author Sam Lantinga <>
Tue, 04 Jan 2011 11:39:52 -0800
changeset 4953 4f40b11e1045
parent 4726 9076cdb027af
child 4957 5e42031a8d70
permissions -rw-r--r--
Fixed prototype for SDL_main() FIXME: Still need to pass some arguments - can we get them from the Java class?

 This file links the Java side of Android with libsdl
#include <jni.h>
#include <sys/time.h>
#include <time.h>
#include <android/log.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <pthread.h>

#define DEBUG

static long _getTime(void){
	struct timeval  now;
	gettimeofday(&now, NULL);
	return (long)(now.tv_sec*1000 + now.tv_usec/1000);

JNIEnv* mEnv = NULL;
JNIEnv* mAudioThreadEnv = NULL; //See the note below for why this is necessary
JavaVM* mVM = NULL;

//Main activity
jclass mActivityInstance;

//method signatures
jmethodID midCreateGLContext;
jmethodID midFlipBuffers;
jmethodID midEnableFeature;
jmethodID midUpdateAudio;

extern "C" int SDL_main(int argc, char *argv[]);
extern "C" int Android_OnKeyDown(int keycode);
extern "C" int Android_OnKeyUp(int keycode);
extern "C" void Android_SetScreenResolution(int width, int height);
extern "C" void Android_OnResize(int width, int height, int format);
extern "C" int SDL_SendQuit();
extern "C" void Android_EnableFeature(int featureid, bool enabled);

//If we're not the active app, don't try to render
bool bRenderingEnabled = false;

//Feature IDs
static const int FEATURE_AUDIO = 1;
static const int FEATURE_ACCEL = 2;

//Accelerometer data storage
float fLastAccelerometer[3];

                 Functions called by JNI

//Library init
extern "C" jint JNI_OnLoad(JavaVM* vm, void* reserved){

    JNIEnv* env = NULL;
    jint result = -1;

    if (vm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {
        return result;

    mEnv = env;

    __android_log_print(ANDROID_LOG_INFO, "SDL", "JNI: OnLoad");

    jclass cls = mEnv->FindClass ("org/libsdl/app/SDLActivity"); 
    mActivityInstance = cls;
    midCreateGLContext = mEnv->GetStaticMethodID(cls,"createGLContext","()V");
    midFlipBuffers = mEnv->GetStaticMethodID(cls,"flipBuffers","()V");
    midEnableFeature = mEnv->GetStaticMethodID(cls,"enableFeature","(II)V");
    midUpdateAudio = mEnv->GetStaticMethodID(cls,"updateAudio","([B)V");

    if(!midCreateGLContext || !midFlipBuffers || !midEnableFeature ||
        __android_log_print(ANDROID_LOG_INFO, "SDL", "SDL: Bad mids\n");
#ifdef DEBUG
        __android_log_print(ANDROID_LOG_INFO, "SDL", "SDL: Good mids\n");
    return JNI_VERSION_1_4;

//Start up the SDL app
extern "C" void Java_org_libsdl_app_SDLActivity_nativeInit( JNIEnv* env, 
                                                                jobject obj ){ 
	__android_log_print(ANDROID_LOG_INFO, "SDL", "SDL: Native Init");

	mEnv = env;
	bRenderingEnabled = true;

	Android_EnableFeature(FEATURE_ACCEL, true);

    SDL_main(0, 0);

extern "C" void Java_org_libsdl_app_SDLActivity_onNativeKeyDown(JNIEnv* env, 
               jobject obj, jint keycode){
    int r = Android_OnKeyDown(keycode);
#ifdef DEBUG
    __android_log_print(ANDROID_LOG_INFO, "SDL", 
                        "SDL: native key down %d, %d\n", keycode, r);

extern "C" void Java_org_libsdl_app_SDLActivity_onNativeKeyUp(JNIEnv* env, 
               jobject obj, jint keycode){
    int r = Android_OnKeyUp(keycode);
#ifdef DEBUG
    __android_log_print(ANDROID_LOG_INFO, "SDL", 
                        "SDL: native key up %d, %d\n", keycode, r);

extern "C" void Java_org_libsdl_app_SDLActivity_onNativeTouch(JNIEnv* env, 
               jobject obj, jint action, jfloat x, jfloat y, jfloat p){

#ifdef DEBUG
    __android_log_print(ANDROID_LOG_INFO, "SDL", 
                        "SDL: native touch event %d @ %f/%f, pressure %f\n", 
                        action, x, y, p);

    //TODO: Pass this off to the SDL multitouch stuff

extern "C" void Java_org_libsdl_app_SDLActivity_nativeQuit( JNIEnv*  env, 
                                                                jobject obj ){    

    //Stop rendering as we're no longer in the foreground
	bRenderingEnabled = false;

    //Inject a SDL_QUIT event
    int r = SDL_SendQuit();

    __android_log_print(ANDROID_LOG_INFO, "SDL", "SDL: Native quit %d", r);        

//Screen size
extern "C" void Java_org_libsdl_app_SDLActivity_nativeSetScreenSize(
                JNIEnv*  env, jobject obj, jint width, jint height){

    __android_log_print(ANDROID_LOG_INFO, "SDL", 
                        "SDL: Set screen size on init: %d/%d\n", width, height);
    Android_SetScreenResolution(width, height);

extern "C" void Java_org_libsdl_app_SDLActivity_onNativeResize(
                                        JNIEnv*  env, jobject obj, jint width, 
                                        jint height, jint format){
    Android_OnResize(width, height, format);

extern "C" void Java_org_libsdl_app_SDLActivity_onNativeAccel(
                                        JNIEnv*  env, jobject obj,
                                        jfloat x, jfloat y, jfloat z){
    fLastAccelerometer[0] = x;
    fLastAccelerometer[1] = y;
    fLastAccelerometer[2] = z;   

             Functions called by SDL into Java
extern "C" void Android_CreateContext(){
	__android_log_print(ANDROID_LOG_INFO, "SDL", "SDL: sdl_create_context()\n");

	bRenderingEnabled = true;

    mEnv->CallStaticVoidMethod(mActivityInstance, midCreateGLContext ); 

extern "C" void Android_Render(){


    //When we get here, we've accumulated a full frame    
    mEnv->CallStaticVoidMethod(mActivityInstance, midFlipBuffers ); 

extern "C" void Android_EnableFeature(int featureid, bool enabled){

    mEnv->CallStaticVoidMethod(mActivityInstance, midEnableFeature, 
                                featureid, (int)enabled); 

extern "C" void Android_UpdateAudioBuffer(unsigned char *buf, int len){

    //Annoyingly we can't just call into Java from any thread. Because the audio
    //callback is dispatched from the SDL audio thread (that wasn't made from
    //java, we have to do some magic here to let the JVM know about the thread.
    //Because everything it touches on the Java side is static anyway, it's 
    //not a big deal, just annoying.
        __android_log_print(ANDROID_LOG_INFO, "SDL", "SDL: Need to set up audio thread env\n");

        mVM->AttachCurrentThread(&mAudioThreadEnv, NULL);

        __android_log_print(ANDROID_LOG_INFO, "SDL", "SDL: ok\n");
    jbyteArray arr = mAudioThreadEnv->NewByteArray(len);

    //blah. We probably should rework this so we avoid the copy. 
    mAudioThreadEnv->SetByteArrayRegion(arr, 0, len, (jbyte *)buf);
    __android_log_print(ANDROID_LOG_INFO, "SDL", "SDL: copied\n");

    mAudioThreadEnv->CallStaticVoidMethod(  mActivityInstance, 
                                            midUpdateAudio, arr );

    __android_log_print(ANDROID_LOG_INFO, "SDL", "SDL: invoked\n");