如何检查是否正在运行任何后台任务？

Question

I have an activity in android that is getting data from server using AsyncTask, I'm running the task like the following:

new Task.exectue();

The problem is there are multiple calls to this AsyncTask and I want to cancel all of them when onDestroy or onBackPressed called, how can I achieve that? or as another soultion how can I check if there are any background tasks running in activity?

Answer 1

By Default AsyncTask executes many tasks serially. That means that when the first task finishes it starts the next one and so on. What you can do is

Global Variable:

private Task myTask;

Method:

public void accessWebService(){
   myTask = new Task().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, "Param 1");
}

and then in onDestroy cancel the Task.

Answer 2

how can I check if there are any background tasks running in activity? :

   boolean isTaskRunning =  asyncTaskObj.getStatus().equals(AsyncTask.Status.RUNNING) ;

If you want to cancel that task then use below code :

asyncTaskObj.cancel(true);

Answer 3

Have a list of your Tasks and when you want to cancel them just iterate through list and call .cancel() on every task :

private ArrayList<Task> mTasks = new ArrayList<>();

Each time you want to execute your AsyncTask, add the instance to your list :

mTasks.add(new Task.exectue());

At the end of your onPostExecute() method of your Task, remove it from your list :

@protected void onPostExecute(Long result) {
    ...
    mTasks.remove(this);
}

Finally in your onDestroy() method, cancel all running AsyncTask :

@Override
onDestroy() {
    for(Task task : mTasks) {
        if(task.getStatus().equals(AsyncTask.Status.RUNNING)) {
            task.cancel(true);
        }
    }
}