How run two AsyncTasks in one Activity?
android, android-asynctask
Solution
If you want to run multiple `AsyncTasks` in parallel, you can call `executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR)` instead of `execute()` on your task. By default, `AsyncTasks` run in serial, first come first serve.
Be careful that the two threads do not interact on the same data, this can cause some strange and hard to trace errors.
Problem
I have two `Activity`s (`mainActivity` & `downloadActivity`) and I have 2 `AsyncTask`s in `downloadActivity` In `downloadActivity` first it execute `getFileAsyncTask` for reading a JSON file for adding some images and create a `ListView` from images, if user clicks on an image, the `downloadAsyncTask` was called and it starts to download something from the internet. My problem is here: when the second `AsyncTask` is running I go back to `mainActivity` and comeback again to `downloadActivity` the first `AsyncTask` wasn't called until the `downloadAsyncTask` completed. ``` public class downloadActivity extends ActionBarActivity { @Override protected void onCreate(Bundle savedInstanceState) { ... new getFileAsyncTask().execute(); ... } private class getFileAsyncTask extends AsyncTask<Void, Void, Void> { @Override protected Void doInBackground(Void... params) { //fetch a json file from internet and add images in ListView return null; } } //there is a Base Adapter class //if user clicks on an image it calls this downloadAsyncTask.execute() private class downloadAsyncTask extends AsyncTask<Void, Integer, Void> { @Override protected void onPreExecute() { //download the file } } @Override protected Void doInBackground(Void... unused) { //download the file } } ``` note: I want to write something like shopping apps. For example, user can download file and surf into shop to see products .