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/*
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* Copyright 2013 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.android.basicsyncadapter;
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import android.accounts.Account;
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import android.annotation.TargetApi;
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import android.content.AbstractThreadedSyncAdapter;
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import android.content.ContentProviderClient;
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import android.content.ContentProviderOperation;
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import android.content.ContentResolver;
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import android.content.Context;
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import android.content.OperationApplicationException;
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import android.content.SyncResult;
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import android.database.Cursor;
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import android.net.Uri;
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import android.os.Build;
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import android.os.Bundle;
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import android.os.RemoteException;
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import android.util.Log;
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import com.example.android.basicsyncadapter.net.FeedParser;
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import com.example.android.basicsyncadapter.provider.FeedContract;
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import org.xmlpull.v1.XmlPullParserException;
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import java.io.IOException;
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import java.io.InputStream;
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import java.net.HttpURLConnection;
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import java.net.MalformedURLException;
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import java.net.URL;
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import java.text.ParseException;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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/**
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* Define a sync adapter for the app.
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*
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* <p>This class is instantiated in {@link SyncService}, which also binds SyncAdapter to the system.
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* SyncAdapter should only be initialized in SyncService, never anywhere else.
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*
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* <p>The system calls onPerformSync() via an RPC call through the IBinder object supplied by
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* SyncService.
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*/
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class SyncAdapter extends AbstractThreadedSyncAdapter {
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public static final String TAG = "SyncAdapter";
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/**
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* URL to fetch content from during a sync.
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*
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* <p>This points to the Android Developers Blog. (Side note: We highly recommend reading the
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* Android Developer Blog to stay up to date on the latest Android platform developments!)
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*/
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private static final String FEED_URL = "http://android-developers.blogspot.com/atom.xml";
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/**
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* Network connection timeout, in milliseconds.
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*/
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private static final int NET_CONNECT_TIMEOUT_MILLIS = 15000; // 15 seconds
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/**
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* Network read timeout, in milliseconds.
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*/
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private static final int NET_READ_TIMEOUT_MILLIS = 10000; // 10 seconds
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/**
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* Content resolver, for performing database operations.
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*/
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private final ContentResolver mContentResolver;
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/**
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* Project used when querying content provider. Returns all known fields.
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*/
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private static final String[] PROJECTION = new String[] {
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FeedContract.Entry._ID,
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FeedContract.Entry.COLUMN_NAME_ENTRY_ID,
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FeedContract.Entry.COLUMN_NAME_TITLE,
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FeedContract.Entry.COLUMN_NAME_LINK,
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FeedContract.Entry.COLUMN_NAME_PUBLISHED};
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// Constants representing column positions from PROJECTION.
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public static final int COLUMN_ID = 0;
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public static final int COLUMN_ENTRY_ID = 1;
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public static final int COLUMN_TITLE = 2;
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public static final int COLUMN_LINK = 3;
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public static final int COLUMN_PUBLISHED = 4;
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/**
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* Constructor. Obtains handle to content resolver for later use.
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*/
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public SyncAdapter(Context context, boolean autoInitialize) {
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super(context, autoInitialize);
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mContentResolver = context.getContentResolver();
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}
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/**
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* Constructor. Obtains handle to content resolver for later use.
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*/
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@TargetApi(Build.VERSION_CODES.HONEYCOMB)
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public SyncAdapter(Context context, boolean autoInitialize, boolean allowParallelSyncs) {
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super(context, autoInitialize, allowParallelSyncs);
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mContentResolver = context.getContentResolver();
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}
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/**
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* Called by the Android system in response to a request to run the sync adapter. The work
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* required to read data from the network, parse it, and store it in the content provider is
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* done here. Extending AbstractThreadedSyncAdapter ensures that all methods within SyncAdapter
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* run on a background thread. For this reason, blocking I/O and other long-running tasks can be
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* run <em>in situ</em>, and you don't have to set up a separate thread for them.
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.
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*
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* <p>This is where we actually perform any work required to perform a sync.
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* {@link android.content.AbstractThreadedSyncAdapter} guarantees that this will be called on a non-UI thread,
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* so it is safe to peform blocking I/O here.
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*
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* <p>The syncResult argument allows you to pass information back to the method that triggered
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* the sync.
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*/
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@Override
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public void onPerformSync(Account account, Bundle extras, String authority,
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ContentProviderClient provider, SyncResult syncResult) {
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Log.i(TAG, "Beginning network synchronization");
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try {
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final URL location = new URL(FEED_URL);
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InputStream stream = null;
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try {
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Log.i(TAG, "Streaming data from network: " + location);
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stream = downloadUrl(location);
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updateLocalFeedData(stream, syncResult);
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// Makes sure that the InputStream is closed after the app is
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// finished using it.
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} finally {
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if (stream != null) {
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stream.close();
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}
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}
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} catch (MalformedURLException e) {
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Log.e(TAG, "Feed URL is malformed", e);
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syncResult.stats.numParseExceptions++;
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return;
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} catch (IOException e) {
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Log.e(TAG, "Error reading from network: " + e.toString());
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syncResult.stats.numIoExceptions++;
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return;
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} catch (XmlPullParserException e) {
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Log.e(TAG, "Error parsing feed: " + e.toString());
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syncResult.stats.numParseExceptions++;
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return;
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} catch (ParseException e) {
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Log.e(TAG, "Error parsing feed: " + e.toString());
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syncResult.stats.numParseExceptions++;
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return;
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} catch (RemoteException e) {
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Log.e(TAG, "Error updating database: " + e.toString());
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syncResult.databaseError = true;
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return;
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} catch (OperationApplicationException e) {
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Log.e(TAG, "Error updating database: " + e.toString());
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syncResult.databaseError = true;
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return;
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}
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Log.i(TAG, "Network synchronization complete");
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}
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/**
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* Read XML from an input stream, storing it into the content provider.
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*
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* <p>This is where incoming data is persisted, committing the results of a sync. In order to
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* minimize (expensive) disk operations, we compare incoming data with what's already in our
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* database, and compute a merge. Only changes (insert/update/delete) will result in a database
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* write.
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*
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* <p>As an additional optimization, we use a batch operation to perform all database writes at
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* once.
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*
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* <p>Merge strategy:
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* 1. Get cursor to all items in feed<br/>
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* 2. For each item, check if it's in the incoming data.<br/>
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* a. YES: Remove from "incoming" list. Check if data has mutated, if so, perform
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* database UPDATE.<br/>
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* b. NO: Schedule DELETE from database.<br/>
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* (At this point, incoming database only contains missing items.)<br/>
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* 3. For any items remaining in incoming list, ADD to database.
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*/
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public void updateLocalFeedData(final InputStream stream, final SyncResult syncResult)
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throws IOException, XmlPullParserException, RemoteException,
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OperationApplicationException, ParseException {
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final FeedParser feedParser = new FeedParser();
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final ContentResolver contentResolver = getContext().getContentResolver();
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Log.i(TAG, "Parsing stream as Atom feed");
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final List<FeedParser.Entry> entries = feedParser.parse(stream);
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Log.i(TAG, "Parsing complete. Found " + entries.size() + " entries");
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ArrayList<ContentProviderOperation> batch = new ArrayList<ContentProviderOperation>();
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// Build hash table of incoming entries
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HashMap<String, FeedParser.Entry> entryMap = new HashMap<String, FeedParser.Entry>();
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for (FeedParser.Entry e : entries) {
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entryMap.put(e.id, e);
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}
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// Get list of all items
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Log.i(TAG, "Fetching local entries for merge");
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Uri uri = FeedContract.Entry.CONTENT_URI; // Get all entries
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Cursor c = contentResolver.query(uri, PROJECTION, null, null, null);
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assert c != null;
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Log.i(TAG, "Found " + c.getCount() + " local entries. Computing merge solution...");
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// Find stale data
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int id;
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String entryId;
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String title;
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String link;
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long published;
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while (c.moveToNext()) {
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syncResult.stats.numEntries++;
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id = c.getInt(COLUMN_ID);
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entryId = c.getString(COLUMN_ENTRY_ID);
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title = c.getString(COLUMN_TITLE);
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link = c.getString(COLUMN_LINK);
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published = c.getLong(COLUMN_PUBLISHED);
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FeedParser.Entry match = entryMap.get(entryId);
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if (match != null) {
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// Entry exists. Remove from entry map to prevent insert later.
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entryMap.remove(entryId);
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// Check to see if the entry needs to be updated
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Uri existingUri = FeedContract.Entry.CONTENT_URI.buildUpon()
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.appendPath(Integer.toString(id)).build();
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if ((match.title != null && !match.title.equals(title)) ||
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(match.link != null && !match.link.equals(link)) ||
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(match.published != published)) {
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// Update existing record
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Log.i(TAG, "Scheduling update: " + existingUri);
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batch.add(ContentProviderOperation.newUpdate(existingUri)
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.withValue(FeedContract.Entry.COLUMN_NAME_TITLE, title)
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.withValue(FeedContract.Entry.COLUMN_NAME_LINK, link)
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.withValue(FeedContract.Entry.COLUMN_NAME_PUBLISHED, published)
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.build());
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syncResult.stats.numUpdates++;
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} else {
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Log.i(TAG, "No action: " + existingUri);
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}
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} else {
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// Entry doesn't exist. Remove it from the database.
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Uri deleteUri = FeedContract.Entry.CONTENT_URI.buildUpon()
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.appendPath(Integer.toString(id)).build();
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Log.i(TAG, "Scheduling delete: " + deleteUri);
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batch.add(ContentProviderOperation.newDelete(deleteUri).build());
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syncResult.stats.numDeletes++;
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}
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}
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c.close();
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// Add new items
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for (FeedParser.Entry e : entryMap.values()) {
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Log.i(TAG, "Scheduling insert: entry_id=" + e.id);
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batch.add(ContentProviderOperation.newInsert(FeedContract.Entry.CONTENT_URI)
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.withValue(FeedContract.Entry.COLUMN_NAME_ENTRY_ID, e.id)
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.withValue(FeedContract.Entry.COLUMN_NAME_TITLE, e.title)
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.withValue(FeedContract.Entry.COLUMN_NAME_LINK, e.link)
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.withValue(FeedContract.Entry.COLUMN_NAME_PUBLISHED, e.published)
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.build());
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syncResult.stats.numInserts++;
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}
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Log.i(TAG, "Merge solution ready. Applying batch update");
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mContentResolver.applyBatch(FeedContract.CONTENT_AUTHORITY, batch);
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mContentResolver.notifyChange(
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FeedContract.Entry.CONTENT_URI, // URI where data was modified
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null, // No local observer
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false); // IMPORTANT: Do not sync to network
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// This sample doesn't support uploads, but if *your* code does, make sure you set
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// syncToNetwork=false in the line above to prevent duplicate syncs.
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}
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/**
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* Given a string representation of a URL, sets up a connection and gets an input stream.
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*/
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private InputStream downloadUrl(final URL url) throws IOException {
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HttpURLConnection conn = (HttpURLConnection) url.openConnection();
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conn.setReadTimeout(NET_READ_TIMEOUT_MILLIS /* milliseconds */);
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conn.setConnectTimeout(NET_CONNECT_TIMEOUT_MILLIS /* milliseconds */);
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conn.setRequestMethod("GET");
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conn.setDoInput(true);
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// Starts the query
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conn.connect();
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return conn.getInputStream();
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}
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}