how to wait multiple asynctask to finish their work?

Question

I'm using ThreadPoolExeecutor to make 3 Asynctask to work at the same time. Every thread collected data from a RSS feed in one Arraylist and then I would like to combine these 3 Arraylist into one to updated View in main thread. The problem is I need to do this after all 3 thread finished their work, how to listen on these thread?

Answer 1

Use CountDownLatch . This java class provides you convenient synchronized counter. Init an object with count 3, call await() and then call countDown() on it when each task is finished. Once it is 0 the lock will be released and you can perform your task.

Answer 2

Create a member variable and initialize to 0, increment it on every onPostExecute. Also check if the value is 3 in all onPostExecute and if it is 3 call method to combine the arraylist.

Answer 3

You can call async task get function which waits for it to finish or you can hold a counter where every task will increase in its onPostExecute function. Once the counter value will be the number of async tasks, execute your code.