Android Open Source - 2014-Droid-code Http Example

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License

The source code is released under:

GNU General Public License

Java Source Code

package ca.campbell.httpexample;
/*from  w w w.  j a v  a2s  .c  om*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;

import android.app.Activity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

/*
 * HttpURLConnectionExample
 * 
 * This app sends a URL uses HttpURLConnection class + GET
 * to download a web page and display some of it in a TextView
 * 
 */
public class HttpExample extends Activity {
  private static final String TAG = "HttpURLConn";
  private EditText urlText;
  private TextView textView;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_http_example);

    urlText = (EditText) findViewById(R.id.myURL);
    textView = (TextView) findViewById(R.id.tv);
  }

  /*
   * When user clicks button, executes an AsyncTask to do the download. Before
   * attempting to fetch the URL, makes sure that there is a network
   * connection.
   */
  public void myClickHandler(View view) {
    // Gets the URL from the UI's text field.
    String stringUrl = urlText.getText().toString();
    if (stringUrl.isEmpty()) {
      textView.setText("Gimmey some URLz pleaze.");
    } else {
      if (stringUrl.substring(0, 6) != "http://")
        stringUrl = "http://" + stringUrl;

      // first check to see if we can get on the network
      ConnectivityManager connMgr = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
      NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
      if (networkInfo != null && networkInfo.isConnected()) {
        // invoke the AsyncTask to do the dirtywork.
        new DownloadWebpageText().execute(stringUrl);
      } else {
        textView.setText("No network connection available.");
      }
    }
  } // myClickHandler()

  /*
   * Uses AsyncTask to create a task away from the main UI thread. This task
   * takes a URL string and uses it to create an HttpUrlConnection. Once the
   * connection has been established, the AsyncTask downloads the contents of
   * the webpage via an an InputStream. The InputStream is converted into a
   * string, which is displayed in the UI by the AsyncTask's onPostExecute
   * method.
   */

  private class DownloadWebpageText extends AsyncTask<String, Void, String> {

    // onPostExecute displays the results of the AsyncTask.
    // runs in calling thread (in UI thread)
    protected void onPostExecute(String result) {
      textView.setText(result);
    }

    @Override
    // runs in background (not in UI thread)
    protected String doInBackground(String... urls) {
      // params comes from the execute() call: params[0] is the url.
      try {
        return downloadUrl(urls[0]);
      } catch (IOException e) {
        return "Unable to retrieve web page. URL may be invalid.";
      }
    }
  } // AsyncTask DownloadWebpageText()

  /*
   * Given a URL, establishes an HttpUrlConnection and retrieves the web page
   * content as a InputStream, which it returns as a string.
   */

  private String downloadUrl(String myurl) throws IOException {
    InputStream is = null;
    // Only read the first 500 characters of the retrieved
    // web page content.
    int len = 500;
    HttpURLConnection conn = null;
    URL url = new URL(myurl);
    try {
      // create and open the connection
      conn = (HttpURLConnection) url.openConnection();

      /*
       * set maximum time to wait for stream read read fails with
       * SocketTimeoutException if elapses before connection established
       * 
       * in milliseconds
       * 
       * default: 0 - timeout disabled
       */
      conn.setReadTimeout(10000);
      /*
       * set maximum time to wait while connecting connect fails with
       * SocketTimeoutException if elapses before connection established
       * 
       * in milliseconds
       * 
       * default: 0 - forces blocking connect timeout still occurs but
       * VERY LONG wait ~several minutes
       */
      conn.setConnectTimeout(15000 /* milliseconds */);
      /*
       * HTTP Request method defined by protocol
       * GET/POST/HEAD/POST/PUT/DELETE/TRACE/CONNECT
       * 
       * default: GET
       */
      conn.setRequestMethod("GET");
      // specifies whether this connection allows receiving data
      conn.setDoInput(true);
      // Starts the query
      conn.connect();

      int response = conn.getResponseCode();
      Log.d(TAG, "Server returned: " + response + " aborting read.");

      /*
       *  check the status code HTTP_OK = 200 anything else we didn't get what
       *  we want in the data.
       */
      if (response != HttpURLConnection.HTTP_OK)
        return "Server returned: " + response + " aborting read.";

      // get the stream for the data from the website
      is = conn.getInputStream();
      // read the stream (max len bytes)
      String contentAsString = readIt(is, len);
      return contentAsString;

    } finally {
      /*
       * Make sure that the InputStream is closed after the app is
       * finished using it.
       * Make sure the connection is closed after the app is finished using it.
       */

      if (is != null) {
        try {
          is.close();
        } catch (IOException ignore) {
        }
        if (conn != null)
          try {
            conn.disconnect();
          } catch (IllegalStateException ignore ) {
          }
      }
    }
  } // downloadUrl()

  //
  /*
   * Reads stream from HTTP connection and converts it to a String. See
   * stackoverflow or a good explanation of why I did it this way.
   * http://stackoverflow
   * .com/questions/3459127/should-i-buffer-the-inputstream
   * -or-the-inputstreamreader
   */
  public String readIt(InputStream stream, int len) throws IOException,
  UnsupportedEncodingException {
    char[] buffer = new char[len];
    Reader reader = null;
    reader = new BufferedReader(new InputStreamReader(stream, "UTF-8"), len);
    int count = reader.read(buffer);
    Log.d(TAG, "Bytes read: " + count
        + "(-1 means end of reader so max of " + len + " )");
    return new String(buffer);
  } // readIt()

} // Activity class

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