AsyncTask of 'Activity A' doesn't execute if I re-open 'Activity A' before the original AsyncTask has finished executing

Question

I have an AsyncTask which is implemented as follows:

   AsyncTask asyncTask = new AsyncTask() {
                @Override
                protected Object doInBackground(Object[] params) {
                     //downloading images from google places api
                }

                @Override
                protected void onPostExecute(Object o) {

                    }
                }
            };
            asyncTask.execute(); 

This AsyncTask is triggered to run multiple times and it's executed by the scope of the doInBackground() method of another AsyncTask. It runs fine the first time I load an activity, and if I let all the data download and then exit the activity (so that onStop() is called) and reopen the activity it also runs fine then, but, if I exit the activity before all the data is downloaded it won't run when I reopen the activity.

Does anyone know why this is? Can anyone recommend a better approach that doesn't involve AsynTask?

Note: I have tried using executeOnExecutor() but it hasn't solved the issue.

Thanks in advance

Answer 1

AsyncTasks按照收到的顺序在单个线程上运行。如果在AsyncTask完成之前退出，它将继续运行。如果在完成之前重新启动它，它将在任务队列中等待，直到原始运行完成才能运行。您可以通过告诉它在自己的队列上运行来避免它。虽然一个更好的方法可能是一个Loader，如果它仍然会获取相同的数据（这将允许它不再运行第二次但使用第一次运行的结果）。