Use C ++ lambda expressions in the android JNI environment (with an APK package for testing)

Prerequisites:

Third-party ndk packages that support later GCC versions are required. The default Android version is 4.4.3.

Third-party ndk package download (gcc-4.6.3): http://www.crystax.net/en/android/ndk/7

For more information, see this document.
This test shows the following content:

1. Use STD: function and STD: bind to implement the sigslot mechanism;
2. Use the lambda expression of c ++ 11
3. Callback of Java objects in C ++ code
Example Source:

This test example is from a discussion on the Internet. As a result of lambda expressions, the idea of testing in iOS and Android environments is displayed.

Http://stackoverflow.com/questions/12516239/a-simple-signal-for-a-button-in-c

Main code snippets:

Define callback type

typedef std::function<void(const char *)> callback_t;

Define a global callback function pointer to facilitate calls within the genericbutton class. For initialization, see the following code.

callback_t jni_callback;

Export the JNI function. The main function of this function is to internally find the messageme method of the Java class for callback. The messageme callback method uses three methods: calling directly using jnienv; directly calling Lambda callback function; calling in the genericbutton class (using the sigslot_main function, this function is the main method in the original example ).

extern "C" {  JNIEXPORT jstring JNICALL    Java_com_sigslot_MainActivity_sigSlot( JNIEnv* env, jobject thiz )    {      jstring jstr = env->NewStringUTF("This comes from jni(via JNIEnv directly).\n");      jclass clazz = env->FindClass("com/sigslot/MainActivity");      jmethodID messageMe = env->GetMethodID(clazz, "messageMe", "(Ljava/lang/String;)Ljava/lang/String;");      jobject result = env->CallObjectMethod(thiz, messageMe, jstr);      jni_callback=[env, thiz, messageMe](const char* info){        LOGI(info);        jstring jstr2 = env->NewStringUTF(info);        env->CallObjectMethod(thiz, messageMe, jstr2);      };      jni_callback("Lambda in std::function (via lambda callback).\n");      sigslot_main(); // call GenericButton's pressButton method.      return env->NewStringUTF("sigslot main from JNI C++!");    }}

APK package:

Download, install, and test only for interested users. Download link: http://download.csdn.net/detail/dyw/4674834