Android RecyclerView实现简单的聊天界面

最新推荐文章于 2025-04-08 16:34:27 发布

sinat_41938770

最新推荐文章于 2025-04-08 16:34:27 发布

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本文链接：https://blog.youkuaiyun.com/sinat_41938770/article/details/97526342

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先上效果图：
在这里插入图片描述实现步骤：
1、首先编写activity_main.xml

<?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">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/msg_recycler_view"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <EditText
            android:id="@+id/input_text"
            android:layout_weight="1"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:hint="Type something here"
            android:maxLines="2"/>

        <Button
            android:id="@+id/send"
            android:text="send"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </LinearLayout>
</LinearLayout>

位于上方的RecyclerView的layout_height设置为1，占满除了按钮和输入框之外的全部空间

2、编写RecyclerView子项的布局，新建msg_item.xml

<?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="horizontal"
    android:padding="0dp">

    <LinearLayout
        android:id="@+id/left_layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="left"
        android:background="@drawable/message_left">


        <TextView
            android:id="@+id/left_msg"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_margin="10dp"
            android:textColor="#fff" />
    </LinearLayout>

    <TextView
        android:id="@+id/useless"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        />
    <LinearLayout
        android:id="@+id/right_layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/message_right">

        <TextView
            android:id="@+id/right_msg"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_margin="0dp" />
    </LinearLayout>


</LinearLayout>

这里在left_layout和right_layout之间插入了一个id为useless的TextView，并将这个TextView的layout_weight设置为1，是为了让right_layout能够靠右对齐，因为在horizontal的LinearLayout中，layout_gravity设置为right也是无效的，所以只能用这种方法使得right_layout靠右对齐。

3、定义消息的实体类Msg，新建Msg类

package com.example.uibestpractice;

public class Msg {
    public static final int TYPE_RECEIVED=0;
    public static final int TYPE_SENT=1;
    private String content;//信息内容
    private int type;//信息种类，是接受的信息或发出的信息

    public Msg(String content,int type){
        this.content=content;
        this.type=type;
    }

    public String getContent(){
        return content;
    }
    public int getType(){
        return type;
    }
}

4、定义Msg类的适配器，新建类MsgAdapter
MsgAdapter继承了RecyclerView.Adapter<MsgAdapter.ViewHolder>,需要重写3个方法：onCreateViewHolder,onBindViewHolder,getItemCount

package com.example.uibestpractice;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;

import androidx.recyclerview.widget.RecyclerView;

import java.util.List;

public class MsgAdapter extends RecyclerView.Adapter<MsgAdapter.ViewHolder> {
    private List<Msg> mMsgList;

    static class ViewHolder extends RecyclerView.ViewHolder{
        LinearLayout leftLayout;
        LinearLayout rightLayout;
        TextView leftMsg;
        TextView rightMsg;
        public ViewHolder(View view){
            super(view);
            leftLayout=(LinearLayout)view.findViewById(R.id.left_layout);
            rightLayout=(LinearLayout)view.findViewById(R.id.right_layout);
            leftMsg=(TextView) view.findViewById(R.id.left_msg);
            rightMsg=(TextView)view.findViewById(R.id.right_msg);
        }
    }
    public MsgAdapter(List<Msg> msgList){
        mMsgList=msgList;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent,int viewType){
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.msg_item,parent,false);//加载了msg_item布局
        final ViewHolder holder=new ViewHolder(view);
        holder.rightMsg.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int position=holder.getAdapterPosition();//getAdapterPosition()返回点击数据在Adapter中的位置
                Msg msg=mMsgList.get(position);
                Toast.makeText(view.getContext(),"you clicked view"+msg.getContent(),Toast.LENGTH_SHORT).show();
            }
        });
        return holder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder,int position){
        Msg msg=mMsgList.get(position);
        if(msg.getType()==Msg.TYPE_RECEIVED){//这里判断消息类型来决定由左边还是右边显示消息内容
            holder.leftLayout.setVisibility(View.VISIBLE);
            holder.rightLayout.setVisibility(View.INVISIBLE);
           holder.leftMsg.setText(msg.getContent());
     }
       else if(msg.getType()==Msg.TYPE_SENT){
           holder.rightLayout.setVisibility(View.VISIBLE);
           holder.leftLayout.setVisibility(View.INVISIBLE);
            holder.rightMsg.setText(msg.getContent());}
    }

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

5、修改MainActivity的代码。

package com.example.uibestpractice;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.graphics.Rect;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;

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

public class MainActivity extends AppCompatActivity {

    private List<Msg> msgList=new ArrayList<>();
    private EditText inputText;
    private Button send;
    private RecyclerView msgRecyclerView;
    private MsgAdapter adapter;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initMsgs();
        inputText=(EditText)findViewById(R.id.input_text);
        send=(Button)findViewById(R.id.send);
        msgRecyclerView=(RecyclerView)findViewById(R.id.msg_recycler_view);
        LinearLayoutManager layoutManager=new LinearLayoutManager(this);
        
        msgRecyclerView.addItemDecoration(new SpaceItemDecoration(50));//这里设置了RecyclerView子项的间隔
        msgRecyclerView.setLayoutManager(layoutManager);
        adapter=new MsgAdapter(msgList);
        msgRecyclerView.setAdapter(adapter);
        send.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String content=inputText.getText().toString();
                if(!"".equals(content)){//如果内容非空
                    Msg msg=new Msg(content,Msg.TYPE_SENT);
                    msgList.add(msg);
                    adapter.notifyItemInserted(msgList.size()-1);//调用适配器的notifyItemInserted()方法,用于通知适配器有新的数据插入
                    msgRecyclerView.scrollToPosition(msgList.size()-1);//将显示的数据定位到最后一行
                    inputText.setText("");
                }
            }
        });
    }
    public void initMsgs(){
        Msg msg1=new Msg("hello",Msg.TYPE_RECEIVED);
        msgList.add(msg1);
        Msg msg2=new Msg("hello.who is that",Msg.TYPE_SENT);
        msgList.add(msg2);

    }



    class SpaceItemDecoration extends RecyclerView.ItemDecoration {
        int mSpace;
        
        @Override
        public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
            super.getItemOffsets(outRect, view, parent, state);
            outRect.left = 0;
            outRect.right = 0;
            outRect.bottom =0;
            if (parent.getChildAdapterPosition(view) != 0) {
                outRect.top = mSpace;
            }
            else{
                outRect.top=0;
            }

        }

        public SpaceItemDecoration(int space) {
            this.mSpace = space;
        }
    }
}

其中定义了一个SpaceItemDecoration类，这个类继承自RecyclerView.ItemDecoration,重写其中的getItemOffsets后，就可以自己设置子项之间的间隔，单位为dp