library/src/main/java/com/bumptech/glide/volley/VolleyStreamFetcher.java

package com.bumptech.glide.volley;

import com.android.volley.NetworkResponse;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.toolbox.HttpHeaderParser;
import com.bumptech.glide.Priority;
import com.bumptech.glide.load.data.DataFetcher;

import java.io.ByteArrayInputStream;
import java.io.InputStream;

/**
 * A DataFetcher backed by volley for fetching images via http.
 */
public class VolleyStreamFetcher implements DataFetcher<InputStream> {
    private final RequestQueue requestQueue;
    private final String url;
    private VolleyRequestFuture<InputStream> requestFuture;

    @SuppressWarnings("unused")
    public VolleyStreamFetcher(RequestQueue requestQueue, String url) {
        this(requestQueue, url,  null);
    }

    public VolleyStreamFetcher(RequestQueue requestQueue, String url, VolleyRequestFuture<InputStream> requestFuture) {
        this.requestQueue = requestQueue;
        this.url = url;
        this.requestFuture = requestFuture;
        if (requestFuture == null) {
            this.requestFuture = VolleyRequestFuture.newFuture();
        }
    }

    @Override
    public InputStream loadData(Priority priority) throws Exception {
        GlideRequest request = new GlideRequest(url, requestFuture, glideToVolleyPriority(priority));

        requestFuture.setRequest(requestQueue.add(request));

        return requestFuture.get();
    }

    @Override
    public void cleanup() {
        // Do nothing.
    }

    @Override
    public String getId() {
        return url;
    }

    @Override
    public void cancel() {
        VolleyRequestFuture<InputStream> localFuture = requestFuture;
        if (localFuture != null) {
            localFuture.cancel(true);
        }
    }

    private static Request.Priority glideToVolleyPriority(Priority priority) {
        switch (priority) {
            case LOW:
                return Request.Priority.LOW;
            case HIGH:
                return Request.Priority.HIGH;
            case IMMEDIATE:
                return Request.Priority.IMMEDIATE;
            default:
                return Request.Priority.NORMAL;

        }
    }

    private static class GlideRequest extends Request<byte[]> {
        private final VolleyRequestFuture<InputStream> future;
        private Priority priority;

        public GlideRequest(String url, VolleyRequestFuture<InputStream> future, Priority priority) {
            super(Method.GET, url, future);
            this.future = future;
            this.priority = priority;
        }

        @Override
        public Priority getPriority() {
            return priority;
        }

        @Override
        protected Response<byte[]> parseNetworkResponse(NetworkResponse response) {
            return Response.success(response.data, HttpHeaderParser.parseCacheHeaders(response));
        }

        @Override
        protected void deliverResponse(byte[] response) {
            future.onResponse(new ByteArrayInputStream(response));
        }
    }
}