二、Framework层支持多camera
1、Camera.java文件
首先看一下文件Framework/base/core/java/android/hardware/camera.java。
添加了三个接口函数，分别为getNumberOfCameras()，getCameraInfo()，setCameraId()，它们的CODE如下：
/*** Returns the number of physical cameras available on this device.*/public native static int getNumberOfCameras();/*** Returns the information about a particular camera.* If {@link #getNumberOfCameras()} returns N, the valid id is 0 to N-1.*/public native static void getCameraInfo(int cameraId, CameraInfo cameraInfo);public native static int setCameraId(int cameraId);
同时定义了CameraInfo类，在application层CameraHolder.java和Camera.java这两个文件中引用了该类。其CODE如下：
/*** Information about a camera*/public static class CameraInfo {/*** The facing of the camera is opposite to that of the screen.*/public static final int CAMERA_FACING_BACK = 0;/*** The facing of the camera is the same as that of the screen.*/public static final int CAMERA_FACING_FRONT = 1;/*** The direction that the camera faces to. It should be* CAMERA_FACING_BACK or CAMERA_FACING_FRONT.*/public int facing;
/*** The orientation of the camera image. The value is the angle that the* camera image needs to be rotated clockwise so it shows correctly on* the display in its natural orientation. It should be 0, 90, 180, or 270.** For example, suppose a device has a naturally tall screen. The* back-facing camera sensor is mounted in landscape. You are looking at* the screen. If the top side of the camera sensor is aligned with the* right edge of the screen in natural orientation, the value should be
* 90. If the top side of a front-facing camera sensor is aligned with* the right of the screen, the value should be 270.** @see #setDisplayOrientation(int)* @see #setRotation(int)* @see #setPreviewSize(int, int)* @see #setPictureSize(int, int)* @see #setJpegThumbnailSize(int, int)*/public int orientation;};
2、android_hardware_camera.cpp文件
下面介绍Framework/base/core/jni/android_hardwrea_camera.cpp，该文件为JNI文件。
首先在结构体fields_t中添加了两个成员：facing和orientation，其具体定义为：
struct fields_t {jfieldID context;jfieldID surface;jfieldID facing;jfieldID orientation; jmethodID post_event;};
接下来定义了三个函数，分别为android_hardware_Camera_getNumberOfCameras()，android_hardware_Camera_getCameraInfo()和android_hardware_Camera_setCameraId()。其CODE如下：
static jint android_hardware_Camera_getNumberOfCameras(JNIEnv *env, jobject thiz){return Camera::getNumberOfCameras();}static void android_hardware_Camera_getCameraInfo(JNIEnv *env, jobject thiz,jint cameraId, jobject info_obj){CameraInfo cameraInfo;status_t rc = Camera::getCameraInfo(cameraId, &cameraInfo);if (rc != NO_ERROR) {jniThrowException(env, "java/lang/RuntimeException","Fail to get camera info");return;}env->SetIntField(info_obj, fields.facing, cameraInfo.facing);env->SetIntField(info_obj, fields.orientation, cameraInfo.orientation);}static jint android_hardware_Camera_setCameraId(JNIEnv *env, jobject thiz,jint cameraId){return Camera::setCameraId(cameraId);}
同时修改了JNINativeMethod，将上述三个函数的信息添加进去。
static JNINativeMethod camMethods[] = {{ "getNumberOfCameras","()I",(void *)android_hardware_Camera_getNumberOfCameras },{ "getCameraInfo","(ILandroid/hardware/Camera$CameraInfo;)V",(void*)android_hardware_Camera_getCameraInfo },{ "setCameraId","(I)I",(void *)android_hardware_Camera_setCameraId }, { "native_setup","(Ljava/lang/Object;)V",(void*)android_hardware_Camera_native_setup },{ "native_release","()V",(void*)android_hardware_Camera_release },
修改了函数register_android_hardware_Camera()，将结构体CameraInfo的两个成员添加到了fields_to_find。其CODE如下：
// Get all the required offsets in java class and register native functionsint register_android_hardware_Camera(JNIEnv *env){field fields_to_find[] = {{ "android/hardware/Camera", "mNativeContext", "I", &fields.context },{ "android/view/Surface", "mSurface", "I", &fields.surface },{ "android/hardware/Camera$CameraInfo", "facing", "I", &fields.facing },{ "android/hardware/Camera$CameraInfo", "orientation", "I", &fields.orientation }, };
3、Camera.h文件
Framework/base/include/camera/camera.h是Framework里Camera.java和android_hardware_camera.cpp的接口文件。
首先定义了结构体CameraInfo，其具体定义如下：
enum {
CAMERA_FACING_BACK = 0, /* The facing of the camera is opposite to that of the screen. */
CAMERA_FACING_FRONT = 1 /* The facing of the camera is the same as that of the screen. */
};
struct CameraInfo {
/**
* The direction that the camera faces to. It should be
* CAMERA_FACING_BACK or CAMERA_FACING_FRONT.
*/
int facing;
/**
* The orientation of the camera image. The value is the angle that the
* camera image needs to be rotated clockwise so it shows correctly on
* the display in its natural orientation. It should be 0, 90, 180, or 270.
*
* For example, suppose a device has a naturally tall screen. The
* back-facing camera sensor is mounted in landscape. You are looking at
* the screen. If the top side of the camera sensor is aligned with the
* right edge of the screen in natural orientation, the value should be
* 90. If the top side of a front-facing camera sensor is aligned with
* the right of the screen, the value should be 270.
*/
int orientation;
};
在Camera类中增加了三个成员函数，其定义如下：
static int32_t getNumberOfCameras();static status_t getCameraInfo(int cameraId, struct CameraInfo* cameraInfo);static int32_t setCameraId(int cameraId);
4、Camera.cpp
Framework/base/libs/camera/camera.cpp是对Camera.h文件的实现。它实现了下面三个函数，其CODE如下：
int32_t Camera::getNumberOfCameras(){const sp<ICameraService>& cs = getCameraService();if (cs == 0) return 0;return cs->getNumberOfCameras();}status_t Camera::getCameraInfo(int cameraId,struct CameraInfo* cameraInfo) {const sp<ICameraService>& cs = getCameraService();if (cs == 0) return UNKNOWN_ERROR;return cs->getCameraInfo(cameraId, cameraInfo);}int32_t Camera::setCameraId(int cameraId){const sp<ICameraService>& cs = getCameraService();if (cs == 0) return 0;return cs->setCameraId(cameraId);}
它调用ICameraService.h中的三个接口，下面对ICameraService.h作以介绍。（待续）
