構建自己的Android賬戶與內容同步機制,，例程SampleSyncAdapter的分析

windli筆記 2011-08-08

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裝過Android版的Facebook、lastfm的同學是否對于這些應用的功能感到驚喜,，它們可以定期更新朋友的最新信息,，將最新近況和心情短語集成入聯(lián)系人中。這些應用全部是以Android2.0后的賬戶和同步機制為基礎的,。Google的例程中給出了名為SampleSyncAdpater的例子,，通過分析該例子可以學會Android中的Account驗證、同步Adapter的使用,。

詳細例子代碼可以看sdk samples中提供的源碼,，現(xiàn)在拿2.2中的版本來簡要說明。

首先是 class Authenticator extends AbstractAccountAuthenticator ,，該類是賬戶認證類,，打開手機的Setting里,，有Account&Sync 一項，Authenticator就是實現(xiàn)其中的賬號功能的類,。

// in Authenticator.java
public Bundle addAccount(AccountAuthenticatorResponse response,
String accountType, String authTokenType, String[] requiredFeatures,
Bundle options) {
final Intent intent = new Intent(mContext, AuthenticatorActivity.class);
intent.putExtra(AuthenticatorActivity.PARAM_AUTHTOKEN_TYPE,
authTokenType);
intent.putExtra(AccountManager.KEY_ACCOUNT_AUTHENTICATOR_RESPONSE,
response);
final Bundle bundle = new Bundle();
bundle.putParcelable(AccountManager.KEY_INTENT, intent);
return bundle;
}

其中addAccount方法用來定義需要增加賬號時的操作,，如調用AuthenticatorActivity來進行賬號的添加認證。

在AuthenticatorActivity.java中定義了handleLogin(),，此方法由login_activity.xml中的android:onClick="handleLogin"定義與ui中的okbutton的關聯(lián),。

// in layout/login_activity.xml
<Button
android:id="@+id/ok_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:minWidth="100dip"
android:text="@string/login_activity_ok_button"
android:onClick="handleLogin" />

handleLogin()將ui中的用戶名和密碼取得，并創(chuàng)建一個試圖認證的線程,，通過網(wǎng)絡去服務端驗證,。

NetworkUtilities.java中的 public static boolean authenticate(String username, String password, Handler handler, final Context context)方法展示了通過網(wǎng)絡驗證的具體流程。得到服務端驗證結果后,，在sendResult()中通過handler.post調用來實現(xiàn)onAuthenticationResult()在AuthenticatorActivity中的運行,。onAuthenticationResult()判斷驗證通過則結束AuthenticatorActivity，否則報出用戶名密碼錯,，讓用戶在AuthenticatorActivity中再次嘗試驗證,。

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// AuthenticatorActivity.java中的handleLogin()方法
/**
* Handles onClick event on the Submit button. Sends username/password to
* the server for authentication.
*
* @param view The Submit button for which this method is invoked
*/
public void handleLogin(View view) {
if (mRequestNewAccount) {
mUsername = mUsernameEdit.getText().toString();
}
mPassword = mPasswordEdit.getText().toString();
if (TextUtils.isEmpty(mUsername) || TextUtils.isEmpty(mPassword)) {
mMessage.setText(getMessage());
} else {
showProgress();
// Start authenticating...
mAuthThread =
NetworkUtilities.attemptAuth(mUsername, mPassword, mHandler,
AuthenticatorActivity.this);
}
}

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// NetworkUtilities中的authenticate()方法通過網(wǎng)絡訪問具體來實現(xiàn)服務端的驗證，sendResult()來使調用結果被AuthenticatorActivity的onAuthenticationResult()調用,。
/**
* Connects to the Voiper server, authenticates the provided username and
* password.
*
* @param username The user's username
* @param password The user's password
* @param handler The hander instance from the calling UI thread.
* @param context The context of the calling Activity.
* @return boolean The boolean result indicating whether the user was
* successfully authenticated.
*/
public static boolean authenticate(String username, String password,
Handler handler, final Context context) {
final HttpResponse resp;
final ArrayList<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair(PARAM_USERNAME, username));
params.add(new BasicNameValuePair(PARAM_PASSWORD, password));
HttpEntity entity = null;
try {
entity = new UrlEncodedFormEntity(params);
} catch (final UnsupportedEncodingException e) {
// this should never happen.
throw new AssertionError(e);
}
final HttpPost post = new HttpPost(AUTH_URI);
post.addHeader(entity.getContentType());
post.setEntity(entity);
maybeCreateHttpClient();
try {
resp = mHttpClient.execute(post);
if (resp.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Successful authentication");
}
sendResult(true, handler, context);
return true;
} else {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Error authenticating" + resp.getStatusLine());
}
sendResult(false, handler, context);
return false;
}
} catch (final IOException e) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "IOException when getting authtoken", e);
}
sendResult(false, handler, context);
return false;
} finally {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "getAuthtoken completing");
}
}
}
/**
* Sends the authentication response from server back to the caller main UI
* thread through its handler.
*
* @param result The boolean holding authentication result
* @param handler The main UI thread's handler instance.
* @param context The caller Activity's context.
*/
private static void sendResult(final Boolean result, final Handler handler,
final Context context) {
if (handler == null || context == null) {
return;
}
handler.post(new Runnable() {
public void run() {
((AuthenticatorActivity) context).onAuthenticationResult(result);
}
});
}

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// AuthenticatorActivity.java中的onAuthenticationResult,，來根據(jù)驗證結果來選擇結束認證或重新嘗試。
/**
* Called when the authentication process completes (see attemptLogin()).
*/
public void onAuthenticationResult(boolean result) {
Log.i(TAG, "onAuthenticationResult(" + result + ")");
// Hide the progress dialog
hideProgress();
if (result) {
if (!mConfirmCredentials) {
finishLogin();
} else {
finishConfirmCredentials(true);
}
} else {
Log.e(TAG, "onAuthenticationResult: failed to authenticate");
if (mRequestNewAccount) {
// "Please enter a valid username/password.
mMessage
.setText(getText(R.string.login_activity_loginfail_text_both));
} else {
// "Please enter a valid password." (Used when the
// account is already in the database but the password
// doesn't work.)
mMessage
.setText(getText(R.string.login_activity_loginfail_text_pwonly));
}
}
}

Account的驗證完畢后,，就生成了賬號,，可以開始使用同步功能了。同步的主要邏輯在public class SyncAdapter extends AbstractThreadedSyncAdapter中實現(xiàn),。

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// SyncAdapter.java中的OnPerformSync方法,，主要的同步邏輯
@Override
public void onPerformSync(Account account, Bundle extras, String authority,
ContentProviderClient provider, SyncResult syncResult) {
List<User> users;
List<Status> statuses;
String authtoken = null;
try {
// use the account manager to request the credentials
authtoken =
mAccountManager.blockingGetAuthToken(account,
Constants.AUTHTOKEN_TYPE, true /* notifyAuthFailure */);
// fetch updates from the sample service over the cloud
users =
NetworkUtilities.fetchFriendUpdates(account, authtoken,
mLastUpdated);
// update the last synced date.
mLastUpdated = new Date();
// update platform contacts.
Log.d(TAG, "Calling contactManager's sync contacts");
ContactManager.syncContacts(mContext, account.name, users);
// fetch and update status messages for all the synced users.
statuses = NetworkUtilities.fetchFriendStatuses(account, authtoken);
ContactManager.insertStatuses(mContext, account.name, statuses);
} catch (final AuthenticatorException e) {
syncResult.stats.numParseExceptions++;
Log.e(TAG, "AuthenticatorException", e);
} catch (final OperationCanceledException e) {
Log.e(TAG, "OperationCanceledExcetpion", e);
} catch (final IOException e) {
Log.e(TAG, "IOException", e);
syncResult.stats.numIoExceptions++;
} catch (final AuthenticationException e) {
mAccountManager.invalidateAuthToken(Constants.ACCOUNT_TYPE,
authtoken);
syncResult.stats.numAuthExceptions++;
Log.e(TAG, "AuthenticationException", e);
} catch (final ParseException e) {
syncResult.stats.numParseExceptions++;
Log.e(TAG, "ParseException", e);
} catch (final JSONException e) {
syncResult.stats.numParseExceptions++;
Log.e(TAG, "JSONException", e);
}
}

onPerformSync中的執(zhí)行流程中，使用NetworkUtilities中的fetchFriendUpdates和fetchFriendStatuses來訪問服務端的聯(lián)系人更新,，并使用了例程中自己封裝的ContactManager來讀取、更新聯(lián)系人信息,。

那Account和SyncAdapter及其Service和xml定義之間是如何關聯(lián)的呢,？ AndroidManifest.xml中定義了AccountAuthenticator，SyncAdapter及對應的Service和xml定義的關聯(lián),。

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<application
android:icon="@drawable/icon"
android:label="@string/label">
<service
android:name=".authenticator.AuthenticationService"
android:exported="true">
<intent-filter>
<action
android:name="android.accounts.AccountAuthenticator" />
</intent-filter>
<meta-data
android:name="android.accounts.AccountAuthenticator"
android:resource="@xml/authenticator" />
</service>
<service
android:name=".syncadapter.SyncService"
android:exported="true">
<intent-filter>
<action
android:name="android.content.SyncAdapter" />
</intent-filter>
<meta-data
android:name="android.content.SyncAdapter"
android:resource="@xml/syncadapter" />
<meta-data
android:name="android.provider.CONTACTS_STRUCTURE"
android:resource="@xml/contacts" />
</service>
<activity
android:name=".authenticator.AuthenticatorActivity"
android:label="@string/ui_activity_title"
android:theme="@android:style/Theme.Dialog"
android:excludeFromRecents="true"
>
<!--
No intent-filter here! This activity is only ever launched by
someone who explicitly knows the class name
-->
</activity>
</application>

更詳細的代碼細節(jié)和執(zhí)行流程,，可以去把SDK中的SampleSyncAdapter代碼運行起來體會一下，不過要實現(xiàn)整個流程,，必須搭建聯(lián)系人的服務器端,，例程中在目錄samplesyncadapter_server中也提供了簡單的server端python代碼，需要搭建在google app engine上,。搭建過程遇到一些問題,，由于對python不熟我弄了幾天才解決好搭建成功,，其中遇到的一個model moudle找不到的問題需要你在model中新建一個__init__.py的空文件，來說明是一個python模塊,，如果你也遇到此問題,，希望對你有幫助。