In the third part of our series on callbacks, we’ll discuss what to do if we have a .NET assembly that implements callbacks using a Java-style listener interface. (See part one: using callbacks in .NET-to-Java projects and part two: callbacks in Java-to-.NET projects.) Since JNBridgePro only supports the delegate/event callback style in Java-to-.NET projects, we need to have a way to convert between the two styles. Here’s one such way. Assume we have the following listener interface:

public interface MyCallbackInterface
{
    bool myCallbackMethod(int param1, string param2);  
}

and the following callback generator

public class CallbackGenerator
{
    public static void registerCallback(MyCallbackInterface theCallback) {…}  
    public static void fire() {…}
}

We can create .NET event-style wrappers that can be proxied as follows:

public delegate bool MyCallbackHandler(int param1, string param2);

public class NewCallbackGenerator
{
    // this is the wrapper to convert listeners to events 
    private class MyCallbackHandlerWrapper : MyCallbackInterface
    {
        MyCallbackHandler mch;
        public MyCallbackHandlerWrapper(MyCallbackHandler mch)
        {
            this.mch = mch;
        }
  
        public bool myCallbackMethod(int param1, string param2)
        {   
            return mch(param1, param2);
        }
    }
  
    // here is the event interface
    public static event MyCallbackHandler MyEvent
    {  
        add
        {
            MyCallbackHandlerWrapper mcw = new MyCallbackHandlerWrapper(value);
            CallbackGenerator.registerCallback(mcw);
        }
    }
  
    public static void fireEvents()
    {   
        CallbackGenerator.fire();
    }
}

You should proxy and use MyCallbackHandler and NewCallbackGenerator as you would any other proxied delegate/event-style callback.