前几天，在项目重要节点的时候，突然有个VVM(visual voice mail)的问题被列为重点对象; 由于之前一直疏于查看voice mail相关的代码，所以有些手忙脚乱，虽然问题得到解决，但是对于这种比较少用的功能，还是做个记录，以备不时之需。
这里只是梳理了一个粗漏的代码流程，由于平时很少处理voice mail相关的问题，暂时不对voice mail做深入的学习，所以这里的内容对于不熟悉这部分代码的人可能会有点帮助。如果想深入学习voice mail相关的知识，还是要结合相关协议，仔细研读代码; 下面两个连接的内容或许有些帮助。
https://www.gsma.com/newsroom/all-documents/omtp-visual-voice-mail-interface-specification-v-1-3/
https://shubs.io/breaking-international-voicemail-security-via-vvm-exploitation/
Android O将voicemail相关的实现从TeleService挪到了Dialer， 所以下面内容所涉及到的code主要在packages/apps/Dialer库下，此外也涉及到了packages/service/Telephony库。
主要内容：
1. Voice mail的存储。
2. OMTP visual voice mail的启动。
3. Visual voice mail的接收。
4. Visual voice mail的显示。
5. Visual voice mail的播放。
1. Voice mail的存储
Voice mail存储在CallLog.db数据库里面，相关表是voicemail_status和calls。voicemail_status表用于存储voice mail状态相关的信息，比如用于voice mail的apk，account，vvm的类型等信息; calls表用于存储具体voice mail的信息， 比如日期，持续时间等。
CallLogProvider运行在进程android.process.acore内，开机后便会被创建，然后就是一系列的操作来创建CallLog.db; 这部分流程就不细说了，可参考TelephonyProvider的创建。相关table的创建可以查看CallLogDatabaseHelper.java。
VoicemailContract
VoicemailContract.java作为voicemail provider和应用间的纽带，内部定义了相关的URI和字段。
由于有两张表，所以字段比较多， 就不贴code了，贴两张截图吧。
VoicemailContentProvider
VoicemailContentProvider.java用于voice mail相关的查询，插入等数据库相关的操作。
由于需要操作两个表， 所以VoicemailContentProvider.onCreate方法创建了VoicemailContentTable.java和VoicemailStatusTable.java类型的两个对象，分别用于操作表calls和voicemail_status。
2. OMTP visual voice mail的启动：
在PhoneApp的AndroidMenifext.xml里面定义了下面的receiver:
<receiver
android:name="com.android.phone.vvm.VvmSimStateTracker"
android:exported="false"
androidprv:systemUserOnly="true">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED"/>
<action android:name="android.telephony.action.CARRIER_CONFIG_CHANGED"/>
<action android:name="android.intent.action.SIM_STATE_CHANGED"/>
</intent-filter>
</receiver>VvmSimStateTracker在系统里注册了三个广播的监听，ACTION_CARRIER_CONFIG_CHANGED广播和启动关系最大。单单用语言描述这个流程有些困难，画了一个简单的时序图， 如下：
当收到ACTION_CARRIER_CONFIG_CHANGED后，VvmSimStateTracker.onCarrierConfigChanged方法被调用，而参数就是根据广播信息查询到的PhoneAccountHandle对象。
private void onCarrierConfigChanged(Context context, PhoneAccountHandle phoneAccountHandle) {
if (!isBootCompleted()) {//判断系统是否完成了启动， 如果没有完成，那么保存PhoneAccountHandle信息后返回。
sPreBootHandles.add(phoneAccountHandle);
return;
}
/*如果完成了启动，继续执行下面的code*/
TelephonyManager telephonyManager = getTelephonyManager(context, phoneAccountHandle);
if(telephonyManager == null){
int subId = context.getSystemService(TelephonyManager.class).getSubIdForPhoneAccount(
context.getSystemService(TelecomManager.class)
.getPhoneAccount(phoneAccountHandle));
VvmLog.e(TAG, "Cannot create TelephonyManager from " + phoneAccountHandle + ", subId="
+ subId);
// TODO(b/33945549): investigate more why this is happening. The PhoneAccountHandle was
// just converted from a valid subId so createForPhoneAccountHandle shouldn't really
// return null.
return;
}
if (telephonyManager.getServiceState().getState()
== ServiceState.STATE_IN_SERVICE) {//手机已经注册上了网络
sendConnected(context, phoneAccountHandle);
sListeners.put(phoneAccountHandle, null);
} else {
listenToAccount(context, phoneAccountHandle);
}
}sendConnected方法比较简单，只是调用了RemoteVvmTaskManager.startCellServiceConnected, 后者代码如下:
public static void startCellServiceConnected(Context context,
PhoneAccountHandle phoneAccountHandle) {
Intent intent = new Intent(ACTION_START_CELL_SERVICE_CONNECTED, null, context,
RemoteVvmTaskManager.class);
intent.putExtra(VisualVoicemailService.DATA_PHONE_ACCOUNT_HANDLE, phoneAccountHandle);
context.startService(intent);
}RemoteVvmTaskManager继承了Service类，startCellServiceConnected方法只是启动了RemoteVvmTaskManager; 相应的onStartCommand方法被调用，该方法会调用RemoteVvmTaskManager.send方法，第二个参数为VisualVoicemailService.MSG_ON_CELL_SERVICE_CONNECTED(后续会用到)。
下面看看send方法的实现：
private void send(ComponentName remotePackage, int what, Bundle extras) {
Assert.isMainThread();
if (getBroadcastPackage(this) != null) {
/*
* Temporarily use a broadcast to notify dialer VVM events instead of using the
* VisualVoicemailService.
* b/35766990 The VisualVoicemailService is undergoing API changes. The dialer is in
* a different repository so it can not be updated in sync with android SDK. It is also
* hard to make a manifest service to work in the intermittent state.
*/
VvmLog.i(TAG, "sending broadcast " + what + " to " + remotePackage);
Intent intent = new Intent(ACTION_VISUAL_VOICEMAIL_SERVICE_EVENT);
intent.putExtras(extras);
intent.putExtra(EXTRA_WHAT, what);
intent.setComponent(remotePackage);
sendBroadcast(intent);
return;
}
Message message = Message.obtain();//构建Message对象
message.what = what;//将VisualVoicemailService.MSG_ON_CELL_SERVICE_CONNECTED放进Message对象。
message.setData(new Bundle(extras));
if (mConnection == null) {
mConnection = new RemoteServiceConnection();
}
mConnection.enqueue(message);//将Message对象放进队列。
if (!mConnection.isConnected()) {//首次调用，connection还没有连接，所以会去bind service。
Intent intent = newBindIntent(this);//构建一个action为"android.telephony.VisualVoicemailService"的 Intent对象。
intent.setComponent(remotePackage);
VvmLog.i(TAG, "Binding to " + intent.getComponent());
bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
}bind 的service是OmtpService，继承自VisualVoicemailService。VisualVoicemailService.onBind方法比较简单，只是将成员变量mMessager的binder做为返回值return了。现在返回RemoteVvmTaskManager.RemoteServiceConnection看看service 连接之后做了哪些操作？
public void onServiceConnected(ComponentName className,
IBinder service) {
mRemoteMessenger = new Messenger(service);//这个service就是mMessager的binder对象
mConnected = true;
runQueue();//继续处理队列里面的消息，我们在前面放了VisualVoicemailService.MSG_ON_CELL_SERVICE_CONNECTED消息。
}
...
private void runQueue() {
Assert.isMainThread();
Message message = mTaskQueue.poll();
while (message != null) {
message.replyTo = mMessenger;
message.arg1 = getTaskId();
try {
mRemoteMessenger.send(message);//此处send的消息会在VisualVoicemailService.mMessenger内处理。
} catch (RemoteException e) {
VvmLog.e(TAG, "Error sending message to remote service", e);
}
message = mTaskQueue.poll();
}
}VisualVoicemailService的mMessenger其实是匿名内部类的对象：
private final Messenger mMessenger = new Messenger(new Handler() {
@Override
public void handleMessage(final Message msg) {
final PhoneAccountHandle handle = msg.getData()
.getParcelable(DATA_PHONE_ACCOUNT_HANDLE);
VisualVoicemailTask task = new VisualVoicemailTask(msg.replyTo, msg.arg1);
switch (msg.what) {
case MSG_ON_CELL_SERVICE_CONNECTED://OmtpService重写了onCellServiceConnected
onCellServiceConnected(task, handle);
break;
case MSG_ON_SMS_RECEIVED:
VisualVoicemailSms sms = msg.getData().getParcelable(DATA_SMS);
onSmsReceived(task, sms);
break;
case MSG_ON_SIM_REMOVED:
onSimRemoved(task, handle);
break;
case MSG_TASK_STOPPED:
onStopped(task);
break;
default:
super.handleMessage(msg);
break;
}
}
});总结：bind 完service后，这条逻辑线就走通了。RemoteVvmTaskManager负责发送任务(SMS reveived, SIM removed)，而OmtpService负责处理任务。
OmtpService.onCellServiceConnected方法内会用到OmtpVvmCarrierConfigHelper以及VVM相关的配置信息，具体信息看code吧。
3. Visual voice mail的接收
对于VVM的接收，以VisualVoicemailSmsFilter.filer为起点画了一个时序图，涵盖了主要节点。
VisualVoicemailSmsFilter.filer会对VVM按照协议做解析; OmtpMessageReceiver.OnReceive会对收到的mail，按照不同的协议做不同的处理， 主要是更新DB以及和IMAP server通信。
4. Visual voice mail的显示
现在针对voice mail已经有很多第三方应用，实现的方式也不尽相同。有些应用可以让用户设置显示的方式(calllog或者应用内部),有些应用直接将显示放在了第三方应用里。这里说下call log部分对于voice mail的显示。DialtactsActivity启动(上次关闭时没有保存状态)的时候会创建ListsFragment，ListsFragment.onResume会调用CallLogQueryHandler.fetchVoicemailStatus查询voice mail 的状态。
public void fetchVoicemailStatus() {
StringBuilder where = new StringBuilder();
List<String> selectionArgs = new ArrayList<>();
VoicemailComponent.get(mContext)
.getVoicemailClient()
.appendOmtpVoicemailStatusSelectionClause(mContext, where, selectionArgs);
if (TelecomUtil.hasReadWriteVoicemailPermissions(mContext)) {
startQuery(
QUERY_VOICEMAIL_STATUS_TOKEN,
null,
Status.CONTENT_URI, //“content://com.android.voicemail/status"，VoicemailContentProvider.query方法根据这个URI，会找到voicemail_status表。
VoicemailStatusQuery.getProjection(),
where.toString(),
selectionArgs.toArray(new String[selectionArgs.size()]),
null);
}
}当获取查询结果后， ListsFragment.onVoicemailStatusFetched方法会被调用, 下面摘录了这个方法里最重要的一句。
public void onVoicemailStatusFetched(Cursor statusCursor) {
....
/*Update hasActiveVoicemailProvider, which controls the number of tabs displayed.*/
boolean hasActiveVoicemailProvider =
mVoicemailStatusHelper.getNumberActivityVoicemailSources(statusCursor) > 0;
...
}下面看VoicemailStatusHelper的getNumberActivityVoicemailSources方法，这个方法的注释写的很清楚：
返回值是已经安装的有效voicemail sources的数量，而这个数量是通过查询voicemail_status表获取的。
/**
* Returns the number of active voicemail sources installed.
*
* <p>The number of sources is counted by querying the voicemail status table.
*
* @param cursor The caller is responsible for the life cycle of the cursor and resetting the
* position
*/
public int getNumberActivityVoicemailSources(Cursor cursor) {
int count = 0;
if (!cursor.moveToFirst()) {
return 0;
}
do {
if (isVoicemailSourceActive(cursor)) {
++count;
}
} while (cursor.moveToNext());
return count;
}有效的Voicemail sources要满足下面的条件voicemail_status表里获取的package 名字存在，并且configuration state 不是NOT_CONFIGURED。所以如果第三方应用在voicemail_status表里存储了这些信息，那么call log里会显示voice mail相关的UI。
/**
* Returns whether the source status in the cursor corresponds to an active source. A source is
* active if its' configuration state is not NOT_CONFIGURED. For most voicemail sources, only OK
* and NOT_CONFIGURED are used. The OMTP visual voicemail client has the same behavior pre-NMR1.
* NMR1 visual voicemail will only set it to NOT_CONFIGURED when it is deactivated. As soon as
* activation is attempted, it will transition into CONFIGURING then into OK or other error state,
* NOT_CONFIGURED is never set through an error.
*/
private boolean isVoicemailSourceActive(Cursor cursor) {
return cursor.getString(VoicemailStatusQuery.SOURCE_PACKAGE_INDEX) != null
&& cursor.getInt(VoicemailStatusQuery.CONFIGURATION_STATE_INDEX)
!= Status.CONFIGURATION_STATE_NOT_CONFIGURED;
}5. Visual voice mail的播放
ListsFragment.onCreateView方法会创建DialtactsPagerAdapter，当我们选择voice mail的tab(TAB_INDEX_VOICEMAIL)的时候，DialtactsPagerAdapter.getItem会返回VisualVoicemailCallLogFragment对象，如果需要，会创建新对象。VisualVoicemailCallLogFragment继承自CallLogFragment，所以也继承了很多逻辑实现，只有一部分方法做了重写。VVM的播放，是从UI操作开始的，对于UI 布局就不详细写了， 写太多容易精神崩溃，直接从VoicemailPlaybackPresenter.requestContent开始，简单画了一个时序图，可以让这个流程更清晰些。
VoicemailPlaybackPresenter.requestContent方法里面有个异步任务，这个任务在执行的时候会发action为ACTION_FETCH_VOICEMAIL的广播。
protected boolean requestContent(int code) {
"...省略..."
mAsyncTaskExecutor.submit(
Tasks.SEND_FETCH_REQUEST,
new AsyncTask<Void, Void, Void>() {
@Override
protected Void doInBackground(Void... voids) {
"...省略..."
// Send voicemail fetch request.
Intent intent = new Intent(VoicemailContract.ACTION_FETCH_VOICEMAIL, mVoicemailUri);
intent.setPackage(sourcePackage);
LogUtil.i(
"VoicemailPlaybackPresenter.requestContent",
"Sending ACTION_FETCH_VOICEMAIL to " + sourcePackage);
mContext.sendBroadcast(intent);
}
return null;
}
});
return true;
}FetchVoicemailReceiver.java会接收并处理上面的广播，
@Override
public void onReceive(final Context context, Intent intent) {
if (!VoicemailComponent.get(context).getVoicemailClient().isVoicemailModuleEnabled()) {
return;
}
if (VoicemailContract.ACTION_FETCH_VOICEMAIL.equals(intent.getAction())) {//处理ACTION_FETCH_VOICEMAIL广播
VvmLog.i(TAG, "ACTION_FETCH_VOICEMAIL received");
mContext = context;
mContentResolver = context.getContentResolver();
mUri = intent.getData();
if (mUri == null) {
VvmLog.w(TAG, VoicemailContract.ACTION_FETCH_VOICEMAIL + " intent sent with no data");
return;
}
if (!context
.getPackageName()
.equals(mUri.getQueryParameter(VoicemailContract.PARAM_KEY_SOURCE_PACKAGE))) {
// Ignore if the fetch request is for a voicemail not from this package.
VvmLog.e(TAG, "ACTION_FETCH_VOICEMAIL from foreign pacakge " + context.getPackageName());
return;
}
/*根据uri，从数据库获取对应的phone account信息*/
Cursor cursor = mContentResolver.query(mUri, PROJECTION, null, null, null);
if (cursor == null) {
VvmLog.i(TAG, "ACTION_FETCH_VOICEMAIL query returned null");
return;
}
try {
if (cursor.moveToFirst()) {
mUid = cursor.getString(SOURCE_DATA);
String accountId = cursor.getString(PHONE_ACCOUNT_ID);
if (TextUtils.isEmpty(accountId)) {
TelephonyManager telephonyManager =
(TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
accountId = telephonyManager.getSimSerialNumber();
if (TextUtils.isEmpty(accountId)) {
VvmLog.e(TAG, "Account null and no default sim found.");
return;
}
}
mPhoneAccount =
new PhoneAccountHandle(
ComponentName.unflattenFromString(cursor.getString(PHONE_ACCOUNT_COMPONENT_NAME)),
cursor.getString(PHONE_ACCOUNT_ID));//构造PhoneAccountHandle对象
TelephonyManager telephonyManager =
context
.getSystemService(TelephonyManager.class)
.createForPhoneAccountHandle(mPhoneAccount);
if (telephonyManager == null) {
// can happen when trying to fetch voicemails from a SIM that is no longer on the
// device
VvmLog.e(TAG, "account no longer valid, cannot retrieve message");
return;
}
if (!VvmAccountManager.isAccountActivated(context, mPhoneAccount)) {
mPhoneAccount = getAccountFromMarshmallowAccount(context, mPhoneAccount);
if (mPhoneAccount == null) {
VvmLog.w(TAG, "Account not registered - cannot retrieve message.");
return;
}
VvmLog.i(TAG, "Fetching voicemail with Marshmallow PhoneAccountHandle");
}
VvmLog.i(TAG, "Requesting network to fetch voicemail");
mNetworkCallback = new fetchVoicemailNetworkRequestCallback(context, mPhoneAccount);
mNetworkCallback.requestNetwork();//请求网络连接
}
} finally {
cursor.close();
}
}
}fetchVoicemailNetworkRequestCallback继承自VvmNetworkRequestCallback，后者在构造方法里便创建了NetworkRequest对象：
/**
* @return NetworkRequest for a proper transport type. Use only cellular network if the carrier
* requires it. Otherwise use whatever available.
*/
private NetworkRequest createNetworkRequest() {
NetworkRequest.Builder builder =
new NetworkRequest.Builder().addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
TelephonyManager telephonyManager =
mContext
.getSystemService(TelephonyManager.class)
.createForPhoneAccountHandle(mPhoneAccount);
// At this point mPhoneAccount should always be valid and telephonyManager will never be null
Assert.isNotNull(telephonyManager);
if (mCarrierConfigHelper.isCellularDataRequired()) {//如果carrier config里面配置了使用cellular data的要求，那么就要使用NetworkCapabilities.TRANSPORT_CELLULAR。
VvmLog.d(TAG, "Transport type: CELLULAR");
builder
.addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR)
.setNetworkSpecifier(telephonyManager.getNetworkSpecifier());
} else {
VvmLog.d(TAG, "Transport type: ANY");
}
return builder.build();
}当网络可用之后fetchVoicemailNetworkRequestCallback.onAvailable方法会被调用，该方法会调用fetchVoicemailNetworkRequestCallback.fetchVoicemail。
private void fetchVoicemail(final Network network, final VoicemailStatus.Editor status) {
Executor executor = Executors.newCachedThreadPool();
executor.execute(
new Runnable() {
@Override
public void run() {
try {
while (mRetryCount > 0) {//尝试次数，FetchVoicemailReceiver定义了一个常量NETWORK_RETRY_COUNT，值为3
VvmLog.i(TAG, "fetching voicemail, retry count=" + mRetryCount);
try (ImapHelper imapHelper =
new ImapHelper(mContext, mPhoneAccount, network, status)) {
boolean success =
imapHelper.fetchVoicemailPayload(
new VoicemailFetchedCallback(mContext, mUri, mPhoneAccount), mUid);//这里就是用来下载的。
if (!success && mRetryCount > 0) {
VvmLog.i(TAG, "fetch voicemail failed, retrying");
mRetryCount--;
} else {
return;
}
} catch (InitializingException e) {
VvmLog.w(TAG, "Can't retrieve Imap credentials ", e);
return;
}
}
} finally {
if (mNetworkCallback != null) {
mNetworkCallback.releaseNetwork();
}
}
}
});
}fetchVoicemailNetworkRequestCallback.fetchVoicemail方法构造了ImapHelper对象，并调用了fetchVoicemailPayload方法，这个方法完成了下载。看似很简单，但是ImapHelper对象的构造和fetchVoicemailPayload方法的调用完成了很多工作。