So I have some application, on startup it launches a splash screen activity and checks to see if a user account has been linked to the app. If one has the app launches the main activity and bypasses the splash silently. If there is no user account it pulls down a database in a AsyncTask and asks the user to Login/Create an Account.
On first startup the app syncs with a server and pulls down a database. I'm trying to get a DialogFragment with an indeterminate progress bar to display as this database is pulled down. Right now the DialogFragment is created in the onPreExecute() of the AsyncTask, the AsyncTask is executed in the Activity's onStart() method the problem I'm having is that the dialog is not being drawn to the screen.
I have debug logging that shows that the dialog's onCreate() is executing and the sync is successful. The dialog is shown/dismissed in onPreExecute() and onPostExecute() respectively both of which execute on the UI thread. I realize that if the database download is fast this won't display very long but I'm not seeing even a brief flash of the dialog in the emulator.
Could this be a 'problem' with the emulator where all the dialog's frames are being skipped or am I not creating the dialog at a point where it would actually be drawn to the screen.
From your description I see 2 possible reasons:
1. Maybe you doesn't show right the DialogFragment, see example.
2. The AsyncTask is launched in a different thread (Not on UIThread), so if you need to access the UIThread (from the AsuncTask), try to override onProgressUpdate see tutorial.
Hope it was helpfull.
Related
I am trying to make an App which is going to display Some Images and Videos. So I am planning to add a splash screen of around 2seconds. After 2 seconds the user will be taken to the Main Screen of the App.
I want to start the loading of the Images, Video when then user is at the splash screen itself so that the user should wait for the least time when he is at the Main Screen.
So the loading will be started at the Splash Screen and then after two second the user will be taken to main screen irrespective of the completion of the loading.
Now since this involves two activities should I use a Async task or should I Use a service with an Async Task(For the callback of completion of code) within it?
Which one would be better. Also in Android 8.0 are there any restriction in using Services?
I think using a Async Task between two screens may cause Memory leak if not coded properly.
Any help would be really grateful.
EDIT: My app is having one more feature hence cannot make the user wait in the Splash Screen till the loading is over.
It is not very good to use AsyncTask for sharing results between 2 activities, because AsyncTack created in Splash activity will be destoyed (stopped) when switched to Main activity. Better to use service in this case and Main screen will subscribe for result.
So basically you want to start the download in the splash screen and continue the download in the activity that follows. In this way, you still have to implement a loading animation. In your case, I would recommend finishing your splash screen, as soon as everything is downloaded. In that way, you don't have to download anything anymore inside the app's lifecycle.
AsyncTasks continue to run even after switching to a new activity. You can try the following flow:
1. Splash screen
2. Trigger Async Task
3. Main Activity
4. Show Images/Videos
The only catch is, you will not be able to fix a time for #2 to complete to be able to start #4. This is the nature of AsyncTasks. You can workaround by using the OnPostExecute within AsyncTask.
Example: OnPostExecute call another method that will enable a button. Users can click on the button to view Images/Videos. But then, this might not be a good user experience to see some button suddenly getting enabled.
In that case I would rather create some Singleton with own Handler (that works in separate Thread), that will be started at Splash screen. After Main screen will start, it should ask that Singleton about respective data or should sign himself for receiving that data.
So this is a tuff one. I have a activity that calls a class that call a http downloader which is the async task. What I want to do is have a please wait loading screen notification for the user while the activity is getting all the data from the web. I don't have a clue on how to get the loading screen to be called. Usually you would have it in the async task but my async task does not have a view. How to best go about doing this?
Thank you for any help.
My http client does have a doInBackground() so should I put the on preExecute and postExecute there? But then how would my main method which is twice removed know when its down and when its not.
What is happening is that when a button is clicked it starts the activity and starts to process all the methods, but it linger on the first activity until everything is done loading. I don't want that I want the progress dialog. It just won't show. Any thoughts on this?
NEW UPDATES
Ok so now I got this set up a bit better so now at least the progress dialog now shows up. the problem is the Async task does not stop running.
You should use an AsyncTask. It doesn't have to have a view, it's just a background process just like a thread.
Refer to this on how to use an AsyncTask properly with a ProgressDialog.
Do your methods in the doInBackground() method of the AsyncTask.
I want to execute a piece of code (say, for example, display a Toast) every time that the app is opened. So far I have managed to do this every time the app is launched by putting the code into my MyApp.java file that extends Application.
However, if I press the homescreen or back out of the app and then go into it, the message doesn't reappear. It only does when I relaunch the app. Any idea how to do this?
EDIT:
basically im asking how to execute code everytime the whole APP is brought to foreground (this can be first time open, after another app was used, after user backed out of app, etc). Where would I place onResume code? It wouldn't be in a particular activity, would it, since I want it to apply when entire app appears in foreground, not just particular activity.
You can try writing that code in your activity's #Override-d onResume() method.
The only way to do this is,
Determine which app is currently in the foreground
.Follow this discussion for getting an idea for the best way to do it.
[Determining the current foreground application from a background task or service
Suppose, if the function name is 'getCurrentForgroundApp()',
You need a service to execute getCurrentForgroundApp(); every one second
(1-second interval is depending on your purpose, can be lower or higher).
Now, you can identify which app is running foreground in every second.
So, check if your app is the one running foreground. If true, then execute the toast or code you need.
This is how app-locker apps showing lock screen over selected apps, whenever they come to the foreground.
You have to use the onResume callback:
Android API
Example of use from previous SO question
In activity class:
#Override
protected void onResume() {
super.onResume();
//your code here
}
I have an Splash Screen activity that launches an Asynctask that goes off and downloads and processess alot of data. It takes a while (20ish seconds) and it's a refresh of data so I dont wait for it and so send my users to a main activity where they can view the last cached data (with an indicator data is still downloading).
What is the best way (or any way) for the async task to notify the main activity (or any other current activity the user is viewing) that its done and to refresh screen and stop the indicator?
FYI, I dont want to just launch the AsyncTask from the Main as there are 3 other activitys that the user may have navigated to that all would need to know when it is done and to stop showing the indicator.
Your AsyncTask can broadcast an Intent when the data is available. The current Activity can set up a listener for that broadcast Intent and refresh the screen when it get it.
Over the past months I have been developing a versatile real-time game engine, and I have learned a lot, but I still feel very naive when it comes to the application life cycle. Specifically, I am trying to implement an Activity which can be shuffled in to the background by the user, then properly resumed.
My current architecture is as such: I have a an XML menu launcher activity which can create a real-time Game activity using intent. Relevant data in this Game activity is referenced through static data structures and variables. The Game activity creates worker threads in the onSurfaceCreate() callback of my SurfaceView object.
When a user presses the back button, the activity is destroyed, and they are sent back to the XML menu in the launcher activity. Fine, good for now. When the user presses the home button, the Activity is sent to the background. OK, great. My problems arise when the user tries to find their way back in the Game activity once is has been sent to the background. When the user touches the launcher icon, the Game is destroyed and the menu is re-launched. Also, when the user resumes the game through the task manager, the onSurfaceCreate() callback fires and the worker threads are started, but the game is frozen.
So, I have two questions. First, how do I resume my activity through the launcher icon, instead of re-launching the game? Second, when I resume my activity, what actions are necessary to restart my worker threads while persisting the game data?
Thanks!
EDIT: By request, I am including some code below. My onSurfaceCreate is a little bit complicated, it sends a message to another thread, which then implements the callback. I have verified that this implementation function fires when the Game activity is resumed.
protected void surfaceCreate()
{
Log.e(TAG, "surfaceCreate");
Thread gameThread = createGameThread();
gameThread.start();
}
protected final void onResume()
{
super.onResume();
resume();
}
protected final void onPause()
{
super.onPause();
pause();
}
These cryptic pause() and resume() methods simply set a boolean variable which prevents some game logic from being executed, they do nothing to hinder the worker threads, which should continue looping.
EDIT: Thanks Mohammad, for solving my first (although smaller) problem. It turns out that the launcher icon behaves differently when not connected by USB to the IDE. The second problem remains unresolved.
EDIT: All working! The second problem turned out to be an issue unique to my code, I apologize for that. I hope that this question can still be useful for those dealing with the launcher and IDEs.
There are multiple possible problems/solutions listed in this post. This includes misunderstanding of activity lifecycle and launchMode settings.
First, how do I resume my activity through the launcher icon, instead
of re-launching the game?
You are most likely missing definition for your onResume() and onPause() methods. Examples are here:
http://developer.android.com/training/basics/activity-lifecycle/pausing.html
Straight from the API:
onPause() Called as part of the activity lifecycle when an
activity is going into the background, but has not (yet) been killed.
onResume() Called after onRestoreInstanceState(Bundle),
onRestart(), or onPause(), for your activity to start interacting with
the user.
Check the Android Activity Lifecycle out:
http://developer.android.com/reference/android/app/Activity.html
One theory on your issue may be is that you're most likely going to onStop() (by hitting the home button) and the Android OS is looking for your onRestart(), but can't find it hence freezing/restarting.
Second, when I resume my activity, what actions are necessary to
restart my worker threads while persisting the game data?
Careful how you use the word restart. You want to pause and resume the application (not restart). Save data in onPause() (use a database or any other save feature you'd like). Load data in onResume(). Although, the activity should resume as normal if you just fill up these methods.
Now, if you want to save state for when you restart the application, you should save states in onStop() and/or onDestroy(). You should load states in onStart(). In order to save states, you can check this out:
https://stackoverflow.com/a/151940/2498729
For those using Eclipse (or any other IDE to run/test your application):
From what have you described you probably have overridden
android:launchMode in AndroidManifest.xml or if you are testing by
"run as" from Eclipse try exiting the application after installing and
auto-starting. Then start again from the emulator and test the Home
button behavior. I suppose this is because Android does not put
Activities on the OS stack when started from Eclipse and then the Home
button behavior is not as usual. If this does not solve your problem,
try reading
http://developer.android.com/guide/topics/fundamentals.html#lmodes.
I had launchMode set in my StartupActivity. THen I removed that (it
was set to "singleTask", it behaves like I want it; the app is
"resumed" to the Activity I expect, ie not StartupActivity but
MainActivity.
Source:
https://stackoverflow.com/a/1619461/2498729
http://developer.android.com/guide/topics/manifest/activity-element.html
According to this:
https://stackoverflow.com/a/3002890/2498729
You should change your andoird:launchMode to "Standard" (or "default").
Standard: A > B > HOME > B (what you want)
SingleTask: A > B > HOME > A (what you don't want)