Time for action – determining JNI method signatures

Let's define a Java interface that native C/C++ code will call back through JNI:

1. Create a StoreListener.java, which contains an interface defining a few callbacks, one for integers, one for strings, and one for colors, as follows:

   package com.packtpub.store;
   
   public interface StoreListener {
       void onSuccess(int pValue);
   
       void onSuccess(String pValue);
   
       void onSuccess(Color pValue);
   }

2. Open Store.java and make a few changes.

   • Declare a member delegate StoreListener, to which success callbacks are sent

   • Change the Store constructor to inject the delegate listener, which is going to be StoreActivity

     Public class Store implements StoreListener {
         private StoreListener mListener;
         public Store(StoreListener pListener) {
             mListener = pListener;
         }
         ...

     Finally, implement the StoreListener interface and its corresponding methods, which simply forwards calls to the delegate:

         ...
         public void onSuccess(int pValue) {
     ...