Java tutorial
/*- * Copyright (C) 2009 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 com.google.android.demos.atom.app; import com.google.android.demos.atom.R; import com.google.android.demos.atom.provider.AtomContract.Entries; import com.google.android.demos.atom.provider.AtomContract.Feeds; import com.google.android.demos.atom.widget.EntryDialog; import com.google.android.demos.atom.widget.FeedAdapter; import android.app.AlertDialog; import android.app.Dialog; import android.app.SearchManager; import android.content.Context; import android.content.Intent; import android.content.SharedPreferences; import android.database.Cursor; import android.database.DataSetObserver; import android.net.Uri; import android.os.Bundle; import android.preference.PreferenceManager; import android.support.v4.app.FragmentActivity; import android.support.v4.app.LoaderManager; import android.support.v4.content.Loader; import android.view.Menu; import android.view.MenuInflater; import android.view.MenuItem; import android.view.View; import android.view.Window; import android.widget.AdapterView; import android.widget.ListView; import java.text.MessageFormat; /** * A feed activity loads and displays a list of items in an Atom feed. * <p> * Feed entries are displayed in a dialog managed by the feed for efficiency. */ public class FeedActivity extends FragmentActivity implements LoaderManager.LoaderCallbacks<Cursor>, AdapterView.OnItemClickListener, View.OnClickListener { private static final int DIALOG_ENTRY = 1; private static final int DIALOG_INVALID_URL = 2; private static final int LOADER_ENTRIES = 1; /** * Preference key for the URL of the last accessed feed. This is a really * simple Atom viewer that only remembers one subscription. */ private static final String PREFERENCE_FEED = "feed"; /** * A default feed to use when the application is started for the first time. */ private static final String DEFAULT_FEED = "http://www.atomenabled.org/atom.xml"; private FeedAdapter mAdapter; private EntryDialog mEntryDialog; private SharedPreferences mPreferences; private String mInvalidUrl; private View mEmpty; private View mLoading; private View mError; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS); setContentView(R.layout.list_activity); ListView listView = (ListView) findViewById(android.R.id.list); mEmpty = findViewById(R.id.empty); mLoading = findViewById(R.id.loading); mError = findViewById(R.id.error); mError.findViewById(R.id.retry).setOnClickListener(this); // Loader from last Activity instance may still be loading mLoading.setVisibility(View.VISIBLE); mEmpty.setVisibility(View.GONE); mError.setVisibility(View.GONE); mPreferences = PreferenceManager.getDefaultSharedPreferences(this); mAdapter = new FeedAdapter(this); mAdapter.registerDataSetObserver(new TitleObserver()); listView.setAdapter(mAdapter); listView.setOnItemClickListener(this); getSupportLoaderManager().initLoader(LOADER_ENTRIES, Bundle.EMPTY, this); } private Uri getContentUri() { Intent intent = getIntent(); Uri data = intent.getData(); String type = intent.resolveType(this); if (Entries.CONTENT_TYPE.equals(type)) { return data; } else if ("application/atom+xml".equalsIgnoreCase(type)) { return Entries.contentUri(data.toString()); } else { String channelUrl = mPreferences.getString(PREFERENCE_FEED, DEFAULT_FEED); return Entries.contentUri(channelUrl); } } /** * {@inheritDoc} */ public Loader<Cursor> onCreateLoader(int id, Bundle args) { mLoading.setVisibility(mAdapter.isEmpty() ? View.VISIBLE : View.GONE); mEmpty.setVisibility(View.GONE); mError.setVisibility(View.GONE); setWindowIndeterminateProgressVisible(!mAdapter.isEmpty()); Context context = this; Uri uri = getContentUri(); return FeedAdapter.createLoader(context, uri); } /** * {@inheritDoc} */ public void onLoadFinished(Loader<Cursor> loader, Cursor data) { mAdapter.swapCursor(data); mLoading.setVisibility(View.GONE); mEmpty.setVisibility(mAdapter.isEmpty() && !mAdapter.hasError() ? View.VISIBLE : View.GONE); mError.setVisibility(mAdapter.isEmpty() && mAdapter.hasError() ? View.VISIBLE : View.GONE); setWindowIndeterminateProgressVisible(false); } /** * {@inheritDoc} */ public void onLoaderReset(Loader<Cursor> loader) { mAdapter.swapCursor(null); mLoading.setVisibility(View.GONE); mEmpty.setVisibility(View.GONE); mError.setVisibility(View.GONE); setWindowIndeterminateProgressVisible(false); } private void setWindowIndeterminateProgressVisible(boolean value) { getWindow().setFeatureInt(Window.FEATURE_INDETERMINATE_PROGRESS, value ? Window.PROGRESS_VISIBILITY_ON : Window.PROGRESS_VISIBILITY_OFF); } @Override protected void onNewIntent(Intent intent) { // This method is called when the search interface is used to specify a // different feed URL. The same activity instance is reused, so it needs // to be updated to show a different feed. You don't need to worry about // implementing this method unless you have set launchMode="singleTop". setIntent(intent); String action = intent.getAction(); if (Intent.ACTION_SEARCH.equals(action)) { String feedUrl = intent.getStringExtra(SearchManager.QUERY); if (Feeds.isValidFeedUrl(feedUrl)) { // Save this feed URL in the preferences, so that it will be // opened the next time the application is started. SharedPreferences.Editor editor = mPreferences.edit(); editor.putString(PREFERENCE_FEED, feedUrl); editor.commit(); } else { mInvalidUrl = feedUrl; showDialog(DIALOG_INVALID_URL); } } reload(); } @Override protected Dialog onCreateDialog(int id) { if (id == DIALOG_ENTRY) { mEntryDialog = new EntryDialog(this); return mEntryDialog; } else if (id == DIALOG_INVALID_URL) { AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setTitle(R.string.atom_title); builder.setMessage(R.string.atom_error_invalid_url); builder.setPositiveButton(R.string.atom_button_ok, null); builder.setCancelable(true); return builder.create(); } else { return super.onCreateDialog(id); } } @Override protected void onPrepareDialog(int id, Dialog dialog) { super.onPrepareDialog(id, dialog); if (id == DIALOG_INVALID_URL) { AlertDialog d = (AlertDialog) dialog; String template = getString(R.string.atom_error_invalid_url); CharSequence message = MessageFormat.format(template, mInvalidUrl); d.setMessage(message); } } /** * {@inheritDoc} */ public void onItemClick(AdapterView<?> l, View v, int position, long id) { Object item = l.getItemAtPosition(position); Cursor cursor = mAdapter.getCursor(); if (item != null && item == cursor) { showDialog(DIALOG_ENTRY); FeedAdapter.setEntryData(mEntryDialog, cursor); mEntryDialog.scrollToTop(); } } @Override public boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu); MenuInflater inflater = getMenuInflater(); inflater.inflate(R.menu.feed_menu, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case R.id.menu_refresh: reload(); return true; case R.id.menu_search: onSearchRequested(); return true; default: return super.onOptionsItemSelected(item); } } /** * {@inheritDoc} */ public void onClick(View v) { switch (v.getId()) { case R.id.retry: reload(); break; } } private void reload() { getSupportLoaderManager().restartLoader(LOADER_ENTRIES, Bundle.EMPTY, this); } private final class TitleObserver extends DataSetObserver { @Override public void onChanged() { Cursor cursor = mAdapter.getCursor(); Bundle extras = cursor.getExtras(); String title = extras.getString(Feeds.TITLE_PLAINTEXT); if (title != null) { setTitle(title); } } } }