How to implement a listener
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 开发者_如何学Goit provides in the answer, author creates a listener which just extends the system-defined listener. E.g onClick, you would do some validation & then call another method called "whenValidatedListener"
I need to define listeners which are not linked to existing event listeners. Basically there would be some processing going on in native(C/C++) code & in the Android code I need a listener to respond to certain messages from it.
I think I could do this using handlers. But AsyncTask is the recommended approach for multithreading.
Is there a way to implement a user-defined-listener using AsyncTask?
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.
Just to clear things up;
you do exactly what @hackbod said and add this :
the activity
which encloses the class (with the method setListener(Listener listen)
), implements Listener
and in it's oncreate
or onResume
or where-ever you call yourClass.setListener(this)
.
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