Java tutorial
/* * Copyright 2013 Kirk Rader * 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 us.rader.tapset; import us.rader.tapset.item.Item; import android.app.Activity; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.app.ListFragment; import android.view.View; import android.widget.AbsListView; import android.widget.AdapterView; import android.widget.ArrayAdapter; import android.widget.ListView; /** * A list fragment representing a list of SettingsItems. 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 ItemSelectedListener} interface. */ public class ItemListFragment extends ListFragment { /** * A callback interface that all activities containing this fragment must * implement. This mechanism allows activities to be notified of item * selections. */ public interface ItemSelectedListener { /** * Callback for when an item has been selected. * * @param id * the {@link Item} id of the selected item */ public void onItemSelected(String id); } /** * A dummy implementation of the {@link ItemSelectedListener} interface that * does nothing. Used only when this fragment is not attached to an * activity. */ private static ItemSelectedListener dummyItemSelectedListener; /** * 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"; //$NON-NLS-1$ static { dummyItemSelectedListener = new ItemSelectedListener() { @Override public void onItemSelected(String id) { // deliberately empty method implementation } }; } /** * The current activated item position. Only used on tablets. */ private int activatedPosition; /** * The fragment's current callback object, which is notified of list item * clicks. */ private ItemSelectedListener itemSelectedListener; /** * Initialize this instance to its inactive state */ public ItemListFragment() { itemSelectedListener = dummyItemSelectedListener; activatedPosition = AdapterView.INVALID_POSITION; } /** * Attach this {@link ItemListFragment} to the given {@link Activity} * * Note that the given {@link Activity} must implement * {@link ItemSelectedListener}, a fact that is checked at run time due to * the failure to impose generic constraints on this method at compile time * * @param activity * the {@link Activity} * * @see Fragment#onAttach(Activity) */ @Override public void onAttach(Activity activity) { super.onAttach(activity); // Activities containing this fragment must implement its callbacks. if (!(activity instanceof ItemSelectedListener)) { throw new IllegalStateException("Activity must implement fragment's callbacks."); //$NON-NLS-1$ } itemSelectedListener = (ItemSelectedListener) activity; } /** * Initialize this instance * * @param savedInstanceState * persisted state or <code>null</code> * * @see Fragment#onCreate(Bundle) */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setListAdapter(new ArrayAdapter<Item<?>>(getActivity(), android.R.layout.simple_list_item_1, android.R.id.text1, Item.getSettingsItems())); } /** * Detach this instance from any {@link ItemSelectedListener} to which it is * attached * * @see android.support.v4.app.Fragment#onDetach() */ @Override public void onDetach() { super.onDetach(); // Reset the active callbacks interface to the dummy implementation. itemSelectedListener = dummyItemSelectedListener; } /** * Handle a click event * * @param listView * the {@link ListView} on which the user clicked * * @param view * the container {@link View} * * @param position * the position of the item on which the user clicked * * @param id * the id of the item on which the user clicked * * @see ListFragment#onListItemClick(ListView, View, int, long) */ @Override public void onListItemClick(ListView listView, View view, int position, long id) { super.onListItemClick(listView, view, position, id); String settingsItemId = Item.getSettingsItems().get(position).getId(); itemSelectedListener.onItemSelected(settingsItemId); } /** * Persist any relevant app state on behalf of this instance * * @param outState * the {@link Bundle} in which to put the persisted state * * @see Fragment#onSaveInstanceState(Bundle) */ @Override public void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); if (activatedPosition != AdapterView.INVALID_POSITION) { // Serialize and persist the activated item position. outState.putInt(STATE_ACTIVATED_POSITION, activatedPosition); } } /** * * @param view * the container {@link View} * * @param savedInstanceState * the {@link Bundle} containing persisted state data for this * instance, or <code>null</code> * * @see ListFragment#onViewCreated(View, Bundle) */ @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)); } } /** * Update the selected item in this {@link ItemListFragment} * * @param position * the newly activated position */ public void setActivatedPosition(int position) { if (position == AdapterView.INVALID_POSITION) { getListView().setItemChecked(activatedPosition, false); } else { getListView().setItemChecked(position, true); } activatedPosition = position; } /** * @param activateOnItemClick * value indicating whether or not an item should be activated * automatically when it is clicked 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 ? AbsListView.CHOICE_MODE_SINGLE : AbsListView.CHOICE_MODE_NONE); } }