Android-一个小界面

Msg 消息类

public class Msg {

    public static final int TYPE_RECEIVED=0;
    public static final int TYPE_SENT=1;
    private String content;//消息内容
    private int type;
    public Msg(String content,int type){
        this.content=content;
        this.type=type;
    }
    public String getContent(){
        return content;
    }
    public int getType(){
        return type;
    }
    

}

MsgAdapter

public class MsgAdapter extends RecyclerView.Adapter<MsgAdapter.ViewHoler> {

    private List<Msg> mMsgList;

    static class ViewHoler extends RecyclerView.ViewHolder{
        LinearLayout leftLayout;
        LinearLayout rightLayout;
        TextView leftMsg;
        TextView rightMsg;
        public ViewHoler(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 ViewHoler onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate
                (R.layout.msg_item,parent,false);
        return new ViewHoler(view);
    }

    @Override
    public void onBindViewHolder(ViewHoler holder, int position) {
        Msg msg = mMsgList.get(position);
        if (msg.getType()==Msg.TYPE_RECEIVED){
            holder.leftLayout.setVisibility(View.VISIBLE);//显示
            holder.rightLayout.setVisibility(View.GONE);//隐藏
            holder.leftMsg.setText(msg.getContent());
        }else if (msg.getType()==Msg.TYPE_SENT){
            holder.rightLayout.setVisibility(View.VISIBLE);
            holder.leftLayout.setVisibility(View.GONE);
            holder.rightMsg.setText(msg.getContent());
        }
    }

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

}

MainActivity

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.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)){
                    Msg msg = new Msg(content, Msg.TYPE_SENT);
                    msgList.add(msg);
                    adapter.notifyItemInserted(msgList.size() - 1);//更新消息
                    msgRecyclerView.scrollToPosition(msgList.size() - 1);//定位到消息中最后一行
                    inputText.setText("");//清空
                }
            }
        });

    }

    private void initMsgs() {
        Msg msg1= new Msg("你好呀",Msg.TYPE_RECEIVED);
        msgList.add(msg1);
        Msg msg2 = new Msg("你好，你是谁呐",Msg.TYPE_SENT);
        msgList.add(msg2);
        Msg msg3= new Msg("我是小明同学，很高兴认识你~",Msg.TYPE_RECEIVED);
        msgList.add(msg3);
    }
}

msg_item.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="5dp">

    <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="4dp"
            android:textColor="#fff"/>

    </LinearLayout>

    <LinearLayout
        android:id="@+id/right_layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        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="2dp"
            android:textColor="#fff"/>

    </LinearLayout>

</LinearLayout>

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#d8e0e8">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/msg_recycler_view"
        android:layout_height="0dp"
        android:layout_width="match_parent"
        android:layout_weight="1"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <EditText
            android:id="@+id/input_text"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="请输入"
            android:maxLines="2"/>

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


</LinearLayout>