I have an app that contains a sequence of listviews, and those lists are populated with data retrieve from a webservice. I want to refresh this data when the user presses back to go to the previous list.
I have currently tried overriding the onWindowFocusChanged method, but this doesn't work, since when I start a webservice download, I bring up a progress dialog and close it upon completion. This causes a recursive effect (the dialog closes and gives focus back to the list activity).
Is there any way I can get when the activity is first shown? Similar to viewWillAppear for iOS?
Just override onResume() in the Activity. Just make sure to do whatever internet communication you do in a separate thread.
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The question is more conceptual than coding-related.
I have an app with Activity A and B.
I call an AsyncTask from Activity A, while the call is being made, I don't want to block the user showing the progressdialog, so my user can freely move around the application without getting bored of waiting.
Now, the query is AsyncTask or lets say a Service is being called from Activity A which is responsible for downloading some kind of data from the server. While the call is being made, the user has changed the Activity and Activity A has gone to background.
Now, while the user is freely moving around the application, he just wants to come back to Activity A to check the download status,(which is something lets say I set some data to my TextView).
Now the question is, once the download is over , while my Activity A is still in background, my UI should be updated while Activity is still in background. This way the user feels he gets the data before he switches to Activity A.
Is this possible, if so how?
Summarizing my question, can I update the UI of an Activity while it is still in background with the Asynctask or Service which the Activity invoked to fetch data from server.
One post suggested that ideally I need to update the **UI in onResume(). My question is, is this the only approach?
once the download is over , while my Activity A is still in background, my UI should be updated while Activity is still in background. This way the user feels he gets the data before he switches to Activity A.
It isn't possible. You see, the Activity has to pass through the onCreate() and onResume() callbacks for the UI to be changed.
Also, you should be using a bound Service to update the Activity when it returns to the foreground.
onResume() would be the best approach. You may save the changes in a SharedPreferenes or Pass the data using Intent and show the changes before the UI is visible.
Another approach would be running a service and checking if the activity is visible. If its visible immediately update the UI or wait until user visits the activity. To check if the activity is currently visible see here,
How to check if activity is in foreground or in visible background?
I have an application which stores data in SQLite database. Main activity is just a screen with a single button. When user clicks this buton the second activity opens. The second activity is a list (ListActivity) which should contain all the records from database. Here is the question: which approaches fits better: 1) when button is clicked, start AsyncTask, in doInBackground method pull data from database and send pulled data to the second activity as a parcelable array or 2) start the second activity, in onCreate method pull the data from database and display progress bar while selecting data. I believe it is not based on primary opinion and there should be valuable pros and cons. But I am new to Android and I'm struggling to identify better approach for this. Thanks for your attention.
First approach is not user friendly. Because when user press a button to open different activity(In terms of UI), then user except to show a transition, Not the stuck in first activity. Actually it depend on your application UX design. Also first approach has another problem. If you load data in first activity then you have to transfer many data when you call another activity.
Use the slightly modified second approach. First start the second activity, then call the AsyncTask(in onCreate method) to load the data.
Well, I think the best is starting AsyncTask on clicking button and process data in doInBackground as You said. In onCreate() of second acivity display progress bar, and in doInBackground() send data and display items. It seems to be the best from point of performance.
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
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...
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())
use intent service to do that ask task means call ask task in a intent service that one is capable to handle background task without hang UI
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!
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.
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.
Fire up and display your loading dialogs in your onCreate() of the Activity being called, then call Dialog.dismiss() in your AsyncTask's onPostExecute().
I suppose the title is a bit confusing but here is what I'm trying to do:
I have a class called ManageClass which lists the entries of a database. I have written another private class within ManageClass which extends AsyncTask so that I can display a progress dialog while I'm getting the data from the database. Now when I click on an item I create a new Intent which takes me to my ViewItem class. I've added a button there so that the user can delete that particular entry that he/she is looking at. All of the above work fine.
Now I want after deleting that entry to kill the activity and go back to the previous one (the one displaying the list) but I want to refresh the listings.
My problem is that I cant use onResume() cause it will also be called when the activity is resumed after the AsyncTask finishes.
Could anyone help me with that? I'm really stuck... all ideas are welcome!!!
If I understand your app workflow you should use startActivityForResult instead of launching a new Activity via intent.
Look at here fore some example
Basically you can launch a new Activity and wait for a result via callback on the "opener" activity. so you can avoid to put your logic into onResume method