App crashes when user changes fragment during AsyncTask

Question

I've got the following problem. In my app I'm loading data in an AsyncTask. The problem is, when the user now clicks on the icon to open the Navigation Drawer and opens up another fragment the app crashes. When the AsyncTask is finished the app doesn't crash. The problem that is encountering is, that when I switch the fragment (The fragments are always the same, just with another content dependent on the NavigationDrawer Item click) the app crashes.

I guess the problem is, that the async task isn't finished, I'm calling the same fragment again want to display different data.

So what would be my approach to handle this? Use for every different view a different fragment? I thought using the same fragment every time is much easier, since it's just displaying different data but the structure, layout etc. is all the same. Just the data that it gets is different.

I also thought about somehow "blocking" the user from doing any other actions while the asynctask but still show him that the app is processing. But that would be not the definition of an AsyncTask.

How would you approach it? Use different fragments for every different display? Or how? Block somehow? If a user clicks on an item of the navigation drawer the asynctask needs to stop all its actions (if some are done) and then restart doing all the actions. Is there a way to do it?

Please note that the fragment where the async is executed and the activity where the fragments are called are in two different files

Answer 1

You can either block the screen with a loading screen (not that good UX wise...) or you could cancel the asynctask when you change the fragment, in the destroy or detach method.

You didnt show the errors, but I would guess that the app crashes because you are trying to acess something in the asynctask onPostExecute method and it is no longer available...

Answer 2

I guess that it crashes because your AsyncTask is sending data to a class instance that doens't exist.You should change the Class that receives callbacks from asynctask. Anyway i can't give you a better answer till i will see your real code of AsyncTask ( at least onPostExecute() and onProgressUpdate())

Answer 3

使用Intent服务来执行询问任务意味着在能够挂载UI的情况下能够处理后台任务的Intent服务中调用Ask任务