EChat(简易聊天项目)七、保存聊天记录

（二）使用LitePal数据库保存用户聊天记录
分析：
首先需要进行数据库的创建，需要一张表（自定义类HistoryChat）来保存聊天记录信息，
其次，需要将聊天的记录增加到数据库对应记录中；最后需要对数据库中对应的用户和对应的聊天记录查询，设置查询条件约束（其中包含了对用户和聊天对象和聊天记录的绑定，如点击不同好友是显示的不同的历史信息）等等。
 
主要部分代码实现：
① 由于之前已有用于存储用户名和密码的LitePal数据库，直接添加对应部分代码
litepal.xml<mapping class="com.example.androidlogin.HistoryChat"></mapping>
 
新建一个类HistoryChat

/*
聊天记录历史记录实体类
*/
public class HistoryChat extends DataSupport{
String sendtext;
String receivetext;
String Sender;
String Receiver;
String time;

public String getSender() {
return Sender;
}

public void setSender(String sender) {
Sender = sender;
}

public String getReceiver() {
return Receiver;
}

public void setReceiver(String receiver) {
Receiver = receiver;
}

public String getReceivetext() {
return receivetext;
}

public void setReceivetext(String receivetext) {
this.receivetext = receivetext;
}

public String getSendtext() {
return sendtext;
}

public void setSendtext(String sendtext) {
this.sendtext = sendtext;
}

public String getTime() {
return time;
}

public void setTime(String time) {
this.time = time;
}

}

 
② 新建一个用于展示聊天记录的HistoryActivitypublic class HistoryActivity extends AppCompatActivity {

private List<Msg> msgList = new ArrayList<>();
public String username;
public String receiver;
private RecyclerView msgRecyclerView;
private MsgAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.history_layout);

Intent intent = getIntent();
username = intent.getStringExtra("username");
receiver = intent.getStringExtra("receiver");

initMsg();//写入历史记录
msgRecyclerView = (RecyclerView) findViewById(R.id.msg_recycle_view);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
msgRecyclerView.setLayoutManager(layoutManager);
adapter = new MsgAdapter(msgList);
msgRecyclerView.setAdapter(adapter);

}

//数据库查找对应聊天记录
public void initMsg() {
List<HistoryChat> historylist = DataSupport.where("Sender = ? and Receiver = ?",username,receiver).find(HistoryChat.class);
for (HistoryChat historychat : historylist){
if (historychat.getReceivetext() == null) {
String text = historychat.getSendtext();
String time = historychat.getTime();
Msg msg = new Msg(text + "--" + time, null, Msg.TYPE_SENT);
msgList.add(msg);
}
if(historychat.getReceivetext() != null){
String text1 = historychat.getReceivetext();
String time1 = historychat.getTime();
Msg msg1 = new Msg(text1 + " --" + time1, null, Msg.TYPE_RECEIVED);
msgList.add(msg1);
}

}
}
}
③ 新建的history_layout.xml中添加代码（即原有聊天界面去掉下方发送栏即可） <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="#d8e0e8">

<android.support.v7.widget.RecyclerView
android:id="@+id/msg_recycle_view"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"/>

</LinearLayout>
 
④在MessageActivity中进行代码修改，发送消息和设置初始消息部分添加了将数据增加到数据库中的操作/*
选择好友后进入的聊天界面
*/

public class MessageActivity extends AppCompatActivity {

private List<Msg> msgList = new ArrayList<>();
private EditText inputText;
private Button send;
private Button more;
public String username;
public String receiver;

private ImageView imageView;

//调用系统相册-选择图片
private static final int IMAGE = 1;

private RecyclerView msgRecyclerView;
private MsgAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

Intent intent = getIntent();
username = intent.getStringExtra("username");
receiver = intent.getStringExtra("receiver");

//将正在创建的活动添加到活动管理器中
ActivityCollector.addActivity(this);
setContentView(R.layout.message__layout);

Connector.getDatabase();

initMsg();//初始化消息数据
//新建LitePal数据库

inputText = (EditText) findViewById(R.id.input_text);
send = (Button) findViewById(R.id.send);
msgRecyclerView = (RecyclerView) findViewById(R.id.msg_recycle_view);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
msgRecyclerView.setLayoutManager(layoutManager);
adapter = new MsgAdapter(msgList);
msgRecyclerView.setAdapter(adapter);

send.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String content = inputText.getText().toString();
if (!"".equals(content)){
Msg msg = new Msg(content,null,Msg.TYPE_SENT);
msgList.add(msg);
adapter.notifyItemInserted(msgList.size() - 1);//当有新消息时，刷新RecyclerView中的显示
msgRecyclerView.scrollToPosition(msgList.size() - 1);//将RecyclerView定位到最后一行
inputText.setText("");//清空输入框中的内容
//获取系统当前时间
SimpleDateFormat format = new SimpleDateFormat("yyyy.MM.dd. HH:mm:ss");
Date date = new Date(System.currentTimeMillis());
String time = format.format(date);

//存储数据到数据库
HistoryChat historyChat = new HistoryChat();
historyChat.setReceiver(receiver);
historyChat.setSender(username);
historyChat.setSendtext(content);
historyChat.setTime(time);
historyChat.save();
}
}
});

...

private void initMsg() {

//获取系统当前时间
SimpleDateFormat format = new SimpleDateFormat("yyyy.MM.dd. HH:mm:ss");
Date date = new Date(System.currentTimeMillis());
String time = format.format(date);

Msg msg1 = new Msg("Hello guy.",null, Msg.TYPE_RECEIVED);
msgList.add(msg1);
HistoryChat historyChat = new HistoryChat();
historyChat.setReceiver(receiver);
historyChat.setSender(username);
historyChat.setReceivetext("Hello guy.");
historyChat.setTime(time);
historyChat.save();

Msg msg2 = new Msg("Hello.Who is that?",null, Msg.TYPE_SENT);
msgList.add(msg2);
HistoryChat historyChat1 = new HistoryChat();
historyChat1.setReceiver(receiver);
historyChat1.setSender(username);
historyChat1.setSendtext("Hello.Who is that?");
historyChat1.setTime(time);
historyChat1.save();

Msg msg3 = new Msg("This is Tom. Nice talking to you.",null,Msg.TYPE_RECEIVED);
msgList.add(msg3);
HistoryChat historyChat2 = new HistoryChat();
historyChat2.setReceiver(receiver);
historyChat2.setSender(username);
historyChat2.setReceivetext("This is Tom. Nice talking to you.");
historyChat2.setTime(time);
historyChat2.save();
}

...
}


 
运行效果（先选择聊天对象）