(转)JNI参数传递|Surface && sign签名对应

最新推荐文章于 2022-11-17 21:48:32 发布

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最新推荐文章于 2022-11-17 21:48:32 发布

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本文介绍如何通过JNI在Java层与Native层之间传递Surface对象。具体实现方式为使用JNIEnv对象的GetFieldID方法获取成员变量ID，再通过GetObjectField与GetIntField方法获取对应的Java对象与整型值。

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http://blog.youkuaiyun.com/stefzeus/article/details/6622011

char* Get_Surface(JNIEnv *env, jclass cls, jobject param, int sdk_version)
{
        // Java层
        jfieldID surface = env->GetFieldID(cls, "mSurface", "Landroid/view/Surface;");
        jobject surface_cls = env->GetObjectField(param, surface);

        // Native层
       jclass surface_class = env->FindClass("android/view/Surface");
       jfieldID surface_native = env->GetFieldID(surface_class, "mSurface", "I"); //"I"指整型

        // the JNI also supports other functions such as GetIntField and SetFloatField for accessing instance fields of primitive types.
        return (char*)(Surface*)env->GetIntField(surface_cls, surface_native);

}


理解GetIntField
(char*)(Surface*)env->GetIntField(surface_cls, surface_native);

Once you have obtained the field ID, you can pass the object reference and the field ID to the appropriate instance field access function:

 jstr = (*env)->GetObjectField(env, obj, fid);