CODEWITHSUNDEEP
androidlistviewandroid-asynctasklistactivity
Drider
Drider

Reputation: 9

Display loading screen using AsyncTask with ListActivity

I've got an app that uses ListActivity to give users a list of actions. When they click one I use an Intent to launch a separate activity.

My problem is that the actions that the app performs take about 20 seconds to finish, and since I don't want the user to receive that nasty ANR dialog, I tried to use AsyncTask to present them with a loading screen in the mean time. I tried using setContentView(R.layout.loading); on onPreExecute(), but it throws a NullPointerException which as far as I have figured out is due to the fact that loading.xml is not "a ListView whose ID is android.R.id.list".

So what can I do now? How can I show that loading screen? Is there a way around this pretty annoying situation? Any help would be greatly appreciated. Thanks!

Upvotes: 0

Views: 866

Answers (3)

Jade Byfield
Jade Byfield

Reputation: 4816

Fire up and display your loading dialogs in your onCreate() of the Activity being called, then call Dialog.dismiss() in your AsyncTask's onPostExecute().

Upvotes: 0

Jon O
Jon O

Reputation: 6591

I am not sure exactly what your use case is; you have a list of items that are populated immediately, and upon selecting one an action is taken? The action that is taken is to launch another Activity which performs background processing?

Or does it take that long to populate the list of actions?

If the former, you can use an AsyncTask for the long-running activity instead of an Intent to launch another Activity: in the callback you get for the click on the item in question, you would create the AsyncTask, and in doInBackground you would perform the long-running activity, with onPostExecute refreshing or manipulating your list as necessary.

Another thing to consider is using a dialog box to show a loading screen, if the loading is required to happen before you launch a new Activity.

If you can further describe your use case, I can help you more.

Upvotes: 1

Sparky
Sparky

Reputation: 8477

It's not the loading screen you need to have on the AsyncTask, it's that 20-second Activity initialization. I would look for a way to do all the setup in a background thread in a Service while the user is free to merrily bop around in other Activities. I'd try hard to find a way not to just stall the user for 20 seconds. Maybe take them to the target Activity and show them data cached from their last visit until the new set is ready.

Upvotes: 0

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