<?xml version="1.0" encoding="utf-8"?>

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

     android:orientation="vertical" android:layout_width="match_parent"

     android:layout_height="match_parent">

     <TextView

         android:layout_width="match_parent"

         android:layout_height="wrap_content"

         android:id="@+id/tv_control"

         android:layout_marginTop="20dp"

         android:gravity="center"

         android:text="聊天室效果，点击添加聊天记录，长按删除聊天记录"

         />

     <LinearLayout

         android:orientation="vertical"

         android:layout_width="match_parent"

         android:layout_height="200dp">

         <TextView

             android:layout_width="match_parent"

             android:layout_height="match_parent"

             android:id="@+id/tv_bbs"

             android:layout_marginTop="20dp"

             android:scrollbars="vertical"

             android:textColor="@color/text_color"

             android:textSize="17sp"/>

     </LinearLayout>

 </LinearLayout>

 package com.example.alimjan.hello_world;

 import android.app.Activity;

 import android.content.Context;

 import android.content.DialogInterface;

 import android.content.Intent;

 import android.os.Bundle;

 import android.support.annotation.Nullable;

 import android.support.v7.app.AppCompatActivity;

 import android.text.format.DateUtils;

 import android.text.method.ScrollingMovementMethod;

 import android.view.Gravity;

 import android.view.View;

 import android.widget.TextView;

 /**

  * Created by alimjan on 6/30/2017.

  */

 public class class__2_3_1_2 extends AppCompatActivity implements DialogInterface.OnClickListener,View.OnLongClickListener, View.OnClickListener {

     private TextView tv_bbs,tv_control;

     @Override

     protected void onCreate(@Nullable Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         setContentView(R.layout.code_2_3_1_2);

         tv_control = (TextView) findViewById(R.id.tv_control);

         tv_control.setOnClickListener(this);

         tv_control.setOnLongClickListener(this);

         tv_bbs = (TextView) findViewById(R.id.tv_bbs);

         tv_bbs.setOnClickListener(this);

         tv_bbs.setOnLongClickListener(this);

         tv_bbs.setGravity(Gravity.LEFT|Gravity.BOTTOM);

         tv_bbs.setLines(8);

         tv_bbs.setMaxLines(8);

         tv_bbs.setMovementMethod(new ScrollingMovementMethod());

     }

     private String[] mChatStr={"你吃饭了吗honey？","今天天气超级热！你们那儿呢？","我中奖啦！","走不走看电影~","你在干什么？"};

     public static void startHome(Context mContext) {

         Intent intent = new Intent(mContext, class__2_3_1_2.class);

         mContext.startActivity(intent);

     }

     @Override

     public void onClick(DialogInterface dialog, int which) {

     }

     @Override

     public boolean onLongClick(View v) {

         if(v.getId() == R.id.tv_control || v.getId() == R.id.tv_bbs){

             tv_bbs.setText("");

         }

         return true;

     }

     @Override

     public void onClick(View v) {

         if(v.getId() == R.id.tv_control || v.getId() == R.id.tv_bbs){

             int random = (int) ((Math.random()*10)%5);

             String newstr = String.format("%s\n%s%s",tv_bbs.getText().toString(), DateUtil.getCurDateStr(),mChatStr[random]);

             tv_bbs.setText(newstr);

         }

     }

 }