JSON stands for JavaScript Object Notation.It is an independent data exchange format and is the best alternative for XML. This chapter explains how to parse the JSON file and extract necessary information from it.
Android provides four differnet classes to manipulate JSON data. These classes are JSONArray,JSONObject,JSONStringer and JSONTokenizer.
The first step is to identify the fields in the JSON data in which you are interested in. For example. In the JSON given below we interested in getting temperature only.
Example:
{ "sys": { "country":"GB", "sunrise":1381107633, "sunset":1381149604 }, "weather":[ { "id":711, "main":"Smoke", "description":"smoke", "icon":"50n" } ], "main": { "temp":304.15, "pressure":1009, } }
Following is the content of the modifed main activity file src/com.example.jsonparser/MainActivity.java. package com.example.jsonparser;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
public class MainActivity extends Activity {
private String url1 = "http://api.openweathermap.org/data/2.5/weather?q=";
private EditText location,country,temperature,humidity,pressure;
private HandleJSON obj;
@Override
protected void onCreate(Bundle savedInstanceState)
{ super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
location = (EditText)findViewById(R.id.editText1);
country = (EditText)findViewById(R.id.editText2);
temperature = (EditText)findViewById(R.id.editText3);
humidity = (EditText)findViewById(R.id.editText4);
pressure = (EditText)findViewById(R.id.editText5);
}
@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;
}
public void open(View view)
{
String url = location.getText().toString();
String finalUrl = url1 + url;
country.setText(finalUrl);
obj = new HandleJSON(finalUrl);
obj.fetchJSON();
while(obj.parsingComplete);
country.setText(obj.getCountry());
temperature.setText(obj.getTemperature());
humidity.setText(obj.getHumidity());
pressure.setText(obj.getPressure()); } }
Following is the content of src/com.example.jsonparser/HandleXML.java.
package com.example.jsonparser;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection; import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import org.json.JSONObject;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserFactory;
import android.annotation.SuppressLint;
public class HandleJSON
{
private String country = "county";
private String temperature = "temperature";
private String humidity = "humidity";
private String pressure = "pressure";
private String urlString = null;
public volatile boolean parsingComplete = true;
public HandleJSON(String url)
{
this.urlString = url;
}
public String getCountry()
{
return country;
}
public String getTemperature()
{ return temperature;
}
public String getHumidity()
{
return humidity;
}
public String getPressure()
{
return pressure;
}
@SuppressLint("NewApi")
public void readAndParseJSON(String in)
{
try
{
JSONObject reader = new JSONObject(in);
JSONObject sys = reader.getJSONObject("sys");
country = sys.getString("country");
JSONObject main = reader.getJSONObject("main");
temperature = main.getString("temp");
pressure = main.getString("pressure");
humidity = main.getString("humidity");
parsingComplete = false;
}
catch (Exception e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void fetchJSON()
{
Thread thread = new Thread(new Runnable()
{
@Override
public void run()
{
try
{
URL url = new URL(urlString);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(10000 /* milliseconds */);
conn.setConnectTimeout(15000 /* milliseconds */);
conn.setRequestMethod("GET");
conn.setDoInput(true);
// Starts the query conn.connect();
InputStream stream = conn.getInputStream();
String data = convertStreamToString(stream);
readAndParseJSON(data);
stream.close();
}
catch (Exception e)
{
e.printStackTrace();
}
}
});
thread.start();
}
static String convertStreamToString(java.io.InputStream is)
{
java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
return s.hasNext() ? s.next() : "";
} }
Following is the modified content of the xml res/layout/activity_main.xml.
<RelativeLayout
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:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context=".MainActivity" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginTop="15dp"
android:text="@string/location"
android:textAppearance="?android:attr/textAppearanceMedium" />
<EditText android:id="@+id/editText1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBottom="@+id/textView1" android:layout_alignParentRight="true" android:ems="10" /> <TextView android:id="@+id/textView2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/textView1" android:layout_below="@+id/textView1" android:layout_marginTop="68dp" android:text="@string/country" android:textAppearance="?android:attr/textAppearanceSmall" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textView2"
android:layout_marginTop="19dp"
android:text="@string/temperature"
android:textAppearance="?android:attr/textAppearanceSmall" />
<TextView
android:id="@+id/textView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView3"
android:layout_below="@+id/textView3"
android:layout_marginTop="32dp"
android:text="@string/humidity"
android:textAppearance="?android:attr/textAppearanceSmall" />
<TextView
android:id="@+id/textView5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView4"
android:layout_below="@+id/textView4"
android:layout_marginTop="21dp"
android:text="@string/pressure"
android:textAppearance="?android:attr/textAppearanceSmall" />
<EditText
android:id="@+id/editText2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/textView3"
android:layout_toRightOf="@+id/textView3"
android:ems="10" >
<requestFocus />
</EditText>
<EditText android:id="@+id/editText3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBaseline="@+id/textView3" android:layout_alignBottom="@+id/textView3" android:layout_alignLeft="@+id/editText2" android:ems="10" /> <EditText android:id="@+id/editText4" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_above="@+id/textView5" android:layout_alignLeft="@+id/editText1" android:ems="10" /> <EditText android:id="@+id/editText5" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBaseline="@+id/textView5" android:layout_alignBottom="@+id/textView5" android:layout_alignRight="@+id/editText4" android:ems="10" /> <Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/editText2" android:layout_below="@+id/editText1" android:onClick="open" android:text="@string/weather" /> </RelativeLayout>
Following is the content of the res/values/string.xml.
<?xml version="1.0" encoding="utf-8"?> <resources> <string name="app_name">JSONParser</string> <string name="action_settings">Settings</string> <string name="hello_world">Hello world!</string> <string name="location">Location</string> <string name="country">Country:</string> <string name="temperature">Temperature:</string> <string name="humidity">Humidity:</string> <string name="pressure">Pressure:</string> <string name="weather">Weather</string> </resources>
Following is the content of AndroidManifest.xml file.
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.jsonparser" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="17" /> <uses-permission android:name="android.permission.INTERNET"/> <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="com.example.jsonparser.MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
