【GT-安卓应用开发之会话列表实现】

前言：今天休假回来的第一天，突然不知道该写点什么了，打开微信也找不到人聊天。。。无聊只好翻阅聊天记录，突然有了想法：今天写一下聊天记录的实现。

        我们的聊天记录是保存在本地的，利用安卓自带的轻量化数据库SQlite实现。设计思路是这样的，对于会话列表我们只保存与某一好友聊天的最后一条记录，而进入会话界面后再查询所有记录，也就是会话列表与聊天记录实际上是两个表，在这里我们一起来了解一下会话记录的实现。

        Step1，设计界面

        整个会话记录界面其实就是一个首部与一个列表组成，首部即朋友圈消息，列表则是展现会话记录，每一条会话记录由对方头像、昵称、最后一条消息以及时间构成，界面整体布局代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.administrator.parentproject.activity.AllWorkActivity">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="@dimen/dp_72"
        android:background="@drawable/text_bg">

        <TextView
            android:id="@+id/title_tv"
            android:layout_width="wrap_content"
            android:layout_height="@dimen/dp_72"
            android:layout_centerHorizontal="true"
            android:gravity="center"
            android:paddingTop="27dp"
            android:text="消息"
            android:textColor="@color/white"
            android:textSize="@dimen/text_14_sp" />
        <ImageView
            android:layout_width="@dimen/dp_20"
            android:layout_height="@dimen/dp_20"
            android:layout_alignParentRight="true"
            android:layout_marginRight="@dimen/dp_10"
            android:layout_marginTop="37dp"
            android:id="@+id/iv_friend"
            android:src="@drawable/friend"/>
    </RelativeLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/dp_5">
        <ImageView
            android:layout_width="40dp"
            android:layout_height="40dp"
            android:layout_marginLeft="@dimen/dp_20"
            android:id="@+id/iv_friend_circle"
            android:src="@drawable/friendcircle"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_toRightOf="@id/iv_friend_circle"
            android:layout_marginLeft="@dimen/dp_30"
            android:layout_marginTop="@dimen/dp_2"
            android:id="@+id/tv_friend_circle"
            android:textColor="#00DB00"
            android:text="班级圈"/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_toRightOf="@id/iv_friend_circle"
            android:layout_below="@id/tv_friend_circle"
            android:layout_marginLeft="@dimen/dp_30"
            android:layout_marginTop="@dimen/dp_2"
            android:text="语文老师 发表了一个动态"/>

    </RelativeLayout>

    <TextView
        android:layout_width="match_parent"
        android:layout_height="@dimen/dp_1"
        android:layout_marginTop="@dimen/dp_5"
        android:background="@color/lineColor" />
    <TextView
        android:layout_width="match_parent"
        android:layout_height="@dimen/dp_1"
        android:layout_marginTop="@dimen/dp_10"
        android:background="@color/lineColor" />
    <ListView
        android:id="@+id/ddjl_lv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginLeft="@dimen/dp_5"
        android:layout_marginRight="@dimen/dp_5"
        android:layout_marginTop="@dimen/dp_5"
        android:divider="@color/lineColor"
        android:dividerHeight="@dimen/dp_1"
        android:scrollbars="none" />
</LinearLayout>

        Step2，数据库设计

        在这里只分析会话记录表结构，我们假定会话表具备这几个字段

private static final String ID = "id";//唯一标识
private static final String SENDERID = "sender_id";//发送者id
private static final String ACCEPTERID = "accetter_id";//接受者id
private static final String GROUPID = "group_id";//群id（临时无用）
private static final String MSG = "msg";//消息
private static final String CREATETIME = "create_time";//时间
private static final String USERNAME = "user_name";//昵称
private static final String ICONURL = "icon_url";//头像地址

      创建数据表sql语句如下：

public static final String SQL_CREATE_TABLE = "create table " + TABLE_NAME + "(" +
        ID + " integer primary key," +
        SENDERID + " integer," +
        ACCEPTERID + " integer," +
        GROUPID + " varchar(50)," +
        MSG + " varchar(50)," +
        CREATETIME + " varchar(50)," +
        USERNAME + " varchar(50)," +
        ICONURL + " varchar(50)" +
        ")";

        由于我们设计的会话记录只保存最后一条，因此每次有新消息的时候需要删除之前的并写入新记录，并且考虑到实际情况，应该支持用户删除所有的会话记录，因此实现其删除、增加与查询方法，代码如下：

//保存
public void saveSession(int uid1,int uid2,ChatRecord cr){
    clearById(uid1,uid2);
    insert(cr);
}

public void clearById(int uid1,int uid2) {
    SQLiteDatabase db = dbHelper.getWritableDatabase();
    String sql = "delete from " + TABLE_NAME + " where ( sender_id = " + uid1+" and accetter_id = "+uid2+" ) or (sender_id = " + uid2+" and accetter_id = "+uid1+")";
    try {
        db.execSQL(sql);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        db.close();
    }
}

public void insert(ChatRecord cr) {
    SQLiteDatabase db = dbHelper.getWritableDatabase();
    ContentValues cv = new ContentValues();
    cv.put(SENDERID, cr.getSenderid());
    cv.put(ACCEPTERID, cr.getAccepterid());
    cv.put(GROUPID, cr.getGroupid());
    cv.put(MSG, cr.getMsg());
    cv.put(CREATETIME, cr.getCreatetime());
    cv.put(ICONURL, cr.getIconurl());
    cv.put(USERNAME, cr.getUsername());
    db.insert(TABLE_NAME, null, cv);
    db.close();
}

/*获取会话列表*/
public List<ChatRecord> queryAll(String userid) {
    SQLiteDatabase db = dbHelper.getReadableDatabase();
    List<ChatRecord> list = new ArrayList<>();
    Cursor cursor = db.rawQuery("select * from " + TABLE_NAME +" where (sender_id = "+userid+" or accetter_id = "+userid+") order by create_time desc",null);
    for (cursor.moveToFirst();!cursor.isAfterLast();cursor.moveToNext()) {
        ChatRecord history=new ChatRecord(cursor.getInt(cursor.getColumnIndex(SENDERID)),cursor.getInt(cursor.getColumnIndex(ACCEPTERID)),cursor.getString(cursor.getColumnIndex(MSG)),cursor.getString(cursor.getColumnIndex(CREATETIME)),cursor.getString(cursor.getColumnIndex(GROUPID)),cursor.getString(cursor.getColumnIndex(ICONURL)),cursor.getString(cursor.getColumnIndex(USERNAME)));
        list.add(history);
    }
    if (cursor != null) {
        cursor.close();
    }
    if (db != null) {
        db.close();
    }
    return list;
}

        需要注意的是，为防止删除后添加失败的情况，可以利用事务进行处理

        Step3，获取会话列表

        在第二步中，我们已经定义了获取会话列表的方法，为什么要传递一个Userid参数呢，之所以这么做是考虑到一台终端可能支持多个用户登录，如果不做处理会导致会话记录混乱，我们定义一个适配器，并利用这个适配器将数据渲染到界面（listView）中。

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userList = DBSessionDao.getInstance().queryAll(userId);
if(userList.size()==0){
    Toast.makeText(MyApplication.getContextObject(),"暂无数据",Toast.LENGTH_SHORT).show();
}
myListViewAdapter = new MyListViewAdapter(MyApplication.getContextObject(), userList, "session","session");
ltLv.setAdapter(myListViewAdapter);
ltLv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
        Log.e("icon111",userList.get(i).getIconurl());
        Intent intent = new Intent(MyApplication.getContextObject(), com.example.administrator.parentproject.chat.MainActivity.class);
        if((userList.get(i).getSenderid()+"").equals(userId)){
            intent.putExtra("toid", userList.get(i).getAccepterid()+"");
        }else{
            intent.putExtra("toid", userList.get(i).getSenderid()+"");
        }
        intent.putExtra("nickName", userList.get(i).getUsername());
        intent.putExtra("chatType", "1");
        intent.putExtra("avatar", userList.get(i).getIconurl());
        startActivity(intent);
    }
});