Java tutorial
/* * Copyright 2012 Google Inc. * * 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 net.abcdroid.devfest12.ui; import net.abcdroid.devfest12.provider.ScheduleContract.Announcements; import net.abcdroid.devfest12.util.UIUtils; import net.abcdroid.devfest12.R; import android.content.Intent; import android.database.ContentObserver; import android.database.Cursor; import android.net.Uri; import android.os.Bundle; import android.os.Handler; import android.support.v4.app.Fragment; import android.support.v4.app.LoaderManager.LoaderCallbacks; import android.support.v4.content.CursorLoader; import android.support.v4.content.Loader; import android.support.v4.view.PagerAdapter; import android.support.v4.view.ViewPager; import android.text.TextUtils; import android.text.format.DateUtils; import android.view.LayoutInflater; import android.view.View; import android.view.View.OnClickListener; import android.view.ViewGroup; import android.widget.LinearLayout; import android.widget.TextView; /** * A fragment used in {@link HomeActivity} that shows either a countdown, * announcements, or 'thank you' text, at different times (before/during/after * the conference). */ public class WhatsOnFragment extends Fragment implements LoaderCallbacks<Cursor> { private Handler mHandler = new Handler(); private TextView mCountdownTextView; private ViewGroup mRootView; private Cursor mAnnouncementsCursor; private LayoutInflater mInflater; private int mTitleCol = -1; private int mDateCol = -1; private int mUrlCol = -1; private static final int ANNOUNCEMENTS_LOADER_ID = 0; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { mInflater = inflater; mRootView = (ViewGroup) inflater.inflate(R.layout.fragment_whats_on, container); refresh(); return mRootView; } @Override public void onDetach() { super.onDetach(); mHandler.removeCallbacks(mCountdownRunnable); getActivity().getContentResolver().unregisterContentObserver(mObserver); } private void refresh() { mHandler.removeCallbacks(mCountdownRunnable); mRootView.removeAllViews(); final long currentTimeMillis = UIUtils.getCurrentTime(getActivity()); // Show Loading... and load the view corresponding to the current state if (currentTimeMillis < UIUtils.CONFERENCE_START_MILLIS) { setupBefore(); } else if (currentTimeMillis > UIUtils.CONFERENCE_END_MILLIS) { setupAfter(); } else { setupDuring(); } } private void setupBefore() { // Before conference, show countdown. mCountdownTextView = (TextView) mInflater.inflate(R.layout.whats_on_countdown, mRootView, false); mRootView.addView(mCountdownTextView); mHandler.post(mCountdownRunnable); } private void setupAfter() { // After conference, show canned text. mInflater.inflate(R.layout.whats_on_thank_you, mRootView, true); } private void setupDuring() { // Start background query to load announcements getLoaderManager().initLoader(ANNOUNCEMENTS_LOADER_ID, null, this); getActivity().getContentResolver().registerContentObserver(Announcements.CONTENT_URI, true, mObserver); } /** * Event that updates countdown timer. Posts itself again to * {@link #mHandler} to continue updating time. */ private final Runnable mCountdownRunnable = new Runnable() { public void run() { int remainingSec = (int) Math.max(0, (UIUtils.CONFERENCE_START_MILLIS - UIUtils.getCurrentTime(getActivity())) / 1000); final boolean conferenceStarted = remainingSec == 0; if (conferenceStarted) { // Conference started while in countdown mode, switch modes and // bail on future countdown updates. mHandler.postDelayed(new Runnable() { public void run() { refresh(); } }, 100); return; } final int secs = remainingSec % 86400; final int days = remainingSec / 86400; final String str; if (days == 0) { str = getResources().getString(R.string.whats_on_countdown_title_0, DateUtils.formatElapsedTime(secs)); } else { str = getResources().getQuantityString(R.plurals.whats_on_countdown_title, days, days, DateUtils.formatElapsedTime(secs)); } mCountdownTextView.setText(str); // Repost ourselves to keep updating countdown mHandler.postDelayed(mCountdownRunnable, 1000); } }; @Override public Loader<Cursor> onCreateLoader(int id, Bundle args) { return new CursorLoader(getActivity(), Announcements.CONTENT_URI, null, null, null, Announcements.ANNOUNCEMENT_DATE + " DESC"); } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { if (getActivity() == null) { return; } if (data != null && data.getCount() > 0) { mTitleCol = data.getColumnIndex(Announcements.ANNOUNCEMENT_TITLE); mDateCol = data.getColumnIndex(Announcements.ANNOUNCEMENT_DATE); mUrlCol = data.getColumnIndex(Announcements.ANNOUNCEMENT_URL); showAnnouncements(data); } else { showNoAnnouncements(); } } @Override public void onLoaderReset(Loader<Cursor> loader) { mAnnouncementsCursor = null; } /** * Show the the announcements */ private void showAnnouncements(Cursor announcements) { mAnnouncementsCursor = announcements; ViewGroup announcementsRootView = (ViewGroup) mInflater.inflate(R.layout.whats_on_announcements, mRootView, false); final ViewPager pager = (ViewPager) announcementsRootView.findViewById(R.id.announcements_pager); final View previousButton = announcementsRootView.findViewById(R.id.announcements_previous_button); final View nextButton = announcementsRootView.findViewById(R.id.announcements_next_button); final PagerAdapter adapter = new AnnouncementsAdapter(); pager.setAdapter(adapter); pager.setPageMargin(getResources().getDimensionPixelSize(R.dimen.announcements_margin_width)); pager.setPageMarginDrawable(R.drawable.announcements_divider); pager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() { @Override public void onPageSelected(int position) { previousButton.setEnabled(position > 0); nextButton.setEnabled(position < adapter.getCount() - 1); } }); previousButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View view) { pager.setCurrentItem(pager.getCurrentItem() - 1); } }); nextButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View view) { pager.setCurrentItem(pager.getCurrentItem() + 1); } }); previousButton.setEnabled(false); nextButton.setEnabled(adapter.getCount() > 1); mRootView.removeAllViews(); mRootView.addView(announcementsRootView); } /** * Show a placeholder message */ private void showNoAnnouncements() { mInflater.inflate(R.layout.empty_announcements, mRootView, true); } public class AnnouncementsAdapter extends PagerAdapter { @Override public Object instantiateItem(ViewGroup pager, int position) { mAnnouncementsCursor.moveToPosition(position); LinearLayout rootView = (LinearLayout) mInflater.inflate(R.layout.pager_item_announcement, pager, false); TextView titleView = (TextView) rootView.findViewById(R.id.announcement_title); TextView subtitleView = (TextView) rootView.findViewById(R.id.announcement_ago); titleView.setText(mAnnouncementsCursor.getString(mTitleCol)); final long date = mAnnouncementsCursor.getLong(mDateCol); final String when = UIUtils.getTimeAgo(date, getActivity()); final String url = mAnnouncementsCursor.getString(mUrlCol); subtitleView.setText(when); rootView.setTag(url); if (!TextUtils.isEmpty(url)) { rootView.setClickable(true); rootView.setOnClickListener(mAnnouncementClick); } else { rootView.setClickable(false); } pager.addView(rootView, 0); return rootView; } private final OnClickListener mAnnouncementClick = new OnClickListener() { @Override public void onClick(View v) { String url = (String) v.getTag(); if (!TextUtils.isEmpty(url)) { UIUtils.safeOpenLink(getActivity(), new Intent(Intent.ACTION_VIEW, Uri.parse(url))); } } }; @Override public void destroyItem(ViewGroup pager, int position, Object view) { pager.removeView((View) view); } @Override public int getCount() { return mAnnouncementsCursor.getCount(); } @Override public boolean isViewFromObject(View view, Object object) { return view.equals(object); } @Override public int getItemPosition(Object object) { return POSITION_NONE; } } private final ContentObserver mObserver = new ContentObserver(new Handler()) { @Override public void onChange(boolean selfChange) { if (getActivity() == null) { return; } Loader<Cursor> loader = getLoaderManager().getLoader(ANNOUNCEMENTS_LOADER_ID); if (loader != null) { loader.forceLoad(); } } }; }