什么是json

• json是一種與開發(fā)語言無關(guān)的千所、輕量級的數(shù)據(jù)格式。全稱JavaScript Object Notation.

• 優(yōu)點： 易于人的閱讀和編寫没宾，易于程序解析與生產(chǎn)

• 一個簡單的JSON樣例

    {
        "name":"JSON快速入門(java版本)"凌彬，
        "autor":"李廣"沸柔，
        "content":["JSON基礎(chǔ)入門"，"常用JSON處理"]铲敛，
        "time":{
            "value"：30褐澎，
            "unit":"分鐘"
            }
     }
  

• 數(shù)據(jù)結(jié)構(gòu)-Object

  使用花括號{}包含的鍵值對結(jié)構(gòu)，key必須是string類型伐蒋，value為任何基本類型或數(shù)據(jù)結(jié)構(gòu)

• 數(shù)據(jù)結(jié)構(gòu)-Array

  使用中括號[]來起始工三，并用逗號，來分隔元素

• json例子

  { 
    "name":"王小二"先鱼，
    "age":25.2,
    "birthday":"1992-11-01",
    "school":"藍(lán)翔"俭正，
    "major":["理發(fā)"，"挖掘機(jī)"]型型，
    "has_girlfriend":false,
    "car":null,
    "house":null,
    "comment":"這是一個注釋"
    }
  
  
    1）Android原生技術(shù)
    
    特點：編程相對麻煩段审，但是是Google官方提供的，有些JSON數(shù)據(jù)必須要Android原生技術(shù)來解析闹蒜。Google官方?jīng)]有提供將Java轉(zhuǎn)換成json數(shù)據(jù)的API
    數(shù)據(jù)之間轉(zhuǎn)換：
    (1)將JSON格式的字符串{}轉(zhuǎn)換成Java對象
    API：JSONObject(String json)：將json字符串解析為json對象
    Xxx getXxx (String name)：根據(jù)name寺枉，在.json對象中得到對應(yīng)的value
    Xxx optXxx (String json)：根據(jù)name，在.json對象中得到對應(yīng)的value
    get和opt的區(qū)別而：optXxx會在對應(yīng)的key中的值不存在的時候返回一個空字符串或者你指定的默認(rèn)值绷落，而getString會出現(xiàn)空指針異常的錯誤
    
    (2)將JSON格式的字符串[]轉(zhuǎn)換成Java對象的List
    API：JSONArray(String json)：將json字符串解析為json數(shù)組
    int length ()：得到j(luò)son數(shù)組中元素的個數(shù)
    Xxx getXxx (String name)：根據(jù)name姥闪，在.json對象中得到對應(yīng)的value
    Xxx optXxx (String json)：根據(jù)name，在.json對象中得到對應(yīng)的value
    get和opt的區(qū)別而：optXxx會在對應(yīng)的key中的值不存在的時候返回一個空字符串或者你指定的默認(rèn)值砌烁，而getString會出現(xiàn)空指針異常的錯誤
    (3)復(fù)雜json的數(shù)據(jù)解析
    (4)特殊json的數(shù)據(jù)解析
  

效果

xiaoguo.png

代碼：

    package com.junjie.jsondemo;
import android.os.Handler;
import android.os.Message;
import android.provider.DocumentsContract;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ListView;
import android.widget.Toast;

import com.junjie.jsondemo.adapter.NewsAdapter;
import com.junjie.jsondemo.entity.Tngou;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import org.xml.sax.helpers.LocatorImpl;

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

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

public class MainActivity extends AppCompatActivity {
private Handler mHandler;
private List<Tngou> tngouList;
private ListView listView;
private NewsAdapter newsAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    listView = (ListView) findViewById(R.id.lv_list);
    mHandler = new Handler(new InnerCallBack());
    tngouList =new ArrayList<>();
    newsAdapter =new NewsAdapter(this,tngouList);
    listView.setAdapter(newsAdapter);

}

public void doClick(View v) {
    String url = "http://www.tngou.net/api/top/classify";
    OkHttpClient okHttpClient = new OkHttpClient();
    Request request = new Request.Builder().url(url).build();

    okHttpClient.newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(Call call, IOException e) {

        }

        @Override
        public void onResponse(Call call, Response response) throws IOException {
            Message message = new Message();
            message.what = 0;
            String string = response.body().string();
            message.obj = string;
            mHandler.sendMessage(message);
        }
    });
}


private class InnerCallBack implements Handler.Callback {
    @Override
    public boolean handleMessage(Message msg) {
        if (msg.what == 0) {
            String content = (String) msg.obj;
            analysisJsonContent(content);
        }
        return false;
    }
}

/**
 * 解析json
 *
 * @param content
 */
private void analysisJsonContent(String content) {
    try {
        List<Tngou> tngous =new ArrayList<>();
        JSONObject rootObject = new JSONObject(content);
        boolean status = rootObject.getBoolean("status");
        JSONArray tngou = rootObject.getJSONArray("tngou");
        Tngou tngou1 =null;
        for (int i = 0; i < tngou.length(); i++) {
             tngou1 = new Tngou();
            JSONObject jsonObject = tngou.getJSONObject(i);
            tngou1.setDescription(jsonObject.getString("description"));
            tngou1.setTitle(jsonObject.getString("title"));
            tngou1.setId(jsonObject.getInt("id"));
            tngou1.setKeywords(jsonObject.getString("keywords"));
            tngou1.setName(jsonObject.getString("name"));
            tngou1.setSeq(jsonObject.getInt("seq"));
            tngous.add(tngou1);
        }
        tngouList.clear();
        tngouList.addAll(tngous);
        newsAdapter.notifyDataSetChanged();
    } catch (JSONException e) {
        e.printStackTrace();
    }


}

}

adapter中

package com.junjie.jsondemo.adapter;
import android.content.Context;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.junjie.jsondemo.R;
import com.junjie.jsondemo.entity.Tngou;

import java.util.List;

public class NewsAdapter extends BaseAdapter<Tngou> {
    public NewsAdapter(Context context, List<Tngou> list) {
        super(context, list);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder = null;
        if (viewHolder == null) {
            viewHolder = new ViewHolder();
            convertView = getInflater().inflate(R.layout.item_news_list, null);
            viewHolder.tvId = (TextView) convertView.findViewById(R.id.tv_id);
            viewHolder.tvDescription = (TextView) convertView.findViewById(R.id.tv_description);
            viewHolder.tvKeywords = (TextView) convertView.findViewById(R.id.tv_keywords);
            viewHolder.tvName = (TextView) convertView.findViewById(R.id.tv_name);
            viewHolder.tvSeq = (TextView) convertView.findViewById(R.id.tv_seq);
            viewHolder.tvTitle = (TextView) convertView.findViewById(R.id.tv_title);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        Tngou tngou = getList().get(position);
        viewHolder.tvTitle.setText(tngou.getTitle());
        viewHolder.tvDescription.setText(tngou.getDescription());
        viewHolder.tvName.setText(tngou.getName());
        viewHolder.tvId.setText(tngou.getId() + "");
        viewHolder.tvSeq.setText(tngou.getSeq() + "");
        viewHolder.tvKeywords.setText(tngou.getKeywords());
        return convertView;
    }

    class ViewHolder {
        TextView tvId;
        TextView tvDescription;
        TextView tvKeywords;
        TextView tvName;
        TextView tvSeq;
        TextView tvTitle;
    }


}



    package com.junjie.jsondemo.adapter;
    import android.content.Context;
    import android.view.LayoutInflater;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public abstract class BaseAdapter<T> extends android.widget.BaseAdapter {
    
        private Context context;
        private LayoutInflater inflater;
        private List<T> list;
    
        public BaseAdapter(Context context, List<T> list) {
            this.context = context;
            setList(list);
            inflater = LayoutInflater.from(context);
    
        }
    
        public LayoutInflater getInflater() {
            return inflater;
        }
    
        public List<T> getList() {
            return list;
        }
    
    
        public void setList(List<T> list) {
            if (list == null) {
                list = new ArrayList<>();
            }
            this.list = list;
        }
    
        @Override
        public int getCount() {
            return list.size();
        }
    
        @Override
        public Object getItem(int position) {
            return null;
        }
    
        @Override
        public long getItemId(int position) {
            return 0;
        }
    
    }

實體類

    package com.junjie.jsondemo.entity;
    
    
    public class Tngou {
        private String description;
        private int id;
        private String keywords;
        private String name;
        private int seq ;
        private String title;
    
        public String getDescription() {
            return description;
        }
    
        public void setDescription(String description) {
            this.description = description;
        }
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public String getKeywords() {
            return keywords;
        }
    
        public void setKeywords(String keywords) {
            this.keywords = keywords;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public int getSeq() {
            return seq;
        }
    
        public void setSeq(int seq) {
            this.seq = seq;
        }
    
        public String getTitle() {
            return title;
        }
    
        public void setTitle(String title) {
            this.title = title;
        }
    
        @Override
        public String toString() {
            return "Tngou{" +
                    "description='" + description + '\'' +
                    ", id=" + id +
                    ", keywords='" + keywords + '\'' +
                    ", name='" + name + '\'' +
                    ", seq=" + seq +
                    ", title='" + title + '\'' +
                    '}';
        }
    }