/*
* Copyright 2013 The Android Open Source Project
*
* 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.example.android.network.sync.basicsyncadapter;
import android.accounts.Account;
import android.content.AbstractThreadedSyncAdapter;
import android.content.ContentProviderClient;
import android.content.ContentProviderOperation;
import android.content.ContentResolver;
import android.content.Context;
import android.content.OperationApplicationException;
import android.content.SyncResult;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.os.RemoteException;
import android.util.Log;
import com.example.android.network.sync.basicsyncadapter.net.FeedParser;
import com.example.android.network.sync.basicsyncadapter.provider.FeedContract;
import org.xmlpull.v1.XmlPullParserException;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
/**
* Define a sync adapter for the app.
*
* <p>This class is instantiated in {@link SyncService}, which also binds SyncAdapter to the system.
* SyncAdapter should only be initialized in SyncService, never anywhere else.
*
* <p>The system calls onPerformSync() via an RPC call through the IBinder object supplied by
* SyncService.
*/
class SyncAdapter extends AbstractThreadedSyncAdapter {
public static final String TAG = "SyncAdapter";
/**
* URL to fetch content from during a sync.
*
* <p>This points to the Android Developers Blog. (Side note: We highly recommend reading the
* Android Developer Blog to stay up to date on the latest Android platform developments!)
*/
private static final String FEED_URL = "http://android-developers.blogspot.com/atom.xml";
/**
* Network connection timeout, in milliseconds.
*/
private static final int NET_CONNECT_TIMEOUT_MILLIS = 15000; // 15 seconds
/**
* Network read timeout, in milliseconds.
*/
private static final int NET_READ_TIMEOUT_MILLIS = 10000; // 10 seconds
/**
* Content resolver, for performing database operations.
*/
private final ContentResolver mContentResolver;
/**
* Project used when querying content provider. Returns all known fields.
*/
private static final String[] PROJECTION = new String[] {
FeedContract.Entry._ID,
FeedContract.Entry.COLUMN_NAME_ENTRY_ID,
FeedContract.Entry.COLUMN_NAME_TITLE,
FeedContract.Entry.COLUMN_NAME_LINK,
FeedContract.Entry.COLUMN_NAME_PUBLISHED};
// Constants representing column positions from PROJECTION.
public static final int COLUMN_ID = 0;
public static final int COLUMN_ENTRY_ID = 1;
public static final int COLUMN_TITLE = 2;
public static final int COLUMN_LINK = 3;
public static final int COLUMN_PUBLISHED = 4;
/**
* Constructor. Obtains handle to content resolver for later use.
*/
public SyncAdapter(Context context, boolean autoInitialize) {
super(context, autoInitialize);
mContentResolver = context.getContentResolver();
}
/**
* Constructor. Obtains handle to content resolver for later use.
*/
public SyncAdapter(Context context, boolean autoInitialize, boolean allowParallelSyncs) {
super(context, autoInitialize, allowParallelSyncs);
mContentResolver = context.getContentResolver();
}
/**
* Called by the Android system in response to a request to run the sync adapter. The work
* required to read data from the network, parse it, and store it in the content provider is
* done here. Extending AbstractThreadedSyncAdapter ensures that all methods within SyncAdapter
* run on a background thread. For this reason, blocking I/O and other long-running tasks can be
* run <em>in situ</em>, and you don't have to set up a separate thread for them.
.
*
* <p>This is where we actually perform any work required to perform a sync.
* {@link AbstractThreadedSyncAdapter} guarantees that this will be called on a non-UI thread,
* so it is safe to peform blocking I/O here.
*
* <p>The syncResult argument allows you to pass information back to the method that triggered
* the sync.
*/
@Override
public void onPerformSync(Account account, Bundle extras, String authority,
ContentProviderClient provider, SyncResult syncResult) {
Log.i(TAG, "Beginning network synchronization");
try {
final URL location = new URL(FEED_URL);
InputStream stream = null;
try {
Log.i(TAG, "Streaming data from network: " + location);
stream = downloadUrl(location);
updateLocalFeedData(stream, syncResult);
// Makes sure that the InputStream is closed after the app is
// finished using it.
} finally {
if (stream != null) {
stream.close();
}
}
} catch (MalformedURLException e) {
Log.wtf(TAG, "Feed URL is malformed", e);
syncResult.stats.numParseExceptions++;
return;
} catch (IOException e) {
Log.e(TAG, "Error reading from network: " + e.toString());
syncResult.stats.numIoExceptions++;
return;
} catch (XmlPullParserException e) {
Log.e(TAG, "Error parsing feed: " + e.toString());
syncResult.stats.numParseExceptions++;
return;
} catch (ParseException e) {
Log.e(TAG, "Error parsing feed: " + e.toString());
syncResult.stats.numParseExceptions++;
return;
} catch (RemoteException e) {
Log.e(TAG, "Error updating database: " + e.toString());
syncResult.databaseError = true;
return;
} catch (OperationApplicationException e) {
Log.e(TAG, "Error updating database: " + e.toString());
syncResult.databaseError = true;
return;
}
Log.i(TAG, "Network synchronization complete");
}
/**
* Read XML from an input stream, storing it into the content provider.
*
* <p>This is where incoming data is persisted, committing the results of a sync. In order to
* minimize (expensive) disk operations, we compare incoming data with what's already in our
* database, and compute a merge. Only changes (insert/update/delete) will result in a database
* write.
*
* <p>As an additional optimization, we use a batch operation to perform all database writes at
* once.
*
* <p>Merge strategy:
* 1. Get cursor to all items in feed<br/>
* 2. For each item, check if it's in the incoming data.<br/>
* a. YES: Remove from "incoming" list. Check if data has mutated, if so, perform
* database UPDATE.<br/>
* b. NO: Schedule DELETE from database.<br/>
* (At this point, incoming database only contains missing items.)<br/>
* 3. For any items remaining in incoming list, ADD to database.
*/
public void updateLocalFeedData(final InputStream stream, final SyncResult syncResult)
throws IOException, XmlPullParserException, RemoteException,
OperationApplicationException, ParseException {
final FeedParser feedParser = new FeedParser();
final ContentResolver contentResolver = getContext().getContentResolver();
Log.i(TAG, "Parsing stream as Atom feed");
final List<FeedParser.Entry> entries = feedParser.parse(stream);
Log.i(TAG, "Parsing complete. Found " + entries.size() + " entries");
ArrayList<ContentProviderOperation> batch = new ArrayList<ContentProviderOperation>();
// Build hash table of incoming entries
HashMap<String, FeedParser.Entry> entryMap = new HashMap<String, FeedParser.Entry>();
for (FeedParser.Entry e : entries) {
entryMap.put(e.id, e);
}
// Get list of all items
Log.i(TAG, "Fetching local entries for merge");
Uri uri = FeedContract.Entry.CONTENT_URI; // Get all entries
Cursor c = contentResolver.query(uri, PROJECTION, null, null, null);
assert c != null;
Log.i(TAG, "Found " + c.getCount() + " local entries. Computing merge solution...");
// Find stale data
int id;
String entryId;
String title;
String link;
long published;
while (c.moveToNext()) {
syncResult.stats.numEntries++;
id = c.getInt(COLUMN_ID);
entryId = c.getString(COLUMN_ENTRY_ID);
title = c.getString(COLUMN_TITLE);
link = c.getString(COLUMN_LINK);
published = c.getLong(COLUMN_PUBLISHED);
FeedParser.Entry match = entryMap.get(entryId);
if (match != null) {
// Entry exists. Remove from entry map to prevent insert later.
entryMap.remove(entryId);
// Check to see if the entry needs to be updated
Uri existingUri = FeedContract.Entry.CONTENT_URI.buildUpon()
.appendPath(Integer.toString(id)).build();
if ((match.title != null && !match.title.equals(title)) ||
(match.link != null && !match.link.equals(link)) ||
(match.published != published)) {
// Update existing record
Log.i(TAG, "Scheduling update: " + existingUri);
batch.add(ContentProviderOperation.newUpdate(existingUri)
.withValue(FeedContract.Entry.COLUMN_NAME_TITLE, title)
.withValue(FeedContract.Entry.COLUMN_NAME_LINK, link)
.withValue(FeedContract.Entry.COLUMN_NAME_PUBLISHED, published)
.build());
syncResult.stats.numUpdates++;
} else {
Log.i(TAG, "No action: " + existingUri);
}
} else {
// Entry doesn't exist. Remove it from the database.
Uri deleteUri = FeedContract.Entry.CONTENT_URI.buildUpon()
.appendPath(Integer.toString(id)).build();
Log.i(TAG, "Scheduling delete: " + deleteUri);
batch.add(ContentProviderOperation.newDelete(deleteUri).build());
syncResult.stats.numDeletes++;
}
}
c.close();
// Add new items
for (FeedParser.Entry e : entryMap.values()) {
Log.i(TAG, "Scheduling insert: entry_id=" + e.id);
batch.add(ContentProviderOperation.newInsert(FeedContract.Entry.CONTENT_URI)
.withValue(FeedContract.Entry.COLUMN_NAME_ENTRY_ID, e.id)
.withValue(FeedContract.Entry.COLUMN_NAME_TITLE, e.title)
.withValue(FeedContract.Entry.COLUMN_NAME_LINK, e.link)
.withValue(FeedContract.Entry.COLUMN_NAME_PUBLISHED, e.published)
.build());
syncResult.stats.numInserts++;
}
Log.i(TAG, "Merge solution ready. Applying batch update");
mContentResolver.applyBatch(FeedContract.CONTENT_AUTHORITY, batch);
mContentResolver.notifyChange(
FeedContract.Entry.CONTENT_URI, // URI where data was modified
null, // No local observer
false); // IMPORTANT: Do not sync to network
// This sample doesn't support uploads, but if *your* code does, make sure you set
// syncToNetwork=false in the line above to prevent duplicate syncs.
}
/**
* Given a string representation of a URL, sets up a connection and gets an input stream.
*/
private InputStream downloadUrl(final URL url) throws IOException {
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(NET_READ_TIMEOUT_MILLIS /* milliseconds */);
conn.setConnectTimeout(NET_CONNECT_TIMEOUT_MILLIS /* milliseconds */);
conn.setRequestMethod("GET");
conn.setDoInput(true);
// Starts the query
conn.connect();
return conn.getInputStream();
}
}