Android Volley Singleton Pattern如何根据标签添加/取消请求

Question

根据https://developer.android.com/training/volley/requestqueue.html#singleton 不鼓励使用在Application.onCreate（）中设置RequestQueue的旧方法来实现单例类。

提供的＆＃34;新＆＃34;如下所示，更加模块化的方式并不包含向请求添加标记并使用这些标记取消标记的方法。

public class MySingleton {
private static MySingleton mInstance;
private RequestQueue mRequestQueue;
private ImageLoader mImageLoader;
private static Context mCtx;

private MySingleton(Context context) {
    mCtx = context;
    mRequestQueue = getRequestQueue();

    mImageLoader = new ImageLoader(mRequestQueue,
            new ImageLoader.ImageCache() {
        private final LruCache<String, Bitmap>
                cache = new LruCache<String, Bitmap>(20);

        @Override
        public Bitmap getBitmap(String url) {
            return cache.get(url);
        }

        @Override
        public void putBitmap(String url, Bitmap bitmap) {
            cache.put(url, bitmap);
        }
    });
}

public static synchronized MySingleton getInstance(Context context) {
    if (mInstance == null) {
        mInstance = new MySingleton(context);
    }
    return mInstance;
}

public RequestQueue getRequestQueue() {
    if (mRequestQueue == null) {
        // getApplicationContext() is key, it keeps you from leaking the
        // Activity or BroadcastReceiver if someone passes one in.
        mRequestQueue = Volley.newRequestQueue(mCtx.getApplicationContext());
    }
    return mRequestQueue;
}

public <T> void addToRequestQueue(Request<T> req) {
    getRequestQueue().add(req);
}

public ImageLoader getImageLoader() {
    return mImageLoader;
}

}

如何从旧方式（在Application.onCreate（）中）添加类似于以下方法的方法：

public <T> void addToRequestQueue(Request<T> req, String tag) {
    // set the default tag if tag is empty
    req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
    getRequestQueue().add(req);
}

public <T> void addToRequestQueue(Request<T> req) {
    req.setTag(TAG);
    getRequestQueue().add(req);
}

public void cancelPendingRequests(Object tag) {
    if (mRequestQueue != null) {
        mRequestQueue.cancelAll(tag);
    }
}