Java tutorial
/* * (C) Copyright 2014 Roberto Estrada Casarrubios. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * */ package me.robertoestrada.rssreader.fragments; import android.app.Activity; import android.content.SharedPreferences; import android.os.Bundle; import android.preference.PreferenceManager; import android.support.v4.app.ListFragment; import android.util.Log; import android.view.View; import android.widget.ListView; import com.koushikdutta.async.future.FutureCallback; import com.koushikdutta.ion.Ion; import org.xml.sax.SAXException; import java.io.IOException; import java.io.InputStream; import java.util.List; import me.robertoestrada.rssreader.R; import me.robertoestrada.rssreader.adapters.RSSItemAdapter; import nl.matshofman.saxrssreader.RssItem; import nl.matshofman.saxrssreader.RssReader; /** * A list fragment representing a list of Items. This fragment * also supports tablet devices by allowing list items to be given an * 'activated' state upon selection. This helps indicate which item is * currently being viewed in a {@link ItemDetailFragment}. * <p/> * Activities containing this fragment MUST implement the {@link Callbacks} * interface. */ public class ItemListFragment extends ListFragment { private static final String TAG = ItemListFragment.class.getName(); /** * The serialization (saved instance state) Bundle key representing the * activated item position. Only used on tablets. */ private static final String STATE_ACTIVATED_POSITION = "activated_position"; /** * The fragment's current callback object, which is notified of list item * clicks. */ private Callbacks mCallbacks = sDummyCallbacks; /** * The current activated item position. Only used on tablets. */ private int mActivatedPosition = ListView.INVALID_POSITION; /** * The feed URL, this loads from the preferences */ private String mFeedURL; /** * A callback interface that all activities containing this fragment must * implement. This mechanism allows activities to be notified of item * selections. */ public interface Callbacks { /** * Callback for when an item has been selected. */ public void onItemSelected(String title, String content, String link); } /** * A dummy implementation of the {@link Callbacks} interface that does * nothing. Used only when this fragment is not attached to an activity. */ private static Callbacks sDummyCallbacks = new Callbacks() { @Override public void onItemSelected(String title, String content, String link) { } }; /** * Contains the feed items to display */ private List<RssItem> mFeedItemList; /** * Mandatory empty constructor for the fragment manager to instantiate the * fragment (e.g. upon screen orientation changes). */ public ItemListFragment() { } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); } @Override public void onViewCreated(View view, Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); // Restore the previously serialized activated item position. if (savedInstanceState != null && savedInstanceState.containsKey(STATE_ACTIVATED_POSITION)) { setActivatedPosition(savedInstanceState.getInt(STATE_ACTIVATED_POSITION)); } SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(getActivity()); mFeedURL = sp.getString("feed_url", getResources().getString(R.string.default_feed_url)); getFeedItemsAsync(mFeedURL); } @Override public void onAttach(Activity activity) { super.onAttach(activity); // Activities containing this fragment must implement its callbacks. if (!(activity instanceof Callbacks)) { throw new IllegalStateException("Activity must implement fragment's callbacks."); } mCallbacks = (Callbacks) activity; } @Override public void onDetach() { super.onDetach(); // Reset the active callbacks interface to the dummy implementation. mCallbacks = sDummyCallbacks; } @Override public void onListItemClick(ListView listView, View view, int position, long id) { super.onListItemClick(listView, view, position, id); // Notify the active callbacks interface (the activity, if the // fragment is attached to one) that an item has been selected. RssItem item = mFeedItemList.get(position); mCallbacks.onItemSelected(item.getTitle(), item.getDescription(), item.getLink()); } @Override public void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); if (mActivatedPosition != ListView.INVALID_POSITION) { // Serialize and persist the activated item position. outState.putInt(STATE_ACTIVATED_POSITION, mActivatedPosition); } } /** * Turns on activate-on-click mode. When this mode is on, list items will be * given the 'activated' state when touched. */ public void setActivateOnItemClick(boolean activateOnItemClick) { // When setting CHOICE_MODE_SINGLE, ListView will automatically // give items the 'activated' state when touched. getListView().setChoiceMode(activateOnItemClick ? ListView.CHOICE_MODE_SINGLE : ListView.CHOICE_MODE_NONE); } private void setActivatedPosition(int position) { if (position == ListView.INVALID_POSITION) { getListView().setItemChecked(mActivatedPosition, false); } else { getListView().setItemChecked(position, true); } mActivatedPosition = position; } private void getFeedItemsAsync(String feedUrl) { Ion.with(this).load(feedUrl).asInputStream().setCallback(new FutureCallback<InputStream>() { @Override public void onCompleted(Exception e, InputStream result) { if (e != null) { Log.e(TAG, e.getMessage()); } else { try { mFeedItemList = RssReader.read(result).getRssItems(); setListAdapter(new RSSItemAdapter(getActivity(), R.layout.feed_item_layout, mFeedItemList)); } catch (IOException feedException) { Log.e(TAG, feedException.getMessage()); } catch (SAXException parseException) { Log.e(TAG, parseException.getMessage()); } } } }); } }