Im building an Android application. It parses a feed which is stored in a DB. Each activity of the app is able to get this data from the DB.
Every activity can also call the Service, and make it refresh the data. When this is done I would like to display a loader. While the Service is downloading, the user is still free to navigate between activities. My question is; how can I display a loader that runs in all activities the user navigates to?
Thanks a lot :)
Here's what I would try to do since it seems to be an uncommon task to me:
I would try to setup a translucent PopupWindow which contains a progress indicator. I would trigger / dismiss this popup to be displayed / or not whenever there's a need to indicate the loading progress...
You could try something like:
Place a "global loader view" in all your activities.
When you start/return to an activity, fire an AsyncTask which will be used to handle updates of the global loader
Override onPreExecute() to prepare the global loader (e.g. setting its state to the current level if the service has been downloading for a while)
Override onProgressUpdate() and use it to update the state of the global loader by asking the Service for the current state (load percentage or something)
In doInBackground you implement:
while( service.isLoading() ) {
publishProgress( service.getLoadPercentage() )
// Maybe add a Thread.sleep() here.
}
Override onPostExecute to set the visibility of the global loader to View.GONE.
You might need to implement a way of killing the AsyncTask if the user switches away from the activity when the loading is not finished yet.
Related
In my activtiy, I am loading a recyclerview that downloads pictures from the internet.
The only problem is, that the acitvity will only become visible when the loading of the pictures is done. I call the function from within the OnCreate() method. Since this made it obvious, I decided to put the function into OnWindowFocusChanged(), yet still the activity will only start showing when the pictures are loaded. (This is like a 1 second delay, but its a litttle too much.)
Where would I call my InitRecView() method to make sure it will start loading once the activity is already visible to the user?
Thanks
You are getting this problem because you are loading images on main thread. It may also cause skipping layouts.
Here is the solution: Use Handler or Async task for download images, show progress till then and once image is downloaded then notify adapter using adapter.notifydatasetchanged().
note:make sure you write UI related code in runOnUiThread since you cannot handle UI elements in background task.
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
in my activity, i have an asynctask that downloads a series of images...(it may take some time depending on the size of the images)... before i execute the asynctask, i display a progress dialog in onPreExecute and a notification (when user clicks on notification it is redirected to my activity with the progress dialog). when my asynctask completes, in onPostExecute, i remove the dialog and the notification.. i handle screen orientation by using onRetainNonConfigurationInstanceto save my asynctask so that when screen is rotated, i check if task is still running and i display the progress dialog if it is still running in onCreate
Problem : sometimes: my asynctask downloads only 1 file and it seems that it gets killed...(no exception in logcat)... as a result, my notication is always there and my progress dialog also... and they remain there indefinitely....
i have tried the solution by Jeff Axelrod there: How can I ensure an AsyncTask is completed before my activity is killed?:
It looks like if I override the onPause() event in my activity, and from within the overridden onPause(), I call cancel(false) on the AsyncTasks, then the activity is not destroyed until the AsyncTasks are completed.
seems to do the trick but problem is that my onPostExecute is not called anymore; all images download fine but as onPostExecute is not executed, notification and progress dialog still remain there forever.
waiting for your solutions guys! i read use asyntask only for short task; will the use of thread and handler solves my problem? will android kills my activity or thread if the latter is not finished??
Best way how to handle Asynctask is described in this article.
In short, the idea is to keep AsyncTask in fragment with setRetainInstance(true); these will keep You AsyncTask alive all time user is in activity holding this fragment and won't be destroyed on configuration change (orientation change).
If You need Your AsyncTask to run after user leaves Activity, for example goes to next Activity but You wish download to continue You should use services.
in my app, i'm uploading some files that can take up to several minutes. i'm thinking of a way to notify the user about activity going on passively by adding a progress bar in my custom title bar. what i want to do is have every activity, each which uses the custom titles, appear with the progress bar until the thread finishes and does a callback which would make invisible the progress bar. can something like this be accomplished?
what seems to make this impossible is that if the user is in an activity with the view loaded, the thread finishing callback would have to manipulate the loaded view resources to disable the progess bar which doesn't seem feasible. are there any suggestions to accomplish this or alternative solutions in keeping a global and passive indication of something going in the background?
You can use a service to achieve this. Services
Basically how it would work, is you bind to the service in each activity when you create the activity. You use this service to start your upload method.
When you bind to the service you pass a handler, which is then used to update your UI in that specific activity. The service will never directly affect the UI (it will be running on a separate thread) instead the handler passes a message back to the UI thread with data in a Bundle, such as upload progress, or a bool to say it's finished.
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().