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POAndroid AsyncTask with notification
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  1. POAndroid AsyncTask with notification
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    copied!<p>I am currently starting to develop Android applications, and I must say that it all came out very very simple and straightforward.</p> <p>I have a small question about the AsyncTask. Maybe I've been doing something wrong, but here's the situation.</p> <p>I have a small app that needs to load a list's content from the web. I developed everything based on fake requests, and it all came out awesome. Then I updated the code with actual requests and got the 'Network on main thread error'. So I decided to switch to AsyncTask. </p> <p>I was wondering if I could let AsyncTask just do the asynchronous work, and handle the result somewhere else (where I actually have the GUI connections and everything). I thought that in terms of readability and logic it makes more sense to have all the code that handles the interface in the Activity, but how could I let the Activity know when a task was completed?</p> <p>I wrote these simple classes and interfaces (and it works) but I wanted to know from you if this is a good thing or there are better methods to do that.</p> <p>So, here's the code:</p> <pre><code>public interface AsyncDelegate { public void executionFinished(LazyLoaderWithDelegate lazyLoaderWithDelegate); } </code></pre> <p>This is a simple interface. The purpose is to have the Activity implement this and handle the 'executionFinished' method. Something like a listener.</p> <pre><code>import android.os.AsyncTask; public class LazyLoaderWithDelegate&lt;Params, Progress, Result&gt; extends AsyncTask&lt;Params, Progress, Result&gt;{ AsyncDelegate delegate; Result result; public LazyLoaderWithDelegate(AsyncDelegate delegate){ this.delegate = delegate; } @Override protected Result doInBackground(Object... params) { //This will be Overridden again from the subclasses anyway. return null; } @Override protected void onPostExecute(Result r){ this.result = r; delegate.executionFinished(this); } public Result getResult(){ return result; } } </code></pre> <p>This class basically gives a skeleton structure to notify the delegate when the task is finished.</p> <p>That's all. Here's an example of using this classes:</p> <pre><code>public class LazyVideoLoader extends LazyLoaderWithDelegate&lt;Void, Void, List&lt;List&lt;Video&gt;&gt;&gt;{ public LazyVideoLoader(AsyncDelegate delegate) { super(delegate); } @Override protected List&lt;Video&gt; doInBackground(Void ...params) { return ServerInterface.getVideos(); } } public class MainActivity extends Activity implements AsyncDelegate { private LazyVideoLoader videoLoader; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); /* * Set up the lazy loaders */ videoLoader = new LazyVideoLoader(this); videoLoader.execute(); } @Override public void executionFinished(LazyLoaderWithDelegate task) { if(task == videoLoader){ List&lt;Video&gt; result = videoLoader.getResult(); //Do whatever you need... } } </code></pre>
 

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