LOCAL_PATH := $(call my-dir)



include $(CLEAR_VARS)



LOCAL_MODULE := native-activity

LOCAL_SRC_FILES := main.c



LOCAL_LDLIBS := -llog -landroid -lEGL -lGLESv1_CM

LOCAL_STATIC_LIBRARIES := android_native_app_glue



include $(BUILD_SHARED_LIBRARY)

$(call import-module,android/native_app_glue)

#include <EGL/egl.h> //这里JNI目前提供的支持，不是很多，只有GL家族作为显示系统了
#include <GLES/gl.h>
#include <android/sensor.h> //感应器的支持
#include <android/log.h>
#include <android_native_app_glue.h> //这里提示大家，c程序必须从main开始，这里必须包含这个，经过改进的伪入口点了。

//定义日志输出
#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "native-activity", __VA_ARGS__))

#define LOGW(...) ((void)__android_log_print(ANDROID_LOG_WARN, "native-activity", __VA_ARGS__))



struct saved_state {

    float angle;
    int32_t x;
    int32_t y;
};

struct engine {

    struct android_app *app;
    ASensorManager *sensorManager;
    const ASensor *accelerometerSensor;
    ASensorEventQueue *sensorEventQueue;
    int animating;
    EGLDisplay display;
    EGLSurface surface;
    EGLContext context;
    int32_t width;
    int32_t height;
    struct saved_state state;
};

//初始化OpenGLES
static int engine_init_display(struct engine *engine) {

    const EGLint attribs[] = {

            EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
            EGL_BLUE_SIZE, 8,
            EGL_GREEN_SIZE, 8,
            EGL_RED_SIZE, 8,
            EGL_NONE
    };

    EGLint w, h, dummy, format;
    EGLint numConfigs;
    EGLConfig config;
    EGLSurface surface;
    EGLContext context;

    EGLDisplay display = eglGetDisplay(EGL_DEFAULT_DISPLAY);

    eglInitialize(display, 0, 0);
    eglChooseConfig(display, attribs, &config, 1, &numConfigs);
    eglGetConfigAttrib(display, config, EGL_NATIVE_VISUAL_ID, &format);

    ANativeWindow_setBuffersGeometry(engine->app->window, 0, 0, format);

    surface = eglCreateWindowSurface(display, config, engine->app->window, NULL);
    context = eglCreateContext(display, config, NULL, NULL);

    if (eglMakeCurrent(display, surface, surface, context) == EGL_FALSE) {

        LOGW("Unable to eglMakeCurrent");
        return -1;
    }



    eglQuerySurface(display, surface, EGL_WIDTH, &w);
    eglQuerySurface(display, surface, EGL_HEIGHT, &h);

    engine->display = display;
    engine->context = context;
    engine->surface = surface;
    engine->width = w;
    engine->height = h;
    engine->state.angle = 0;

    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_FASTEST);
    glEnable(GL_CULL_FACE);
    glShadeModel(GL_SMOOTH);
    glDisable(GL_DEPTH_TEST);
    return 0;
}



static void engine_draw_frame(struct engine *engine) {

    if (engine->display == NULL) {

        // No display.
        return;
    }



    glClearColor(((float) engine->state.x) / engine->width, engine->state.angle,
                 ((float) engine->state.y) / engine->height, 1);

    glClear(GL_COLOR_BUFFER_BIT);
    eglSwapBuffers(engine->display, engine->surface);
}



static void engine_term_display(struct engine *engine) {



    if (engine->display != EGL_NO_DISPLAY) {

        eglMakeCurrent(engine->display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);

        if (engine->context != EGL_NO_CONTEXT) {

            eglDestroyContext(engine->display, engine->context);
        }



        if (engine->surface != EGL_NO_SURFACE) {

            eglDestroySurface(engine->display, engine->surface);
        }



        eglTerminate(engine->display);
    }



    engine->animating = 0;
    engine->display = EGL_NO_DISPLAY;
    engine->context = EGL_NO_CONTEXT;
    engine->surface = EGL_NO_SURFACE;
}



static int32_t engine_handle_input(struct android_app *app, AInputEvent *event) {

    struct engine *engine = (struct engine *) app->userData;
    if (AInputEvent_getType(event) == AINPUT_EVENT_TYPE_MOTION) {

        engine->animating = 1;
        engine->state.x = AMotionEvent_getX(event, 0);
        engine->state.y = AMotionEvent_getY(event, 0);
        return 1;
    }



    return 0;
}



static void engine_handle_cmd(struct android_app *app, int32_t cmd) {

    struct engine *engine = (struct engine *) app->userData;
    switch (cmd) {

        case APP_CMD_SAVE_STATE:

            engine->app->savedState = malloc(sizeof(struct saved_state));
            *((struct saved_state *) engine->app->savedState) = engine->state;
            engine->app->savedStateSize = sizeof(struct saved_state);
            break;

        case APP_CMD_INIT_WINDOW:

            if (engine->app->window != NULL) {

                engine_init_display(engine);
                engine_draw_frame(engine);
            }

            break;

        case APP_CMD_TERM_WINDOW:

            engine_term_display(engine);
            break;

        case APP_CMD_GAINED_FOCUS:

            if (engine->accelerometerSensor != NULL) {

                ASensorEventQueue_enableSensor(engine->sensorEventQueue, engine->accelerometerSensor);
                ASensorEventQueue_setEventRate(engine->sensorEventQueue, engine->accelerometerSensor, (1000L / 60) * 1000);
            }

            break;

        case APP_CMD_LOST_FOCUS:

            if (engine->accelerometerSensor != NULL) {

                ASensorEventQueue_disableSensor(engine->sensorEventQueue, engine->accelerometerSensor);
            }



            engine->animating = 0;
            engine_draw_frame(engine);
            break;
    }

}



&ltb>/</b>**
 * 这里是伪main入口点，所有的初始化的确从这里开始
 * android_native_app_glue 库调用以下函数，向其传递预定义的状态结构。 它还起包装器作用，能够简化 NativeActivity 回调的处理。 
 * @param state 
 */
void android_main(struct android_app *state) {



    struct engine engine;
    app_dummy();
    memset(&engine, 0, sizeof(engine));
    state->userData = &engine;
    state->onAppCmd = engine_handle_cmd;
    state->onInputEvent = engine_handle_input;

    engine.app = state;
    engine.sensorManager = ASensorManager_getInstance();
    engine.accelerometerSensor = ASensorManager_getDefaultSensor(engine.sensorManager, ASENSOR_TYPE_ACCELEROMETER);
    engine.sensorEventQueue = ASensorManager_createEventQueue(engine.sensorManager, state->looper, LOOPER_ID_USER, NULL, NULL);

    if (state->savedState != NULL) {

        // We are starting with a previous saved state; restore from it.
        engine.state = *(struct saved_state *) state->savedState;
    }



    // loop waiting for stuff to do.
    while (1) {

        // Read all pending events.
        int ident;
        int events;
        struct android_poll_source *source;

        // If not animating, we will block forever waiting for events.
        // If animating, we loop until all events are read, then continue
        // to draw the next frame of animation.
        while ((ident = ALooper_pollAll(engine.animating ? 0 : -1, NULL, &events, (void **) &source)) >= 0) {

            // Process this event.
            if (source != NULL) {

                source->process(state, source);
            }



            // If a sensor has data, process it now.
            if (ident == LOOPER_ID_USER) {

                if (engine.accelerometerSensor != NULL) {

                    ASensorEvent event;
                    while (ASensorEventQueue_getEvents(engine.sensorEventQueue, &event, 1) > 0) {

                        LOGI("accelerometer: x=%f y=%f z=%f",
                             event.acceleration.x,
                             event.acceleration.y,
                             event.acceleration.z);
                    }

                }

            }



            // Check if we are exiting.
            if (state->destroyRequested != 0) {

                engine_term_display(&engine);
                return;
            }

        }





        if (engine.animating) {

            // Done with events; draw next animation frame.
            engine.state.angle += .01f;
            if (engine.state.angle > 1) {

                engine.state.angle = 0;
            }



            // Drawing is throttled to the screen update rate, so there
            // is no need to do timing here.
            engine_draw_frame(&engine);
        }

    }

}