构建自己的Android账户与内容同步机制,例程SampleSyncAdapter的分析

鉴客 发布于 2012/02/21 11:51
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装过Android版的Facebook、lastfm的同学是否对于这些应用的功能感到惊喜,它们可以定期更新朋友的最新信息,将最新近况和心情短语集成入联系人中。这些应用全部是以Android2.0后的账户和同步机制为基础的。Google的例程中给出了名为SampleSyncAdpater的例子,通过分析该例子可以学会Android中的Account验证、同步Adapter的使用。

详细例子代码可以看sdk samples中提供的源码,现在拿2.2中的版本来简要说明。

首先是 class Authenticator extends AbstractAccountAuthenticator ,该类是账户认证类,打开手机的Setting里,有Account&Sync 一项,Authenticator就是实现其中的账号功能的类。

// 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方法用来定义需要增加账号时的操作,如调用AuthenticatorActivity来进行账号的添加认证。

在AuthenticatorActivity.java中定义了handleLogin(),此方法由login_activity.xml中的android:onClick="handleLogin"定义与ui中的okbutton的关联。

// 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()将ui中的用户名和密码取得,并创建一个试图认证的线程,通过网络去服务端验证。

NetworkUtilities.java中的 public static boolean authenticate(String username, String password, Handler handler, final Context context)方法展示了通过网络验证的具体流程。

得到服务端验证结果后,在sendResult()中通过handler.post调用来实现onAuthenticationResult()在AuthenticatorActivity中的运行。onAuthenticationResult()判断验证通过则结束AuthenticatorActivity,否则报出用户名密码错,让用户在AuthenticatorActivity中再次尝试验证。

// 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);
        }
    }

// NetworkUtilities中的authenticate()方法通过网络访问具体来实现服务端的验证,sendResult()来使调用结果被AuthenticatorActivity的onAuthenticationResult()调用。
    /**
     * 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);
            }
        });
    }

// AuthenticatorActivity.java中的onAuthenticationResult,来根据验证结果来选择结束认证或重新尝试。
    /**
     * 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的验证完毕后,就生成了账号,可以开始使用同步功能了。同步的主要逻辑在public class SyncAdapter extends AbstractThreadedSyncAdapter中实现。
// SyncAdapter.java中的OnPerformSync方法,主要的同步逻辑
    @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中的执行流程中,使用NetworkUtilities中的fetchFriendUpdates和fetchFriendStatuses来访问服务端的联系人更新,并使用了例程中自己封装的ContactManager来读取、更新联系人信息。

那Account和SyncAdapter及其Service和xml定义之间是如何关联的呢? AndroidManifest.xml中定义了AccountAuthenticator,SyncAdapter及对应的Service和xml定义的关联。

    <application
        android:icon="@drawable/icon"
        android:label="@string/label">
        <!-- The authenticator service -->
        <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>

更详细的代码细节和执行流程,可以去把SDK中的SampleSyncAdapter代码运行起来体会一下,不过要实现整个流程,必须搭建联系人的服务器端,例程中在目录samplesyncadapter_server中也提供了简单的server端python代码,需要搭建在google app engine上。搭建过程遇到一些问题,由于对python不熟我弄了几天才解决好搭建成功,其中遇到的一个model moudle找不到的问题需要你在model中新建一个__init__.py的空文件,来说明是一个python模块,如果你也遇到此问题,希望对你有帮助。
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亭子happy
亭子happy
学习了,请问有没有源码下载啊?
亭子happy
亭子happy
知道了,原来android源码中有例子。
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