是否有必要明确调用的System.loadLibrary访问的NativeActivity的子类中的本地方法？ [英] Is it necessary to call system.loadLibrary explicitly for accessing the native methods in a NativeActivity sub class?

问题描述

我有从NativeActivity的衍生这样一个活动的Andr​​oid应用：

I have an Android app with an activity derived from NativeActivity like this:

public class MyNativeActivity extends android.app.NativeActivity 
{
    public native void TellNativeSide(int info);

    static {
        System.loadLibrary("MyNatAct");  // <--- is this necessary?
    }

    public int OtherMethods(...) ...
}

在C / C ++的一面，我有

On the C/C++ side, I have

extern "C" void  
Java_mycom_nativity_MyNativeActivity_TellNativeSide(JNIEnv *env,
    jobjectactivityobj, jint info)
{
    ... do something
} // java native TellNativeSide() method //

extern "C" jint JNI_OnLoad(JavaVM *vm, void *)
{
    LOGI("***JNI_OnLoad called...");
}

的libMyNatAct.so库由NativeActivity的类自动加载和确实android_main（）和一切有或没有的System.loadLibrary（）线正常运行。然而，JNI_OnLoad（）将永远不会被调用和TellNativeSide（）方法也无法在Java端，除非

The libMyNatAct.so library is loaded automatically by the NativeActivity class and indeed android_main() and everything runs correctly with or without the system.loadLibrary() line. However, JNI_OnLoad() would never be called and the TellNativeSide() method is also not available on the Java side unless the

system.loadLibrary("MyNatAct");

通话有没有在静态类初始化块。

call is there in the static class init block.

如此看来，本机的.so必须加载两次。一旦在init块由NativeActivity的类使用的所有本机方法，并得到JNI_OnLoad（）调用，其他时间但不通过的System.loadLibrary（）？

So it seems that the native .so has to be loaded twice. Once in the init block to make available all the native methods and get JNI_OnLoad() called, and another time by the NativeActivity class but not through system.loadLibrary()?

这是正确的行为？

推荐答案

这是正确的。您必须显式调用的System.loadLibrary（）有绑定到.so文件的导出函数的本地Java方法

That's right. You must explicitly call system.loadLibrary() to have the native Java methods bound to exported functions of the .so file

这篇关于是否有必要明确调用的System.loadLibrary访问的NativeActivity的子类中的本地方法？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！