How to implement a listener

Question

I have a design issue. I need to implement a listener. I saw the following SO question: How to create our own Listener interface in android?

But in the link it provi

Answer 1

AsyncTask has nothing to do with implementing a listener.

Here's a listener:

public interface TheListener {
    public void somethingHappened();
}

Call it however you want. For example, here's a class doing something like View:

public class Something {
    private TheListener mTheListener;

    public void setTheListener(TheListener listen) {
        mTheListener = listen;
    }

    private void reportSomethingChanged() {
        if (mTheListener != null) {
            mTheListener.somethingHappened();
        }
    }
}

You can make this as complicated as you want. For example, instead of a single listener pointer you could have an ArrayList to allow multiple listeners to be registered.

Calling this from native code also has nothing to do with implementing a listener interface. You just need to learn about JNI to learn how native code can interact with Java language code.