private final Response mResponse;
private final Runnable mRunnable;
public ResponseDeliveryRunnable(Request request, Response response, Runnable runnable) {
mRequest = request;
mResponse = response;
mRunnable = runnable;
}
@SuppressWarnings("unchecked")
@Override
public void run() {
// If this request has canceled, finish it and don't deliver.
if (mRequest.isCanceled()) {
mRequest.finish("canceled-at-delivery");
return;
}
// Deliver a normal response or error, depending.
if (mResponse.isSuccess()) {
mRequest.deliverResponse(mResponse.result);
} else {
mRequest.deliverError(mResponse.error);
}
// If this is an intermediate response, add a marker, otherwise we're done
// and the request can be finished.
if (mResponse.intermediate) {
mRequest.addMarker("intermediate-response");
} else {
mRequest.finish("done");
}
// If we have been provided a post-delivery runnable, run it.
if (mRunnable != null) {
mRunnable.run();
}
}
}
}
其构造方法唯一目的就是实例化了Excutor类型的mResponsePoster，Volley默认调用的是第一个构造方法，也就是包装了一个Handler.该类最主要的方法是postResponse，其核心的实现
mResponsePoster.execute(new ResponseDeliveryRunnable(request, response, runnable));
执行的是ResponseDeliveryRunnable的run方法,而run方法中是通过
mRequest.deliverResponse(mResponse.result);
而Request的该方法则是由有其具体的实现类 StringRequest,JsonRequest,ImageRequest实现，其实现都一致，则是
@Override
protected void deliverResponse(T response) {
mListener.onResponse(response);
}
调用回调方法。
因此，整个分发过程就清晰了，通过Dispatcher进行处理的每个Request,对request进行处理完，则通过ResponseDelivery进行交付，其交付通过得到一个UI线程的handler，通过该Handler的post,调用Request类的delivery方法，在该方法中，又会调用我们构造request时，传入的回调方法。