Why is the return value is null
I'm trying to create something like a news feed using packages JSON but to no avail.
My code:
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.BasicHttpParams;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
public class MainFragment extends Fragment {
private ListView songList;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v = inflater.inflate(R.layout.main_layout, container, false);
songList = (ListView)v.findViewById(R.id.listView_news);
AsynDataClass jsonAsync = new AsynDataClass();
jsonAsync.execute("");
return v;
}
// @Override
// public boolean onCreateOptionsMenu(Menu menu) {
//
//// Inflate the menu; this adds items to the action bar if it is present.
//
// getMenuInflater().inflate(R.menu.menu_main, menu);
//
// return true;
//
// }
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private class AsynDataClass extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
// TODO Auto-generated method stub
HttpClient httpClient = new DefaultHttpClient(new BasicHttpParams());
HttpPost httpPost = new HttpPost("http://192.168.1.3/song.json");
String jsonResult = "";
try {
HttpResponse response = httpClient.execute(httpPost);
jsonResult = inputStreamToString(response.getEntity().getContent()).toString();
System.out.println("Returned Json object " + jsonResult.toString());
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return jsonResult;
}
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
System.out.println("Resulted Value: " + result);
List<ItemObject> parsedObject = returnParsedJsonObject(result);
CustomAdapter jsonCustomAdapter = new CustomAdapter(getActivity(), parsedObject);
songList.setAdapter(jsonCustomAdapter);
}
private StringBuilder inputStreamToString(InputStream is) {
String rLine = "";
StringBuilder answer = new StringBuilder();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
try {
while ((rLine = br.readLine()) != null) {
answer.append(rLine);
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return answer;
}
}
private List<ItemObject> returnParsedJsonObject(String result){
List<ItemObject> jsonObject = new ArrayList<ItemObject>();
JSONObject resultObject = null;
JSONArray jsonArray = null;
ItemObject newItemObject = null;
try {
resultObject = new JSONObject(result);
System.out.println("Testing the water " + resultObject.toString());
jsonArray = resultObject.optJSONArray("African_Music");
} catch (JSONException e) {
e.printStackTrace();
}
if (jsonArray != null){
for(int i = 0; i < jsonArray.length(); i++){
JSONObject jsonChildNode = null;
try {
jsonChildNode = jsonArray.getJSONObject(i);
String songName = jsonChildNode.getString("title");
String songYear = jsonChildNode.getString("title");
String songAuthor = jsonChildNode.getString("title");
String newLine = jsonChildNode.getString("_id");
newItemObject = new ItemObject(songName, songYear, songAuthor, newLine);
jsonObject.add(newItemObject);
} catch (JSONException e) {
e.printStackTrace();
}
}
}
return jsonObject;
}
}
JSON packet: click
Gradle output:
06-27 14:59:09.260 22223-22223/ru.yktdevelopers.childrensofasia E/AndroidRuntime: FATAL EXCEPTION: main
Process: ru.yktdevelopers.childrensofasia, PID: 22223
java.lang.NullPointerException: Attempt to invoke virtual method 'int org.json.JSONArray.length()' on a null object reference
at ru.yktdevelopers.childrensofasia.MainFragment.returnParsedJsonObject(MainFragment.java:198)
at ru.yktdevelopers.childrensofasia.MainFragment.access$100(MainFragment.java:30)
at ru.yktdevelopers.childrensofasia.MainFragment$AsynDataClass.onPostExecute(MainFragment.java:137)
at ru.yktdevelopers.childrensofasia.MainFragment$AsynDataClass.onPostExecute(MainFragment.java:81)
at android.os.AsyncTask.finish(AsyncTask.java:651)
at android.os.AsyncTask.-wrap1(AsyncTask.java)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:668)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
06-27 14:59:38.079 22223-22230/ru.yktdevelopers.childrensofasia W/art: Suspending all threads took: 28.442ms
06-27 15:05:14.971 22223-22230/ru.yktdevelopers.childrensofasia E/art: Failed to send JDWP packet HPIF to debugger (-1 of 52): Broken pipe
06-27 15:05:14.971 22223-22230/ru.yktdevelopers.childrensofasia E/art: Failed sending reply to debugger: Broken pipe
06-27 15:05:15.020 22223-22230/ru.yktdevelopers.childrensofasia I/art: Debugger is no longer active
06-27 15:06:24.739 22223-22223/ru.yktdevelopers.childrensofasia I/Process: Sending signal. PID: 22223 SIG: 9
why the return value is converted to null
where did I go wrong? can not understand
