Develop Reference

Can't display data on recyclerView

This app is supposed to display movie's tittles fetched from an API into a RecyclerView. I know I am getting the data right because of logs I made on the movies Arraylist, but for some reason, I can't display the info. The app does not crash, it just shows an empty view. I do really appreciate your help.
Disclaimers: I am a newbie, and this solution might be quite simple for experienced people. I usually don't ask questions unless I can't solve the issue, actually this is my first question ever. I've been around this for a few days now and I can't find a way. I understand that this code might have more than one problem on it, and you are very welcome to point them all out.
SO, this is my main activity
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
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.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
public static final String LOG_TAG = MainActivity.class.getSimpleName();
private static final String MOST_POPULAR_MOVIES = "http://api.themoviedb.org/3/discover/movie?sort_by=popularity.desc&api_key=XXXXXXXXXXXXXXXXXXX";
ArrayList<Pelicula> ArrayDePeliculas;
private RecyclerView mPelisList;
private AdapterRV adapterRV;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
PeliculasAsyncTask task = new PeliculasAsyncTask();
task.execute(createUrl(MOST_POPULAR_MOVIES));
adapterRV = new AdapterRV(getApplicationContext(),/*Aca puede faltar algo*/ new ArrayList<Pelicula>());
mPelisList = findViewById(R.id.rv_pelis);
GridLayoutManager layoutManager = new GridLayoutManager(this, 2);
mPelisList.setLayoutManager(layoutManager);
mPelisList.setAdapter(adapterRV);
}
public void updateUi(ArrayList<Pelicula> peliculas) {
}
/**
* Returns new URL object from the given string URL.
*/
private URL createUrl(String stringUrl) {
URL url = null;
try {
url = new URL(stringUrl);
} catch (MalformedURLException exception) {
Log.e(LOG_TAG, "Error with creating URL", exception);
return null;
}
return url;
}
/**
* Make an HTTP request to the given URL and return a String as the response.
*/
private String makeHttpRequest(URL url) throws IOException {
String jsonResponse = "";
// If the URL is null, then return early.
if (url == null) {
return jsonResponse;
}
HttpURLConnection urlConnection = null;
InputStream inputStream = null;
try {
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setReadTimeout(10000 /* milliseconds */);
urlConnection.setConnectTimeout(15000 /* milliseconds */);
urlConnection.connect();
// If the request was successful (response code 200),
// then read the input stream and parse the response.
if (urlConnection.getResponseCode() == 200) {
inputStream = urlConnection.getInputStream();
jsonResponse = readFromStream(inputStream);
} else {
Log.e(LOG_TAG, "Error response code: " + urlConnection.getResponseCode());
}
} catch (IOException e) {
Log.e(LOG_TAG, "Problem retrieving the earthquake JSON results.", e);
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
if (inputStream != null) {
// function must handle java.io.IOException here
inputStream.close();
}
}
return jsonResponse;
}
/**
* Convert the {#link InputStream} into a String which contains the
* whole JSON response from the server.
*/
private String readFromStream(InputStream inputStream) throws IOException {
StringBuilder output = new StringBuilder();
if (inputStream != null) {
InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
BufferedReader reader = new BufferedReader(inputStreamReader);
String line = reader.readLine();
while (line != null) {
output.append(line);
line = reader.readLine();
}
}
return output.toString();
}
/**
* TODO modificar la url que le estas pasando
*/
public ArrayList<Pelicula> extractFeatureFromJson(String jsonResponse) {
ArrayList<Pelicula> arraydePelis = new ArrayList<>();
try {
JSONObject baseJsonResponse = new JSONObject(jsonResponse);
JSONArray resultsArray = baseJsonResponse.getJSONArray("results");
for (int i = 0; i < resultsArray.length(); i++) {
// If there are results in the features array
if (resultsArray.length() > 0) {
// Extract out the first feature (which is an earthquake)
JSONObject firstResult = resultsArray.getJSONObject(i);
String tittle = firstResult.getString("title");
Pelicula pelicula = new Pelicula(tittle);
arraydePelis.add(pelicula);
}
}
} catch (JSONException e) {
Log.e(LOG_TAG, "Problem parsing the earthquake JSON results", e);
}
return arraydePelis;
}
private class PeliculasAsyncTask extends AsyncTask<URL, Void, ArrayList<Pelicula>> {
#Override
protected ArrayList<Pelicula> doInBackground(URL... urls) {
// Create URL object
URL url = createUrl(MOST_POPULAR_MOVIES);
// Perform HTTP request to the URL and receive a JSON response back
String jsonResponse = "";
try {
jsonResponse = makeHttpRequest(url);
} catch (IOException e) {
Log.e(LOG_TAG, "Problem making the HTTP request.", e);
}
// Extract relevant fields from the JSON response and create an {#link Event} object
ArrayList<Pelicula> ArrayPeliculas = extractFeatureFromJson(jsonResponse);
// Return the {#link Event} object as the result fo the {#link TsunamiAsyncTask}
return ArrayPeliculas;
}
#Override
protected void onPostExecute(ArrayList<Pelicula> data) {
if (data == null) {
return;
}
adapterRV.notifyDataSetChanged();
mPelisList.setAdapter(adapterRV);
Log.e("Nada", data.get(6).getTittle());
super.onPostExecute(data);
}
}
}
The Movie class
public class Pelicula {
//Fields
private String mTittle;
//Constructor
public Pelicula(String Tittle){
mTittle= Tittle;
}
//Methods
public String getTittle (){
return mTittle;
}
}
And finally, the recyclerView adapter
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;
import java.util.List;
public class AdapterRV extends RecyclerView.Adapter<AdapterRV.PelisViewHolder> {
//Fields
List<Pelicula> mPeliculas;
private Context context;
/* TODO, comprobar que no necesitas esto: mNumberItems = numberOfItems; y poner autofit en grid view */
//Constructor
public AdapterRV (Context context, ArrayList<Pelicula> peliculas){
mPeliculas = peliculas;
this.context= context;
}
//Metodos
#NonNull
#Override
public PelisViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
Context context = parent.getContext();
int layoutForListItem = R.layout.item_layout;
LayoutInflater inflater= LayoutInflater.from(context);
View view = inflater.inflate(layoutForListItem, parent, false);
PelisViewHolder viewHolder = new PelisViewHolder(view);
return viewHolder;
}
#Override
public void onBindViewHolder(#NonNull PelisViewHolder holder, int position) {
Pelicula peliculas = mPeliculas.get(position);
TextView textView = holder.listItemTittleView;
textView.setText(peliculas.getTittle());
}
#Override
public int getItemCount() {
return mPeliculas.size();
}
public class PelisViewHolder extends RecyclerView.ViewHolder{
TextView listItemTittleView;
public PelisViewHolder(#NonNull View itemView) {
super(itemView);
listItemTittleView = itemView.findViewById(R.id.tv_title);
}
}
}

The problem is that you are passing new ArrayList<Pelicula>() to your adapter, and this list is remaining empty. I suggest you declare a global reference of Pelicula list inside your MainActivity and then pass it to the adapter. Whenever that list changes, then notifyDataSetChanged.
If you don't want to declare a global reference, just declare a method inside your adapter:
public void setList(ArrayList list){
this.list = list;
}
and in your MainActivity, just everything you get a new list, setList(newPeliculaList) and adapterRV.notifyDataSetChanged()
Edit:
in onCreate() before declaring the AdapterRV:
just put this:
ArrayDePeliculas = new ArrayList<Pelicula>();

Do you see these 2 lines in onCreate()
adapterRV = new AdapterRV(getApplicationContext(),new ArrayList<Pelicula>());
...
...
mPelisList.setAdapter(adapterRV);
Move them to onPostExecute() of the asyncTask and pass the data instead of a new ArrayList<Pelicula>():
#Override
protected void onPostExecute(ArrayList<Pelicula> data) {
//assuming the list is full and all is good
if (data == null) {
return;
}
//here...
adapterRV = new AdapterRV(getApplicationContext(),data);
mPelisList.setAdapter(adapterRV);
Log.e("Nada", data.get(6).getTittle());
super.onPostExecute(data);
}
UPDATE:
Its because you don't initialize the list in the adapter:
public class AdapterRV extends RecyclerView.Adapter<AdapterRV.PelisViewHolder> {
//Fields
//here you must initialize like this:
List<Pelicula> mPeliculas = new ArrayList<Pelicula>();
.....

App Crashes while switching from one Activity to another

Aim: Building app on Google API to fetch the data about the books the user searches
Problem Explanation:
Whenever I hit the submit Button, my app crashes.
This is my first approach in making a network request app and I need guidance.
MainActivityClass
package com.example.vidit.books;
import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final EditText query = (EditText) findViewById(R.id.query);
Button submit= (Button) findViewById(R.id.submit);
submit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent= new Intent(MainActivity.this,Request.class);
intent.putExtra ( "text", query.getText().toString() );
startActivity(intent);
}
});
}
}
Second Class
package com.example.vidit.books;
import android.content.Intent;
public class Request {
Intent i = getIntent();
String text = i.getStringExtra ("text");
public static final String LOG_TAG = Request.class.getSimpleName();
String APIURL="https://www.googleapis.com/books/v1/volumes?q= " + text;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_request);
}
public void UpdateUi(Book book)
{
BookAdapter bookAdapter = new BookAdapter(this,book);
ListView listView= (ListView) findViewById(R.id.listview_all);
}
private class BookAsyncTask extends AsyncTask<URL,Void,Book>
{
#Override
protected Book doInBackground(URL... urls) {
URL url = createUrl(APIURL);
String jsonResponse = "";
try {
jsonResponse = makeHttpRequest(url);
} catch (IOException e) {
// TODO Handle the IOException
}
final Book book = extractFeatureFromJson(jsonResponse);
return book;
}
/**
* Make an HTTP request to the given URL and return a String as the response.
*/
private String makeHttpRequest(URL url) throws IOException {
String jsonResponse = "";
HttpURLConnection urlConnection = null;
InputStream inputStream = null;
try {
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setReadTimeout(10000 /* milliseconds */);
urlConnection.setConnectTimeout(15000 /* milliseconds */);
urlConnection.connect();
if(urlConnection.getResponseCode()==200) {
inputStream = urlConnection.getInputStream();
jsonResponse = readFromStream(inputStream);
}
} catch (IOException e) {
// TODO: Handle the exception
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
if (inputStream != null) {
// function must handle java.io.IOException here
inputStream.close();
}
}
return jsonResponse;
}
/**
* Convert the {#link InputStream} into a String which contains the
* whole JSON response from the server.
*/
private String readFromStream(InputStream inputStream) throws IOException {
StringBuilder output = new StringBuilder();
if (inputStream != null) {
InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
BufferedReader reader = new BufferedReader(inputStreamReader);
String line = reader.readLine();
while (line != null) {
output.append(line);
line = reader.readLine();
}
}
return output.toString();
}
/**
* Returns new URL object from the given string URL.
*/
private URL createUrl(String stringUrl) {
URL url = null;
try {
url = new URL(stringUrl);
} catch (MalformedURLException exception) {
Log.e(LOG_TAG, "Error with creating URL", exception);
return null;
}
return url;
}
private Book extractFeatureFromJson(String bookJSON) {
try {
JSONObject baseJsonResponse = new JSONObject(bookJSON);
JSONArray items = baseJsonResponse.getJSONArray("items");
// If there are results in the features array
for(int i=0;i<10;i++)
{
JSONObject firstFeature = items.getJSONObject(i);
JSONArray author=firstFeature.getJSONArray("author");
for(int j=0;j<author.length();j++)
{
JSONObject authorFeature=author.getJSONObject(j);
}
String title = items.getString(Integer.parseInt("title"));
// Create a new {#link Event} object
return new Book(title,author);
}
} catch (JSONException e) {
Log.e(LOG_TAG, "Problem parsing the earthquake JSON results", e);
}
return null;
}
}
}
BookAdapter Class:
package com.example.vidit.books;
import android.app.Activity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;
import java.util.List;
public class BookAdapter extends ArrayAdapter<Book> {
public BookAdapter(Activity context, Book book)
{
super(context,0, (List<Book>) book);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View listItemView = convertView;
if(listItemView == null) {
listItemView = LayoutInflater.from(getContext()).inflate(
R.layout.list_item, parent, false);
}
Book cbook=getItem(position);
TextView title = (TextView) listItemView.findViewById(R.id.title);
title.setText(cbook.getmTitle());
TextView author=(TextView) listItemView.findViewById(R.id.author);
author.setText((CharSequence) cbook.getmAuthor());
return listItemView;
}
}
Showing error in statement:
String text = i.getStringExtra ("text");
Need guidance

I don't know how your code gets compiled when you have overridden onCreate() in Request class and the Request class isn't extending Activity or AppCompatActivity.
Secondly, this line :
Intent i = getIntent();
String text = i.getStringExtra ("text");
should be inside the onCreate() method.

Showing error in statement : String text = i.getStringExtra ("text");
Request for Guidance
Well you need to get the data passed inside onCreate like below.
String APIURL;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_request);
Bundle bundle = getIntent().getExtras();
String text = bundle.getString("text");
APIURL="https://www.googleapis.com/books/v1/volumes?q= " + text;
}
And although you have the asyncTask class i can't see where exactly you execute the class. You need to do that inside onCreate as well.

Try moving this code to your onCreate method
Intent i = getIntent();
String text = i.getStringExtra ("text");
The intent extras is not available in the constructor for your Request class.

Selective news from a particular rss newsfeed

In my application I want to display RSS feed of a particular website. But I do not want it to display full Rss feed, I want only some particular tags to be searched and display and only its related links should display on screen.
here is my code of the Parser Class:-
package com.example.sara.rssfeed;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import android.util.Xml;
import com.example.sara.rssfeed.RssItem;
public class PcWorldRssParser {
// We don't use namespaces
private final String ns = null;
public List<RssItem> parse(InputStream inputStream) throws XmlPullParserException, IOException {
try {
XmlPullParser parser = Xml.newPullParser();
parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false);
parser.setInput(inputStream, null);
parser.nextTag();
return readFeed(parser);
} finally {
inputStream.close();
}
}
private List<RssItem> readFeed(XmlPullParser parser) throws XmlPullParserException, IOException {
parser.require(XmlPullParser.START_TAG, null, "rss");
String title = null;
String link = null;
List<RssItem> items = new ArrayList<RssItem>();
while (parser.next() != XmlPullParser.END_DOCUMENT) {
if (parser.getEventType() != XmlPullParser.START_TAG) {
continue;
}
String name = parser.getName();
if (name.equals("title")) {
title = readTitle(parser);}
else if (name.equals("link")) {
link = readLink(parser);}
if (title=="Top Stories - Google News" && link=="http://news.google.com/news?hl=en&ned=us") {
RssItem item = new RssItem(title, link);
items.add(item);
title = null;
link = null;
}
}
return items;
}
private String readLink(XmlPullParser parser) throws XmlPullParserException, IOException {
parser.require(XmlPullParser.START_TAG, ns, "link");
String link = readText(parser);
parser.require(XmlPullParser.END_TAG, ns, "link");
return link;
}
private String readTitle(XmlPullParser parser) throws XmlPullParserException, IOException {
parser.require(XmlPullParser.START_TAG, ns, "title");
String title = readText(parser);
parser.require(XmlPullParser.END_TAG, ns, "title");
return title;
}
// For the tags title and link, extract their text values.
private String readText(XmlPullParser parser) throws IOException, XmlPullParserException {
String result = "";
if (parser.next() == XmlPullParser.TEXT) {
result = parser.getText();
parser.nextTag();
}
return result;
}
}
Error:
on line if (title=="Top Stories - Google News" &&
link=="http://news.google.com/news?hl=en&ned=us")if I put
tittle!=nullandlink!=null`
it displays full rss feed. but If i give it particular link and title tag to search it displays nothing, only a blank screen.
Please help what am I doing wrong.
Thanks in Advance.

Android app crashes by switching the activity

I have a Problem with my android app. It always crashes, when I push the Button to go to the new Activity.
Error:
FATAL EXCEPTION: main
Process: PID: 15534
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.realliferpgadac.thomas.adacapp/com.realliferpgadac.thomas.adacapp.Feed}: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.view.ViewGroup
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.view.ViewGroup
at android.app.BackStackRecord.configureTransitions(BackStackRecord.java:1244)
at android.app.BackStackRecord.beginTransition(BackStackRecord.java:978)
at android.app.BackStackRecord.run(BackStackRecord.java:707)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1535)
at android.app.FragmentController.execPendingActions(FragmentController.java:325)
at android.app.Activity.performStart(Activity.java:6252)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Source code of the activity that crashes: (It should be a RSS Feed)
import android.os.AsyncTask;
import android.os.Bundle;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.app.ListFragment;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import java.io.StringReader;
public class Feed extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_feed);
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.tvFeed, new PlaceholderFragment())
.commit();
}
}
//#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;
//}
#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();
if (id == R.id.tvFeed) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends ListFragment {
// private TextView mRssFeed;
public PlaceholderFragment() {
}
// #Override
// public View onCreateView(LayoutInflater inflater, ViewGroup container,
// Bundle savedInstanceState) {
// View rootView = inflater.inflate(R.layout.fragment_main, container, false);
// mRssFeed = (TextView) rootView.findViewById(R.id.rss_feed);
// return rootView;
// }
#Override
public void onStart() {
super.onStart();
new GetAndroidPitRssFeedTask().execute();
}
private String getAndroidPitRssFeed() throws IOException {
InputStream in = null;
String rssFeed = null;
try {
URL url = new URL("http://www.androidpit.com/feed/main.xml");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
in = conn.getInputStream();
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
for (int count; (count = in.read(buffer)) != -1; ) {
out.write(buffer, 0, count);
}
byte[] response = out.toByteArray();
rssFeed = new String(response, "UTF-8");
} finally {
if (in != null) {
in.close();
}
}
return rssFeed;
}
private class GetAndroidPitRssFeedTask extends AsyncTask<Void, Void, List<String>> {
#Override
protected List<String> doInBackground(Void... voids) {
List<String> result = null;
try {
String feed = getAndroidPitRssFeed();
result = parse(feed);
} catch (XmlPullParserException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
private List<String> parse(String rssFeed) throws XmlPullParserException, IOException {
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
XmlPullParser xpp = factory.newPullParser();
xpp.setInput(new StringReader(rssFeed));
xpp.nextTag();
return readRss(xpp);
}
private List<String> readRss(XmlPullParser parser)
throws XmlPullParserException, IOException {
List<String> items = new ArrayList<>();
parser.require(XmlPullParser.START_TAG, null, "rss");
while (parser.next() != XmlPullParser.END_TAG) {
if (parser.getEventType() != XmlPullParser.START_TAG) {
continue;
}
String name = parser.getName();
if (name.equals("channel")) {
items.addAll(readChannel(parser));
} else {
skip(parser);
}
}
return items;
}
private List<String> readChannel(XmlPullParser parser)
throws IOException, XmlPullParserException {
List<String> items = new ArrayList<>();
parser.require(XmlPullParser.START_TAG, null, "channel");
while (parser.next() != XmlPullParser.END_TAG) {
if (parser.getEventType() != XmlPullParser.START_TAG) {
continue;
}
String name = parser.getName();
if (name.equals("item")) {
items.add(readItem(parser));
} else {
skip(parser);
}
}
return items;
}
private String readItem(XmlPullParser parser) throws XmlPullParserException, IOException {
String result = null;
parser.require(XmlPullParser.START_TAG, null, "item");
while (parser.next() != XmlPullParser.END_TAG) {
if (parser.getEventType() != XmlPullParser.START_TAG) {
continue;
}
String name = parser.getName();
if (name.equals("title")) {
result = readTitle(parser);
} else {
skip(parser);
}
}
return result;
}
// Processes title tags in the feed.
private String readTitle(XmlPullParser parser)
throws IOException, XmlPullParserException {
parser.require(XmlPullParser.START_TAG, null, "title");
String title = readText(parser);
parser.require(XmlPullParser.END_TAG, null, "title");
return title;
}
private String readText(XmlPullParser parser)
throws IOException, XmlPullParserException {
String result = "";
if (parser.next() == XmlPullParser.TEXT) {
result = parser.getText();
parser.nextTag();
}
return result;
}
private void skip(XmlPullParser parser) throws XmlPullParserException, IOException {
if (parser.getEventType() != XmlPullParser.START_TAG) {
throw new IllegalStateException();
}
int depth = 1;
while (depth != 0) {
switch (parser.next()) {
case XmlPullParser.END_TAG:
depth--;
break;
case XmlPullParser.START_TAG:
depth++;
break;
}
}
}
#Override
protected void onPostExecute(List<String> rssFeed) {
if (rssFeed != null) {
setListAdapter(new ArrayAdapter<>(
getActivity(),
android.R.layout.simple_list_item_1,
android.R.id.text1,
rssFeed));
}
}
}
}
}
XML file of the activity that crashes:
<?xml version="1.0" encoding="utf-8"?>
<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="com.realliferpgadac.thomas.adacapp.Feed">
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New Text"
android:id="#+id/tvFeed"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
</ScrollView>
</RelativeLayout>
Where is the problem and how can I solve it?
I hope you can help me.
Thank you,
emt

Replace R.id.tvFeed with Framelayout's id or default id android.R.id.content.
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(android.R.id.content, new PlaceholderFragment())
.commit();
}
and remove the code from the onOptionsItemSelected() method.
if (id == R.id.tvFeed) {
return true;
}

can't fetch rss feed - android

I'm trying to develop a simple application that reads rss feeds from a certain URL and then displays the results in a list view.
Here is my rss reader, which is the main thing in the app:
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserFactory;
public class RssReader {
private String title = null;
private String link = null;
private String description = null;
private ArrayList<RssItem> posts = new ArrayList<RssItem>();
private Thread thread;
private String urlString = null;
private XmlPullParserFactory xmlFactoryObject;
public volatile boolean parsingComplete = true;
public RssReader(String url) {
this.urlString = url;
}
public boolean getParsingComplete() {
return this.parsingComplete;
}
public ArrayList<RssItem> getPosts() {
return posts;
}
public void parseXML(XmlPullParser parser) {
int event;
try {
event = parser.getEventType();
while (event != XmlPullParser.END_DOCUMENT) {
String name = parser.getName();
switch (event) {
case XmlPullParser.START_TAG:
break;
case XmlPullParser.END_TAG:
if (name.equals("title")) {
title = parser.getText();
} else if (name.equals("link")) {
link = parser.getText();
} else if (name.equals("description")) {
description = parser.getText();
}
break;
}
if(title != null && link != null && description != null) {
RssItem item = new RssItem(this.title,this.description,this.link);
posts.add(item);
this.title = this.description = this.link = null;
}
event = parser.next();
}
parsingComplete = false;
} catch (Exception e) {
e.printStackTrace();
}
}
public void fetchXML() {
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();
xmlFactoryObject = XmlPullParserFactory.newInstance();
XmlPullParser myparser = xmlFactoryObject.newPullParser();
myparser.setFeature(
XmlPullParser.FEATURE_PROCESS_NAMESPACES, false);
myparser.setInput(stream, null);
parseXML(myparser);
stream.close();
} catch (Exception e) {
} finally {
parsingComplete = true;
}
}
});
thread.start();
}
And here is my MainActivity:
package com.example.ynetrssproject;
import java.util.ArrayList;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.widget.ListView;
import android.os.Bundle;
public class MainActivity extends ActionBarActivity {
private ListView news;
private String rssUrl = "http://www.themarker.com/cmlink/1.144";
private ArrayList<RssItem> list;
private RssItemAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
news = (ListView) findViewById(R.id.news);
RssReader reader = new RssReader(rssUrl);
reader.fetchXML();
while(true) {
Log.d("Runnning", "Run");
if(reader.getParsingComplete()) {
list = reader.getPosts();
break;
}
}
adapter = new RssItemAdapter(this, R.layout.post_item_list, list);
news.setAdapter(adapter);
}
}
The problem is that everytime I call fetchXML, eventually it returns me an empty ArrayList. Therefore, my listview keeps being empty.
My adapter isn't such a big deal. It works fine. The problem is that I keep getting an empty array list from the object RssReader. I know this because I performed a little if statement at the end of the code just to check if the ArrayList is empty.
P.S I have tried with multiple RSS urls but none of them works. Also, I added the permission of Internet in my manifest.
What's wrong with my code?

Your approach is a classic java approach. With android, you should use an IntentService or an AsyncTask that perform the RSS-fetch and then sends the read items to your activity.
http://developer.android.com/reference/android/app/IntentService.html
http://developer.android.com/reference/android/os/AsyncTask.html
Don't use while(true) to poll if the reader is ready.
Be aware that, when the user rotates the screen, onCreate is executed again.