Android NDK Call Java From C ++

Source: Internet
Author: User

I search the Android NDK document and Internet a bit, and cocould not find anything useful to help me play sound with C ++ under the Android NDK. most of topics are about how to play sound with Java, so I grape an idea that why not call Java from C ++. I tried along this way, and finally all those stuff works as I expected before.

 

Implement Java static function

A Sound player class implemented in Java class. in addition to play sound basic feature, I also make it expose a static function that will be called from C ++. the reason why I used a static function here is that static function cocould allow me correctly find the right Java object instance, the one with sound pool initialized well and file loaded OK will be the correct one.

public class SoundManager {    ......        public static void sPlaySound(int sound)    {        if ( null != sInstance )            sInstance.PlaySound(sound);    }    }

 

Call Java function from C/C ++
static JavaVM* g_JavaVM = NULL;static const char *g_JavaClassName = "com/easygame/SoundManager";JNIEXPORT jint JNI_OnLoad(JavaVM* jvm, void* reserved){    g_JavaVM = jvm;    JNIEnv *env = NULL;    if (jvm->GetEnv((void**) &env, JNI_VERSION_1_6) != JNI_OK)        return -1;    return JNI_VERSION_1_6;}JNIEXPORT void JNI_OnUnload(JavaVM* jvm, void* reserved){    g_JavaVM = NULL;    JNIEnv *env = NULL;    if (jvm->GetEnv((void**) &env, JNI_VERSION_1_6) != JNI_OK)        return;}void SysPlaySound(int soundId){    if (g_JavaVM == NULL)        return;    int status = -1;    JNIEnv *env = NULL;    bool isAttached = false;    status = g_JavaVM->GetEnv((void**) &env, JNI_VERSION_1_6);    if (status < 0)      {        status = g_JavaVM->AttachCurrentThread(&env, NULL);        if (status < 0)            return;        isAttached = true;    }    if ( env != NULL )    {        jclass cls = env->FindClass(g_JavaClassName);        if ( cls != 0 )        {            jmethodID mid = env->GetStaticMethodID(cls, "sPlaySound", "(I)V");            if ( mid != 0 )                env->CallStaticVoidMethod(cls, mid, soundId);        }    }    if ( isAttached )        g_JavaVM->DetachCurrentThread();    }

Function JNI_OnLoad and JNI_OnUnload are Android NDK system call back functions, that will allow us to get the current Java virtual machine. we need to get the class static method or object member function from the Java virtual machine. now we cocould call function SysPlaySound as a C/C ++ native function.

 

Reference

Http://blog.csdn.net/airun_zou/article/details/7110101

Http://www.cnblogs.com/luxiaofeng54/archive/2011/08/17/2142000.html

Http://qfqf16.blog.163.com/blog/static/128109527201281263955386/

Http://blog.chinaunix.net/uid-7448773-id-310170.html

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.