SectionListFragment.java

/*
 * Copyright (C) 2013 Ian G. Clifton
 * Code featured in Android User Interface Design: Turning Ideas and
 * Sketches into Beautifully Designed Apps (ISBN-10: 0321886739;
 * ISBN-13: 978-0321886736).
 *
 * 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 com.iangclifton.auid.appendixc;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.view.View;
import android.widget.ListAdapter;
import android.widget.ListView;

import com.iangclifton.auid.appendixc.sections.Section;
import com.iangclifton.auid.appendixc.sections.SectionAdapter;

/**
 * A list fragment representing a list of Sections. 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 SectionDetailFragment}.
 * <p>
 * Activities containing this fragment MUST implement the {@link Callbacks}
 * interface.
 */
public class SectionListFragment extends ListFragment {

	/**
	 * 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;

	/**
	 * 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(Section section);
	}

	/**
	 * 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(Section section) {
		}
	};

	/**
	 * Mandatory empty constructor for the fragment manager to instantiate the
	 * fragment (e.g. upon screen orientation changes).
	 */
	public SectionListFragment() {
	}

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		// Get Sections
		final Section[] sections = Section.values();

		// Create Adapter
		final ListAdapter adapter = new SectionAdapter(getActivity(), sections);
		
		// And set it
		setListAdapter(adapter);
	}

	@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));
		}
	}

	@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.
		final SectionAdapter adapter = (SectionAdapter) getListAdapter();
		mCallbacks.onItemSelected(adapter.getItem(position));
	}

	@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;
	}
	
}