Android :: Understanding Life Cycle When Screen Goes Off And On?
Aug 4, 2010
My device is a Nexus One with 2.2 and I have tested two projects, one on 1.5 and one on 2.1. Problem: I have trouble to understand the life cycle of my application when the screen is turned off and on. Here is my output
// activity starts
08-04 17:24:17.643: ERROR/PlayActivity(6215): onStart executes ...
08-04 17:24:17.643: ERROR/PlayActivity(6215): onResume executes ...
// screen goes off
08-04 17:24:28.943: ERROR/PlayActivity(6215): onPause executes ...
08-04 17:24:32.113: ERROR/PlayActivity(6215): onStop executes ...
08-04 17:24:32.113: ERROR/PlayActivity(6215): onDestroy executes ...
08-04 17:24:32.983: ERROR/PlayActivity(6215): onStart executes .....................
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May 9, 2010
The core of this Widget is an AppWidgetProvider which registers a ContentObserver to the CallLog content URI. This means that my widget is updated every time a call (incoming, outgoing, missed) is recorded. This works fine for a while, until *something happens* and my ContentObserver stops getting called (no error message seen in trace). I would rather that this ContentObserver persisted until the user removes the Widget.
I am guessing that my JVM has been destroyed (due to low memory?), ContentObserver garbage collected and/or ContentObserver unregistered (or just pointing to nothing), but I don't know how to debug this without restarting my code (and thereby re-registering). I can hide this bug by periodically re-registering my Content provider, but I would rather understand the cause and have a more optimal solution..............
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Nov 12, 2009
The main activity is running, then there is a interrupt. What was happended, onPause(), onStop() or other change of life cycle? 1. pressed the volume_down key and ringer volume toast occured, the life of main activity will not change? why? 2. short press the power key and the OS sleep,how about the activity ? 3. long press the power key and the phone options appear, how? 4. long press the home key and the tast list appear, how? 5. notifications curtain appear, how? 6. press the back key,how?
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Aug 18, 2010
When my ListView activity loads it creates the Adapter which fills the screen as it should do. Is there an event or way to find out when the Adapter has finished getting enough data to fill the screen. I want to show a spinner the first time the Activity loads and have it go away once the screen has its first load of data from the Adapter.
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Mar 7, 2010
When starting a new Activity, I want to pass a complex object and do so by using this approach:
MyActivity.COMPLEX_OBJ = myComplexObj; // which is definitely NOT NULL! Intent intent = new Intent(); intent.setClass(this, MyActivity.class); startActivity(intent);
and then in MyActivity:
@Override public void onCreate(Bundle bundle) { if (COMPLEX_OBJ == null) { // report to Flurry ... } ...
}
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Jun 6, 2010
I am having a really hard time grokking the Activity life cycle concept. The main issue is with onStop() and onDestory() not being guaranteed to be called before the process is killed. I though I had it figured out when I saw that the system calls onSaveInstanceState() when it's shutting down the activity to claim some memory. Thing is that the docs says onSaveInstanceState() will be called before onPause() but how does the system know at this point whether the activity will be killed by the system or the user?
Here is a use case:
1) My activity starts up and is running. 2) At some point I want to show a web page so I use an Intent to start an activity. 3) The web browser covers my app/activity so I would expect onPause() to be called followed by onStop(). At this point it's my understanding that all bets are off and I can be killed at any point without be called. 4) Since the system has enough memory onSaveInstance() doesn't get called. 5) The user presses home and decides to open some app which requires a lot of memory. 6) System wants more memory and decides to kill my app but I am already stopped (onPause() has been called).
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Sep 30, 2009
When I start my application I prompt the user for the password and use it to instantiate my data adapter object that I will need throughout the application. So I store it in Application object. My activity A prompts user for pwd, instantiates data adapter, sticks it to Application object and later starts activity B which in turn starts the built int gallery activity. When fooling around with gallery and capturing pictures for some time coming back to activity B I discover that Application.myDataAdapter is null. I found out that during me playing with camera the Application.onTerminate() method was called. So it seems like Android killed my process and when B was supposed to become visible it started a process again jumping directly to activity B bypassing A? Is that how it works? Should I then never assume that Application.myField will survive? and init it not only when A is started but whenever I discover it is null?
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Aug 25, 2009
I have a service that polls for data. To indicate this to the user I have a persistent notification in the statusbar. In some cases when the device goes low on memory it destroys the service but OnDestroy is not called. Later when there is available memory OnCreate is called. Is this normal behavior? I had hoped that OnDestroy would be called to I could remove the notification in the statusbar. Now the user thinks that the service is still running, while it has been stopped by the OS.
In order to restart the polling how do I know that the OnCreate is really a restart event and not first time creation of the service? I thought about checking for the presence of the notification in the statusbar, but I couldn't find a API to check if a notification was showing or not. I have not tried "SetForeground" on the service, since the service isn't that important to the user, but maybe that would minimize the problem.
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Jul 27, 2009
Finally after many days of getting StackOverflowError, I've tracked down the issue and fixed it, only to find that my game's serialization takes about 5 -10 seconds on the emulator and most likely around that in the target. So far my the lifecycle of my game is as follows
onCreate - check if serialization file exists, if it does, de- serializes it. (~ 5-10 seconds) onPause - if the game is not complete, then serialize it (~ 5-10 seconds) I remember reading somewhere that another activity's onResume will NOT get called UNTIL the previous activity's onPause has ended. So I am worried that my game is delaying another activity that wants to start from doing so i.e like a phone call etc. I think speeding up the serialization is not going to be feasible, so any ideas on what I can do? Can I serialize in the onDestroy instead of the onPause? I read that the onPause is the only safest place to store the state.
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May 30, 2010
I have an Android activity which in turn starts a thread. In the thread I open a persistent TCP socket connection. When the socket connects to the server dynamic data is downloaded. The thread sends messages using Handler-class to the activity when data has been received. Now if the user happens to switch from portrait to landscape mode the activity gets an onDestroy call. At this moment I close the socket and stop the thread. When Android has switched landscape mode it calls onCreate yet again and I have to do a socket re-connect. Also, all of the data the activity received needs to be downloaded once more because the server does not have the ability to know what has been sent before, i.e. there is no "resume" feature.
Thus the problem is that there is alot of data which is resent all the time when landscape mode is changed. What are my options here? Should I create a service which handles the socket traffic towards the server thus I always got all the data which the server has sent in the service. Or should I disable landscape mode all together perhaps? Or would my best bet be to rewrite my server which is a VERY BIG job
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Jul 24, 2010
I have a scrollable map app which for now has a huge bitmap. It loads fine on startup, but when it looses foreground status and the user brings it backs again im getting an out of memory error. In onPause it trashes the bitmap using recycle, and marks it as null. The onResume checks to see if map==null and will load the bitmap back again, which is crashing the program despite me recycling the bitmap...Here are some bits of code. All of the other references to Bitmap map first check if it is null before loading/drawing..............
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Jan 2, 2014
My app is a launcher. It gets killed frequently by OS when it running in background. It has to restart and reload data, which taks a long time.How to make it get less chances of being killed ?
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Aug 16, 2010
The Xperia X10, X10 mini and X10 mini pro smartphones will all receive software upgrades during their lifecycle to improve performance and add new communication and entertainment experiences. From Q3 2010 onwards, the Xperia™ X10, X10 mini and X10 mini pro smartphones will be upgraded to run on the Android 2.1 operating system in selected markets. The Xperia™ X10's position as the best multimedia Android smartphone will be strengthened through the addition of HD video recording as part of the same Q3 upgrade. A further upgrade to the Xperia™ X10 in Q4 will make it possible to connect wirelessly to and display content on your television and enhance the Timescape™ and Mediascape applications..................
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Apr 16, 2011
Is it possible for the lock screen wallpaper to cycle or rotate through my pictures, similar to a slideshow?Is this functionality achievable through an app/tweak of some sort?
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Jun 8, 2012
My Motorola maxx has a broken screen, there is no image at all. The device appears to power cycle, and when connected to win 7 there are 2 drives to explore, both appear as unformatted.
How to recover my files ? When I connect my new maxx the folders are also unreadable.
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Mar 26, 2010
I'm not fully understanding Sense UI. What makes Sense UI so relevant, or not relevant? What exactly is it?
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May 14, 2009
I need some help to understand the use of permission-group tag in AndroidManifest files. Is there any need of using permission-group and what benefit offers this grouping? Is there a plus security using it? Does anyone know an example when to use it?
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Jul 22, 2010
I'm trying to wrap my head around activities and how they begin and end in Android. I've read what the Developer Guide has to say regarding activities and I'm still a little fuzzy on how I should appropriately handle their navigation in my application. As an example, say I have a main activity that starts a secondary activity. Once the secondary activity has completed it's purpose, I want to close it and return to the main activity. I recall having read that the activity stack was just that, a stack of activities that are pushed and popped. So I assumed that calling finish on the secondary activity would return me to my existing main activity. Calling finish on the secondary activity didn't actually do anything, visibly at least. Is there further reading that anyone can recommend to me? Chris Stewart cstewart@gmail.com http://www.androidsdkforum.com
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Feb 17, 2009
I am trying the FaceDetector class using the code as shown in the following link: http://www.anddev.org/quick_and_easy_facedetector_demo-t3856.html Everything works fine as far as the activity drawing the bitmaps is concerned but I haven't had any success in getting Android to recognize a face. Has anyone tried this feature? Could anyone please help in understanding the parameters of the images to use or please post a link to some image that has worked for them?
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Dec 3, 2009
I'm having trouble with my activities when they go in the background. I have two activities, A and B. Only A can launch B (manifest copied below).This is very confusing. It's like Android knows my app is running, and puts a new instance of A on top of the old B instance running. I'd just expect that the application gets paused in-place, and whenever the user hits the app icon again, it just picks up where it left off (in this case, just show B again!) Below is the manifest, and the activity classes for this test are completely empty (except A which has a button to launch B).
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Mar 1, 2010
I am having trouble understanding content providers in Android. Do you use intents to call content providers as well as managed queries?
Also, an activity has an intent filter. The intent filter has a element which has a mimeType attribute. How does Android know which content provider this mimetype is referring to?
The tag in the manifest just lists an authority but not the full content_uri. Further, the content_uri is typically defined in an encapsulated class that seems to only consist of constants but no methods, so I don't see how that links over to the content provider class.
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Mar 25, 2010
I am trying to understand the use of the broadcast receiver and the way of activate it. There's two ways isn't it? Register it from an activity or declare it in the manifest. So my question is: If I code a broadcast receiver which is watching incoming messages and I register it in the manifest, when a message comes my broadcast receiver will catch it automatically although any activity of my app had registered it. In a nutshells, I don't have to activate it so it works, only register it either in the manifest or in an activity.
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May 19, 2010
I'm attempting to add four controls to a layout; <label> <text> <seek> <radio> I want the seek widget to occupy all the available screen space between the edittext control and the radio control. However if I give it the value android:layout_width="wrap_content" only a small seek control is displayed and if I set the value to fill_parent it overwrites the radio control. I would have thought there would be a mechanism to occupy the free space between the text and radio controls dynamically. The xml file I am using is below You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscribe@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
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Jan 20, 2010
Trying to replicate the behavior of ItemizedOverlay.boundCenterBottom(), inside of one of my Overlay classes. I am fairly certain that I can do this using setBounds(), but I am utterly lost as to what setBounds() is actually doing.
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Oct 6, 2010
I am a beginner in writing Android apps and would like to be a part of the group to get a more in depth understanding.
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Jan 11, 2010
the app I'm trying to implement allows the user to select a sound file (MP3 or WAV) to play at a specific date and time showing a dialog with a progress bar and an OK/Cancel button allowing the user to stop the playing of the sound file. I want it to behave something like the countdown apps I've seen or even the built-in alarm clock app. As I'm implementing this simple (I thought!) app, I'm trying to better understand the platform and make the application conform to the Android way.
As I've been writing the app, I learn more about how things are supposed to work on the Android platform. And here's where I'm getting a bit confused. During my attempts to get the alarm to fire and display, I'm learning that properly formed Android applications are not supposed to show dialogs as a result of a background service or broadcast receiver being invoked through Android's alarm service. Instead, I think, the app is supposed to use a notification on the status bar to alert the user. The user then has the option to look at the notification to see what the app is trying to tell them..............
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Jun 25, 2009
Can someone please explain how to understand a logcat from an android force close. This crash occurs when I called finish() in the onPause(). Here is the DDMS screenshot http://www.2ql.net/uploads/1245827534.png
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Jun 13, 2009
I see this example of MenuCallback code, but i don't understand where is the reference 'ImageManager.IImage image' comes from? How is that image get created and passed it to MemuCallback?
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Aug 26, 2010
First and foremost, are there many android developers here? Is this a good place for Android related discussions?I seem to be missing a rather large concept of Android development. The gist is I am struggling understanding how to tie an application together. I'm not sure how to explain it, so I thought I would do my best with an example from the Android ApiDemo... assuming you are familiar with it.
Inside the com.example.android.apis.view namespace of the ApiDemo, there is a class called Animation3.java.Animation3 inherits the activity class and there is some code inside to display animation.I can't find a reference to the class (Animation3) anywhere in the demo code (except for its definition obviously). The only mention I found is in the manifest xml file. So how the heck does this activity get started? Don't we need to create an instance of the class somewhere and fire off a method to start it? I don't understand how to generate the code that ultimately glues this class to the rest of the application.Additionally, what about other classes like views or viewgroups? How do I generate code outside the class that initiates/starts/uses/calls (insert proper term) the class.I would appreciate any code examples as well as any concept explanation or reference documents. So far I've read pages and pages on activities and views but I'm really struggling how to tie things together.
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Dec 21, 2009
I had posted a similar thread a while back and received no feedback, so let me try to be more clear.I am able to use Androids components to build the most basic layouts, which include images, buttons, text areas, etc. These are like Android Lego! I can build the castle. BUT I want to design my own component, my own Lego, that draws on the screen and uses the available area that the Android components have not used. ie, I want to have a top layer of buttons, and the rest of the screen, whatever it is, I want to use to draw 2d graphics. So, I want to make my own Lego, and use it with the other Android Lego. However, I'm also trying to be a good developer and making this for whatever resolution is thrown my way. What is the best way to do this considering the deluge of different resolutions Android developers must cope with? Is there a way to do a table view and return the remaining screen size? Or, am I stuck making an entire new box of Lego here?
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