Android新闻客户端案列

来源：互联网发布：淘宝仿真左轮编辑：程序博客网时间：2024/04/30 02:06

前言：这是一个仿照网易客户端模仿的简易新闻客户端案例，主要是为了对知识点更深入的了解和整合

1 需求

第一次进入新闻客户端需要请求服务器获取新闻数据，做listview的展示，为了第二次再次打开新闻客户端时能快速显示新闻，需要将数据缓存到数据库中，下次打开可以直接去数据库中获取新闻直接做展示。

2 程序流程

1.写布局listview

2.找到listview，设置条目的点击事件。

3.获取数据提供给listview做展示。       //☆☆☆

4.创建一个Adapter继承BaseAdapter,封装4个方法，需要接收获取的新闻数据

5.将adapter设置给listview。   3

3 用到的知识点

1 Handler机制 2 ListView 3 BaseAdapter(适配器） 4 SqliteOpenHelper 数据库操作 5 自定义组件（MyImageView）
6 数据传输json 等

4 服务器端

用到的jar包 java-json.jar

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package com.itheima.service;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.json.JSONArray;
import org.json.JSONObject;
import com.itheima.service.bean.NewsBean;
import com.itheima.service.dao.NewsDao;
public class GetNewsServlet extends HttpServlet {
public GetNewsServlet() {
super();
}
public void destroy() {
super.destroy();
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
/*
新闻请求路径：
// http://192.168.1.103:8080/itheima72/servlet/GetNewsServlet
json格式：
用{}包含的是一个JsonObject 用[]包含的是一个JsonArray
*/
try{
//从数据库获取新闻数据
ArrayList<NewsBean> news = NewsDao.getNews();
//将list中的数据封装成一个jsonArray对象
JSONArray jsonArray = new JSONArray();
for (NewsBean newsBean : news) {
JSONObject newsJson = new JSONObject();
newsJson.put("id", newsBean.getId());
newsJson.put("title", newsBean.getTitle());
newsJson.put("des", newsBean.getDes());
newsJson.put("icon_url", newsBean.getIcon_url());
newsJson.put("news_url", newsBean.getNews_url());
newsJson.put("type", newsBean.getType());
newsJson.put("time", newsBean.getTime());
newsJson.put("comment", newsBean.getComment());
jsonArray.put(newsJson);
}
//将jsonArray对象作为一个json对象，用来返回给客户端
JSONObject allNewsJson = new JSONObject();
allNewsJson.put("newss", jsonArray);
response.getOutputStream().write(allNewsJson.toString().getBytes("gbk"));
}catch (Exception e) {
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
public void init() throws ServletException {
}
}

5 Android 客户端
5.1 强新闻数据封装成NewsBean
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public class NewsBean {
 public String title;
 public String des;
 public String news_url;
 public int id;
 public int comment;
 public int type;
 public String time;
 public String icon_url;
}

5.2 数据库的操作
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package com.example.dao;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
* Created by ls on 2016/9/24.
*/
public class NewsOpenHelper extends SQLiteOpenHelper {


 public NewsOpenHelper(Context context) {
 super(context, "news", null, 1);
 }

 @Override
 public void onCreate(SQLiteDatabase db) {
 db.execSQL("create table news (_id integer primary key ,title varchar(200),des varchar(300),icon_url varchar(200),news_url varchar(200)," +
 " type integer , time varchar(100),comment integer)");
 }

 @Override
 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

 }
}
DAO 层
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package com.example.dao;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import com.example.bean.NewsBean;
import java.util.ArrayList;
public class NewsDaoUtils {
 private NewsOpenHelper openHelper;
 public NewsDaoUtils(Context context) {
 //创建一个帮助类对象
 openHelper = new NewsOpenHelper(context);
 }
 //删除数据库中缓存的旧数据
 public void delete() {
 //通过帮助类对象获取数据库操作对象
 SQLiteDatabase database = openHelper.getReadableDatabase();
 database.delete("news", null, null);
 database.close();
 }
 //向数据库中添加新闻数据
 public void saveNews(ArrayList<NewsBean> list) {
 //通过帮助类对象获取数据库操作对象
 SQLiteDatabase db = openHelper.getReadableDatabase();
 for (NewsBean newsBean:list) {
 ContentValues values = new ContentValues();
 values.put("_id", newsBean.id);
 values.put("title", newsBean.title);
 values.put("des", newsBean.des);
 values.put("icon_url", newsBean.icon_url);
 values.put("news_url", newsBean.news_url);
 values.put("type", newsBean.type);
 values.put("time", newsBean.time);
 values.put("comment", newsBean.comment);
 db.insert("news", null, values);
 }
 db.close();
 }

 //从数据库中获取缓存的新闻数据
 public ArrayList<NewsBean> getNews() {
 ArrayList<NewsBean> list = new ArrayList<>();
 //通过帮助类对象获取数据库操作对象
 SQLiteDatabase db = openHelper.getReadableDatabase();
 Cursor cursor = db.rawQuery("select * from news ", null);
 while (cursor.moveToNext()) {
 NewsBean newsBean = new NewsBean();
 //1 根据列名获取列索引
 // newsBean. id = cursor.getInt(cursor.getColumnIndex("_id"));

 //2 根据列的索引直接读取 比如第0列的值
 newsBean. id = cursor.getInt(0);
 newsBean. title = cursor.getString(1);
 newsBean. des = cursor.getString(2);
 newsBean. icon_url = cursor.getString(3);
 newsBean. news_url = cursor.getString(4);
 newsBean. type = cursor.getInt(5);
 newsBean. time = cursor.getString(6);
 newsBean. comment = cursor.getInt(7);

 list.add(newsBean);
 }
 db.close();
 cursor.close();
 return list;
 }

}
5.3 适配器
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package com.example.adapter;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import com.example.bean.NewsBean;
import com.example.newslist.R;
import com.example.view.MyImageView;
import java.util.ArrayList;
public class NewsAdapter extends BaseAdapter {
 Context context;
 ArrayList<NewsBean> list;
 //通过构造方法接收要显示的新闻类数据集合
 public NewsAdapter(Context context) {
 this.context = context;
 }
 public NewsAdapter(Context context, ArrayList<NewsBean> list) {
 this.list = list;
 this.context = context;
 }
 @Override
 public Object getItem(int position) {
 return list.get(position);
 }

 @Override
 public long getItemId(int position) {
 return position;
 }

 @Override
 public int getCount() {
 return list.size();
 }

 @Override
 public View getView(int position, View convertView, ViewGroup parent) {
 View view = null;
 //1 复用convertView 优化listView ,创建一个view作为getView的返回值，用来显示条目
 if (convertView != null) {
 view =convertView;
 }else{
 //context:上下文 resource:要转换成view对象的layout的id;
 //root:将layout用root(ViewGroup) 作为codify的返回值，一般传null

 //通过LayoutInflater将布局转换成view对象
 // view = LayoutInflater.from(context).inflate(R.layout.item_news_layout, null);
 //通过context获取系统服务得到一个LayoutInflater,通过LayoutInflater将一个布局转换成view对象
 LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
 view = inflater.inflate(R.layout.item_news_layout,null);
 }
 //获取view上的子控件对象
 MyImageView myImageView = (MyImageView)view.findViewById(R.id.item_img_icon);
 TextView title = (TextView)view.findViewById(R.id.item_tv_title);
 TextView des = (TextView)view.findViewById(R.id.item_tv_des);
 TextView comment = (TextView)view.findViewById(R.id.item_tv_comment);
 TextView type = (TextView)view.findViewById(R.id.item_tv_type);
 //获取positon位置条目，对应的list集合中的新闻数据，Bean对象
 NewsBean newsBean = list.get(position);
 myImageView.setImageUrl(newsBean.icon_url);
 title.setText(newsBean.title);
 des.setText(newsBean.des);
 comment.setText("评论："+newsBean.comment);

 //0头条 1娱乐 2 新闻
 switch (newsBean.type) {
 case 0:
 type.setText("头条");
 break;
 case 1:
 type.setText("娱乐");
 break;
 case 2:
 type.setText("新闻");
 break;
 default:
 break;
 }
 return view;
 }
}

5.4 请求服务端数据，并封装成List<NewsBean>返回这一步也是最关键的
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package com.example.utils;
import android.content.Context;
import com.example.bean.NewsBean;
import com.example.dao.NewsDaoUtils;
import org.json.JSONArray;
import org.json.JSONObject;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
public class NewsUtils {
 public static String newsPath_url = "http://192.168.1.106:8080/itheima74/servlet/GetNewsServlet";

 //封装新闻的假数据到list中返回
 public static ArrayList<NewsBean> getAllNewsForNetWork(Context context) {
 ArrayList<NewsBean> list = new ArrayList<>();
 try {
 //请求服务器获取新闻数据
 URL url = new URL(newsPath_url);
 HttpURLConnection connection = (HttpURLConnection) url.openConnection();
 //设置连接的方式和超时
 connection.setRequestMethod("GET");
 connection.setConnectTimeout(2000);
 //获取请求的响应码
 int code = connection.getResponseCode();

 if (code == 200) {
 //获取请求到的流信息
 InputStream is = connection.getInputStream();
 String result = StreamUtils.stream2String(is);
 //2解析获取的新闻数据到list集合中
 JSONObject jsonObject = new JSONObject(result);//将一个字符串封装成一个json对象
 JSONArray jsonArray = jsonObject.getJSONArray("newss");//获取json_root中newss作为jsonArray对象
 for (int i = 0; i < jsonArray.length(); i++) {//循环遍历新闻array
 JSONObject news_json = jsonArray.getJSONObject(i);//获取一条新闻的json
 NewsBean newsBean = new NewsBean();
 newsBean.id = news_json.getInt("id");
 newsBean.comment = news_json.getInt("comment");//评论数
 newsBean.type = news_json.getInt("type");//新闻的类型，0 ：头条 1 ：娱乐 2.体育
 newsBean.time = news_json.getString("time");
 newsBean.des = news_json.getString("des");
 newsBean.title = news_json.getString("title");
 newsBean.news_url = news_json.getString("news_url");
 newsBean.icon_url = news_json.getString("icon_url");

 list.add(newsBean); //封装成对象添加到list集合中
 }
 //清楚数据库中的旧的数据，把新的数据缓存到数据库中
 new NewsDaoUtils(context).delete();
 new NewsDaoUtils(context).saveNews(list);
 }
 } catch (Exception e) {
 e.printStackTrace();
 }
 return list;
 }
 //从数据库中获取上次缓存的数据
 public static ArrayList<NewsBean> getAllNewsFromDB(Context context) {
 return new NewsDaoUtils(context).getNews();
 }
}
中间用到了一个工具类流转字符串
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package com.example.utils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

/**
* Created by ls on 2016/9/24.
*/
public class StreamUtils {
 public static String stream2String(InputStream is) {

 //返回一个字节数组写入流
 ByteArrayOutputStream bos = new ByteArrayOutputStream();
 byte[] buffer = new byte[1024];
 int size = 0;
 String retValue = "";
 try {
 while ((size = is.read(buffer)) != -1) {
 bos.write(buffer, 0, size);
 }
 retValue = new String(bos.toByteArray(), "gbk");
 } catch (IOException e) {
 e.printStackTrace();
 }
 return retValue;
 }
}

5.5 自定义处理图片的组件
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package com.example.view;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.widget.ImageView;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
/**
* Created by ls on 2016/9/24.
* 自定义显示图片的组件
*/
public class MyImageView extends ImageView {

 public MyImageView(Context context) {
 super(context);
 }

 public MyImageView(Context context, AttributeSet attrs) {
 super(context, attrs);
 }

 public MyImageView(Context context, AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);
 }

 private Handler handler = new Handler(){
 @Override
 public void handleMessage(Message msg) {
 Bitmap bitmap =(Bitmap) msg.obj;
 MyImageView.this.setImageBitmap(bitmap);
 }
 };
 public void setImageUrl(final String url_str) {
 new Thread(new Runnable() {
 @Override
 public void run() {
 try {
 URL url = new URL(url_str);
 HttpURLConnection connection = (HttpURLConnection)url.openConnection();
 connection.setRequestMethod("GET");
 connection.setConnectTimeout(2000);
 int code = connection.getResponseCode();
 if (code == 200) {
 InputStream is=connection.getInputStream();
 Bitmap bitmap = BitmapFactory.decodeStream(is);
 Message message = Message.obtain();
 message.obj = bitmap;
 handler.sendMessage(message);
 }
 } catch (Exception e) {
 e.printStackTrace();
 }
 }
 }).start();
 }
}
5.6 MainActivity
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package com.example.newslist;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import com.example.adapter.NewsAdapter;
import com.example.bean.NewsBean;
import com.example.utils.NewsUtils;

import java.util.ArrayList;
public class MainActivity extends Activity implements AdapterView.OnItemClickListener{
 private Context mcontext;
 private ListView listView;
 private Handler handler = new Handler(){
 @Override
 public void handleMessage(Message msg) {

 ArrayList<NewsBean> allnews = (ArrayList<NewsBean>)msg.obj;
 if (allnews != null && allnews.size() > 0) {
 for (NewsBean newsBean: allnews) {
 NewsAdapter adapter = new NewsAdapter(mcontext,allnews);
 listView.setAdapter(adapter);
 }
 }
 }
 };

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 mcontext = this;
 setContentView(R.layout.activity_main);
 listView = (ListView) findViewById(R.id.listview);
 //1先去数据库中去获取缓存的新闻数据,显示到新闻列表中
 ArrayList<NewsBean> list = NewsUtils.getAllNewsFromDB(mcontext);
 if (list != null && list.size() >0) {
 //创建一个adapter设置给listview
 NewsAdapter adapter = new NewsAdapter(mcontext,list);
 listView.setAdapter(adapter);
 }
 //2通过网络去获取服务器上的新闻数据，用list封装，获取网络数据需要在子线程中去做
 new Thread(new Runnable() {
 @Override
 public void run() {
 //请求网络数据通过
 ArrayList<NewsBean> allnews = NewsUtils.getAllNewsForNetWork(mcontext);
 //通过handler,将数据发送到主线程中去更新
 Message message = Message.obtain();
 message.obj=allnews;
 handler.sendMessage(message);
 }
 }).start();
 //设置listView条目的点击事件
 listView.setOnItemClickListener(this);
 }
 //listview 条目点击时会调用这些方法，parent 代表listview ;view 点击条目上的那个view对象
 // positon 条目的位置 ; id 条目的id
 @Override
 public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
 //需要获取条目上的bean对象中url做跳转
 NewsBean newsBean = (NewsBean) parent.getItemAtPosition(position);
 String url = newsBean.news_url;
 //跳转到浏览器
 Intent intent = new Intent();
 intent.setAction(Intent.ACTION_VIEW);
 intent.setData(Uri.parse(url));
 startActivity(intent);
 }
}
6 Layout布局
activity_main.xml
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<?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">
 <ListView
 android:id="@+id/listview"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 />
</LinearLayout>

行布局 item_news_layout.xml
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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:paddingBottom="20dp"
 android:paddingTop="20dp"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="horizontal">

 <com.example.view.MyImageView
 android:id="@+id/item_img_icon"
 android:layout_width="60dp"
 android:background="#ff0000"
 android:layout_height="60dp"
 android:scaleType="fitXY"
 android:layout_gravity="center"
 android:src="@drawable/ic_launcher"
 android:layout_marginRight="10dp"

 />
 <LinearLayout
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:layout_gravity="center"
 android:orientation="vertical"
 >

 <TextView
 android:id="@+id/item_tv_title"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:layout_marginBottom="3dp"
 android:singleLine="true"
 android:text="title"
 android:textColor="#000000"
 android:textSize="20sp"
 />

 <TextView
 android:id="@+id/item_tv_des"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:layout_marginBottom="3dp"
 android:maxLines="2"
 android:text="des"
 android:textColor="#666666"
 android:textSize="16sp"
 />
 <RelativeLayout
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:layout_gravity="center"
 >
 <TextView
 android:id="@+id/item_tv_comment"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_alignParentLeft="true"
 android:text="comment"
 android:textColor="#666666"
 android:textSize="16sp"
 />
 <TextView
 android:id="@+id/item_tv_type"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_alignParentRight="true"
 android:text="娱乐"
 android:textColor="#666666"
 android:textSize="16sp"
 android:layout_marginRight="10dp"
 />


 </RelativeLayout>

 </LinearLayout>
</LinearLayout>
7 权限
<uses-permission android:name="android.permission.INTERNET"></uses-permission>

0 1

Android新闻客户端案列

前言：这是一个仿照网易客户端模仿的简易新闻客户端案例，主要是为了对知识点更深入的了解和整合

1 需求

2 程序流程

3 用到的知识点

1 Handler机制 2 ListView 3 BaseAdapter(适配器） 4 SqliteOpenHelper 数据库操作 5 自定义组件（MyImageView）

6 数据传输json 等

4 服务器端

用到的jar包 java-json.jar

5 Android 客户端

5.1 强新闻数据封装成NewsBean

5.2 数据库的操作

5.3 适配器

5.4 请求服务端数据，并封装成List<NewsBean>返回 这一步也是最关键的

5.5 自定义处理图片的组件

5.6 MainActivity

6 Layout布局

7 权限

5.4 请求服务端数据，并封装成List<NewsBean>返回这一步也是最关键的