标签：android style blog http io ar color os sp
<1>JSON Service
In the previous section, you learned how to consume XML web services by using HTTP to connect to the web server and then obtain the
results in XML. You also learned how to use DOM to parse the result of the XML document.
However, manipulating XML documents is a computationally expensive operation for mobile devices, for the following reasons:
<i> XML documents are lengthy.
They use tags to embed information, and the size of an XML document can get very big pretty quickly. A large XML document means
that your device has to use more bandwidth to download it, which translates into higher cost.
<ii> XML documents are more difficult to process.
As shown earlier, you have to use DOM to traverse the tree in order to locate the information you want. In addition, DOM itself has
to build the entire document in memory as a tree structure before you can traverse it. This is both memory and CPU intensive.
JSON (JavaScript Object Notation) is a lightweight data-interchange format that is easy for humans to read and write
It is also easy for machines to parse and generate.
[ { “appeId”:”1”, “survId”:”1”, “location”:””, “surveyDate”:”2008-03 14”, “surveyTime”:”12:19:47”, “inputUserId”:”1”, “inputTime”:”2008-03-14 12:21:51”, “modifyTime”:”0000-00-00 00:00:00” }, { “appeId”:”2”, “survId”:”32”, “location”:””, “surveyDate”:”2008-03-14”, “surveyTime”:”22:43:09”, “inputUserId”:”32”, “inputTime”:”2008-03-14 22:43:37”, “modifyTime”:”0000-00-00 00:00:00” }, { “appeId”:”3”, “survId”:”32”, “location”:””, “surveyDate”:”2008-03-15”, “surveyTime”:”07:59:33”, “inputUserId”:”32”, “inputTime”:”2008-03-15 08:00:44”, “modifyTime”:”0000-00-00 00:00:00” } ]
information is represented as a collection of key/value pairs. each key/value pair is grouped into an ordered list of objects.
Unlike XML, there are no lengthy tag names, only brackets and braces.
package mirror.android.jsonservice; import java.io.BufferedReader; import java.io.InputStream; import java.io.InputStreamReader; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.StatusLine; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpGet; import org.apache.http.impl.client.DefaultHttpClient; import org.json.JSONArray; import org.json.JSONException; import org.json.JSONObject; import android.app.Activity; import android.os.AsyncTask; import android.os.Bundle; import android.util.Log; import android.widget.Toast; public class JSONActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_json); new ReadJSONFeedTask().execute("https://twitter.com/statuses/user_timeline/weimenglee.json"); } public String ReadJSONFeed(String URL){ StringBuilder stringBuilder = new StringBuilder(); HttpClient client = new DefaultHttpClient(); HttpGet httpGet = new HttpGet(URL); try { HttpResponse response = client.execute(httpGet); StatusLine statusLine = response.getStatusLine(); int statusCode = statusLine.getStatusCode(); if(statusCode == 200){ HttpEntity entity = response.getEntity(); InputStream in = entity.getContent(); BufferedReader reader = new BufferedReader(new InputStreamReader(in)); String line; while((line = reader.readLine()) != null){ stringBuilder.append(line); } } else{ Log.e("JSON", "Failed to download file"); } } catch (Exception e) { e.printStackTrace(); } return stringBuilder.toString(); } private class ReadJSONFeedTask extends AsyncTask<String, Void, String>{ @Override protected String doInBackground(String... urls) { return ReadJSONFeed(urls[0]); } @Override protected void onPostExecute(String result) { try { JSONArray jsonArray = new JSONArray(result); Log.i("JSON", "Number of surveys in feed:" + jsonArray.length()); for (int i = 0; i < jsonArray.length(); i++) { JSONObject jsonObject = jsonArray.getJSONObject(i); Toast.makeText(getApplication(), jsonObject.getString("text") + " - " + jsonObject.getString("created_at"), Toast.LENGTH_SHORT).show(); } } catch (JSONException e) { e.printStackTrace(); } } } }
Chapter 10 Networking/JSON Services
标签：android style blog http io ar color os sp
原文地址：http://www.cnblogs.com/iMirror/p/4117266.html
