Run multiple Asynctask one after another when a condition is satisfied

Question

I have multiple asynctasks in my application, I want to execute it when a specific condition is satisfied. For example,

class Task1 extends AsyncTask...

class Task2 extends AsyncTask..

class Task3 extends AsyncTask...

I have a while loop which is used to iterate some values from a map. eg:

while(iterator.next())

{

 Map.Entry pair = (Map.Entry) it.next();

            String title = pair.getKey().toString();

if(title.equals("one"))

{

//execute task1;

}else if(title.equals("two"))

{

//execute task2;

}

etc..
}

This is a sample code i currently used. Each Task contains a progress dialog, which is starting on onPreExcecute() and dismissed on onPostExecute().

My Problem is that I want to execute only one task at a time. In my code all tasks are started at same time and progress dialog will overlap each other. So there is any way to execute only one task at a time, Thanks is advance.

start with one Asynctask call the next one on onPostExecute. — Dhinakaran Thennarasu, Jul 27 '15 at 07:30
keep a queue of tasks, when the first ends it calls the next one in postExe — user3290180, Jul 27 '15 at 07:44
Thanks for replay, but i can not call Asynctask from onPostExecute, because i have a hash map with a list of strings, based on that strings , i want to execute tasks. So i don't want to execute all the task. — userDroid, Jul 27 '15 at 08:02

score 1 · Answer 1 · edited May 23 '17 at 10:27

The problem here is while loop. The loop will continue to run even if a task is running in background. So you must modify your code such a way that the loop condition is triggered only if one task is completed.

To handle the progressbar issue, create a global progressbar object which can be shared by all the asyncTasks.

Refer the following link for checking status of AsynTasks. AsynTask Status

score 0 · Answer 2 · answered Jul 27 '15 at 08:05

0

The main reason that overlap the progressDialog is running the multipple asnyntask . so you start first asyntask and the call next form its postExcecutive.

answered Jul 27 '15 at 08:05

sijo jose

130
9

score 0 · Answer 3 · answered Jul 27 '15 at 08:23

You have misunderstanding of AsyncTask. The default executor of AsyncTask is a serial executor, which means that it will executes tasks one at a time in serial order in a particular process. But why the process dialogs are shown at a time? After you read the code of AsyncTask, you can find the reason in function executeOnExecutor:

public final AsyncTask<Params, Progress, Result> executeOnExecutor(Executor exec,
            Params... params) {
    mStatus = Status.RUNNING;
    onPreExecute();
    mWorker.mParams = params;
    exec.execute(mFuture);
    return this;
}

You can find that method onPreExecute is called before execute, ie it is not serial called. So the progress dialogs are appearing at the same time.

I think you can modify your code by using only one progress dialog in your main activity and show or hide the dialog by its status.

Run multiple Asynctask one after another when a condition is satisfied

3 Answers3