Android Volley Singleton Pattern如何基于标签添加/取消请求 [英] Android Volley Singleton Pattern how to add/cancel requests based on tag
问题描述
根据 https://developer.android.com/training/volley/requestqueue.html#singleton 不鼓励通过在Application.onCreate()
According to https://developer.android.com/training/volley/requestqueue.html#singleton it is discouraged to use the old way of implementing a singleton class by setting up the RequestQueue in Application.onCreate()
所提供的新的"模块化方式如下所示,但是不包含将标签添加到请求并使用这些标签取消它们的方法.
The provided "new" more modular way as seen below however doesn't contain a method for adding tags to requests and cancelling them using these tags.
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;
}
}
我该如何添加与旧方法(在Application.onCreate()中)类似的方法:
How do I go about adding the methods similar to the ones below from the old way (in Application.onCreate()):
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);
}
}
推荐答案
关于RequestQueue的任何方面都没有改变.您只是从与Application类不同的单例访问它.始终以相同的方式将标签添加到请求中:
Nothing about RequestQueue has changed in that respect. You're just accessing it from a different singleton than the Application class. Add the tags to the requests the same way you always would:
ImageRequest request = new ImageRequest(...);
request.setTag(MY_TAG);
MySingleton.getInstance(this).addToRequestQueue(request);
-编辑-
进一步阐述:这与从其他任何地方获取RequestQueue对象相同.它仍然只是一个RequestQueue.
Further elaboration: it's the same as if you were to get the RequestQueue object from anywhere else. It's still just a RequestQueue.
所以这个:
mRequestQueue.cancelAll(tag);
成为:
MySingleton.getRequestQueue().cancelAll(tag);
您之前使用RequestQueue所做的所有其他操作也是如此.示例MySingleton类只是为您保留了请求队列.它没有改变.
The same goes for anything else you were previously doing with a RequestQueue. The example MySingleton class there is just acting to hold on to the request queue for you. It isn't changing it.
要取消所有内容,无论使用什么标签:
To cancel absolutely everything, no matter what tag:
MySingleton.getRequestQueue().cancelAll(new RequestQueue.RequestFilter() {
@Override
public boolean apply(Request<?> request) {
return true;
}
});
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