這個例子只是簡單的實現了單機版的聊天功能，自己跟自己聊，啦啦~~

主要還是展示RecyclerView控制元件的使用吧~

參考我之前寫的文章：

android中RecyclerView控制元件的使用

android中使用Nine-Patch圖片

1、先新增一個關於聊天內容的Chat.java類：

package com.example.chenrui.common;

public class Chat {

    private String targetUser;
    private String content;

    
 
public Chat(String targetUser, String content) {
        this.targetUser = targetUser;
        this.content = content;
    }

    public String getTargetUser() {
        return targetUser;
    }

    public void setTargetUser(String targetUser) {
        this.targetUser = targetUser;
    }

    
 
public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }
}

Chat.java這個類有兩個屬性：聊天物件和聊天內容

2、新增一個RecyclerView控制元件子項chat_item.xml，這個是實現了聊天內容項的展示：

<?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="wrap_content"
    android:orientation="vertical">

    <TextView
        android:id="@+id/chatText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/chat"
        android:gravity="center_vertical"
        android:text="TextView" />
</LinearLayout>

3、新增RecyclerView控制元件的介面卡ChatAdapter.java類：

package com.example.chenrui.app1;

import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;

import com.example.chenrui.common.Chat;

import java.util.List;

public class ChatAdapter extends RecyclerView.Adapter<ChatAdapter.ViewHolder> {

    private List<Chat> chatList;

    public ChatAdapter(List<Chat> chatList) {
        this.chatList = chatList;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.chat_item,viewGroup,false);
        ViewHolder viewHolder = new ViewHolder(view);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder viewHolder, int i) {
        Chat chat = chatList.get(i);
        viewHolder.chatText.setText(chat.getContent());
        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(viewHolder.chatText.getLayoutParams());
        if(chat.getTargetUser().equals("張三")) {
            params.gravity = Gravity.LEFT;
        } else {
            params.gravity = Gravity.RIGHT;
        }
        viewHolder.chatText.setLayoutParams(params);
    }

    @Override
    public int getItemCount() {
        return chatList.size();
    }

    static  class ViewHolder extends  RecyclerView.ViewHolder {

        TextView chatText;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            chatText = itemView.findViewById(R.id.chatText);
        }
    }
}

上面的程式碼，設定的是，如果聊天物件是張三，就把聊天內容顯示在列表的左側，否則就顯示在列表的右側。這個是模擬自己和別人對話的展示效果

4、最後就是主Activity了

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


    <android.support.v7.widget.RecyclerView
        android:id="@+id/chatList"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toTopOf="@+id/linearLayout3"
        app:layout_constraintTop_toTopOf="parent" />

    <LinearLayout
        android:id="@+id/linearLayout3"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:background="@android:color/darker_gray"
        android:orientation="horizontal"
        app:layout_constraintBottom_toTopOf="@+id/linearLayout4">

        <Spinner
            android:id="@+id/targetUser"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1" />

        <EditText
            android:id="@+id/chatContent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="3"
            android:inputType="textPersonName" />
    </LinearLayout>

    <LinearLayout
        android:id="@+id/linearLayout4"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:orientation="horizontal"
        app:layout_constraintBottom_toBottomOf="parent">

        <Button
            android:id="@+id/chatSubmit"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="發言" />
    </LinearLayout>

</android.support.constraint.ConstraintLayout>

MainActivity.java

package com.example.chenrui.app1;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;

import com.example.chenrui.common.Chat;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final RecyclerView chatList = findViewById(R.id.chatList);

        final List<Chat> chatData = new ArrayList<Chat>();
        final ChatAdapter chatAdapter = new ChatAdapter(chatData);
        chatList.setAdapter(chatAdapter);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        chatList.setLayoutManager(layoutManager);

        final Spinner targetUser = findViewById(R.id.targetUser);
        String[] data = {"張三","李四"};
        ArrayAdapter<String> adapter = new ArrayAdapter<String> (this,R.layout.support_simple_spinner_dropdown_item,data);
        targetUser.setAdapter(adapter);

        final EditText chatContent = findViewById(R.id.chatContent);

        Button chatSubmit = findViewById(R.id.chatSubmit);
        chatSubmit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(!chatContent.getText().toString().equals("")) {
                    String user = targetUser.getSelectedItem().toString();
                    chatData.add(new Chat(user, chatContent.getText().toString()));

                    chatAdapter.notifyItemInserted(chatData.size() - 1);
                    chatList.scrollToPosition(chatData.size() - 1);
                    chatContent.setText("");
                }
            }
        });
    }
}

顯示效果：