Android9.0-Camera代码调用流程
1.App中调用open函数
mCamera = CameraEx.openLegacy(Integer.parseInt(mCameraId), halVersion);
(1) return Camera.openLegacy(cameraId, halVersion); 指定hal api版本以及指定打开某个摄像头，如果当前设备不支持指定的hal版本，则抛出RuntimeException。
(2) return Camera.open(cameraId); 指定打开某一个摄像头
(3) return Camera.open(); 默认打开后置摄像头
实际都是去new Camera()，只是构造函数中的参数不一样。
2. frameworks/base/core/java/android/hardware/Camera.java 中的open函数
public static Camera openLegacy(int cameraId, int halVersion) {
if (halVersion < CAMERA_HAL_API_VERSION_1_0) {
throw new IllegalArgumentException("Invalid HAL version " + halVersion);
}
return new Camera(cameraId, halVersion);
}
Camera构造器的核心实现在cameraInitVersion中，并传入参数cameraId和HAL的版本。
private Camera(int cameraId, int halVersion) {
int err = cameraInitVersion(cameraId, halVersion);
......
}
private int cameraInitVersion(int cameraId, int halVersion) {
......
return native_setup(new WeakReference<Camera>(this), cameraId, halVersion,
ActivityThread.currentOpPackageName());
}
用户通过cameraInitNormal --> cameraInitVersion调用本地方法native_setup()，由此进入到android_hardware_Camera.cpp中：
3.base/core/jni/android_hardware_Camera.cpp
native_setup()被动态注册到JNI，通过JNI调用android_hardware_Camera_native_setup()方法。
static const JNINativeMethod camMethods[] = {
......
{ "native_setup",
"(Ljava/lang/Object;IILjava/lang/String;)I",
(void*)android_hardware_Camera_native_setup },
......
};
android_hardware_Camera_native_setup()方法的实现：
// connect to camera service
static jint android_hardware_Camera_native_setup(JNIEnv *env, jobject thiz,
jobject weak_this, jint cameraId, jint halVersion, jstring clientPackageName)
{
// Convert jstring to String16
const char16_t *rawClientName = reinterpret_cast<const char16_t*>(
env->GetStringChars(clientPackageName, NULL));
jsize rawClientNameLen = env->GetStringLength(clientPackageName);
String16 clientName(rawClientName, rawClientNameLen);
env->ReleaseStringChars(clientPackageName,
reinterpret_cast<const jchar*>(rawClientName));
sp<Camera> camera;
if (halVersion == CAMERA_HAL_API_VERSION_NORMAL_CONNECT) {
// Default path: hal version is don't care, do normal camera connect.
camera = Camera::connect(cameraId, clientName,
Camera::USE_CALLING_UID, Camera::USE_CALLING_PID);
} else {
jint status = Camera::connectLegacy(cameraId, halVersion, clientName,
Camera::USE_CALLING_UID, camera);
if (status != NO_ERROR) {
return status;
}
}
......
return NO_ERROR;
}
调用Camera::connect()方法请求连接CameraService服务。
clientName 是通过将clientPackageName从jstring转换为String16格式得到；
Camera::USE_CALLING_UID 是定义在Camera.h中的枚举类型，其值为ICameraService::USE_CALLING_UID（同样为枚举类型，值为-1）。
Camera::connect() 位于Camera.cpp中，由此进入到Library层。
4. Camera Client 和 Camera Service
Camera类继承模板类CameraBase，Camera::connect()调用了CameraBase.cpp中的connect()方法
// Camera.cpp (av\camera)
sp<Camera> Camera::connect(int cameraId, const String16& clientPackageName,
int clientUid, int clientPid)
{
return CameraBaseT::connect(cameraId, clientPackageName, clientUid, clientPid);
}
CameraBaseT是定义在CameraBase.h中的变量： typedef CameraBase CameraBaseT;
// CameraBase.cpp (av\camera)
template <typename TCam, typename TCamTraits>
sp<TCam> CameraBase<TCam, TCamTraits>::connect(int cameraId,
const String16& clientPackageName,
int clientUid, int clientPid)
{
ALOGV("%s: connect", __FUNCTION__);
sp<TCam> c = new TCam(cameraId);
sp<TCamCallbacks> cl = c;
const sp<::android::hardware::ICameraService> cs = getCameraService();
binder::Status ret;
if (cs != nullptr) {
TCamConnectService fnConnectService = TCamTraits::fnConnectService;
ret = (cs.get()->*fnConnectService)(cl, cameraId, clientPackageName, clientUid,
clientPid, /*out*/ &c->mCamera);
}
if (ret.isOk() && c->mCamera != nullptr) {
IInterface::asBinder(c->mCamera)->linkToDeath(c);
c->mStatus = NO_ERROR;
} else {
ALOGW("An error occurred while connecting to camera %d: %s", cameraId,
(cs == nullptr) ? "Service not available" : ret.toString8().string());
c.clear();
}
return c;
}
new TCam(cameraId)生成BnCameraClient对象，BnCameraClient定义在ICameraClient.h文件中，继承自模板类BnInterface。getCameraService()方法返回CameraService的服务代理BpCameraService，BpCameraService同样继承自模板类BnInterface。然后通过Binder通信发送CONNECT命令，当BnCameraService收到CONNECT命令后调用CameraService的connect()成员函数来做相应的处理。
connect() 函数在BpCameraService和BnCameraService的父类ICameraService中声明为纯虚函数，在BpCameraService和CameraService中分别给出了实现，BpCameraService作为代理类，提供接口给客户端，真正实现在BnCameraService的子类CameraService中。
在BpCameraService中，connect()函数实现如下：
status_t BnCameraService::onTransact(){
}
CameraService::connect() -->connectHelper()实现的核心是调用makeClient()函数根据HAL不同API的版本创建不同的client实例。
sp<BasicClient> tmp = nullptr;
if(!(ret = makeClient(this, cameraCb, clientPackageName, cameraId, 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);
makeClient根据HAL不同API的版本创建不同的client实例：
Status CameraService::makeClient(const sp<CameraService>& cameraService,
const sp<IInterface>& cameraCb, const String16& packageName, const String8& cameraId,
int facing, int clientPid, uid_t clientUid, int servicePid, bool legacyMode,
int halVersion, int deviceVersion, apiLevel effectiveApiLevel,
/*out*/sp<BasicClient>* client) {
if (halVersion < 0 || halVersion == deviceVersion) {
// Default path: HAL version is unspecified by caller, create CameraClient
// based on device version reported by the HAL.
switch(deviceVersion) {
case CAMERA_DEVICE_API_VERSION_1_0:
if (effectiveApiLevel == API_1) { // Camera1 API route
sp<ICameraClient> tmp = static_cast<ICameraClient*>(cameraCb.get());
*client = new CameraClient(cameraService, tmp, packageName, cameraIdToInt(cameraId),
facing, clientPid, clientUid, getpid(), legacyMode);
} else { // Camera2 API route
ALOGW("Camera using old HAL version: %d", deviceVersion);
return STATUS_ERROR_FMT(ERROR_DEPRECATED_HAL,
"Camera device \"%s\" HAL version %d does not support camera2 API",
cameraId.string(), deviceVersion);
}
break;
case CAMERA_DEVICE_API_VERSION_3_4:
if (effectiveApiLevel == API_1) { // Camera1 API route
sp<ICameraClient> tmp = static_cast<ICameraClient*>(cameraCb.get());
*client = new Camera2Client(cameraService, tmp, packageName, cameraIdToInt(cameraId),
facing, clientPid, clientUid, servicePid, legacyMode);
} else { // Camera2 API route
sp<hardware::camera2::ICameraDeviceCallbacks> tmp =
static_cast<hardware::camera2::ICameraDeviceCallbacks*>(cameraCb.get());
*client = new CameraDeviceClient(cameraService, tmp, packageName, cameraId,
facing, clientPid, clientUid, servicePid);
}
break;
default:
// Should not be reachable
ALOGE("Unknown camera device HAL version: %d", deviceVersion);
return STATUS_ERROR_FMT(ERROR_INVALID_OPERATION,
"Camera device \"%s\" has unknown HAL version %d",
cameraId.string(), deviceVersion);
}
} else {
// A particular HAL version is requested by caller. Create CameraClient
// based on the requested HAL version.
if (deviceVersion > CAMERA_DEVICE_API_VERSION_1_0 &&
halVersion == CAMERA_DEVICE_API_VERSION_1_0) {
// Only support higher HAL version device opened as HAL1.0 device.
sp<ICameraClient> tmp = static_cast<ICameraClient*>(cameraCb.get());
*client = new CameraClient(cameraService, tmp, packageName, cameraIdToInt(cameraId),
facing, clientPid, clientUid, servicePid, legacyMode);
} else {
// Other combinations (e.g. HAL3.x open as HAL2.x) are not supported yet.
ALOGE("Invalid camera HAL version %x: HAL %x device can only be"
" opened as HAL %x device", halVersion, deviceVersion,
CAMERA_DEVICE_API_VERSION_1_0);
return STATUS_ERROR_FMT(ERROR_ILLEGAL_ARGUMENT,
"Camera device \"%s\" (HAL version %d) cannot be opened as HAL version %d",
cameraId.string(), deviceVersion, halVersion);
}
}
return Status::ok();
}
CameraClient::initialize函数：
status_t CameraClient::initialize(sp<CameraProviderManager> manager,
const String8& /*monitorTags*/) {
int callingPid = getCallingPid();
status_t res;
......
char camera_device_name[10];
snprintf(camera_device_name, sizeof(camera_device_name), "%d", mCameraId);
mHardware = new CameraHardwareInterface(camera_device_name);
res = mHardware->initialize(manager);
if (res != OK) {
ALOGE("%s: Camera %d: unable to initialize device: %s (%d)",
__FUNCTION__, mCameraId, strerror(-res), res);
mHardware.clear();
return res;
}
mHardware->setCallbacks(notifyCallback,
dataCallback,
dataCallbackTimestamp,
handleCallbackTimestampBatch,
(void *)(uintptr_t)mCameraId);
......
return OK;
}
-
mHardware = new CameraHardwareInterface(camera_device_name); 新建Camera硬件接口，camera_device_name为设备名
-
mHardware->initialize(&module->common)调用底层硬件的初始化方法；
-
mHardware->setCallbacks将CamerService处的回调函数注册到HAL处。
5. HAL：CameraHardwareInterface.h
CameraHardwareInterface的作用在于链接Camera Server和驱动，通过实现CameraHardwareInterface可以屏蔽不同的driver对Camera Server的影响。
mHardware->initialize中通过cameraModule->open_legacy打开摄像头模组。 mHardware-> set_callbacks中，__notify_cb、__data_cb、__data_cb_timestamp和__get_memory分别消息回调，数据回调，时间戳回调，以及内存相关操作的回调。