Android, Java, AsyncTaskLoader.

AsyncTaskLoader.java

public class MainActivity extends AppCompatActivity implements
    LoaderManager.LoaderCallbacks<String> {
    
    private static final int LOADER_ID = 22;
    private static final String SEARCH_QUERY_URL_EXTRA = "query";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        Bundle queryBundle = new Bundle();
        queryBundle.putString(SEARCH_QUERY_URL_EXTRA, searchUrl.toString());

        LoaderManager loaderManager = getSupportLoaderManager();
        Loader<String> searchLoader = loaderManager.getLoader(LOADER_ID);
        if (searchLoader == null) {
            loaderManager.initLoader(LOADER_ID, queryBundle, this);
        } else {
            loaderManager.restartLoader(LOADER_ID, queryBundle, this);
        }
    }    
    
    @Override
    public Loader<String> onCreateLoader(int id, final Bundle args) {
        return new AsyncTaskLoader<String>(this) {
            // query response cache
            String mJson;

            @Override
            protected void onStartLoading() {
                if (args == null) {
                    return;
                }
                if (mJson != null) {
                    deliverResult(mJson);
                } else {
                    forceLoad();
                }
            }

            @Override
            public String loadInBackground() {
                String searchQueryUrlString = args.getString(SEARCH_QUERY_URL_EXTRA);
                
                if (searchQueryUrlString == null || searchQueryUrlString.isEmpty()) {
                    return null;
                }
                
                try {
                    URL url = new URL(searchQueryUrlString);
                    String searchResults = NetworkUtils.getResponseFromHttpUrl(url);
                    return searchResults;
                } catch (IOException e) {
                    e.printStackTrace();
                    return null;
                }
            }

            @Override
            public void deliverResult(String json) {
                mJson = json;
                super.deliverResult(json);
            }
        };
    }

    @Override
    public void onLoadFinished(Loader<String> loader, String data) {
        if (null == data) {
            showErrorMessage();
        } else {
            showJsonData(data);
        }
    }

    @Override
    public void onLoaderReset(Loader<String> loader) {
        // not used
    }    
}