MyHandler对'desc'消息的处理

case 'desc': { //从消息msg里的"result"字段得到错误码的值 int32_t result; CHECK(msg->findInt32("result", &result)); ALOGI("DESCRIBE completed with result %d (%s)", result, strerror(-result)); if (result == OK) { //如果result的值为OK，说明成功收到了服务端发送过来的应答消息 //从消息msg的"response"字段获取服务端发送过来的应答消息对象response sp<RefBase> obj; CHECK(msg->findObject("response", &obj)); sp<ARTSPResponse> response = static_cast<ARTSPResponse *>(obj.get()); if (response->mStatusCode == 301 || response->mStatusCode == 302) { //对从服务端发送过来的应答消息的状态码为301或者302的情况进行处理 //本文不分析对301,301状态码的处理流程 ssize_t i = response->mHeaders.indexOfKey("location"); CHECK_GE(i, 0); mOriginalSessionURL = response->mHeaders.valueAt(i); mSessionURL = mOriginalSessionURL; // Strip any authentication info from the session url, we don't // want to transmit user/pass in cleartext. AString host, path, user, pass; unsigned port; if (ARTSPConnection::ParseURL( mSessionURL.c_str(), &host, &port, &path, &user, &pass) && user.size() > 0) { mSessionURL.clear(); mSessionURL.append("rtsp://"); mSessionURL.append(host); mSessionURL.append(":"); mSessionURL.append(AStringPrintf("%u", port)); mSessionURL.append(path); ALOGI("rewritten session url: '%s'", mSessionURL.c_str()); } sp<AMessage> reply = new AMessage('conn', this); mConn->connect(mOriginalSessionURL.c_str(), reply); break; } //代码执行到这里说明该从服务端发送过来的应答消息的 //状态码不为301,302 if (response->mStatusCode != 200) { //如果状态码不为200，将错误码UNKNOWN_ERROR赋值给result result = UNKNOWN_ERROR; } else if (response->mContent == NULL) { //代码执行到这里说明。状态码为200， //但是应答消息的内容为空， //则将错误码ERROR_MALFORMED赋值给result result = ERROR_MALFORMED; ALOGE("The response has no content."); } else { //代码执行到这里说明状态码为200 //并且应答消息的内容也不为空 //创建一个会话描述对象 mSessionDesc = new ASessionDescription; //将应答消息的内容的缓冲区赋值给该会话描述对象mSessionDesc mSessionDesc->setTo( response->mContent->data(), response->mContent->size()); if (!mSessionDesc->isValid()) { //如果mSessionDesc->isValid()的返回值是false //则说明该会话描述对象是无效的 //将错误码ERROR_MALFORMED赋值给result ALOGE("Failed to parse session description."); result = ERROR_MALFORMED; } else { //代码执行到这里说明该会话描述对象是有效的 //从应答消息对象response的mHeaders //成员变量获取key为"content-base"的值 ssize_t i = response->mHeaders.indexOfKey("content-base"); if (i >= 0) { //将获取到key为"content-base"的值赋值给mBaseURL mBaseURL = response->mHeaders.valueAt(i); } else { //代码执行到这里 //说明i的值小于０，即不存在key为"content-base"的头部 //则需要查询key为"content-location"的头部 i = response->mHeaders.indexOfKey("content-location"); if (i >= 0) { //将key为"content-location"头部的 //内容赋值给mBaseURL mBaseURL = response->mHeaders.valueAt(i); } else { //代码执行到这里 //说明在应答消息对象response里 //即不存在key为"content-base" //也不存在key为"content-location"的头部 //则将mSessionURL的值赋值给mBaseURL mBaseURL = mSessionURL; } } //判断该媒体是否能被seek //如果不为直播媒体流则可以被seek mSeekable = !isLiveStream(mSessionDesc); if (!mBaseURL.startsWith("rtsp://")) { //mBaseURL.startsWith("rtsp://")的值为fasle //说明服务端给出的是相对的url //需要将该相对url与绝对url合并在一起来定位媒体的位置 // Some misbehaving servers specify a relative // URL in one of the locations above, combine // it with the absolute session URL to get // something usable... ALOGW("Server specified a non-absolute base URL" ", combining it with the session URL to " "get something usable..."); AString tmp; //合并相对url和绝对url //相对url是mBaseURL.c_str() //绝对url是mSessionURL.c_str() //具体是怎样的合并规则后续再研究介绍给大家 CHECK(MakeURL( mSessionURL.c_str(), mBaseURL.c_str(), &tmp)); mBaseURL = tmp; } //对于Control信息的处理 //详细的处理过程后续介绍 mControlURL = getControlURL(); if (mSessionDesc->countTracks() < 2) { //如果会话描述的媒体的Tracks小于２ //则将错误码ERROR_UNSUPPORTED赋值给result // There's no actual tracks in this session. // The first "track" is merely session meta // data. ALOGW("Session doesn't contain any playable " "tracks. Aborting."); result = ERROR_UNSUPPORTED; } else { //创建索引为１的tarck setupTrack(1); } } } } if (result != OK) { //如果在上面过程中result的值不为OK //发送消息消息名为'disc'取消连接 sp<AMessage> reply = new AMessage('disc', this); mConn->disconnect(reply); } break; }

　　小结：MyHandler对’desc’消息的处理的主要工作就是创建一个会话对象。