【Android】17.0 UI开发（八）——利用RecyclerView列表控件实现精美的聊天界面

1.0 首先新建一个项目，名叫：UIBestPractice，目录如下：

2.0 这里需要先准备两张图片，放在app\src\main\res\drawable-xhdpi目录下。

这里图片名称已经制作成为Nine-Patch图片，原本的名字没有“.9”字样。在目录下鼠标选中图片，右击，选择“”即可进入Nine-Patch图片编辑环境，

     

将可见是如下的画面,鼠标点击就会在边上添加黑色线条，意味着该线条所对应的边是允许变形的，按住shift键再点击，即可取消黑边，而且鼠标只有停在图片的四条边才可以操作，才会出现黑边，鼠标也才会变成成为双箭头图案：

可以看到右侧是拉伸时的形状预览。

保存即可，自动生成相同名字的后缀名为“.9.png”的图片。

3.0 在主活动界面设置布局，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"
    android:background="#ffffff"
    tools:context=".MainActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/msg_recycler_view"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toTopOf="@+id/linear"
        app:layout_constraintEnd_toEndOf="@+id/linear"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_weight="1" />

    <LinearLayout
        android:id="@+id/linear"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent">

        <EditText
            android:id="@+id/input_text"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="在这里键入内容"
            android:maxLines="2"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toLeftOf="@+id/send"/>

        <Button
            android:id="@+id/send"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:baselineAligned="false"
            android:text="发送"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintLeft_toRightOf="@+id/input_text"/>

    </LinearLayout>

</android.support.constraint.ConstraintLayout>

效果如下：

4.0 设置聊天适配器Msg.java：

package com.example.uibestpractice;

public class Msg {
    public static final int TYPE_RECEIVED = 0;
    public static final int TYPE_SENT = 1;
    private String content;
    private int type;

//    content 消息的内容
//    type 消息的类型
//    TYPE_RECEIVED 表示这是一条收到的信息
//    TYPE_SENT 表示这是一条发出的信息
    public Msg(String content,int type){
        this.content =content;
        this.type = type;
    }

    public String getContent(){
        return  content;
    }

    public int getType(){
        return type;
    }

}

5.0 MsgAdapter.java

package com.example.uibestpractice;

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.view.View;

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 viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.msg_item,viewGroup,false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(ViewHolder viewHolder, int i) {
        Msg msg = mMsgList.get(i);
        if (msg.getType() == Msg.TYPE_RECEIVED){
            //如果是收到的信息，则显示在左边的消息布局，将右边的消息布局隐藏
            viewHolder.leftLayout.setVisibility(View.VISIBLE);
            viewHolder.rightLayout.setVisibility(View.GONE);
            viewHolder.leftMsg.setText(msg.getContent());
        }else if (msg.getType() == Msg.TYPE_SENT){
            //如果是发出的信息，则显示在右边的消息布局，将左边的消息布局隐藏
            viewHolder.leftLayout.setVisibility(View.GONE);
            viewHolder.rightLayout.setVisibility(View.VISIBLE);
            viewHolder.rightMsg.setText(msg.getContent());
        }
    }

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

6.0 针对聊天显示进行布局设置，msg_item.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="wrap_content"
    android:padding="10dp">

    <LinearLayout
        android:id="@+id/left_layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/juxingqipao_left"
        android:gravity="left"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <TextView
            android:id="@+id/left_msg"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="left" />
    </LinearLayout>

    <LinearLayout
    android:id="@+id/right_layout"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/juxingqipao_right"
    android:gravity="right"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintTop_toTopOf="parent">

    <TextView
    android:id="@+id/right_msg"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:gravity="right" />
    </LinearLayout>
</android.support.constraint.ConstraintLayout>

7.0 主函数 ：MainActivity.java

package com.example.uibestpractice;

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

import java.util.ArrayList;
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();//初始化数据
        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.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, 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
                }
            }
        });
    }

    private void initMsgs() {
        Msg msg1 = new Msg("你好，张三", Msg.TYPE_RECEIVED);
        msgList.add(msg1);
        Msg msg2 = new Msg("你好，请问你是？", Msg.TYPE_SENT);
        msgList.add(msg2);
        Msg msg3 = new Msg("我是tuituitui的小仙女一只，很高兴认识你啊！", Msg.TYPE_RECEIVED);
        msgList.add(msg3);

    }
}

8.0 运行效果(真机)如下: