【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:

巴特西

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

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