<== Chapter 3 -- Chapter 5 ==>

Chapter 4 - JNI Native Class

We need to create a Java class with the JNI to allow our Java functions to get sent down to the Native functions. Tango JNI Native Class

• Just as we did forTangoInitializationHelper we need to create another Java class and we will call it TangoJniNative
• The first thing we need to do is call TangoInitializationHelper.loadTangoSharedLibrary() and make sure we loaded the library correctly otherwise no point to continue.
• We know need to load the Native C/C++ code into our application by loading it using System.loadLibrary("tango_ndk_tutorial");
  • As of now in the tutorial we have not yet wrote this code, but when we do, this is how we call it
  • Take notice that these two loading of native code (Tango Library and our NDK code) takes place right away in the flow of the program
  • IMPORTANT: the string tango_ndk_tutorial in this case must match the LOCAL_MODULE library without the lib prefix
    • This is more explain in detail in Chapter 9
• Each function we plan to call down to the native layer we need to make a native java function declaration
  • Example: public static native void onCreate(Activity callerActivity);
    • In this example we will pass the instance of the Activity object to our native code when the Activity calls onCreate
• The public static native int valueFromJNI(int myNumber); is going to be our example of how we send the value myNumber and get a int value returned
• Side note, I removed the public native String stringFromJNI(); auto generated from the boilerplate

<== Chapter 3 -- Chapter 5 ==>