We have been using this code in our application to fetch data from an online database, but whatever we tried, it keeps saying "null" as an output by album and duration. It could be a very small detail, but since we are beginning developers, we don't really know a lot about JSON. Has anyone got any suggestions?
package com.example.androidhive;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.text.Html;
import android.util.Log;
import android.widget.TextView;
import com.example.androidhive.helper.AlertDialogManager;
import com.example.androidhive.helper.ConnectionDetector;
import com.example.androidhive.helper.JSONParser;
public class SingleTrackActivity extends Activity {
// Connection detector
ConnectionDetector cd;
// Alert dialog manager
AlertDialogManager alert = new AlertDialogManager();
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jsonParser = new JSONParser();
// tracks JSONArray
JSONArray albums = null;
// Album id
String album_id = null;
String song_id = null;
String album_name, song_name, duration;
// single song JSON url
// GET parameters album, song
private static final String URL_SONG = "http://api.androidhive.info/songs/track.php";
// ALL JSON node names
private static final String TAG_NAME = "name";
private static final String TAG_DURATION = "duration";
private static final String TAG_ALBUM = "album";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_single_track);
cd = new ConnectionDetector(getApplicationContext());
// Check if Internet present
if (!cd.isConnectingToInternet()) {
// Internet Connection is not present
alert.showAlertDialog(SingleTrackActivity.this, "Internet Connection Error",
"Please connect to working Internet connection", false);
// stop executing code by return
return;
}
// Get album id, song id
Intent i = getIntent();
album_id = i.getStringExtra("album_id");
song_id = i.getStringExtra("song_id");
// calling background thread
new LoadSingleTrack().execute();
}
/**
* Background Async Task to get single song information
* */
class LoadSingleTrack extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(SingleTrackActivity.this);
pDialog.setMessage("Loading song ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting song json and parsing
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// post album id, song id as GET parameters
params.add(new BasicNameValuePair("album", album_id));
params.add(new BasicNameValuePair("song", song_id));
// getting JSON string from URL
String json = jsonParser.makeHttpRequest(URL_SONG, "GET",
params);
// Check your log cat for JSON reponse
Log.d("Single Track JSON: ", json);
try {
JSONObject jObj = new JSONObject(json);
if(jObj != null){
song_name = jObj.getString(TAG_NAME);
album_name = jObj.getString(TAG_ALBUM);
duration = jObj.getString(TAG_DURATION);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting song information
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
TextView txt_song_name = (TextView) findViewById(R.id.song_title);
TextView txt_album_name = (TextView) findViewById(R.id.album_name);
TextView txt_duration = (TextView) findViewById(R.id.duration);
// displaying song data in view
txt_song_name.setText(song_name);
txt_album_name.setText(Html.fromHtml("<b>Album:</b> " + album_name));
txt_duration.setText(Html.fromHtml("<b>Duration:</b> " + duration));
// Change Activity Title with Song title
setTitle(song_name);
}
});
}
}
}
Looking at the tutorial you link to, it appears this is what a request would look like:
http://api.androidhive.info/songs/track.php?album=3&song=1
and the response is:
{"id":1,"name":"Born to Die","duration":"4:46","album_id":"3","album":"Lana Del Rey - Born to Die"}
Given that ... there's nothing wrong with your JSON parsing.
You need to verify the "album" ( album_id
) and "song" ( song_id
) parameters are what you think they are when you do your GET
.
The PHP script doesn't return any data if they are empty (eg http://api.androidhive.info/songs/track.php?album=&song=
) and simply returns no album
if they aren't something it recognizes. It would appear that's what is occurring and therefore the output of your program is null
for the values.
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