前言

1. 简单定义Msg类

package com.bytedance.sjtu.msgclass Msg(val msg: String, val msgType: Int) {companion object {const val SEND = 0 //定义消息类型，0为发送， 1为收取const val GET = 1}}

2. ChatActivity

class ChatActivity : AppCompatActivity() {private val tvName : TextView by lazy {findViewById(R.id.tvName) }private val recyclerView : RecyclerView by lazy {findViewById(R.id.recyclerView) }private val editMsg : EditText by lazy {findViewById(R.id.editMsg) }private val sendMsg : TextView by lazy {findViewById(R.id.sendMsg) }override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContentView(R.layout.activity_chat)window.addFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS) //设置隐藏状态栏val msgList = mutableListOf(Msg( "你好", Msg.SEND),Msg( "嗯嗯", Msg.GET),Msg( "How are you?", Msg.SEND),Msg( "I'm fine, thanks.", Msg.GET),)recyclerView.layoutManager = LinearLayoutManager(this)recyclerView.adapter = ChatAdapter(this, msgList) //简单初始化聊天信息editMsg.addTextChangedListener(object : TextWatcher {//监听消息输入框的输入状态override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {}override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {}override fun afterTextChanged(p0: Editable?) {if (editMsg.text.isNotEmpty()) {sendMsg.setTextColor(resources.getColor(R.color.silver_red)) //输入框有内容，发布字体变红色} else {sendMsg.setTextColor(resources.getColor(R.color.light_gray)) //否则变灰色}}})sendMsg.setOnClickListener {if (editMsg.text.isNotEmpty()) {val msgType = Random.nextInt(0, 2) //随机生成 0 和 1msgList.add(Msg(editMsg.text.toString(), msgType)) //模拟“发送消息”和“接收消息”recyclerView.adapter = ChatAdapter(this, msgList) //更新适配器数据recyclerView.scrollToPosition(msgList.size - 6)recyclerView.smoothScrollBy(0, 1000, DecelerateInterpolator(), 1500) //平滑刷新消息界面，有bugeditMsg.text = null //输入框置空}}}}

3. activity_chat.XML布局文件

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="/apk/res/android"xmlns:app="/apk/res-auto"xmlns:tools="/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"android:fitsSystemWindows="true"tools:context=".msg.ChatActivity"><FrameLayoutandroid:layout_width="match_parent"android:layout_height="50dp"><ImageViewandroid:id="@+id/imgBack"android:layout_width="50dp"android:layout_height="50dp"android:layout_marginStart="5dp"android:padding="15dp"android:src="@drawable/ic_back" /><TextViewandroid:id="@+id/tvName"android:layout_width="wrap_content"android:layout_height="match_parent"android:layout_gravity="center"android:gravity="center"android:text="name"android:textSize="20sp"android:textColor="@color/black" /><Viewandroid:layout_width="match_parent"android:layout_height="0.1dp"android:layout_gravity="bottom"android:background="@color/light_gray" /></FrameLayout><androidx.recyclerview.widget.RecyclerViewandroid:id="@+id/recyclerView"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"android:background="#EAEDF6" /><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"><EditTextandroid:id="@+id/editMsg"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:layout_margin="10dp"android:padding="12dp"android:hint="输入..."android:textSize="18sp"android:background="@drawable/bg_round_rectangle_2" /><TextViewandroid:id="@+id/sendMsg"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="bottom"android:layout_marginEnd="10dp"android:layout_marginBottom="10dp"android:text="发送"android:textStyle="bold"android:textSize="20sp"android:textColor="@color/light_gray" /></LinearLayout></LinearLayout>

4. ChatAdapter适配器

class ChatAdapter(private val mContext: Context,private val msgList: MutableList<Msg>): RecyclerView.Adapter<ChatAdapter.ViewHolder>() {override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {val view = LayoutInflater.from(parent.context).inflate(R.layout.layout_chat_item_view, parent, false)return ViewHolder(view)}override fun onBindViewHolder(holder: ViewHolder, position: Int) {//绑定数据if (msgList[position].msgType == Msg.SEND) {//发出的消息holder.msgSend.text = msgList[position].msgholder.msgSend.visibility = View.VISIBLEholder.msgGet.visibility = View.GONE} else if (msgList[position].msgType == Msg.GET) {//收到的消息holder.msgGet.text = msgList[position].msgholder.msgGet.visibility = View.VISIBLEholder.msgSend.visibility = View.GONE}holder.itemView.setOnClickListener {// Toast.makeText(mContext, "You click msg $position", Toast.LENGTH_SHORT).show()}}override fun getItemCount(): Int {return msgList.size}class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {val msgSend : TextView = itemView.findViewById(R.id.msgSend)val msgGet : TextView = itemView.findViewById(R.id.msgGet)}}

5. layout_chat_item_view.XML布局文件

其中TextView的background应该设置为9-Patch文件，也就是.9.png文件，可以自己制作。

<?xml version="1.0" encoding="utf-8"?><FrameLayout xmlns:android="/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginHorizontal="10dp"><TextViewandroid:id="@+id/msgSend"android:layout_width="wrap_content"android:layout_height="wrap_content"android:paddingBottom="25dp"android:layout_gravity="end"android:text="这是发送的消息"android:textSize="18sp"android:textColor="@color/white"android:background="@drawable/bg_bubble_1_50" /><TextViewandroid:id="@+id/msgGet"android:gravity="start"android:visibility="visible"android:background="@drawable/bg_bubble_2_50"android:layout_width="wrap_content"android:layout_height="wrap_content"android:paddingBottom="25dp"android:text="这是收到的消息"android:textSize="18sp"android:textColor="@color/black" /></FrameLayout>