I've made the changes suggested by the most kind kris larson, and I'm now not returning the right type from onCreateLoader
return new StoriesLoader(getContext(), uriBuilder.toString());
StoriesLoader:
import android.content.AsyncTaskLoader;
import android.content.Context;
import java.util.List;
/**
* Loads a list of news stories by using an AsyncTask to perform the
* network request to the given URL.
*/
public class StoriesLoader extends AsyncTaskLoader<List<NewsStory>> {
/** Tag for log messages */
private static final String LOG_TAG = StoriesLoader.class.getName();
/** Query URL */
private String mUrl;
/**
* Constructs a new {@link StoriesLoader}.
*
* @param context of the activity
* @param url to load data from
*/
public StoriesLoader(Context context, String url) {
super(context);
mUrl = url;
}
@Override
protected void onStartLoading() {
forceLoad();
}
/**
* This is on a background thread.
*/
@Override
public List<NewsStory> loadInBackground() {
if (mUrl == null) {
return null;
}
// Perform the network request, parse the response, and extract a list of news stories.
List<NewsStory> newsStories = QueryUtils.fetchNewsStoryData(mUrl);
return newsStories;
}
}
I think I'm right to use an AsyncTaskLoader, but I don't get how to wrap / cast what is returned so it's a
Loader<List<NewsStory>>
Is my thinking wrong? Do I have to ditch the AsyncTaskLoader? ~~~
StoriesLoader returns List, from
/**
* This is on a background thread.
*/
@Override
public List<NewsStory> loadInBackground() {
if (mUrl == null) {
return null;
}
// Perform the network request, parse the response, and extract a list of earthquakes.
List<NewsStory> newsStories = QueryUtils.fetchNewsStoryData(mUrl);
return newsStories;
}
I've tried these, to no avail:
return new Loader<(new StoriesLoader(getContext(), uriBuilder.toString()))>();
return new Loader<>(new StoriesLoader(getContext(), uriBuilder.toString()));
If you're out there Kris, your corrections are well appreciated.
~~~~~~~~~ Studio is complaining
Wrong 3rd argument type. Found: 'com.newsreader.guardian.guardiantech.ListOfStoriesFragment', required: 'android.support.v4.app.LoaderManager.LoaderCallbacks'
When met with this
loaderManager.initLoader(mPage, null, this);
I believe it wants a way to reference the loader callbacks as the third parameter, it needs a map to where they are, is this right?
I'm using the Loader in a fragment so that has derailed it. I've tried changing the third parameter to getActivity(), getContext(), tried ListOfStoriesFragment, all to no avail.
The Fragment does implement the LoaderCallbacks interface - the callbacks are beneath it, so why doesn't it work?
I tried Android Studio's suggested fixes. Implement v4.app.LoadManager callbacks, but that broke a world of stuff.
How do I fix this? Can I fix this by importing something different?
Apologies for the question.
import android.content.Context;
import android.content.Intent;
import android.content.Loader;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.LoaderManager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
import static com.newsreader.guardian.guardiantech.BuildConfig.API_KEY;
/**
* Initiates a loader to get JSON from The Guardian
* updates UI with info when the data has returned
*/
public class ListOfStoriesFragment extends Fragment
implements android.app.LoaderManager.LoaderCallbacks<List<NewsStory>> {
/** String for tabs */
public static final String ARG_PAGE = "ARG_PAGE";
private int mPage;
private static final String TAG = ListOfStoriesFragment.class.getName();
/** URL for earthquake data from the USGS dataset */
private static final String GUARDIAN_REQUEST_URL =
"http://content.guardianapis.com/search";
/**
* Constant value for the news story loader ID. We can choose any integer.
* This really only comes into play if you're using multiple loaders.
*/
private static final int NEWSSTORY_LOADER_ID = 1;
/** Adapter for the list of newsStories */
private NewsStoryAdapter mAdapter;
/** TextView that is displayed when the list is empty */
private TextView mEmptyStateTextView;
/** more tabs stuff */
public static ListOfStoriesFragment newInstance(int page) {
Bundle args = new Bundle();
args.putInt(ARG_PAGE, page);
ListOfStoriesFragment fragment = new ListOfStoriesFragment();
fragment.setArguments(args);
return fragment;
}
/** needed for tabs?! */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mPage = getArguments().getInt(ARG_PAGE);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_stories, container, false);
// Find a reference to the {@link ListView} in the layout
ListView newsStoryListView = (ListView) rootView.findViewById(R.id.list);
mEmptyStateTextView = (TextView) rootView.findViewById(R.id.empty_view);
newsStoryListView.setEmptyView(mEmptyStateTextView);
// Create a new adapter that takes an empty list of NewsStory as input
mAdapter = new NewsStoryAdapter(getContext(), new ArrayList<NewsStory>());
// Set the adapter on the {@link ListView}
// so the list can be populated in the user interface
newsStoryListView.setAdapter(mAdapter);
// Get a reference to the ConnectivityManager to check state of network connectivity
ConnectivityManager connMgr = (ConnectivityManager)
getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);
// Get details on the currently active default data network
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
// If there is a network connection, fetch data
if (networkInfo != null && networkInfo.isConnected()) {
// Get a reference to the LoaderManager, in order to interact with loaders.
LoaderManager loaderManager = getLoaderManager();
// Initialize the loader. Pass in the int ID constant defined above and pass in null for
// the bundle. Pass in this activity for the LoaderCallbacks parameter (which is valid
// because this activity implements the LoaderCallbacks interface).
//loaderManager.initLoader(NEWSSTORY_LOADER_ID, null, this);
// number the loaderManager with mPage as may be requesting up to three lots of JSON for each tab
loaderManager.initLoader(mPage, null, this);
} else {
// Otherwise, display error
// First, hide loading indicator so error message will be visible
View loadingIndicator = rootView.findViewById(R.id.loading_indicator);
loadingIndicator.setVisibility(View.GONE);
// Update empty state with no connection error message
mEmptyStateTextView.setText(R.string.no_internet_connection);
}
return rootView;
}
@Override
public Loader<List<NewsStory>> onCreateLoader(int i, Bundle bundle) {
String searchTerm;
switch(mPage) {
case 0:
searchTerm = "windows";
break;
case 1:
searchTerm = "android";
break;
default:
searchTerm = "android wear";
}
Uri baseUri = Uri.parse(GUARDIAN_REQUEST_URL);
Uri.Builder uriBuilder = baseUri.buildUpon();
uriBuilder.appendQueryParameter("q", searchTerm);
uriBuilder.appendQueryParameter("api-key", API_KEY);
uriBuilder.build();
Log.wtf(TAG, uriBuilder.toString());
return new StoriesLoader(getContext(), uriBuilder.toString());
}
@Override
public void onLoadFinished(Loader<List<NewsStory>> loader, List<NewsStory> newsStories) {
// Hide loading indicator because the data has been loaded
View loadingIndicator = getView().findViewById(R.id.loading_indicator);
loadingIndicator.setVisibility(View.GONE);
// Set empty state text to display "No stories found."
mEmptyStateTextView.setText(R.string.no_news_stories);
// Clear the adapter of previous newsStories
mAdapter.clear();
// If there is a valid list of {@link NewsStory}s, then add them to the adapter's
// data set. This will trigger the ListView to update.
if (newsStories != null && !newsStories.isEmpty()) {
mAdapter.addAll(newsStories);
}
}
@Override
public void onLoaderReset(Loader<List<NewsStory>> loader) {
// Loader reset, so we can clear out our existing data.
mAdapter.clear();
}
}
The Fragment does implement the LoaderCallbacks interface - the callbacks are beneath it, so why doesn't it work?
Because you are mixing support library classes with platform classes.
android.content.Loader is not compatible with android.support.v4.app.LoaderManager
The line
LoaderManager loaderManager = getLoaderManager();
is returning a android.support.v4.app.LoaderManager so for
loaderManager.initLoader(mPage, null, this);
to compile, your fragment will need to implement android.support.v4.app.LoaderManager.LoaderCallbacks, not android.app.LoaderManager.LoaderCallbacks.
I've had this problem multiple times.
I will assume you want the support library classes.
Change
import android.content.Loader;
to
import android.support.v4.content.Loader;
Change
public class ListOfStoriesFragment extends Fragment
implements android.app.LoaderManager.LoaderCallbacks<List<NewsStory>> {
to
public class ListOfStoriesFragment extends Fragment
implements LoaderManager.LoaderCallbacks<List<NewsStory>> {
and that should fix your problem.
Make sure StoriesLoader extends android.support.v4.app.Loader and not android.app.Loader. Check your import statements.