Android之JSON格式数据解析
来源：程序员人生 发布时间：2015-01-07 08:13:08 阅读次数：4317次
JSON：JavaScript 对象表示法（JavaScript Object Notation）。独立于语言和平台，比 XML 更小、更快，更容易解析。如今JSON数据已成了互联网中大多数数据的传递方式，所以必须要熟练掌握。
Android平台自带了JSON解析的相干API，可以将文件、输入流中的数据转化为JSON对象，然后从对象中获得JSON保存的数据内容。
Android的JSON解析部份都在包org.json下，主要有以下几个类：
JSONObject：可以看做是1个json对象,这是系统中有关JSON定义的基本单元，其包括1对儿(Key/Value)数值。它对外部(External：利用toString()方法输出的数值)调用的响应体现为1个标准的字符串（例如：{"JSON": "Hello, World"}，最外被大括号包裹，其中的Key和Value被冒号":"分隔）。其对内部(Internal)行动的操作格式稍微，例如：初始化1个JSONObject实例，援用内部的put()方法添加数值：new
JSONObject().put("JSON", "Hello, World!")，在Key和Value之间是以逗号","分隔。Value的类型包括：Boolean、JSONArray、JSONObject、Number、String或默许值JSONObject.NULL object。
JSONStringer：json文本构建类 ，根据官方的解释，这个类可以帮助快速和便捷的创建JSON text。其最大的优点在于可以减少由于 格式的毛病致使程序异常，援用这个类可以自动严格依照JSON语法规则（syntax rules）创建JSON text。每一个JSONStringer实体只能对应创建1个JSON text。。其最大的优点在于可以减少由于格式的毛病致使程序异常，援用这个类可以自动严格依照JSON语法规则（syntax rules）创建JSON text。每一个JSONStringer实体只能对应创建1个JSON
text。
JSONArray：它代表1组有序的数值。将其转换为String输出(toString)所表现的情势是用方括号包裹，数值以逗号”,”分隔（例如：[value1,value2,value3]，大家可以亲身利用简短的代码更加直观的了解其格式）。这个类的内部一样具有查询行动，get()和opt()两种方法都可以通过index索引返回指定的数值，put()方法用来添加或替换数值。一样这个类的value类型可以包括：Boolean、JSONArray、JSONObject、Number、String或默许值JSONObject.NULL
object。
JSONTokener：json解析类
JSONException：json中用到的异常
下面以聚合数据空气质量城市空气PM2.5指数数据接口为例来演示JSON格式数据的解析。
聚合数据空气质量城市空气PM2.5指数数据接口API文档参见：http://www.juhe.cn/docs/api/id/33/aid/79
JSON返回示例：
{ /*JSONObject*/
"resultcode": "200",
"reason": "SUCCESSED!",
"result": [ /*JSONArray*/
{ /*JSONObject*/
"city": "苏州", /*城市*/
"PM2.5": "73", /*PM2.5指数*/
"AQI": "98", /*空气质量指数*/
"quality": "良", /*空气质量*/
"PM10": "50",/*PM10*/
"CO": "0.79", /*1氧化碳*/
"NO2": "65", /*2氧化氮*/
"O3": "28", /*臭氧*/
"SO2": "41", /*2氧化硫*/
"time": "2014⑴2⑵6 11:48:40"/*更新时间*/
}
],
"error_code": 0
}
实例：JSONDemo
运行效果：
代码清单：
布局文件：activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:text="城市："
android:textSize="23sp" />
<EditText
android:id="@+id/city"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="3"
android:inputType="text" />"
</LinearLayout>
<Button
android:id="@+id/query"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="查询"
android:textSize="23sp" />
<TextView
android:id="@+id/result"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
Java源代码文件：MainActivity.java
package com.rainsong.jsondemo;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
EditText et_city;
Button btn_query;
TextView tv_result;
QueryTask task;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
et_city = (EditText)findViewById(R.id.city);
tv_result = (TextView)findViewById(R.id.result);
btn_query = (Button)findViewById(R.id.query);
btn_query.setOnClickListener(new OnClickListener() {
public void onClick(View view) {
String city = et_city.getText().toString();
if (city.length() < 1) {
Toast.makeText(MainActivity.this, "请输入城市名",
Toast.LENGTH_LONG).show();
return;
}
task = new QueryTask(MainActivity.this, tv_result);
task.execute(city);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
Java源代码文件：QueryTask.java
package com.rainsong.jsondemo;
import java.io.IOException;
import java.net.URLEncoder;
import java.util.ArrayList;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.content.Context;
import android.os.AsyncTask;
import android.widget.TextView;
import android.widget.Toast;
public class QueryTask extends AsyncTask<String, Void, String> {
Context context;
TextView tv_result;
private static final String JUHE_URL_ENVIRONMENT_AIR_PM =
"http://web.juhe.cn:8080/environment/air/pm";
private static final String JUHE_APPKEY = "你申请的APPKEY值";
public QueryTask(Context context, TextView tv_result) {
// TODO Auto-generated constructor stub
super();
this.context = context;
this.tv_result = tv_result;
}
@Override
protected String doInBackground(String... params) {
String city = params[0];
ArrayList<NameValuePair> headerList = new ArrayList<NameValuePair>();
headerList.add(new BasicNameValuePair("Content-Type", "text/html; charset=utf⑻"));
String targetUrl = JUHE_URL_ENVIRONMENT_AIR_PM;
ArrayList<NameValuePair> paramList = new ArrayList<NameValuePair>();
paramList.add(new BasicNameValuePair("key", JUHE_APPKEY));
paramList.add(new BasicNameValuePair("dtype", "json"));
paramList.add(new BasicNameValuePair("city", city));
for (int i = 0; i < paramList.size(); i++) {
NameValuePair nowPair = paramList.get(i);
String value = nowPair.getValue();
try {
value = URLEncoder.encode(value, "UTF⑻");
} catch (Exception e) {
}
if (i == 0) {
targetUrl += ("?" + nowPair.getName() + "=" + value);
} else {
targetUrl += ("&" + nowPair.getName() + "=" + value);
}
}
HttpGet httpRequest = new HttpGet(targetUrl);
try {
for (int i = 0; i < headerList.size(); i++) {
httpRequest.addHeader(headerList.get(i).getName(),
headerList.get(i).getValue());
}
HttpClient httpClient = new DefaultHttpClient();
HttpResponse httpResponse = httpClient.execute(httpRequest);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
String strResult = EntityUtils.toString(httpResponse.getEntity());
return strResult;
} else {
return null;
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String result) {
if (result != null) {
try {
JSONObject jsonObject = new JSONObject(result);
int resultCode = jsonObject.getInt("resultcode");
if (resultCode == 200) {
JSONArray resultJsonArray = jsonObject.getJSONArray("result");
JSONObject resultJsonObject = resultJsonArray.getJSONObject(0);
String output = context.getString(R.string.city) + ": " + resultJsonObject.getString("city") + "
"
+ context.getString(R.string.PM25) + ": " + resultJsonObject.getString("PM2.5") + "
"
+ context.getString(R.string.AQI) + ": " + resultJsonObject.getString("AQI") + "
"
+ context.getString(R.string.quality) + ": " + resultJsonObject.getString("quality") + "
"
+ context.getString(R.string.PM10) + ": " + resultJsonObject.getString("PM10") + "
"
+ context.getString(R.string.CO) + ": " + resultJsonObject.getString("CO") + "
"
+ context.getString(R.string.NO2) + ": " + resultJsonObject.getString("NO2") + "
"
+ context.getString(R.string.O3) + ": " + resultJsonObject.getString("O3") + "
"
+ context.getString(R.string.SO2) + ": " + resultJsonObject.getString("SO2") + "
"
+ context.getString(R.string.time) + ": " + resultJsonObject.getString("time") + "
";
tv_result.setText(output);
} else if (resultCode == 202) {
String reason = jsonObject.getString("reason");
tv_result.setText(reason);
} else {
Toast.makeText(context, "查询失败",
Toast.LENGTH_LONG).show();
tv_result.setText("");
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} else {
Toast.makeText(context, "查询失败",
Toast.LENGTH_LONG).show();
tv_result.setText("");
}
}
}
字符串资源：string.xml
<?xml version="1.0" encoding="utf⑻"?>
<resources>
<string name="app_name">JSONDemo</string>
<string name="action_settings">Settings</string>
<string name="hello_world">Hello world!</string>
<string name="city">城市</string>
<string name="PM25">PM2.5指数</string>
<string name="AQI">空气质量指数</string>
<string name="quality">空气质量</string>
<string name="PM10">PM10</string>
<string name="CO">1氧化碳</string>
<string name="NO2">2氧化氮</string>
<string name="O3">臭氧</string>
<string name="SO2">2氧化硫</string>
<string name="time">更新时间</string>
</resources>
API知识点
public class
JSONObject
extends Object
org.json.JSONObject
Class Overview
A modifiable set of name/value mappings. Names are unique, non-null strings. Values may be any mix of JSONObjects, JSONArrays, Strings, Booleans, Integers, Longs, Doubles or NULL. Values may not be null, NaNs, infinities, or of any type not listed here.
JSONObject(String json)
Creates a new JSONObject with name/value mappings from the JSON string.
Object get(String name)
Returns the value mapped by name.
int getInt(String name)
Returns the value mapped by name if it exists and is an int or can be coerced to an int.
String getString(String name)
Returns the value mapped by name if it exists, coercing it if necessary.
JSONArray getJSONArray(String name)
Returns the value mapped by name if it exists and is a JSONArray.
public class
JSONArray
extends Object
org.json.JSONArray
Class Overview
A dense indexed sequence of values. Values may be any mix of JSONObjects, other JSONArrays, Strings, Booleans, Integers, Longs, Doubles, null or NULL. Values may not be NaNs, infinities, or of any type not listed here.
JSONObject getJSONObject(int index)
Returns the value at index if it exists and is a JSONObject.
生活不易，码农辛苦
如果您觉得本网站对您的学习有所帮助,可以手机扫描二维码进行捐赠
