
    public void setUnread(int unread) {
        this.unread=unread;
    }
    public void increaseUnread() {
        this.unread++;
    }
    public void setName(String name) {
        this.name=name;
    }
    public void setBio(String bio) {
        this.bio=bio;
    }
    public void setPicture(String picture) {
        this.picture=picture;
    }

    public String getSender() {
        return this.sender;
    }
    public String getTo() {
        return this.to;
    }
    public int getId() {
        return this.id;
    }
    public int getTime() {
        return this.time;
    }
    public int getUnread() {
        return this.unread;
    }
    public String getName() {
        return this.name;
    }
    public String getBio() {
        return this.bio;
    }
    public String getPicture() {
        return this.picture;
    }
}

解决方案

are you familiar with notifyDataSetChanged() and notifyDataSetInvalidated() methods in your adapter? after every change of data set which is used to be drawn in List/Grid you should call one of these two methods (probably first one) after updateConversations(conversationsList);

also: line new ArrayList<Conversation>(conversationsMap.values()); should do a shallow copy of your map values, check this stack thread about set copying for more info

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