Android :: Threads And Screen Orientation Change
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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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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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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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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Apr 23, 2010
Specifically, I need a way of _not_ performing the onPause functionality I've implemented when it occurs because of a change in screen orientation.
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Jan 21, 2009
From reading Romain Guy's blog post, I understand keep static reference to a Drawable can create huge memory leaks. So what is the recommended solution if I don't want to reload my big Drawable image every time screen orientation changes and effect on performance? Currently my app takes >3 seconds to complete each orientation change.
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Nov 1, 2010
I want to change the screen orientation from portrait to Landscape and vice-versa when the user shakes his/her android mobile phone, can any one help how to achieve this, because I do not know what event is fired, at the time his/her shaking thier android mobile phone. For Instance When the users touch the button in UI, touch event is fired, similarly when the user shakes his android mobile phone, what is fired.
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Mar 15, 2010
I am writing a home screen widget and want to update (modify) the home screen widget when the device orientation changes from portrait to landscape or the other way. How can I make it? Currently, I tried to register to CONFIGURATION_CHANGED action like the code below ...
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Jan 24, 2010
I have a 3 nested ViewFlippers which seem to be working ok except that when I change the screen orientation the view flip back to the first one of my views, giving the user the impression it went back a few steps.I am a bit stumped as to what to do and was hoping someone had some experience with this.
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Mar 12, 2010
I'm trying to find a way to properly handle setting up an activity where its orientation is determined from data in the intent that launched it. This is for a game where the user can choose levels, some of which are int portrait orientation and some are landscape orientation. The problem I'm facing is that setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE) doesn't take effect until the activity is fully loaded. This is a problem for me because I do some loading and image processing during startup, which I'd like to only have to do once.
Currently, if the user chose a landscape level:
the activity starts onCreate(), defaulting to portrait discovers from analysing its launching Intent that it should be in landscape orientation continues regardless all the way to onResume(), loading information and performing other setup tasks at this point setRequestedOrientation kicks in so the application runs through onPause() to onDestroy() it then again starts up from onCreate() and runs to onResume() repeating the setup from earlier
Is there a way to avoid that and have it not perform the loading twice? For example, ideally, the activity would know before even onCreate was called whether it should be landscape or portrait depending on some property of the launching intent, but unless I've missed something that isn't possible. I've managed to hack together a way to avoid repeating the loading by checking a boolean before the time-consuming loading steps, but that doesn't seem like the right way of doing it. I imagine I could override onSaveInstanceState, but that would require a lot of additional coding. Is there a simple way to do this?
Solution:
As per Daniel's answer, this was actually quite easy to fix. I just needed to make a few small changes. In my 'menu' Activity, where the player would choose which level to play, I just had to add an if/else check to choose which class would be started by my Intent. This was done with a simple int representing portrait or landscape, determined when the player selected a level. I then created a second class extending my 'GameLogic' class; this is the class which contained most of the code for the game itself, rather than the menus, instructions, etc.
public class GameLandscape extends GameLogic{}
Literally that simple and completely empty. That way it inherited all the code from my previous activity where I had already coded it to handle things differently depending on the orientation. Lastly I just had to add a line to the manifest stating that GameLandscape would always run in landscape, and GameLogic would always run in portrait.
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Mar 20, 2010
I am relatively new to the Android world and am having some difficultly understanding how the whole screen orientation cycle works. I understand that when the orientation changes from portrait to landscape or vice versa the activity is destroyed and then re-created. Thus all the code in the onCreate function will run again. So here's my situation: I have an app that I am working on where it logs into a website, retrieves data, and displays it to the user. While this is all done in background threads, the code that starts these threads is in the onCreate function. Now, the problem lies in that whenever the user changes the screen orientation, the app will log in, retrieve the data, and display it to the user again. What I would like to do is set a boolean that tells the app if it is logged in or not so it knows whether or not it must log in when the onCreate function is called. So long as the app is in memory the HttpClient will exist and contain the cookies from logging the user in but when the app is killed by the system those will go away. So I would assume that I need to do something like setting the logged in boolean to false when the app is killed but since onDestroy is called when the screen is rotated how is this possible? I also looked into the finalize function and isFinishing() but those seem to not be working.
Shorter version: How can I distinguish between when an app is being killed from memory from when an activity is being rotated and different code for each event?
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Jan 2, 2010
How do we change emulator screen orientation to landscape or portrait?
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Sep 11, 2009
is there a way to make application to completely ignore screen orientation change?
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Aug 13, 2010
It seems when screen orientation changes, the activity's onCreate() method is called. In my onCreate() method, I have an AlertDialog which pops up when the activity is called. The problem is when I switch the screen sideways, the popup is displayed again. How can I avoid this?
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Jun 15, 2009
I found if change screen orientation continouously when a call is ongoing, that is, portrait -> landscape -> portrait- >landscape.
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Nov 24, 2010
In onCreate method of Activity, it binds to a remote service and makes use of AIDL intefaces. Is it required to unbind from the remote service when onDestroy is called on screen orientation change.?
If the activity un-bounded from the remote service in onDestroy and if no other contexts are bound to remote service, is remote service likely to get stopped losing the state that it maintains.?
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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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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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Aug 29, 2010
I'm testing an app on a Droid. It's a kind of card matching game. I'd like to keep the cards physically located in the same place on the screen regardless of a screen rotation. For example, I can put my thumb on a card, rotate the phone any way I please and the card stays fixed under my thumb. However, the orientation of the content of the card will change to match the current phone rotation. I handle this by transforming the card grid in onCreate. This works fine for 90 degree rotations, but if I do a fast 180 degree flip from one landscape mode to another the screen simply flips and the Activity is NOT destroyed and recreated.
This seems contrary to the documentation:
http://developer.android.com/reference/android/R.attr.html#configChanges
"public static final int configChanges Since: API Level 1
Specify one or more configuration changes that the activity will handle itself. If not specified, the activity will be restarted if any of these configuration changes happen in the system. Otherwise, the activity will remain running and its Activity.onConfigurationChanged method called with the new configuration. "
I am NOT specifying any configChanges in my AndroidManifest.xml file, so it seems that the activity SHOULD be destroyed and recreated. Why isn't it? Is there some way I specify that it should be destroy/ recreated?
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Nov 11, 2009
Is there a way to make the home screen change orientation with the accelerometer? On my phone, it will only change when I pull out the physical keyboard, which is not really what I'm looking to do most of the time.It changes just fine in all other applications, but the home screen doesn't. Is this a flaw with my phone or a design decision?
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Nov 25, 2009
I got a question about screen orientation in Android Home screen. The scenario is as following. A G-sensor detects the movement on the device. Then it rotates the screen. If the device is portrait mode, the system sets to landscape mode. With G-sensor, theres is a SensorService to detect that and do some things to reach the function. I want to know how to reach that? Is there a API or a event to do that? I means that hall system, not a activity!
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Jun 10, 2010
I am overriding the onCreateDialog and onPrepareDialog methods or the Dialog class. I have followed the example from Reto Meier's Professional Android Application Development book, Chapter 5 to pull some XML data and then use a dialog to display the info. I have basically followed it exactly but changed the variables to suit my own XML schema as follows:.................
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Nov 12, 2010
I'm new to Android development. I'm trying to use the orientation change to switch between two activities. My idea is to use three Activities one TabActivity and a normal Activity. Here is some pseudo code:
public class Main extends Activity{
// this is the entry point into my app
@Override
public void onCreate(...){
if(this.getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE){
// Start Activity1
} else { //Start Activity2}..............
I'm taking a different approach. As i need a TabActivity, because i want to be able to start different activities in my tabs (I think i have to use a TabActivity in this case). I've edited the Manifest.xml and added android.configChanges="orientation" for the TabActivity and the second Activity. Then I've overridden the onConfigurationChanged() functions. With this approach I'm able to switch from landscape (this is the "normal" activity") to portrait (the TabActivity). The other way round does not work and i don't know why yet. I've exactly the same onConfigurationChanged functions (Copy & Pasted) and only changed the essential parts. Overriding the onConfigurationChanged of the Activities started in the tabs has no effect, too.
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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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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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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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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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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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