网络编程

目标

通过网络接口获得新闻列表的json数据，将新闻列表展示在一个界面中

新闻列表实现的界面如下

接口：http://106.12.97.199:8080/news_list_data.json
返回：新闻列表json

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[
    {
        "id":"cb86cdcd922fe4295d5bd134f82090ac",
        "title":"索帅回忆弗格森当年奇怪表现 首回合输了却很高兴",
        "havePic":true,
        "desc":null,
        "link":"https://sports.sina.com.cn/g/pl/2021-04-17/doc-ikmxzfmk7319050.shtml",
        "source":"新浪",
        "channelId":"5572a10ab3cdc86cf39001e7",
        "channelName":"国际足球最新",
        "pubDate":"2021-04-17 10:32:00",
        "content":null,
        "coverPic":"https://n.sinaimg.cn/sports/transform/69/w510h359/20210417/fb6c-knvsnuf8997548.jpg"
    },

    {
        "id":"373819191b26ce4e12670d18d84bf28e",
        "title":"日美首脑会谈强调同盟关系 菅义伟再展办奥决心",
        "havePic":true,
        "desc":"中新网4月17日电 综合报道，当地时间16日，美国总统拜登在白宫与来访的日本首相菅义伟进行会谈，并举行了联合记者会。这是拜登自上任以来，首次在白宫同外国首脑举行面对面会晤。",
        "link":"http://www.chinanews.com/gj/2021/04-17/9456924.shtml",
        "source":"中国新闻网",
        "channelId":"5572a109b3cdc86cf39001db",
        "channelName":"国内最新",
        "pubDate":"2021-04-17 10:28:56",
        "content":"中新网4月17日电 综合报道，当地时间16日，美国总统拜登在白宫与来访的日本首相菅义伟进行会谈，并举行了联合记者会。这是拜登自上任以来，首次在白宫同外国首脑举行面对面会晤。",
        "coverPic":"http://image1.chinanews.com.cn/cnsupload/big/2021/03-26/4-426/75b9db5df3f64d2d921615127def8e2c.jpg"
        }
]

实现过程

布局文件

新闻界面的xml文件，使用RecyclerView

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<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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"
    tools:context=".ui.course.courseFragment">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/NewsRecyclerView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/news_title"
        tools:layout_editor_absoluteX="1dp"
        tools:layout_editor_absoluteY="1dp" />

    <TextView
        android:id="@+id/news_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="新闻"
        android:gravity="center"
        android:textColor="@color/white"
        android:textSize="20sp"
        android:background="@color/blue"
        android:padding="20dp"
        app:layout_constraintTop_toTopOf="parent"
        tools:layout_editor_absoluteX="158dp"
        tools:layout_editor_absoluteY="5dp" />

</androidx.constraintlayout.widget.ConstraintLayout>

每一个列表项目的xml文件

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<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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">


    <TextView
        android:id="@+id/news_title"
        android:layout_width="274dp"
        android:layout_height="36dp"
        android:text="第一章"
        android:textColor="@color/black"
        android:textSize="20sp"
        android:textStyle="bold"
        android:gravity="left"
        android:maxLines="1"
        android:ellipsize="end"
        app:layout_constraintTop_toTopOf="@+id/new_pic"
        app:layout_constraintLeft_toRightOf="@+id/new_pic"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginLeft="20dp"
        tools:layout_editor_absoluteX="126dp"
        tools:layout_editor_absoluteY="17dp" />

    <ImageView
        android:id="@+id/new_pic"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginTop="20dp"
        android:layout_marginBottom="30dp"
        app:srcCompat="@drawable/default_icon"
        tools:layout_editor_absoluteX="18dp"
        tools:layout_editor_absoluteY="17dp" />

    <TextView
        android:id="@+id/news_date"
        android:layout_width="174dp"
        android:layout_height="wrap_content"
        android:text="2021-04-17 10:28:56"
        android:textSize="15sp"
        app:layout_constraintLeft_toLeftOf="@+id/news_title"
        app:layout_constraintBottom_toBottomOf="@+id/new_pic" />

    <TextView
        android:id="@+id/new_source"
        android:layout_width="104dp"
        android:layout_height="22dp"
        android:textSize="15sp"
        android:text="中国新闻网"
        android:gravity="right"
        app:layout_constraintTop_toTopOf="@+id/news_date"
        app:layout_constraintRight_toRightOf="@+id/news_title"
        tools:layout_editor_absoluteX="288dp"
        tools:layout_editor_absoluteY="68dp" />

    <TextView
        android:id="@+id/itemline"
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:text=""
        android:layout_marginTop="20dp"
        android:layout_marginBottom="20dp"
        app:layout_constraintTop_toBottomOf="@+id/new_pic"
        tools:layout_editor_absoluteX="22dp"
        tools:layout_editor_absoluteY="153dp" />

</androidx.constraintlayout.widget.ConstraintLayout>

Java代码

在总的Activity中使用碎片Fragment，网络请求使用了okhttp,新闻页面的Fragment代码如下

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package com.example.mytest.ui.course;

import android.app.DownloadManager;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.ViewModelProvider;
import androidx.recyclerview.widget.DividerItemDecoration;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import com.example.mytest.R;
import com.example.mytest.data.model.Item;
import com.example.mytest.data.model.NewsItem;
import com.example.mytest.databinding.FragmentHomeBinding;
import com.example.mytest.ui.Constant;
import com.example.mytest.ui.JsonParse;
import com.example.mytest.ui.MyAdapter;
import com.example.mytest.ui.NewsAdapter;

import java.io.IOException;
import java.util.ArrayList;

import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class courseFragment extends Fragment {

    private View view;//定义view用来设置fragment的layout
    public RecyclerView NewsRecyclerView;//定义RecyclerView
    private ArrayList<NewsItem> NewsList = new ArrayList<NewsItem>();
    //自定义recyclerveiw的适配器
    private NewsAdapter newsRecyclerAdapter;
    public static final int Msg_NEWS_OK = 1;
    private MHandler mHandler;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.fragment_home, container, false);
        mHandler = new MHandler();
        //对recycleview进行初始化配置
        initRecyclerView();
        //初始化数据
        initData();
        return view;
    }

    /**
     * TODO 初始化数据
     */
    private void initData() {
        OkHttpClient okHttpClient = new OkHttpClient();
        Request request = new Request.Builder().url(Constant.WEB_SITE+Constant.NEWS_URL).build();
        Call call = okHttpClient.newCall(request);
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                String res = response.body().string();
                Message msg = new Message();
                msg.what = Msg_NEWS_OK;
                msg.obj = res;
                mHandler.sendMessage(msg);
            }
        });

    }
    class MHandler extends Handler {
        public void dispatchMessage(Message msg){
            super.dispatchMessage(msg);
            switch (msg.what) {
                case  Msg_NEWS_OK:
                    if(msg.obj!=null){
                        String vlResult = (String) msg.obj;
                        ArrayList<NewsItem> pythonList = JsonParse.getInstance().getNewsList(vlResult);
                        newsRecyclerAdapter.setData(pythonList);
                    }
                    break;
            }
        }
    }

    /**
     * TODO 对recycleview进行初始化配置
     */

    private void initRecyclerView() {
        //获取RecyclerView
        NewsRecyclerView=(RecyclerView)view.findViewById(R.id.NewsRecyclerView);
        //创建adapter
        newsRecyclerAdapter = new NewsAdapter(getActivity(), NewsList);
        //给RecyclerView设置adapter
        NewsRecyclerView.setAdapter(newsRecyclerAdapter);
        NewsRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false));
        NewsRecyclerView.addItemDecoration(new DividerItemDecoration(getActivity(),DividerItemDecoration.VERTICAL));
    }
}

为新闻列表中的RecyclerView设置适配器

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package com.example.mytest.ui;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;


import com.bumptech.glide.Glide;
import com.example.mytest.R;
import com.example.mytest.data.model.Item;
import com.example.mytest.data.model.NewsItem;

import java.util.ArrayList;

public class NewsAdapter extends RecyclerView.Adapter<NewsAdapter.NewsViewHodler> {

    private Context context;
    private ArrayList<NewsItem> NewsList;

    public NewsAdapter(Context context, ArrayList<NewsItem> ItemList) {
        //将传递过来的数据，赋值给本地变量
        this.context = context;//上下文
        this.NewsList = ItemList;//实体类数据ArrayList
    }

    @NonNull
    @Override
    public NewsViewHodler onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = View.inflate(context, R.layout.news, null);
        return new NewsViewHodler(itemView);
    }

    @Override
    public void onBindViewHolder(NewsViewHodler holder, int position) {
        NewsItem data = NewsList.get(position);
        holder.title.setText(data.getTitle());
        holder.date.setText(data.getPubDate());
        holder.source.setText(data.getSource());
        Glide.with(context)
                .load(data.getCoverPic())
                .error(R.mipmap.ic_launcher)
                .into(holder.pic);
    }

    public void setData(ArrayList<NewsItem> List){
        this.NewsList=List;
        notifyDataSetChanged();
    }

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

    class NewsViewHodler extends RecyclerView.ViewHolder {
        private ImageView pic;
        private TextView title;
        private TextView date;
        private TextView source;
        public NewsViewHodler(View itemView) {
            super(itemView);
            title = (TextView) itemView.findViewById(R.id.news_title);
            date = (TextView) itemView.findViewById(R.id.news_date);
            source = (TextView) itemView.findViewById(R.id.new_source);
            pic = (ImageView) itemView.findViewById(R.id.new_pic);
            //点击事件放在adapter中使用，也可以写个接口在activity中调用
            //方法一：在adapter中设置点击事件
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    //可以选择直接在本位置直接写业务处理
                    //Toast.makeText(context,"点击了xxx",Toast.LENGTH_SHORT).show()
                }
            });

        }
    }
}

json数据的获取和处理使用了Gson库

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package com.example.mytest.ui;

import com.example.mytest.data.model.NewsItem;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import java.lang.reflect.Type;
import java.util.ArrayList;

public class JsonParse {
    private static JsonParse instance;
    private JsonParse(){}
    public static JsonParse getInstance(){
        if(instance == null){
            instance = new JsonParse();
        }
        return instance;
    }
    public ArrayList<NewsItem> getNewsList(String json){
        Gson gson = new Gson();
        Type listType = new TypeToken<ArrayList<NewsItem>>(){}.getType();
        ArrayList<NewsItem> NewsList = gson.fromJson(json,listType);
        return NewsList;
    }
}

单个新闻项目对应的实体类

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package com.example.mytest.data.model;

public class NewsItem {
    private String id; //新闻Id
    private String title; //新闻标题
    private Boolean havePic;//是否有图片
    private String desc; //新闻简述
    private String link; //原文地址
    private String source; //新闻出处
    private String channelId; //频道
    private String channelName; //频道名字
    private String pubDate; //发布时间
    private String content; //新闻内容
    private String coverPic; //封面图片

    public Boolean getHavePic() {
        return havePic;
    }

    public String getChannelId() {
        return channelId;
    }

    public String getChannelName() {
        return channelName;
    }

    public String getContent() {
        return content;
    }

    public String getCoverPic() {
        return coverPic;
    }

    public String getDesc() {
        return desc;
    }

    public String getId() {
        return id;
    }

    public String getLink() {
        return link;
    }

    public String getPubDate() {
        return pubDate;
    }

    public String getSource() {
        return source;
    }

    public String getTitle() {
        return title;
    }

    public void setChannelId(String channelId) {
        this.channelId = channelId;
    }

    public void setChannelName(String channelName) {
        this.channelName = channelName;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public void setCoverPic(String coverPic) {
        this.coverPic = coverPic;
    }

    public void setHavePic(Boolean havePic) {
        this.havePic = havePic;
    }

    public void setId(String id) {
        this.id = id;
    }

    public void setLink(String link) {
        this.link = link;
    }

    public void setPubDate(String pubDate) {
        this.pubDate = pubDate;
    }

    public void setSource(String source) {
        this.source = source;
    }

    public void setTitle(String title) {
        this.title = title;
    }
}

静态常量

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package com.example.mytest.ui;

public class Constant {
    public static final String WEB_SITE = "http://106.12.97.199:8080";
    public static final String NEWS_URL = "/news_list_data.json";
}

项目地址

github项目地址