同步多个AsyncTask数据以完成

Question

i have two asynctasks. One asynctask is called and the other is called in the onPostExecute of the first one. These tasks happened when the user clicks a button. The problem is task one is started when the user clicks the button fast and didn't wait for the second asynctask to complete yet.

Task 1 -> insert into a column, onPostExecute starts Task 2 -> increment column to insert

What ended up happening when users click too fast is that it runs Task 1 -> Task 1 -> Task 2 -> Task 2 This resulted in both column insert mapping onto the same column before the columns even incremented (task 2).

How do i fix this? In a way, i want it to be real time, and it should work with multiple users. I have two different SQL queries, one to update value in a column and one to update current column so next insert is in the next column. I use MYSQL.

Thanks.

Answer 1

sounds like you should be using transaction here. See: Using Transactions

if you don't want to use transaction, another option would be to do a producer/consumer using semaphores. Initalize semaphore with 1 token. Task 1 would first acquire a semaphore. at the end of task 2, task 2 would release a semaphore. Therefore you are ensuring that only 1 chain can be processing at a time.