学习Android camera笔记 & 调用流程

参考:http://blog.csdn.net/xingyu19871124/article/details/7750189
http://blog.csdn.net/BonderWu/article/details/5814278
http://blog.chinaunix.net/uid-2630593-id-3307176.html
http://zhidao.baidu.com/question/388864295.html
等

注:把本文内容复制到source insight中查看效果较好

线程与进程:子进程和父进程有不同的代码和数据空间,而多个线程则共享数据空间,每个线程有自己的执行堆栈和程序计数器为其执行上下文。

Handler与线程: 其实Handler并不是开辟新线程的概念，Android主要的考虑到更新界面的问题，一般情况下，更新界面（Activity）都是在主线程中更新的，
这样就遇到了一个问题，比方说：在下载文件时候我们需要进度条显示下载进度，界面需要更新（数据是不断变的，也就是下载的大小是不断变的，要是直接
在主线程中更新，就会造成程序的堵塞，程序很容易崩溃，通常这样联网耗时的工作需要开辟另外一个线程的，这样就不会影响主程序了），好了，到这里联
网操作一般都需要开辟新线程了吧。
接下来就来说Handler了，刚刚我说了Handler不是开辟新线程，在我看来，Handler更像是主线程的秘书，是一个触发器，负责管理从子线程中得到更新的数据，
然后在主线程中更新界面。简单说下进度条的那个：下载了多少的数据都是在子线程中得到的，在子线程中通过Handler的sendMessage()方法发送得到的下载
的数据，当你调用了sendMessage方法后，Handler就会回调（也就是自动调用）Handler中的 HandlerMessage方法。

启动线程:Android启动线程和JAVA一样有两种方式，一种是直接Thread类的start方法，也就是一般写一个自己的类来继承Thread 类。
另外一种方式其实和这个差不多啊！那就是Runnable接口，然后把Runnable的子类对象传递给Thread类再创建Thread对象.总之都是需要创建Thread对象，
然后调用Thread类的start方法启动线程。区别就是，一个是直接创建Thread对象，另外一个是需要implement了Runnable接口对象作为创建Thread对象的参数.
Runnable其实我们称为线程任务。
第一种方式一般是这样用：
Class MyThread extends Thread{
public void run(){
//你要实现的代码
}
}
在主线程中启动这个线程:
public class Test{
public static void main(String[] args){
new MyThread().start();//启动了我们的线程了
}
}
2，第二种方式一般是这样用：
public class MyRunnable implements Runnable{
public void run(){
//你需要实现的代码
}
}
在主线程中启动这个线程：
public class Test{
public static void main(String[] args){
Thread t=new Thread(new MyRunnable());//这里比第一种创建线程对象多了个任务对象
t.start();
}
}
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
cpp:
LOGD("dyyr - log %s, %s", __FILE__, __FUNCTION__);

打开camera/唤醒camera 大致流程途径源文件:

Camera.java onCreate() log1
开启一个新线程，在此线程中open camera

mCameraOpenThread的run()
log2
运行构造函数中的run()
是上述两种开启线程方法中的第一种

Then do something about rotation and else.
在onCreate()中以mCameraOpenThread.join();这句等待该线程完成它的任务
再开启预览线程mCameraPreviewThread.start();

mCameraPreviewThread的run()
1872 log14

startPreview()
log14.5
mCameraDevice是在log4的位置定义的，是log5返回的一个android.hardware.Camera对象
(因为log5源文件第一句:package android.hardware;)
这个对象的startPreview方法声明在log5下面。481行
而它在log15定义。

Util.java openCamera() log3

CameraHolder.java open() log4

Applications
---------------------------------------------------------------------------------------------------------------------------
Camera.java open() log5

Framework
---------------------------------------------------------------------------------------------------------------------------
android_hardware_camera.cpp
android_hardware_Camera_native_setup()
log6

android_hardware_Camera_startPreview()
log15

Camera.cpp connect() log7

startPreview() log16

CameraService.cpp connect() log8 IServiceManager.cpp ServiceManager.java(comfirmed)
log8.1
log8.2

Client() log8.3~8.8
怎么到下面的log9?

startPreview() log17
startCameraMode() log18
startPreviewMode()log19
JNI
---------------------------------------------------------------------------------------------------------------------------
进入camera之前(开机时),camera初始化
CameraHardwareDevice.cpp Initialize() log'1
ALCameraFactory.cpp device_open() log9 (name=0) V4L2CameraDevice.cpp Initialize() log'2
cameraDeviceOpen() log10

CameraHardware.cpp connectCamera() log11 V4L2Camera.cpp Initialize() log'3

startPreview() log20
doStartPreview() log21

V4L2CameraDevice.cpp connectDevice() log12 V4L2Camera.h WorkerThread() log'4 上述两种开启线程方法中的第一种，但并没有run()，
所以还没有真正开启线程，初始化了一个指针V4L2Camera* camera_dev
openCameraDev() log13
在这个最终打开设备文件的函数中，open()得到文件描述符后，
用iotrl()函数做了一些配置然后返回了

PreviewWindow.cpp startPreview() log22
onNextFrameAvailableHW() log23
通过perform向mPreviewWindow窗体发送消息

打开camera并开启预览的流程跟到这里。

camera.cfg
HAL
---------------------------------------------------------------------------------------------------------------------------
gc0308.c
Sys_config1.fex
Kernel
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
cpp:
LOGD("dyyr - log %s, %s", __FILE__, __FUNCTION__);

Camera.java

1117 public void onCreate(Bundle icicle) { //打开

......

mCameraOpenThread.start(); // 1097

......

}

1097 Thread mCameraOpenThread = new Thread(new Runnable() {
public void run() {
try {
mCameraDevice = Util.openCamera(Camera.this, mCameraId); //Util.java 267
}

.......

}
}

1532 protected void doOnResume() { //唤醒

......

Util.openCamera(this, mCameraId); //Util.java 267

......

}

1836 private void startPreview() {

......

if (mCameraPreviewThread != null) {
synchronized (mCameraPreviewThread) {
mCameraPreviewThread.notify(); //开启预览线程
}
}

......

}

Util.java package/apps/.../camera

267 CameraHolder.instance().open(cameraId);

CameraHolder.java package/apps/.../camera

131 android.hardware.Camera.open(cameraId); //无法自动定位，frameworks/base/core/java/android/hardware/Camera.java 264 open()

packages/apps/camera/src/com/android/camera/ --------> Camera.apk

Applications
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Camera.java frameworks/base/core/java/android/hardware/Camera.java --------> framework.jar

264 public static Camera open(int cameraId) {
return new Camera(cameraId);
} //open函数是一个静态方法，构造一个Camera对象

285 Camera(int cameraId) { //构造函数
mShutterCallback = null;
mRawImageCallback = null;
mJpegCallback = null;
mPreviewCallback = null;
mPostviewCallback = null;
mZoomListener = null;

Looper looper;
if ((looper = Looper.myLooper()) != null) {
mEventHandler = new EventHandler(this, looper);
} else if ((looper = Looper.getMainLooper()) != null) {
mEventHandler = new EventHandler(this, looper);
} else {
mEventHandler = null;
}

native_setup(new WeakReference<Camera>(this), cameraId); //310
}

310 private native final void native_setup(Object camera_this, int cameraId); 其对应于android_hardware_Camera.cpp的android_hardware_Camera_native_setup方法,为什么????
貌似是有函数会去按照camMethods数组匹配

Frameworks
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

android_hardware_camera.cpp frameworks/base/core/jni

458 // connect to camera service
static void android_hardware_Camera_native_setup(JNIEnv *env, jobject thiz,
jobject weak_this, jint cameraId)
{
sp<Camera> camera = Camera::connect(cameraId); //无法自动定位. Camera.cpp 128
//Camera C/S架构的客户端调用connect函数向服务器发送连接请求,
//这个Camera类的声明在Camera.h (android4.0\frameworks\base\include\camera）

if (camera == NULL) {
jniThrowRuntimeException(env, "Fail to connect to camera service");
return;
}

// make sure camera hardware is alive
if (camera->getStatus() != NO_ERROR) {
jniThrowRuntimeException(env, "Camera initialization failed");
return;
}

jclass clazz = env->GetObjectClass(thiz);
if (clazz == NULL) {
jniThrowRuntimeException(env, "Can't find android/hardware/Camera");
return;
}

// We use a weak reference so the Camera object can be garbage collected.
// The reference is only used as a proxy for callbacks.
sp<JNICameraContext> context = new JNICameraContext(env, weak_this, clazz
, camera);

context->incStrong(thiz);
camera->setListener(context);

// save context in opaque field
env->SetIntField(thiz, fields.context, (int)context.get());
}

Camera.cpp frameworks/base/libs/camera

128 sp<Camera> Camera::connect(int cameraId)
{
LOGV("connect");
sp<Camera> c = new Camera();
const sp<ICameraService>& cs = getCameraService(); //获取一个Camera服务实例,本源文件40行
if (cs != 0) {
c->mCamera = cs->connect(c, cameraId); //然后执行服务端的connect()函数，并返回一个ICamera对象赋值给Camera 的mCamera,
//CameraService.cpp 185~254
}
if (c->mCamera != 0) {
c->mCamera->asBinder()->linkToDeath(c);
c->mStatus = NO_ERROR;
} else {
c.clear();
}
return c;
}

40 // establish binder interface to camera service
const sp<ICameraService>& Camera::getCameraService()
{
Mutex::Autolock _l(mLock);
if (mCameraService.get() == 0) {
sp<IServiceManager> sm = defaultServiceManager(); //无法自动定位，调用的是IServiceManager.cpp(frameworks/base/libs/binder) 34
sp<IBinder> binder;
do {
binder = sm->getService(String16("media.camera")); //无法自动定位，搜索符号getService,定位到ServiceManager.java 49
if (binder != 0)
break;
LOGW("CameraService not published, waiting...");
usleep(500000); // 0.5 s
} while(true);
if (mDeathNotifier == NULL) {
mDeathNotifier = new DeathNotifier();
}
binder->linkToDeath(mDeathNotifier);
mCameraService = interface_cast<ICameraService>(binder); //mCameraService是一个ICamerService类型，
//更加具体具体一点来讲应该是BpCameraService，因为在这个类中实现了ICameraService的方法。
}
LOGE_IF(mCameraService==0, "no CameraService!?");
return mCameraService;
}

IServiceManager.cpp frameworks/base/libs/binder

34 sp<IServiceManager> defaultServiceManager()
{
if (gDefaultServiceManager != NULL) return gDefaultServiceManager;

{
AutoMutex _l(gDefaultServiceManagerLock);
if (gDefaultServiceManager == NULL) {
gDefaultServiceManager = interface_cast<IServiceManager>( //得到上面要的sm，它的类型是"sp<IServiceManager>",
//sp<T>是android的智能指针，它持有一个T类实例，并负责在必要时释放此实例
ProcessState::self()->getContextObject(NULL));
}
}

return gDefaultServiceManager;
}

我们有必要关注一下interface_cast，通过代码跟踪:看到它的实现
template<typename INTERFACE>
inline sp<INTERFACE> interface_cast(const sp<IBinder>& obj)
{
return INTERFACE::asInterface(obj);
}
通过模板替换就是:
inline sp< IServiceManager > interface_cast(const sp<IBinder>& obj)
{
return IServiceManager::asInterface(obj);
}
看来asInterface是IServiceManager的一个成员函数，我们打开IServiceManager.cpp/
h文件，我们并没有发现该函数，那它到底在哪儿呢，仔细观察IServiceManager.cpp
，发现里面有个IMPLEMENT_META_INTERFACE(ServiceManager, "android.os.IServiceManager");
在IServiceManager.h里面发现了DECLARE_META_INTERFACE(ServiceManager);
通过跟踪这两个宏发现DECLARE_META_INTERFACE声明了一个变量和两个函数...
interface_cast<IServiceManager>实际上返回了一个BpServiceManager，在创建一个BpServiceManager时，有些细节还是需要注意：...

ServiceManager.java frameworks/base/core/java/android/os

49 public static IBinder getService(String name) {
Log.d(TAG, "dyyr - getService");
try {
IBinder service = sCache.get(name); //sCache是个Hashmap<String,IBinder>,用参数name:"media.camera"get这个IBinder，
//那么，这个media.camera是源代码里配置好的还是开机后添加进去的?何时添加的?
if (service != null) {
return service;
} else {
return getIServiceManager().getService(name);
}
} catch (RemoteException e) {
Log.e(TAG, "error in getService", e);
}
return null;
}

CameraService.cpp frameworks/base/services/camera/libcameraservice

185 sp<ICamera> CameraService::connect( //服务端connect()
const sp<ICameraClient>& cameraClient, int cameraId) {
LOGE("dyyr - CameraService.cpp connect");
int callingPid = getCallingPid();
sp<CameraHardwareInterface> hardware = NULL; //先实例化Camera Hal接口 hardware，
......

246 if (hardware->initialize(&mModule->common) != OK) { //hardware调用initialize()进入HAL层打开Camear驱动, CameraHardwareDevice.cpp 52
hardware.clear();
return NULL;
}

client = new Client(this, cameraClient, hardware, cameraId, info.facing,
callingPid);

mClient[cameraId] = client;
LOG1("CameraService::connect X");
return client; //返回的其实是它内部类client的一个实例。
}

//Camera系统使用的是Server-Client机制，Service和Client位于不同的进程中，进程间使用Binder机制进行通信，
//Service端实际实现相机相关的操作，Client端通过Binder接口调用Service对应的操作。
//如下图所示

android_hardware_camera.cpp fremework/base/core/jni --------> libandroid_runtime.so

|
|
------ | --------------------------
| --------- --------- |
| | Client | | Service |-----------Binder IPC---------
| --------- --------- | |
| libui.so | |
----------------------------------- |
------
|
Camera服务 |
CameraService.cpp等 frameworks/base/camera/libcameraservice/ --------> libcameraservice.so <------------------------------------

( UI 库 frameworks/base/libs/ui/camera --------> libcamera_client.so )

JNI
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

CameraHardwareDevice.cpp device/softwinner/common/hardware/camera/

52 status_t CameraHardwareDevice::Initialize()
{
F_LOG;

// instance V4L2CameraDevice object
mV4L2CameraDevice = new V4L2CameraDevice(this, mCameraID);
if (mV4L2CameraDevice == NULL)
{
LOGE("Failed to create V4L2Camera instance");
return NO_MEMORY;
}

status_t res = mV4L2CameraDevice->Initialize(); //V4L2CameraDevice.cpp 71

......

}

V4L2CameraDevice.cpp device/softwinner/common/hardware/camera/

71 status_t V4L2CameraDevice::Initialize()
{
F_LOG;

return V4L2Camera::Initialize(); //V4L2Camera.cpp 66
}

V4L2Camera.cpp device/softwinner/common/hardware/camera/

66 status_t V4L2Camera::Initialize()
{
LOGE("dyyr - %s, %s", __FILE__, __FUNCTION__);
F_LOG;
if (isInitialized()) {
LOGW("%s: V4L2Camera device is already initialized: mState = %d",
__FUNCTION__, mState);
return NO_ERROR;
}

/* Instantiate worker thread object. */
mWorkerThread = new WorkerThread(this); //V4L2Camera.h 325
if (getWorkerThread() == NULL) {
LOGE("%s: Unable to instantiate worker thread object", __FUNCTION__);
return ENOMEM;
}

mState = ECDS_INITIALIZED;

return NO_ERROR;
}

V4L2Camera.h device/softwinner/common/hardware/camera/

325 inline explicit WorkerThread(V4L2Camera* camera_dev)
: Thread(true), // Callbacks may involve Java calls. //顶层打开/唤醒Camera的流程跟到这里---------------------------未完待续
mCameraDevice(camera_dev),
mThreadControl(-1),
mControlFD(-1)
{
}

------------------------------------------------------------------

下面是camera的HAL层open底层驱动的方法，没有使用传统的这一句:module->methods->open(module, mName.string(),(hw_device_t **)&mDevice),而走的是V4L2途径:

HALCameraFactory.cpp device/softwinner/common/hardware/camera/

201 struct hw_module_methods_t HALCameraFactory::mCameraModuleMethods = {
open: HALCameraFactory::device_open // 160
};

160 int HALCameraFactory::device_open(const hw_module_t* module,
const char* name,
hw_device_t** device)
{
F_LOG;
/*
* Simply verify the parameters, and dispatch the call inside the //只需确定参数，并调用HALCamera 实例.
* HALCameraFactory instance.
*/

......

return gEmulatedCameraFactory.cameraDeviceOpen(atoi(name), device); // 118
}

118 int HALCameraFactory::cameraDeviceOpen(int camera_id, hw_device_t** device)
{
LOGV("%s: id = %d", __FUNCTION__, camera_id);

......

return mHardwareCameras[camera_id]->connectCamera(device); //CameraHardware.cpp 435
}

CameraHardware.cpp device/softwinner/common/hardware/camera/

435 status_t CameraHardware::connectCamera(hw_device_t** device)
{

......

if (camera_dev != NULL) {
/* Connect to the camera device. */
res = getCameraDevice()->connectDevice(); //V4L2CameraDevice 83
if (res == NO_ERROR) {
*device = &common;
}
}

return -res;
}

V4L2CameraDevice.cpp device/softwinner/common/hardware/camera/

83 status_t V4L2CameraDevice::connectDevice()
{

......

// open v4l2 camera device
int ret = openCameraDev(); //448
if (ret != OK)
{
return ret;
}

ret = cedarx_hardware_init(2);// CEDARX_HARDWARE_MODE_VIDEO

......

}

448 int V4L2CameraDevice::openCameraDev()
{
// open V4L2 device
Log.d(TAG, "dyyr - " + __FILE__ + ", " + __FUNCTION__);
mCamFd = open(mDeviceName, O_RDWR | O_NONBLOCK, 0); //至此完成打开底层设备全过程
if (mCamFd == -1)
{
LOGE("ERROR opening V4L interface: %s", strerror(errno));
return -1;
}

struct v4l2_input inp;
inp.index = mDeviceID;
if (-1 == ioctl (mCamFd, VIDIOC_S_INPUT, &inp))
{
LOGE("VIDIOC_S_INPUT error!\n");
return -1;
}

......

}

--------------------------------------------------------------------------

HAL层的配置文件camera.cfg device/softwinner/Dimond_97HD/camera.cfg, 读取配置: CCameraConfig.cpp, xxx()

下面是读取配置信息的一个例子:

CameraHardware.cpp device/softwinner/common/hardware/camera/

105 status_t CameraHardware::Initialize()
{
F_LOG;

if (mCameraConfig == NULL)
{
return UNKNOWN_ERROR;
}

initDefaultParameters(); //145

return NO_ERROR;
}

145 void CameraHardware::initDefaultParameters()
{

......

if (mCameraConfig->cameraFacing() == CAMERA_FACING_BACK) //根据配置信息设置XX
{
p.set(CameraHardware::FACING_KEY, CameraHardware::FACING_BACK);
LOGV("%s: camera is facing %s", __FUNCTION__, CameraHardware::FACING_BACK
);

}
else
{
p.set(CameraHardware::FACING_KEY, CameraHardware::FACING_FRONT);
LOGV("%s: camera is facing %s", __FUNCTION__, CameraHardware::
FACING_FRONT);

}

p.set(CameraHardware::ORIENTATION_KEY, 0);

......

}

HAL
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

gc0308.c drivers/media/video/sun4i_csi/device/gc0308.c

配置文件Sys_config1.fex Tools/pack/Chips/Sun4i/Configs/Crane/Dimod/Sys_config1.fex, 读取函数: ????????

Kernel
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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