Я создаю приложение новостей для Android, чтобы получать данные из газеты новостей Gurdian и показывать его в моем приложении. У меня проблема с работой приложения по AyncTaskLoader Я создаю класс данных
{
/**
* Class to make and define objects of news.
*/
public class NewsClass {
// Define String of News(title,author,description,publishDate).
private String news_title;
private String author_name;
private String description;
private String date;
/**
* Constructor to make objects from News .
*
* @param news_title it takes news title string.
* @param author_name it takes news author name string.
* @param description it takes news description string.
* @param date it takes news publish date string.
*/
NewsClass(String news_title, String author_name, String description, String date) {
this.news_title = news_title;
this.author_name = author_name;
this.description = description;
this.date = date;
}
/**
* @return news title.
*/
String getNews_title() {
return news_title;
}
/**
* @return news author name.
*/
String getAuthor_name() {
return author_name;
}
/**
* @return news description.
*/
String getDescription() {
return description;
}
/**
* @return news publish date.
*/
String getDate() {
return date;
}
}
и класс адаптера
/**
* Custom Adapter to arrange news items in List View.
*/
public class NewsAdapter extends ArrayAdapter<NewsClass> {
private List<NewsClass> newsList = new ArrayList<NewsClass>();
/**
* Constructor.
*
* @param context it takes context.
* @param resource it takes resource id.
* @param news it takes array of data.
*/
NewsAdapter(@NonNull Context context, int resource, ArrayList<NewsClass> news) {
super(context, resource, news);
}
/**
* define view to take list_item elements and put it in layout.
*
* @param position it takes every news element position from the arraylist.
* @param convertView it takes view and inflates list_item in parent.
* @param parent it takes parent.
* @return it returns View of each News Element with its data according to list_item.
*/
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
// Define new View and attach give it convertview.
View view = convertView;
//Check if convertview is null and inflate list_item layout into it.
if (view == null) {
view = LayoutInflater.from(getContext()).inflate(R.layout.list_item,
parent,
false);
}
// create object from NewsClass and get its position.
NewsClass newsClass = getItem(position);
// declare and define news title TextView.
TextView news_title = view.findViewById(R.id.news_title);
// declare and define news Author TextView.
TextView news_author_name = view.findViewById(R.id.news_author_name);
// put element title and attach it to its TextView.
news_title.setText(newsClass.getNews_title());
// put element author and attach it to its TextView.
news_author_name.setText(newsClass.getAuthor_name());
return view;
}
public void setNews(List<NewsClass> data) {
newsList.addAll(data);
notifyDataSetChanged();
}
}
и класс Utils для выполнения HTTP-запроса и выборки данных JSON
/**
* Class to handle HTTP Requests and JSON parsing.
*/
public class Utils {
private static final String LOG_TAG = Utils.class.getSimpleName();
/**
* Fetching data from url and storing it in ArrayList of type NewsClass.
*
* @param requestUrl function requires url.
* @return it return an ArrayList of type NewsClass.
*/
static ArrayList<NewsClass> fetchNewsData(String requestUrl) {
// Create URL object
URL url = createUrl(requestUrl);
// Perform HTTP request to the URL and receive a JSON response back.
String jsonResponse = null;
try {
jsonResponse = makeHttpRequest(url);
} catch (IOException e) {
Log.e(LOG_TAG, "Error closing input stream", e);
}
// Extract relevant fields from the JSON response and create an object.
// Return the {@link NewsClass}
return extractFeatureFromJson(jsonResponse);
}
/**
* Function to create URL object from given String URL.
*
* @param stringUrl it takes String of URL
* @return Returns new URL object from the given string URL.
*/
private static URL createUrl(String stringUrl) {
// declare new URL and initailizing it
URL url = null;
// surround with try and catch
try {
// initialize URL and set param to string to create URL
url = new URL(stringUrl);
} catch (MalformedURLException e) {
e.printStackTrace();
}
// return URL
return url;
}
/**
* Make an HTTP request to the given URL and return a String as the response.
*
* @param url it takes URL which we get from previos function.
* @return it return JSON Response.
* @throws IOException url may make exception of this type
*/
private static String makeHttpRequest(URL url) throws IOException {
// declare new empty String.
String jsonResponse = "";
// Check if the URL is null, then return early.
if (url == null) {
return jsonResponse;
}
// declare new HttpURLConnection.
HttpURLConnection urlConnection = null;
// declare new InputStream.
InputStream inputStream = null;
// surround with try and catch
try {
// create HTTP request.
urlConnection = (HttpURLConnection) url.openConnection();
// set request method.
urlConnection.setRequestMethod("GET");
// connect to server.
urlConnection.connect();
// If the request was successful (response code 200),
// then read the input stream and parse the response.
if (urlConnection.getResponseCode() == 200) {
// get InputStream with data to read it.
inputStream = urlConnection.getInputStream();
// read from stream and return string then saved it in jsonResponse.
jsonResponse = readFromStream(inputStream);
} else {
Log.e(LOG_TAG, "Error response code: " + urlConnection.getResponseCode());
}
} catch (IOException e) {
Log.e(LOG_TAG, "Problem retrieving the News JSON results.", e);
} finally {
// if urlConnection return with data
if (urlConnection != null) {
// then disconnect .
urlConnection.disconnect();
}
// if inputStream return with data.
if (inputStream != null) {
// close the inputStream.
inputStream.close();
}
}
// return jsonResponse with data.
return jsonResponse;
}
/**
* readFromStream to the given InputStream then return String (JSON).
*
* @param inputStream it takes inputStream.
* @return return String of JSON Response.
* @throws IOException inputStream may make exception.
*/
private static String readFromStream(InputStream inputStream) throws IOException {
// initialize StringBuilder.
StringBuilder stringBuilder = new StringBuilder();
// if inputStream return with data.
if (inputStream != null) {
// create and initialize InputStreamReader with two params (inputStream, Symbol rate utf-8).
InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
// create and initialize BufferedReader with one param (InputStreamReader).
BufferedReader reader = new BufferedReader(inputStreamReader);
// new String to save data from BufferedReader line by line.
String line = reader.readLine();
// loop to update String line by line and append this lines to stringBuilder.
while (line != null) {
stringBuilder.append(line);
line = reader.readLine();
}
}
// return String.
return stringBuilder.toString();
}
/**
* extractFeatureFromJson to the given String then return ArrayList<NewsClass>.
*
* @param newsJSON it takes json objects.
* @return ArrayList of data From JSON.
*/
private static ArrayList<NewsClass> extractFeatureFromJson(String newsJSON) {
// If the JSON string is empty or null, then return early.
if (TextUtils.isEmpty(newsJSON)) {
return null;
}
// Create an empty ArrayList that we can start adding news to.
ArrayList<NewsClass> news = new ArrayList<>();
// surround with try and catch.
try {
// initialize baseJSONObject.
JSONObject baseJsonResponse = new JSONObject(newsJSON);
// initialize and get response from baseJSONObject.
JSONObject response = baseJsonResponse.getJSONObject("response");
// initialize JSONArray results to get items array.
JSONArray itemsArray = response.getJSONArray("results");
// loop to get all items in itemsArray.
for (int i = 0; i < itemsArray.length(); i++) {
// JSONObject to get data from each item.
JSONObject firstitem = itemsArray.getJSONObject(i);
// Get News Title.
// String to get news webTitle.
String title;
if (firstitem.has("webTitle")) {
title = firstitem.getString("webTitle");
} else {
title = "Title not Found";
}
//Get News Author.
// String to get news author.
String author;
if (firstitem.has("pillarId")) {
author = firstitem.getString("pillarId");
} else {
author = "Author not Found";
}
//Get News Publishing Date.
// String to get news webPublicationDate.
String date;
if (firstitem.has("webPublicationDate")) {
date = firstitem.getString("webPublicationDate");
} else {
date = "Published Date not Found";
}
// Get News Description Link.
// String to get news webUrl.
String description;
if (firstitem.has("webUrl")) {
description = firstitem.getString("webUrl");
} else {
description = "Description not Found";
}
// add every object from JSON Response to News ArrayList.
news.add(new NewsClass(title, author, description, date));
}
} catch (JSONException e) {
Log.e(LOG_TAG, "Problem parsing the News JSON results", e);
}
// return Arraylist news.
return news;
}
}
и это основное задание
public class MainActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<ArrayList<NewsClass>> {
// Define news title EditText to search for.
EditText news_title;
// Define news search Button to search for.
Button search;
// Define progressBar.
ProgressBar progressBar;
// Define news listView .
ListView listView;
// Define news news Adapter Object.
NewsAdapter newsAdapter;
// Define news API String.
String NEWS_API;
// Define news image ImageView .
ImageView news;
// Define news search string to search for.
String s;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// define views in activity_main_layout.
news_title = findViewById(R.id.edit_txt_news);
search = findViewById(R.id.search_btn);
listView = findViewById(R.id.listview);
news = findViewById(R.id.news);
progressBar = findViewById(R.id.progeress_bar);
//set progressBar visibility to INVISIBLE .
progressBar.setVisibility(View.INVISIBLE);
// create object from newsAdapter and give it context and resource and ArrayList.
newsAdapter = new NewsAdapter(getApplicationContext(), 0, new ArrayList<NewsClass>());
// Attach our Adapter to ListView.
listView.setAdapter(newsAdapter);
// handle listview items clicks to open NewsDetails Activity to show element details.
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
NewsClass currentnews = newsAdapter.getItem(position);
// get every news element data and store it in variables.
String title = currentnews.getNews_title();
String author = currentnews.getAuthor_name();
String Date = currentnews.getDate();
String description = currentnews.getDescription();
// Make new Intent to open NewsDetails Activity.
Intent intent = new Intent(getApplicationContext(), NewsDetail.class);
// send every news element data and store it in variables with the Intent.
intent.putExtra("title", title);
intent.putExtra("author", author);
intent.putExtra("date", Date);
intent.putExtra("desc", description);
startActivity(intent);
}
});
// Check Internet Connectivity.
if (isNetworkConnected()) {
// initiate Loader Manager.
getSupportLoaderManager().initLoader(1, null, this).forceLoad();
// handle search box searches when we click search Button.
search.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// get text entered by user and save it in String s.
s = news_title.getText().toString();
// check if EditText don't have anything "user didn't write anything to search for.
if (s.length() == 0) {
//make a toast message to the user.
Toast.makeText(getApplicationContext(), "Please Enter News to search for ", Toast.LENGTH_LONG).show();
} else {
// hide progressBar
news.setVisibility(View.GONE);
// Enter News Api and store it and give it user search word.
NEWS_API =
"https://content.guardianapis.com/search?q=" + s + "&api-key=fb2fab34-e55f-411f-9892-af1c207c759c";
InputMethodManager inputMethodManager = (InputMethodManager) getSystemService(
Activity.INPUT_METHOD_SERVICE);
if (inputMethodManager != null) {
inputMethodManager.toggleSoftInput(InputMethodManager.HIDE_IMPLICIT_ONLY, 0);
}
// empty search Box after making search.
news_title.setText("");
}
}
});
// hide progress bar.
news.setVisibility(View.GONE);
// Enter News Api and store it to show all news if user did not search anything.
NEWS_API =
"https://content.guardianapis.com/search?api-key=fb2fab34-e55f-411f-9892-af1c207c759c";
} else
// Make Toast to Ask User to Open Internet Connection
Toast.makeText(this, "Please Connect to Internet to fetch Data", Toast.LENGTH_LONG).show();
}
@NonNull
@Override
public Loader<ArrayList<NewsClass>> onCreateLoader(int id, @Nullable Bundle bundle) {
return new NewsAsyncLoader(MainActivity.this, bundle.getString(NEWS_API));
}
@Override
public void onLoadFinished(@NonNull Loader<ArrayList<NewsClass>> loader, ArrayList<NewsClass> data) {
newsAdapter.setNews(data);
}
@Override
public void onLoaderReset(@NonNull Loader<ArrayList<NewsClass>> loader) {
newsAdapter.setNews(new ArrayList<NewsClass>());
}
// Function To check Internet Connectivity
private boolean isNetworkConnected() {
ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
return cm.getActiveNetworkInfo() != null && cm.getActiveNetworkInfo().isConnected();
}
// Class To Load In background by AsyncTaskLoader
class NewsAsyncLoader extends AsyncTaskLoader<ArrayList<NewsClass>> {
public NewsAsyncLoader(Context context, String Url) {
super(context);
Url = NEWS_API;
}
@Override
public ArrayList<NewsClass> loadInBackground() {
if (NEWS_API == null) {
return null;
}
ArrayList<NewsClass> Newslist = Utils.fetchNewsData(NEWS_API);
return Newslist;
}
}
}
, но оно не работает и не извлекает dataTask, но при преобразовании его в AsyncTaskLoader оно запирает