Android JNI Application With NDK (Java as well as in Kotlin)

We will Secure Our API keys using NDK. NDK Stand for Native Development Kit.

Note : Make Sure We have install NDK in Your Android SDK.

 Step 1: Create Jni Folder in Our Main Directory.

• Change Android Directly to Project.
• Create New Jni Directly Under APP > SRC Folder.

Step 2: Now Create 3 File Under Jni Directory 

• Android.mk
• Application.mk
• api-keys.c

• Create Android.mk file and Paste Below Code.

//Code

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := api-keys

LOCAL_SRC_FILES := api-keys.c

include $(BUILD_SHARED_LIBRARY)

• Create Application.mk file and Paste Below Code.

APP_ABI := all

Now at the End ,Create api-keys.c file and Paste Below Code.

#include <jni.h>

//For first API key 

JNIEXPORT jstring JNICALL Java_com_d2dreamdevelopers_myapplication_APIKeyLibrary_getAPIKey(JNIEnv *env, jobject instance) { 

return (*env)-> NewStringUTF(env, "YOUR_AWESOME_API_GOES_HERE"); 

}

Step 3: Now Link Our C File to Gradle.

Right Click on api-keys.c File. And Click on Link C++ Project With Gradle.

In this Dialog, 

        Build System -> ndk-build

        Project Path -> Select Android.mk file of your Project.

In this Dialog Select ndk-build in Build System and Project Path Give Android.mk file.

Step 4 : Write getKeys() in Our MainActivity Class or Where we Need the Key.

For Kotlin :

init {

    System.loadLibrary("api-keys")

}

external fun getKeys() : String

For Java :

public native String getKeys();

static {

        System.loadLibrary("api-keys");

 }

Right Click on this method and Create this method in api-keys.c 

Now Open api-keys.c file and In the Return Statement Write the key.

So That's Guys. We have Successfully Implement NDk in Our Project.

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