Android 多进程同时打开相机

转载：多进程打开相机
多进程打开相机

只要满足一定的条件是可以多进程打开相机

1、CameraService打开相机的入口

Status CameraService::connectDevice(const sp<hardware::camera2::ICameraDeviceCallbacks>& cameraCb,const String16& cameraId,const String16& clientPackageName,int clientUid,/*out*/sp<hardware::camera2::ICameraDeviceUser>* device) {ATRACE_CALL();Status ret = Status::ok();String8 id = String8(cameraId);sp<CameraDeviceClient> client = nullptr;ret = connectHelper<hardware::camera2::ICameraDeviceCallbacks,CameraDeviceClient>(cameraCb, id,/*api1CameraId*/-1,CAMERA_HAL_API_VERSION_UNSPECIFIED, clientPackageName,clientUid, USE_CALLING_PID, API_2,/*legacyMode*/ false, /*shimUpdateOnly*/ false,/*out*/client);if(!ret.isOk()) {logRejected(id, getCallingPid(), String8(clientPackageName),ret.toString8());return ret;}*device = client;return ret;
}

2、进入connectHelper

template<class CALLBACK, class CLIENT>
Status CameraService::connectHelper(const sp<CALLBACK>& cameraCb, const String8& cameraId,int api1CameraId, int halVersion, const String16& clientPackageName, int clientUid,int clientPid, apiLevel effectiveApiLevel, bool legacyMode, bool shimUpdateOnly,/*out*/sp<CLIENT>& device) {binder::Status ret = binder::Status::ok();String8 clientName8(clientPackageName);int originalClientPid = 0;ALOGI("CameraService::connect call (PID %d \"%s\", camera ID %s) for HAL version %s and ""Camera API version %d", clientPid, clientName8.string(), cameraId.string(),(halVersion == -1) ? "default" : std::to_string(halVersion).c_str(),static_cast<int>(effectiveApiLevel));sp<CLIENT> client = nullptr;{// Acquire mServiceLock and prevent other clients from connecting//1)加这个锁的主要目的是防止不同应用同一时刻尝试打开相机，比如一个应用正在打开相机，另外一个应用也在尝试打开相机，这个时候就需要等待了std::unique_ptr<AutoConditionLock> lock =AutoConditionLock::waitAndAcquire(mServiceLockWrapper, DEFAULT_CONNECT_TIMEOUT_NS);if (lock == nullptr) {ALOGE("CameraService::connect (PID %d) rejected (too many other clients connecting).", clientPid);return STATUS_ERROR_FMT(ERROR_MAX_CAMERAS_IN_USE,"Cannot open camera %s for \"%s\" (PID %d): Too many other clients connecting",cameraId.string(), clientName8.string(), clientPid);}// Enforce client permissions and do basic sanity checks//2)这个主要是对应用做一些基本的检查//包括：//1.检测UID是否可信//2.检测PID是否可信//3.检测是否有anddroid.permission.CAMERA权限//4.检测用户是否在mAllowedusers中，即检测是否是有效用户，//mAllowedusers的赋值实在CameraserviceProxy.javaif(!(ret = validateConnectLocked(cameraId, clientName8,/*inout*/clientUid, /*inout*/clientPid, /*out*/originalClientPid)).isOk()) {return ret;}// Check the shim parameters after acquiring lock, if they have already been updated and// we were doing a shim update, return immediatelyif (shimUpdateOnly) {auto cameraState = getCameraState(cameraId);if (cameraState != nullptr) {if (!cameraState->getShimParams().isEmpty()) return ret;}}status_t err;sp<BasicClient> clientTmp = nullptr;std::shared_ptr<resource_policy::ClientDescriptor<String8, sp<BasicClient>>> partial;//3)handleEvictionsLocked是处理多进程互斥逻辑的地方，//多进程同时打开相机的互斥逻辑就是在这个函数实现。//我们重点分析下这个函数if ((err = handleEvictionsLocked(cameraId, originalClientPid, effectiveApiLevel,IInterface::asBinder(cameraCb), clientName8, /*out*/&clientTmp,/*out*/&partial)) != NO_ERROR) {switch (err) {case -ENODEV:return STATUS_ERROR_FMT(ERROR_DISCONNECTED,"No camera device with ID \"%s\" currently available",cameraId.string());case -EBUSY:return STATUS_ERROR_FMT(ERROR_CAMERA_IN_USE,"Higher-priority client using camera, ID \"%s\" currently unavailable",cameraId.string());default:return STATUS_ERROR_FMT(ERROR_INVALID_OPERATION,"Unexpected error %s (%d) opening camera \"%s\"",strerror(-err), err, cameraId.string());}}..............sp<BasicClient> tmp = nullptr;if(!(ret = makeClient(this, cameraCb, clientPackageName,cameraId, api1CameraId, facing,clientPid, clientUid, getpid(), legacyMode,halVersion, deviceVersion, effectiveApiLevel,/*out*/&tmp)).isOk()) {return ret;}client = static_cast<CLIENT*>(tmp.get());LOG_ALWAYS_FATAL_IF(client.get() == nullptr, "%s: CameraService in invalid state",__FUNCTION__);err = client->initialize(mCameraProviderManager, mMonitorTags);............if (shimUpdateOnly) {// If only updating legacy shim parameters, immediately disconnect clientmServiceLock.unlock();client->disconnect();mServiceLock.lock();} else {// Otherwise, add client to active clients listfinishConnectLocked(client, partial);}} // lock is destroyed, allow further connect calls// Important: release the mutex here so the client can call back into the service from its// destructor (can be at the end of the call)device = client;return ret;
}

3、分析handleEvictionsLocked

status_t CameraService::handleEvictionsLocked(const String8& cameraId, int clientPid,apiLevel effectiveApiLevel, const sp<IBinder>& remoteCallback, const String8& packageName,/*out*/sp<BasicClient>* client,std::shared_ptr<resource_policy::ClientDescriptor<String8, sp<BasicClient>>>* partial) {ATRACE_CALL();status_t ret = NO_ERROR;std::vector<DescriptorPtr> evictedClients;DescriptorPtr clientDescriptor;{if (effectiveApiLevel == API_1) {// If we are using API1, any existing client for this camera ID with the same remote// should be returned rather than evicted to allow MediaRecorder to work properly.............}// Get current active client PIDs 获取已经打开相机的所有pidstd::vector<int> ownerPids(mActiveClientManager.getAllOwners());//将当前正在打开相机的应用进程号也保存到ownerPids 中ownerPids.push_back(clientPid);//创建进程priorityScores，states ventorstd::vector<int> priorityScores(ownerPids.size());std::vector<int> states(ownerPids.size());// Get priority scores of all active PIDs  //获取所有ownerPids中的进程priority和statesstatus_t err = ProcessInfoService::getProcessStatesScoresFromPids(ownerPids.size(), &ownerPids[0], /*out*/&states[0],/*out*/&priorityScores[0]);if (err != OK) {ALOGE("%s: Priority score query failed: %d",__FUNCTION__, err);return err;}// Update all active clients' priorities//将上一步获取的进程优先级更新到mActiveClientManager中std::map<int,resource_policy::ClientPriority> pidToPriorityMap;for (size_t i = 0; i < ownerPids.size() - 1; i++) {pidToPriorityMap.emplace(ownerPids[i],resource_policy::ClientPriority(priorityScores[i], states[i]));}mActiveClientManager.updatePriorities(pidToPriorityMap);// Get state for the given cameraId// 获取cameraId相机的状态，Cameraservice启动的时候会获取所有相机的状态auto state = getCameraState(cameraId);if (state == nullptr) {ALOGE("CameraService::connect X (PID %d) rejected (no camera device with ID %s)",clientPid, cameraId.string());// Should never get here because validateConnectLocked should have errored outreturn BAD_VALUE;}// Make descriptor for incoming client//由当前正在打开相机的cameraId，priorityScores，states，clientPid等信息//创建ClientDescriptor对象，key=cameraId；value=null；//ClientDescriptor未填充client，因为还未makeclientclientDescriptor = CameraClientManager::makeClientDescriptor(cameraId,sp<BasicClient>{nullptr}, static_cast<int32_t>(state->getCost()),state->getConflicting(),//当前正在打开相机的priorityScorespriorityScores[priorityScores.size() - 1],clientPid,//当前正在打开相机的statesstates[states.size() - 1]);// Find clients that would be evicted// 在mActiveClientManager查找和上一步创建的ClientDescriptor存在冲突的所有client// 如果有冲突的client，都保存到evicted队列中// evicted队列中的所有client都需要关闭正在使用的相机，// 如果当前正在打开相机的client也在该evicted，说明当前client不能打开相机// 接下来会重点分析该函数实现auto evicted = mActiveClientManager.wouldEvict(clientDescriptor);// If the incoming client was 'evicted,' higher priority clients have the camera in the// background, so we cannot do evictions//如果clientDescriptor（即当前应用）在evicted列表中，则说明当前相机应用的进程优先级较低，则本次打开相机失败，上报的错误log如下if (std::find(evicted.begin(), evicted.end(), clientDescriptor) != evicted.end()) {ALOGE("CameraService::connect X (PID %d) rejected (existing client(s) with higher"" priority).", clientPid);sp<BasicClient> clientSp = clientDescriptor->getValue();String8 curTime = getFormattedCurrentTime();//获取与当前client存在冲突的clientauto incompatibleClients =mActiveClientManager.getIncompatibleClients(clientDescriptor);//打印当前client信息String8 msg = String8::format("%s : DENIED connect device %s client for package %s ""(PID %d, score %d state %d) due to eviction policy", curTime.string(),cameraId.string(), packageName.string(), clientPid,priorityScores[priorityScores.size() - 1],states[states.size() - 1]);//打印与当前client冲突的client信息for (auto& i : incompatibleClients) {msg.appendFormat("\n   - Blocked by existing device %s client for package %s""(PID %" PRId32 ", score %" PRId32 ", state %" PRId32 ")",i->getKey().string(),String8{i->getValue()->getPackageName()}.string(),i->getOwnerId(), i->getPriority().getScore(),i->getPriority().getState());ALOGE("   Conflicts with: Device %s, client package %s (PID %"PRId32 ", score %" PRId32 ", state %" PRId32 ")", i->getKey().string(),String8{i->getValue()->getPackageName()}.string(), i->getOwnerId(),i->getPriority().getScore(), i->getPriority().getState());}// Log the client's attemptMutex::Autolock l(mLogLock);mEventLog.add(msg);return -EBUSY;}//关闭evicted中client正在使用的相机  如果clientDescriptor不在evicted，则强制关闭evicted中其他正在使用相机的应用for (auto& i : evicted) {sp<BasicClient> clientSp = i->getValue();if (clientSp.get() == nullptr) {ALOGE("%s: Invalid state: Null client in active client list.", __FUNCTION__);// TODO: Remove thisLOG_ALWAYS_FATAL("%s: Invalid state for CameraService, null client in active list",__FUNCTION__);mActiveClientManager.remove(i);continue;}ALOGE("CameraService::connect evicting conflicting client for camera ID %s",i->getKey().string());//将有效evicted的client push到evictedClientsevictedClients.push_back(i);// Log the clients evictedlogEvent(String8::format("EVICT device %s client held by package %s (PID"" %" PRId32 ", score %" PRId32 ", state %" PRId32 ")\n - Evicted by device %s client for"" package %s (PID %d, score %" PRId32 ", state %" PRId32 ")",i->getKey().string(), String8{clientSp->getPackageName()}.string(),i->getOwnerId(), i->getPriority().getScore(),i->getPriority().getState(), cameraId.string(),packageName.string(), clientPid,priorityScores[priorityScores.size() - 1],states[states.size() - 1]));// Notify the client of disconnection//通知evicted中client，相机马上就要关闭了clientSp->notifyError(hardware::camera2::ICameraDeviceCallbacks::ERROR_CAMERA_DISCONNECTED,CaptureResultExtras());}}// Do not hold mServiceLock while disconnecting clients, but retain the condition blocking// other clients from connecting in mServiceLockWrapper if heldmServiceLock.unlock();// Clear caller identity temporarily so client disconnect PID checks work correctlyint64_t token = IPCThreadState::self()->clearCallingIdentity();// Destroy evicted clients//关闭所有在evictedClients中的正在使用相机的应用  for (auto& i : evictedClients) {// Disconnect is blocking, and should only have returned when HAL has cleaned upi->getValue()->disconnect(); // Clients will remove themselves from the active client list}IPCThreadState::self()->restoreCallingIdentity(token);for (const auto& i : evictedClients) {ALOGV("%s: Waiting for disconnect to complete for client for device %s (PID %" PRId32 ")",__FUNCTION__, i->getKey().string(), i->getOwnerId());ret = mActiveClientManager.waitUntilRemoved(i, DEFAULT_DISCONNECT_TIMEOUT_NS);if (ret == TIMED_OUT) {ALOGE("%s: Timed out waiting for client for device %s to disconnect, ""current clients:\n%s", __FUNCTION__, i->getKey().string(),mActiveClientManager.toString().string());return -EBUSY;}if (ret != NO_ERROR) {ALOGE("%s: Received error waiting for client for device %s to disconnect: %s (%d), ""current clients:\n%s", __FUNCTION__, i->getKey().string(), strerror(-ret),ret, mActiveClientManager.toString().string());return ret;}}evictedClients.clear();// Once clients have been disconnected, relockmServiceLock.lock();// Check again if the device was unplugged or something while we weren't holding mServiceLockif ((ret = checkIfDeviceIsUsable(cameraId)) != NO_ERROR) {return ret;}*partial = clientDescriptor;return NO_ERROR;
}

4、分析mActiveClientManager.wouldEvict(clientDescriptor);

实现函数为wouldEvictLocked

ClientManager<KEY, VALUE, LISTENER>::wouldEvict(const std::shared_ptr<ClientDescriptor<KEY, VALUE>>& client) const {Mutex::Autolock lock(mLock);return wouldEvictLocked(client);
}

//returnIncompatibleClients为默认值false
template<class KEY, class VALUE, class LISTENER>
std::vector<std::shared_ptr<ClientDescriptor<KEY, VALUE>>>
ClientManager<KEY, VALUE, LISTENER>::wouldEvictLocked(const std::shared_ptr<ClientDescriptor<KEY, VALUE>>& client,bool returnIncompatibleClients) const {std::vector<std::shared_ptr<ClientDescriptor<KEY, VALUE>>> evictList;// Disallow null clients, return inputif (client == nullptr) {evictList.push_back(client);return evictList;}//获取当前进程的现关信息const KEY& key = client->getKey(); //key就是cameraidint32_t cost = client->getCost();   //cost 在getCameraState会介绍ClientPriority priority = client->getPriority();  //获取优先级int32_t owner = client->getOwnerId();   //获取进程pidint64_t totalCost = getCurrentCostLocked() + cost;// Determine the MRU of the owners tied for having the highest priority//获取所有打开相机应用中优先级最高的pidint32_t highestPriorityOwner = owner;ClientPriority highestPriority = priority;for (const auto& i : mClients) {ClientPriority curPriority = i->getPriority();if (curPriority <= highestPriority) {// 值越小优先级越高highestPriority = curPriority;highestPriorityOwner = i->getOwnerId();}}if (highestPriority == priority) {// Switch back owner if the incoming client has the highest priority, as it is MRUhighestPriorityOwner = owner;}// Build eviction list of clients to remove//创建eviction list，这个队列就是存在冲突的clientfor (const auto& i : mClients) {const KEY& curKey = i->getKey();int32_t curCost = i->getCost();ClientPriority curPriority = i->getPriority();int32_t curOwner = i->getOwnerId();// 判断是否冲突://1.camera id 相同，存在冲突//isConflicting检查底层是否存在冲突bool conflicting = (curKey == key || i->isConflicting(key) ||client->isConflicting(curKey));if (!returnIncompatibleClients) {  //默认returnIncompatibleClients=false// Find evicted clients//查找冲突clientif (conflicting && curPriority < priority) {// Pre-existing conflicting client with higher priority exists//之前存在的client具有较高优先级，在将当前client添加到evictList中，//表示当前clieng不能打开相机evictList.clear();evictList.push_back(client);return evictList;} else if (conflicting || ((totalCost > mMaxCost && curCost > 0) &&(curPriority >= priority) &&!(highestPriorityOwner == owner && owner == curOwner))) {//在满足下边的条件时，将正在使用相机的client添加到evictList，表示在打开当前相机时，//正在使用相机的client因为和正在打开相机的client冲突需要关闭正在使用相机的client使用的相机。//1）存在冲突，且正在使用相机的client优先级低//2) 不存在冲突，但是totalCost 大于最大允许值mMaxCost //在当满足如下条件时也需要将正在使用相机的client添加到evictList：//1.如果正在打开相机的client和正在使用相机的client不是同一进程而且//正在打开相机的client优先级高于或者等于正在使用相机的client//2.如果正在打开相机的client和正在使用相机的client是同一进程//但是该进程不是最高优先级。// Add a pre-existing client to the eviction list if:// - We are adding a client with higher priority that conflicts with this one.// - The total cost including the incoming client's is more than the allowable//   maximum, and the client has a non-zero cost, lower priority, and a different//   owner than the incoming client when the incoming client has the//   highest priority.evictList.push_back(i);totalCost -= curCost;}} else {// Find clients preventing the incoming client from being added// 这个条件上一步已经涵盖了if (curPriority < priority && (conflicting || (totalCost > mMaxCost && curCost > 0))) {// Pre-existing conflicting client with higher priority existsevictList.push_back(i);}}}// Immediately return the incompatible clients if we are calculating these insteadif (returnIncompatibleClients) {return evictList;}// If the total cost is too high, return the input unless the input has the highest priority//如果经过上一步检测，totalCost还是超过最大允许值且当前client不具有最高优先级，则将当前client添加到evictList，//表示当前client不能打开相机if (totalCost > mMaxCost && highestPriorityOwner != owner) {evictList.clear();evictList.push_back(client);return evictList;}return evictList;}

4、分析getCameraState

std::shared_ptr<CameraService::CameraState> CameraService::getCameraState(const String8& cameraId) const {std::shared_ptr<CameraState> state;{Mutex::Autolock lock(mCameraStatesLock);auto iter = mCameraStates.find(cameraId);if (iter != mCameraStates.end()) {state = iter->second;}}return state;
}

mCameraStates的赋值时在CameraService::enumerateProviders()，

主要是 mCameraStates.emplace(id8, std::make_shared(id8, cost.resourceCost, conflicting));

就是从HAL层获取，cameraid为id8的相机的resourceCost和conflicting列表（和那些相机存在冲突）

至此分析完成，可以得到的结论是：
多进程可以在满足一定条件是能都同时打开相机，需要满足的条件有：
evictList为空且totalCost <= mMaxCost.
如果totalCost <= mMaxCost不成立，可以适当调大mMaxCost。如果evictList不为空，则可能需要调剂下进程优先级或者在cameraservice中强制改下进程优先级

Android 多进程同时打开相机相关推荐

Android使用CameraX打开相机拍照简单使用
1.首先是效果图 2.布局及依赖布局: <?xml version="1.0" encoding="utf-8"?> <androidx.c ...
Android 调用系统打开相机，打开相册获取图片路径
我们在开发中经常遇到一些功能需要调取系统相机拍照获取图片,或者有的时候直接打开图库获取图片,那我们怎么获取呢,今天分享下, 第一步,打开相机 public static final int CAMER ...
Android WebView中打开相机拍照和选择相册
一般在项目中与js交互,可能会遇到上传文件图片等操作,避免不了一些坑,下面简单说一下,Android 在不同版本中webView调用相机,选择相册的方法是不一样的,3.0以下的调用 public vo ...
Android 之打开相机打开相册
Android 之打开系统摄像头拍照打开系统相册,并展示 1,清单文件 AndroidManifest.xml ``` <uses-permission android:name=" ...
Android Camera2教程之打开相机、开启预览、实现PreviewCallback、拍照
转载请注明出处: http://blog.csdn.net/lb377463323/article/details/52740411 Android API 21新增了Camera2,这与之前的cam ...
OpenCV学习笔记（六）—— OpenCV for Android打开相机
在之前的篇章中,我们完成了Android平台开发环境的配置,也找到了剔除OpenCV Manager API的办法,那么接下来我们开始从零开始,完成一个个人的程序,实现功能如下: 1.识别指定的图片, ...
android 7.0之后的打开相机拍摄头像上传
今天一天都在搞这个头像相关的android开发,不断的在网上查找资料,什么都不懂,然后就照抄. 就是一个什么问题呢,现在android打开一个相机不再简单的请求打开就行了,按照我今天查到的资料,就是说 ...
android调取手机相册或打开相机选择图片并显示
作为一个android小白,自己想尝试写一个小项目,因此写个小博客记录一下自己的开发历程.这一篇记录自己学习调取手机相册以及打开相机选择图片并显示示例是采用PopupWindow弹出底部菜单,选择相 ...
详记Android打开相机拍照流程
写在前面本文并不是基于Camera2的,所以想要了解Camera2的同学可以先散了.文题加了详记二字,因为相机整个打开的流程的确是比较复杂的,稍有疏忽可能就会引发一系列问题.我也是看了一下Andro ...