Android :: Avoid Restarting Background Threads On Orientation Change
May 19, 2010
I start a number of background threads in my Activity onCreate that do work to keep the UI free. I was originally destroying these threads in onDestroy. However, the idea of shutting down and restarting these background threads every time there is an orientation change seems like a waste of time to me. What is the preferred way of avoiding the shutdown of my background threads on an orientation change? I supposed I could set a flag in onSaveInstanceState and then not destroy my threads if this flag is set. Is this a valid approach or is there a more standard framework approach that I am overlooking?
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Aug 11, 2009
when i open my keyboard, it restarts the activity. i use only landscape mode and dont want the activity to restart.
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Aug 30, 2009
In the following sequence of events:
1. Start a new thread (as a result of a button click - or similar).
2. User changes the screen orientation (causing the Activity that started the thread to be destroyed).
3. Thread finishes, and wants to do some dialog (or any UI) work. However, doing a showDialog, dismissDialog, ... will crash, as the thread it still referring to the old Activity.
This can be solved by updating the data in the thread to refer to the new Activity upon a screen orientation change.
However, couldn't the Android framework just forward any requests from a destroyed activity, to the newly created Activity, saving us developers of handling it ourselves?
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Jun 8, 2010
I have an image set as my background and when it is vertical, the image looks fine. However, when the orentation is changed, the image get streched out. If there a way that I can change the image based on the orentation of the device?
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Apr 6, 2010
i've developed an android app that's fetches an xml file and displays this data via several markers on the map. This works fine so far. The problem right now is that when i switch the orientation of the phone (portrait->landscape or vice versa) the markers disappear for a small moment, the xml processing is started again and then they reappear. Is there a way to prevent this re-loading of the file? It only takes about 2-3 seconds.
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Sep 29, 2010
I download some data from internet in background thread (I use AsyncTask) and display a progress dialog while downlaoding. Orientation changes, Activity is restarted and then my AsyncTask is completed.I want to dismiss the progess dialog and start a new Activity. But calling dismissDialog sometimes throws an exception (probably because the Activity was destroyed and new Activity hasn't been started yet).What is the best way to handle this kind of problem (updating UI from background thread that works even if user changes orientation)? Did someone from Google provide some "official solution"?
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Jul 10, 2009
My program does some network activity in a background thread. Before starting, it pops up a progress dialog. The dialog is dismissed on the handler.This all works fine, except when screen orientation changes while the dialog is up (and the background thread is going). At this point the app either crashes, or deadlocks, or gets into a weird stage where the app does not work at all until all the threads have been killed.How can I handle the screen orientation change gracefully?
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Jun 7, 2010
I have an Android Activity with a RelativeLayout and I have implemented the following method to prevent the activity from being recreated on change of Orientation:
CODE:..............
I am obviously not doing anything in this method, but it worked perfect when using a LinearLayout. Now however, using RelativeLayout, my layout is all messed up when changing to landscape orientation.
What is the most efficient way to have the screen redraw correctly without having the activity restarted again with a call to onCreate?
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May 14, 2009
I have created an activity for my game which handles all orientation changes by itself and has a fixed "portrait" layout. Actually it uses the accelerometer and is rendered using 2D canvas methods. If the level has been completed I show up a highscore dialog in which the user can enter his name. The dialog is floating above the underlying level screen which gets blurred out nicely. This generally works.
Problem is that the dialog does not get rotated if the orientation of the phone changes. So even if the keyboard is exposed the dialog is shown in portrait mode instead of landscape. I have tried to use an activity with dialog theme instead but the behavior didn't change. After several tries it seems that I have found the reason for this: Once there's an activity with fixed orientation in the activity stack then all subsequent activities keep this orientation, too. They will not react on orientation changes anymore (e.g. if the keyboard gets exposed).
After upgrading to 1.5 SDK the described behavior changed a little bit. Now at subactivities indead react on orientation changes like expected. However, the need to have an opaque background! That means that neither dialogs nor activities with dialog theme will work. Those will stick with the orientation of the underlaying activity. So my workaround is to first start a sub-activity with an opaque black background. This activity then shows my highscore dialog on top. It looks quite okay but I wonder if there's a better solution? Is it possible to show a dialog above a fixed portrait or landscape activity which automatically adapts to orientation changes?
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Oct 15, 2010
In a start activity of our android application we're using a linearlayout with an background image for whole space. The image size is 320x480 - the same as device resolution, we're using for testing. The problem is, the image will be scaled und looks not so nice. I tried to use imageview instead, but I've got black borders.
Some ideas, how to avoid scaling or how to get the proper size for background image?!
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Jan 9, 2010
hi, i run my application in an emulator/device automatically one drawable image other than default image i used my image coming for my application as background.how can avoid it?
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Mar 1, 2009
As is mentioned above,What i'm trying is to protect a sub- thread,and keep it going on as long as the App that starts it is still alive.In other words,If the system need more resources,Let it kill both the App main thread and the sub-thread started from it,Instead of just kill the sub-thread.Is there any way i can do this ?? And another question here,The android system seems to be "rude",As it killed my thread without telling me,even in the logs,Is this the case?
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Aug 26, 2009
This application I've been working on has databases with multiple megabytes of data to sift through. A lot of the activities are just ListViews descending through various levels of data within the databases until we reach "documents", which is just HTML to be pulled from the DB(s) and displayed on the phone. The issue I am having is that some of these activities need to have the ability to search through the databases by capturing keystrokes and re-running the query with a "like %blah%" in it. This works reasonably quickly except when the user is first loading the data and when the user first enters a keystroke. I am using a ResourceCursorAdapter and I am generating the cursor in a background thread, but in order to do a listAdapter.changeCursor(), I have to use a Handler to post it to the main UI thread. This particular call is then freezing the UI thread just long enough to bring up the dreaded ANR dialog. I'm curious how I can offload this to a background thread totally so the user interface remains responsive and we don't have ANR dialogs popping up.
Just for full disclosure, I was originally returning an ArrayList of custom model objects and using an ArrayAdapter, but (understandably) the customer pointed out it was bad memory-manangement and I wasn't happy with the performance anyways. I'd really like to avoid a solution where I'm generating huge lists of objects and then doing a listAdapter.notifyDataSetChanged/Invalidated()
Here is the code in question:
CODE:.....................
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Oct 10, 2010
I need my Android app to save it's state to disk when its activity is put in the background or killed. It's been suggested that I start a thread when onPause() is called and perform any expensive I/O procedures there (see http://stackoverflow.com/questions/3894668/saving-loading-document-state-quickly-and-robustly-for-image-editor).
In what situations will the OS kill the thread and how commonly do these situations occur?
I assume it will be like how Activities are dealt with where the OS can arbitrary decide to kill the thread but will mostly only do this when resources are extremely limited. It would be nice to find some specific documentation of this though.
From playing around, with some test code, a background thread started in onPause() will run indefinitely in the background on my device (I tried loading lots of apps and couldn't get it to be killed).
For my specific app, I'm writing a bitmap editor where I'm using the Command pattern and the Memento pattern to allow undo and redo of edits. I'd like the user to be able to undo/redo their edits even e.g. the user gets a phone call and the activity is killed when it is put in the background. The best solution I can think of is to use a background thread to constantly save my command and memento objects to disk during application use and to finish up saving any objects that are left in a background thread if onPause is called. In the worse case, if the thread is killed I'll only lose some edits.
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Jul 30, 2009
I have a notification that starts my activity and passes a messages using the intent's putExtra() function. The message is then displayed to the user in the activity's onCreate function. When the application is restarted due to a orientation change, the message is shown again as it is still in the intent's bundled data.
How can I remove the extra data?
I tried the following:
Bundle bundle = getIntent().getExtras();
if (bundle.getBoolean("showMessage")) {
// ... show message that is in bundle.getString("message")
// remove message
bundle.remove("showMessage");
}
But the message will still be shown after the orientation changed, seems like the intent used is not the one I changed, but the original one. The only workaround I found is to save the showMessage additionally in onSaveInstanceState(). Is there another way? Or is this the way to go?
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Jul 22, 2010
I have a widget which has say, a dimension of 294*72(portrait). But when the orientation is changed, I need to change this dimension of the widget to another dimension which would look good on the landscape orientation.
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May 22, 2010
I'd like to check for memory leaks in my Android app using the DDMS feature in Eclipse. When I launch an emulated device, the threads display properly for the emulated device, starting with 8600 and up.
However, when I connect my Droid to the PC, the device shows up just fine in DDMS. The logcat is generated correctly, and I can view the file structure. However, threads do not display. I get "no client selected" in the Threads pane, and there is no drop-down icon next to the device listing.
Do I need to change some particular setting in Eclipse? Is this maybe a driver issue?
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May 21, 2010
I have the following linear layout. What I don't understand is if I set the background to another image, the padding information are reset. Is there a way to prevent this?
<LinearLayout android:id="@+id/aPanel"
android:orientation="horizontal" android:layout_width="fill_parent"
android:layout_height="wrap_content" android:background="@drawable/bkground"
android:paddingLeft="15dp" android:paddingRight="15dp">
<!-- some children here -->
</LinearLayout>
I see the position of the children get shifted when I change the backround drawable of the linearlayout 'aPanel'.
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Apr 13, 2010
What are the advantages/disadvantages in placing a lengthy network access code in a thread in an activity or a thread in a service? How would it affect the application? I am writing a streaming audio player and from what I've read so far putting the code in a service will still end up blocking the application so a new thread is needed, does anyone know if it makes more sense to put this piece of code in a service.
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Mar 25, 2009
I am building a AlertDialog in java code, so by default it is portrait but I want to show it in landscape orientation. How to do it in Java code?
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Oct 8, 2009
I notice when using the emulator that when the screen is flipped, I get a following logcat message:
INFO/WindowManager(589): onOrientationChanged, rotation changed to 1
How can I catch this in the code? I want to know whenever the orientation changes. I assume I have to set a listener, but I can't find an example anywhere.
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Mar 5, 2010
I'm doing an APP that shows some dialogs. Those dialogs are Alert dialogs, and when they are being showed if I change the orientation of the mobile I lost them...they are not being kept on the screen.
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Oct 1, 2009
Do Views know changes in orientation? In my case, I create popups from TextView and need to know when the orientation changes(porttrait<-- >landscape). I cannot depend on activity's onOrientationChange.
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Feb 11, 2009
I am making an Android app which is currently coming along nicely - I've hit upon a couple of stumbling blocks.
1) How do I stop the screen from going dim/off and the phone locking while the application is running?
2) Can I force the phone to enter landscape mode on running my application?
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Jul 1, 2009
My app *sometimes* when orientation change, leaks Activities (getInstanceCount() increases from time to time) and i cannot figure out where references to my Activity or rather Context are kept - tried to use jhat but it couldn't help me much.
what is strange: it doesn't always happen on orientation change, so its even harder to fix.
btw when doing normal app life cycle - start, do something, exit - everything is ok - getInstanceCount() always returns 1.
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Apr 28, 2010
I have an activity that checks stuffs online when it's created (is the GPS on and if not it asks if the user wants to turn it on).
The problem I'm having is that it is also doing it everytime I change the orientation of the screen.
I've read some comments on onConfigurationChanged() but is there a better way to be sure I'm checking the GPS only when the activity is first created?
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Jun 23, 2010
built a simple app that displays an alertDialog with two buttons.The problem is it's not getting dismissed when i change orientation. After change i get a leak warning on debugger and the dialog appears twice(pressing back hides the first dialog, only a second back dismisses it completely).
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Nov 6, 2010
I want to know how to change the orientation of my layout inside of eclipse but when I click the "layout" button it still shows it as a vertical layout.
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Nov 6, 2010
I want to know how to change the orientation of my layout inside of eclipse.
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Mar 17, 2009
consider the simple layout:
CODE:..................
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