JNI

源码地址：

　　base\services\core\jni\com_android_server_lights_LightsService.cpp

功能：

　　定义JNI接口函数供Framework调用，主要设置init_native和setLight_native

　　init_native：获得HAL层支持的light devices，保存在devices中

　　setLight_native：配置不同light设备的set_light方法

源码分析：

申明JNI接口函数，关注init_native和setLight_native

static JNINativeMethod method_table[] = {
    { "init_native", "()J", (void*)init_native },
    { "finalize_native", "(J)V", (void*)finalize_native },
    { "setLight_native", "(JIIIIII)V", (void*)setLight_native },
};

先暂时关注LIGHT_ID_BACKLIGHT，去除不相关code。

init_native:　　

　　1：load HAL的so文件

　　2：依次查找支持的light设备，并且保存在devices->lights[]中

　　　　devices->lights[]中存储了HAL不同lights设备对应的light_device_t（其中包含了set_light方法）

　　3：返回devices

static jlong init_native(JNIEnv *env, jobject clazz)
{
　　devices = (Devices*)malloc(sizeof(Devices));

　　hw_get_module(LIGHTS_HARDWARE_MODULE_ID, (hw_module_t const**)&module);
　　// devices->lights[]中存储了HAL不同lights设备
　　devices->lights[LIGHT_INDEX_BACKLIGHT] = get_device(module, LIGHT_ID_BACKLIGHT);
　　　　module->methods->open(module, name, &device);　　// 将会call HAL的open_lights，返回HAL的light_device_t，其中包含set_light方法
　　　　　　return (light_device_t*)device;
　　devices->lights[LIGHT_INDEX_NOTIFICATIONS]
                = get_device(module, LIGHT_ID_NOTIFICATIONS);
　　...

　　return (jlong)devices;
}

 setLight_native：

　　配置不同light设备的set_light方法

static void setLight_native(JNIEnv *env, jobject clazz, jlong ptr,
        jint light, jint colorARGB, jint flashMode, jint onMS, jint offMS, jint brightnessMode)
{
    Devices* devices = (Devices*)ptr;
    light_state_t state;

    // 配置state
    memset(&state, 0, sizeof(light_state_t));
    state.color = colorARGB;
    state.flashMode = flashMode;
    state.flashOnMS = onMS;
    state.flashOffMS = offMS;
    state.brightnessMode = brightnessMode;

    devices->lights[light]->set_light(devices->lights[light], &state);
}