How to call parent activity function from ASyncTask?
setAccountAuthenticatorResult
can be called from the Activity, which extends AccountAuthenticatorActivity
. My activity extends that, but launches ASyncTask and hence this setAccountAuthenticatorResult
should be called from ASyncTask (or, the result of ASyncTask should be passed back to the main thread).
How to do it?
What is wrong in the code below?
AsyncTask<Uri, Void, Bundle> task = new RetrieveAccessTokenTask(this, consumer, provider, prefs).execut开发者_JS百科e(uri);
public class RetrieveAccessTokenTask extends AsyncTask<Uri, Void, Bundle> {
private Context context;
public RetrieveAccessTokenTask(Context context, OAuthConsumer consumer,
OAuthProvider provider, SharedPreferences prefs) {
this.context = context;
}
@Override
protected void onPostExecute(Bundle result) {
context.setAccountAuthenticatorResult(); // doesn't work
}
When you create the AsyncTask, you can add a new constructor to it, and pass in a reference to the Activity:
AsyncTask myTask = new MyTask(this);
And then from the onPostExecute() method in the AsyncTask you can call the method on the Activity.
public class MyTask extends AsyncTask<String, String, String>
{
public MyActivity activity;
public MyTask(MyActivity a)
{
this.activity = a;
}
// ......
protected void onPostExecute(String result)
{
activity.myMethod();
}
}
Use Interface
Follow these steps:
1) Create an interface
public interface AsyncTaskListener{
public void updateResult(String result);
}
2) Use the listener in your AsyncTask
DownloadSongTask extends AsyncTask<String,Integer,String>{
private AsyncTaskListener listener;
public DownloadSongTask(Context context)
{
listener= (AsyncTaskListener)context; // Typecast
}
@Override
public void doInbackGround(String... params)
{
// Download code
int downloadPerc = // calculate that
publish(downloadPerc);
}
@Override
public void onPostExecute(String result)
{
listener.updateResult(String result); // Use it
}
}
3) Implement the interface in your Activity and Override the interface method
public class YourActivity extends AppcompatActivity implements AsyncTaskListener{
// Activity code //
new DownloadSongTask(this).execute("Paradise.mp3"); // this is how you start Task
public void yourMethod(String arg)
{
// Your method related Stuff
}
@Override
public void updateResult(String result){
yourMethod(result);
}
}
Advantege of using interface?
This seems a lengthy approach at first but if you use this approach
You can make a loosely coupled AsyncTask. Which means you can use same AsyncTask with any Activity in Future without even changing code in your AsyncTask.
Relevant Links:
For better understanding you can read this ANSWER
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