Android :: Activity / Process Lifecycle - Save / Load Data To / From Disk
Nov 26, 2009
My app is made of two activities, A and B. I'm considering this sequence of steps: Activity A is started. A launches B [A is paused, B is running]. B launches a map intent [A and B are both paused now]. Now the user is using the maps application and the system decides it needs more memory. Can the system kill only one of my activities for memory, or will it always kill all activities in a "process" in this situation?
Both activities share some static data like:
class Data {
public static String mName;
public void save() {
// write to file: mName;...................
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Mar 16, 2009
I'd been using my own Camera class for taking images and my own database but soon enough I couldn't really keep up with changes and I decided to use the built in camera application in Android to do the job, but I can't seem to get it to save file. What am I missing here? The application seems to save the file but it's just 0 bytes. I looked up the source code of the Camera application and it's looking for the "output" in Extras to save the file.
Public class CameraTest extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);...............
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Mar 18, 2009
how to measure Disk Activity and Disk Usage on android ? Unfortunately iostat is not available in Android. I would like to monitor Data read and Data written for disk activity and Utilized and Free space for Disk Usage. I found diskstats but I don't know how to read it.
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Mar 14, 2010
I think i'm getting senile because I was convinced that to give a name to your application, you had to fill this part of the manifest: <application android:icon="@drawable/icon" android:label="MyApplicationName"> However for a reason I don't understand, my application gets the name of my first activity, in which I load data, henceforce, It is called "Loading"...(defined as follows in the manifest) <activity android:name="AccueilSplash" android:label="Loading">
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Nov 12, 2010
i am fetching XML from the web, parsing it and display it on the screen. The problem which i am getting is that the activity tries to load the data from web each time the activity is called.(Actually, my mobile app requires frequent trips to the server) So i am in search of the below solution: On Re-launch of an activity, the data from web should not be loaded again. (But it should load data from the cache or local database that we have created while calling the web-xml for the first time). creating a class that i can use to transparently make application faster by selectively caching items in memory. And thus, making users very happy and This class can even apply individual refresh times to each cached item.
So, i think i need to store the data in Cache , or in local database or something like that. Is there any way/technique to implement such thing ? so that it need not to load from web every-time on Re-launch of an activity. [Note: I want to do to make client happy by decreasing the loading time and running the application efficiently and optimizing application's loading time]
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Apr 11, 2010
I have a widget that supposed to call an Activity of the main app when the user clicks on widget body. My setup works for a single widget instance but for a second instance of the same widget the PendingIntent gets reused and as result the vital information that I'm sending as extra gets overwritten for the 1st instance. So I figured that I should pass widget ID as Intent data however as soon as I add Intent#setData I would see in the log that 2 separate Intents are appropriately fired but the Activity fails to pick it up so basically Activity will not come up and nothing happens (no error or warning ether)
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Sep 27, 2009
This is with the 1.6 & 1.5 SDKs, not tried earlier ones. When you switch from portrait to landscape the onSaveInstanceState()/ onRestoreInstanceState() pair are called once, but when going back from landscape to portrait they are called twice, unless I've missed something. To test, see the log after creating a default Hello World app and change the main class like this: code...
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Oct 5, 2010
In the Android Application Fundamentals it says that after the call to the onStart()-method of the activity lifecycle either the callback method Resume() or onStop() is called. In case of an "normal" Start of an activity the system calls onCreate(), onStart(), onResume().But does somebody know an example where onStart() - onStop() are executed one after another?
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Jul 14, 2009
I just ran into a situation where it looks like a static variable reference is persisted across activity sessions. I didn't expect that because I thought that when an activity exits, it's de-referenced and garbage collected. I am wondering if anyone can shed some (more) light on when the VM eliminates object references for Activities and Services and in particular when static variables get reset to default values?
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Aug 7, 2009
http://developer.android.com/reference/android/app/Activity.html
The Activity Lifecycle could have implementation and or design bug: One case is to initialize a big image in onCreate(), try to reuse the image during the whole lifecycle, and then recycle the image in onDestroy(). Test showed that onCreate() is called every time one navigate away from the activity and back again, but onDestroy() is not called at all. This behavour causes memory leaking for the big image (size 960*1920). After 6+ times away and back to activity, the system runs out of memory and has to kill the process.
One workaround is to initialize the big image in onResume() and recycle in onPause(), but that's not so good reuse.
Could it be better to change the process (as shown in the diagram) a little bit such as: Call onDestroy() first when a process is killed?
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Sep 22, 2009
I am doing a painting program (KIds Paint - you can find in Android Market) and I have a lot of requests to save the content on disk or to wallpaper. I have been searching around but cannot find solution. My guess is that I probably wanted to get the bitmap from the canvas, but I can't find ways to get it. Then I try to set an empty bitmap into the canvas and draw on the canvas, and save the bitmap... but I got an empty bitmap..........
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Mar 4, 2010
I have a problem with the activity lifecycle specifically on Nexus One (2.1 running on emulator works fine). If I just create a simple empty Activity with no special launchModes that logs the calls on the onStart and onStop methods, this is what I see: - launch app: onStart called; - home button: onStop NOT called; - launch app: onStart NOT called; - home button: onStop NOT called: and so on. Sometimes if I press the back button then the onStop is not called, but the when i launch the activity again the onStart is called and right after the onStop is called. Similar results with different launchModes. What is going on? Can anyone confirm this?
i found an android issue for the problem here: http://code.google.com/p/android/issues/detail?id=6094 and a similar thread here http://groups.google.com/group/android-developers/browse_thread/threa.
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Jul 12, 2010
I have a custom view on which I need to call a method from my activity after the view has been measured in onMeasure. I would like to know exactly when onMeasure is called in the View layout process. It looks like onMeasure is called after my activity´s onCreate, onStart, and onResume. I could override onMeasure and maintain a variable that contains whether the view has been measured or not. However it would be nice to know if there is a rule that relates onMeasure to the activity lifecycle?
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Sep 15, 2010
I'm binding to a local Service (that is, not using IPC and AIDL) from several activities. I want to ensure that I'm not holding references to this service from activities that the user isn't using. My options are: 1.) to bind to the service in onCreate() and unbind in onDestroy(). 2.) bind in onStart() and unbind in onStop(). 3.) bind in onResume() and unbind in `onPause(). Or some combination of these. Which is the best-practice way of binding and unbinding to a local service? Do I not need to be concerned with holding local connections from stopped activities? Additionally, once bound to this particular service I am retrieving a Cursor which is attached to my ListActivity via a CursorAdapter. The data retrieved by the Cursor may have changed while the Activity was out of view so I want to requery it when the Activity is shown again. If I bind in onCreate() I can requery in onRestart(). If I bind in onResume() each time the data will be fresh because I'll query it in the Service's connected callback.
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Oct 4, 2010
I'm having a couple of problems with an alarm app I am developing.
The first thing that I think is a bit weird is that when an alarm goes of and wakes the phone up. These things happend.
oncreate
onresume
onpause
onresume
Why are they run in that order? The last two should not be called? And this is what's causes me big trouble, because when i press home or back on the phone, onPause is run, which I want to call finish() from. And that part works as it should, but that does not work when the phone wakes upp from sleep bacause of the onPause call...
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Apr 20, 2010
I have creating application with 3 activities, where A - list of categories, B - list of items, C - single item. Data displayed in B and C is parsed from online XML. But, if I go trough A -> B1 -> C, then back to A and then back to B1 I would like to have it's data cached somewhere so I wouldn't have to request XML again.I'm new to Android and Java programming, I've googled a lot and still can't find (or simply do not have an idea where to look) a way to do what I want.Would storing all received data in main activity A (HashMaps? ContentProviders?) and then passing to B and C (if they get same request that was before) be a good idea?
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Aug 3, 2010
I want to get the size of a view that is in my activity but I am not able to get that information in any of the activity lifecycle callbacks (onCreate, onStart, onResume). I'm assuming this is because the views have not been drawn yet. At what point are views drawn and is there a callback I can put my code so I can get the size of the view?
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Oct 26, 2012
I'm writing an application for Android and have multiple Activities, there are three to be exact. When a user drills down to the record they would like to view, they can modify it.
The issues is that when I click the back button to move to the previous screen, i'd like to refresh it to reflect the update performed by the end user. I can't figure out how to hook onto the appropriate event and then refresh my data on that view.
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Nov 17, 2010
I'm fairly new in Android/Java programming, so some of the basic stuff is still quite confusing. So, lets say my application gets all data (articles) it requires from external XML files, it parses them to data models (Article class) and those articles will be used (displaying in lists or single article) all over the application for all it's lifecycle.
Where should I keep them? Can I create singleton class with an array containing all the articles I've parsed? Or should I save them to database and then query it on demand? (that sounds like too much work, I don't need to cache them for now) What's the best practice here?
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Sep 4, 2010
Is it possible to load a layout XML at runtime and load into activity?
In my app, I have various types of data like Person, Company, City, etc; The requirement is to dynamically load the layout, find views by tags (property names like Person.name, Person.address) and then fill in data. For example, if user has selected an object of type Company, we want to load a company.xml layout, inflate it and then associate various properties (company name, company slogan, city, address, revenue) to tagged views. One possibility I see here is - each view in the layout will be associated with property-name as tag and then appropriate data will be loaded in appropriate views.
What should be the best design you would recommend?
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Aug 4, 2010
I want to save my contacts onto my computer hard drive. Where on disk is the file responsible for saving all the contacts?
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Aug 2, 2010
Whenever the memory needs to be reclaimed, the process is being killed by Activity Manager Service in killPidsForProcess. I have a back button in my activity window on right corner of the title bar.
I want to kill the activity completely on clicking the close button. Can I reuse the same function and will it have any major effect? Please help me out in this.
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Aug 27, 2010
My app is comprised of a set of reusable Activities that other apps can reuse. For various reasons, I would like my Activities to be launched in context of the invoking Activity's process, instead of always being launched in my Activity's process (default behavior on Android). How can I achieve this?
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Jun 14, 2010
I'm interested in android activity lifecycle and I would like to get more detailed description/documentation/reference than widely available basic (onCreate->onStart->onResume) one.
My need comes from realizing that starting new activity (Theme.Dialog styled) from onAttachedToWindow() greatly improves response time if comparing to starting it from onCreate(). I wonder how this onAttachedToWindow() fits into whole android activity lifecycle. Official API ref description "Called when the window has been attached to the window manager" doesn't help a lot.
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Jan 3, 2012
I have device Acer Liquid E , ROM MIUI 1.12.23.
When i listen music (no matter what player is used) system proccess Mediaserver very load CPU, so drain battery (see screenshot) This manifested itself in either the firmware from the 2.2 Android
dl.dropbox.com/u/18014239/%D0%BC%D0%B8%D1%83%D0%B8/device-2012-01-03-100816.png
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Jul 24, 2010
I am a beginner Android developer and I need to know how to Save and Load images (Bitmaps) from the Android Gallery, But I dont even know where to start! Can someone help me to know where to get started, or even look?
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Nov 29, 2009
Snesoid seems to solely rely on save state files and not on actual battery saves used on the original cartridges (.sav) files. These are also smaller in file size and using these instead of savestates makes it feel more like playing an SNES (not being able to use savestates) but relying on the games own way of saving your progress. These .srm battery saves are easy to find so it's much easier to load up my Super Mario Kart with special courses unlocked
Gameboid for GBA games uses the actual battery pack saves, .sav files...
So why isn't snesoid able to do this or am I doing something wrong? I use the Motorola Droid.
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Jul 29, 2010
In order to keep some native code happy, I need to launch an activity in a new process. Does anyone know how to do this?
I can set the activity's process attribute in the manifest, but this will cause *all* instances of the activity to appear in the *same* process, which I can't have.
I'm willing to use internal APIs for this, and I've found Process.start(), but it's not at all clear how this is supposed to be used.
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Jul 21, 2010
Suppose my application P started Activity A, and A started Activity B, then the activity stack contained A and B, with B at the top.
After that, I opened other apps by pressing Home button. Suppose after a while, the process of application P is killed by the OS. Then, I press Home button to select application P. At this time, which activity will be brought to the front, Activity A or Activity B?
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Mar 19, 2010
I'm working on establishing a two-way communication between an Activity and a Service which runs in a different process.
Querying the process from the Activity is no big deal. But I want the process to notify the Activity on events. The idea behind it is this: the service runs independently from the actual app. It queries a webserver periodically. If a new task is found on the webserver the process should notify the activity.
I found this thread over at AndDev.org but it doesn't seem to work for me. I've been messing around with BroadcastReceiver. I've implemented an interface which should notify the Activity but the problem is that the listener is always null since the Broadcast from the process is done via Intent, hence the class that extends BroadcastReceiver will be newly instantiated.
How can I establish a 2-way communication? This has to be possible.
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