Android Loader是否在单独的线程中执行其工作？

Question

I am currently implementing my own Loader in Android, since I am using a library for loading stuff, that exposes its API only through callbacks and I still want to use the benefits of loaders.

The library I want to use can take care of running asynchroneously itself or I can force it to run synchroneously and do the threading myself. The Android documentation tells me the following:

Introduced in Android 3.0, loaders make it easy to asynchronously load data in an activity or fragment. Loaders have these characteristics:

...

• They provide asynchronous loading of data.

...

This I interpret as if a Loader always runs in its own Thread and performs the tasks asynchroneously. However, if I then tell the library I want to perform its requests synchroneously, I get the following exception:

AsyncHttpRequest: Unhandled exception origin cause
    android.os.NetworkOnMainThreadException
            at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1145)

So it seems as if the work I perform in my Loader runs on the Main thread after all, which surprises me. The code looks as follows:

public abstract class AsyncHTTPLoader<E> extends Loader<E> {
    private Network2 mNetwork;
    private String mRequestUrl;

    private AsyncHttpResponseHandler mHandler = new AsyncHttpResponseHandler() {
        @Override
        public void onSuccess(int statusCode, Header[] headers, byte[] responseBody) {
            AsyncHTTPLoader.this.processResponse(new String(responseBody));
        }
    };

    public AsyncHTTPLoader(Context context, String url) {
        super(context);

        mRequestUrl = url;
        mNetwork = new Network2(getContext());
    }

    protected void processResponse(String response) {
        E result = parseResponse(response);
        deliverResult(result);
    }

    @Override
    protected void onForceLoad() {
        super.onForceLoad();
        Utils.log(mRequestUrl);
        mNetwork.get(mRequestUrl, mHandler);
    }

    public abstract E parseResponse(String response);
}

Do I need to take care of the threading in the loader myself or not? If I go with the Async feature of the library I use, does the processResponse() function block the UI Thread of my app?

Answer 1

您可以使用AsyncTaskLoader类为您创建一个backround线程。

Answer 2

This exception due to run Network operations on UI thread, if you want to use loader manager for network operations, you have to extend AsyncTaskLoader, and in the loadInBackground() do your network operations, in fact that this method called on a background thread.

for example:

MyLoader extends AsyncTaskLoader<List<MyItem>> {
    @Override
    public List<SampleItem> loadInBackground() {

       List<MyItem> itemsList = new ArrayList<MyItem>();

       // TODO: 

     return data;
    }
}

for more detailed example, you can refer to this link .