![]() APP_ABI := all – sets the compilation for all the supported CPUs.Not necessary for the compilation, but in our case we specified: include $(BUILD_SHARED_LIBRARY) – ensures that shared library becomes a part of this make.LOCAL_SRC_FILES := native_lib – file that will be compiled in your module, no need to specify headers, the system will take care of it.LOCAL_MODULE :=native_lib– sets the name that is used as the identifier for a module, which is later used in Java. ![]() include$(CLEAR_VARS) – clears all variables that might be set from a previous module build.The macro ‘ my-dir’ is the directory of the Android.mk file. LOCAL_PATH := $(call my-dir) - Android.mk must begin with this definition, this defines the location of the sources.so package, we need to define an Android.mk file in our jni directory.Īndroid.mk file describes to the build system about your sources. We need to return a Java object, so we are doing it through the JniEnv pointer by calling a NewStringUTF() method. Notice that we are returning jstring which is different from C string in our method. Return (*env)->NewStringUTF(env, " Hello from JNI!") JNIEXPORT jstring JNICALL Java_ndk_NDK_1Methods_SayHello(JNIEnv *env, jobject thiz ) specifies the header file that is included #include Step 1: Declare Native Method in Java Classįirst thing that we need to do is to create a native method declaration in our Android application class. Call the Java native declaration method.Implement the header file on the native side in C/C++ class.Create a header file according to native implementation.Potentially, you can increase your application performance, but sometimes it can be just overkill, so use it appropriately. However, in the native code, there is no GC (Garbage collection), hence you need to free memory by yourself. One of the big advantages of the NDK is that you can call custom allocation of memory using malloc() method. NDK will not be interpreted like Java through the JVM, instead it will use the operating system API (in Android case, Linux) for those operations, and thus its performance will be much faster. Using native code in Java is reasonable especially when you are dealing with bits/bytes operations, like bitmaps compression/decompression. The NDK (Native Development Kit) allows you to write code with C/C++ languages and then call it from your Java application using JNI (Java Native Interface). Instead, it will explain how to set up the very basic integration between Java and NDK using simple “Hello World” example. This tutorial will not cover an NDK installation/configuration on your machine. Creating a Header file using javah utility.Step 1: Declare native method in Java class.
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