Android :: Android Static Object Lifecycle
Dec 22, 2009
I am creating event search application, we set search criteria from one screen populate in another screen then user can edit search criteria from 3rd screen and goes to 4th screen.To achieve above task i am using static object which remember the values around the application and i don't need to do any thing extra.But i am afraid if about static object life cycle in android if low memory found android delete static objects?As android supports multi tasking, if user switches to another application and when user comes back application start acting crazy, does static object get removed when it multi task?and also suggest holding static object via singleton method is better approach?
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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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Oct 19, 2010
In my Android application, I have to call the getSharedPreferences in non-activity classes. In order to avoid passing a Context object to each constructor of these classes (and because many of them are classes with only static methods which don't have a constructor), I have implemented these steps : The main activity of my application (which is launched at startup) is called Dispatcher. In the onCreate method of this class, I keep a reference to the created Dispatcher object in a static public variable of the Dispatcher class which can be accessed from any class in the project.
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Mar 20, 2012
I am developing an application which incorporates socket programming. I need to refer to the socket object created in the starting application when connected to a server in any other activity in that application .
Can I define a class in an acitivity and define a socket as a static field in that class and refer to that socket object from any other activity in that application?
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Mar 30, 2010
i want to display a msg to the user (msg box or Toast) when exception happend in a static SQLite Database class that i use. the problem is that i cant call a non static method in a static class , how can i handle this. this is the class
private static SQLiteDatabase getDatabase(Context aContext) {
and i want to add something like this in the class when exception happen but context generates the problem of reference to non static in static class.
Context context = getApplicationContext();
CharSequence text = "Hello toast!";
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, text, duration);
toast.show();
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Feb 7, 2010
I'm having some issues with the old "Cannot make a static reference to a non-static method" error in my Android program. I am creating a sand falling game (similar to the Powder Game) and I created a class called Control to create a Control Bar at the bottom of the screen with a slider for brush size (that works fine) and a button to pop up a Dialog to allow users to pick the selected element. However, when I call DemoActivity.showDialog(2) from my code, it gives the static reference to non-static error (DemoActivity is the main activity of my application). I also tried changing it to just Activity.showDialog(2), but I got exactly the same error!
Here's my code:
CODE:................
I fixed it by adding the following to my Control.java code:
CODE:..........
And then calling control.setActivity(this); from my onResume section of DemoActivity.java!
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May 26, 2010
I am modifying the source code here: http://thinkandroid.wordpress.com/2009/12/30/getting-response-body-of-httpresponse/
I get this error:
code:.............
This error is line 13 on the second box.
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Mar 9, 2009
I have been finding it convenient to extend Handler in many of my activities to handle messages specific to the activity. The handler sublass is an inner class of the activity and needs to access its state. I am wondering if there is any performance difference between making the handler subclass static and passing in the activity explicitly in its constructor or making the subclass an "instance class" and letting the vm worry about my accessing members of the containing activity.
The static approach:
CODE:.............................
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Sep 9, 2009
I want to do some automated testcase with Instrumentation . Suggest that my AUT has 2 Activity. After clicking the button in ther first Activity, the second one will be shown with new content base on what we enter in the first Activity.) Instrumentation provides us the function called startActivitySync() and return the Activity object for processing. My question is how we can get the pointer of the second Activity after the it is shown by clicking the button on the first activity.?
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Jun 8, 2009
I would like to convert a Picture object to Bitmap object in memory, without writing data to disk.
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Mar 18, 2013
I have Eclipse Juno and I'm working on an app with that.
The main activity will have a scrollable menu that takes you to all the other activities.
So the general structure/outline right now:[HIGH]Relative Layout ImageView (header logo type thing) ListView (the actual scrollable menu)[/HIGH]Here's the problem though... I can't find any simple list tutorials. I can easily make a single line list work but I need to make a two line list and one that is static, not dynamic and no examples are out there for that. It's like if you want to make a 2 line list, you can only learn how to do it in the most code-heavy ridiculous way possible.
Essentially what I am looking for with the list is this: Item one: Centred, bold, non selectable title (Resources)
- Item two-??: two line list items, click-able to a new activity, title of the section on first line, description on the second line.
- Item ??: Centred, bold, non selectable title (Tools)
- Item ??-??: two line list items, click-able to a new activity, title of the section on first line, description on the second line.
Nothing dynamic that is ever going to change, no super complex wonkey calculations, just to simply have the data set in stone (preferably via XML) and to call it into the list.
I experimented with some of the other list views and no matter what I did, I could get, via editing the resources and NOT using Java, more that one item on a single line but it wouldn't format it properly according to the layout I guess because I haven't got the ID correct or whatever I don't know.
I mean, all the examples I've seen for a 2 line list are extraordinarily over-coded and just bloated. I mean I have a website I am still working on in C#/ASP.net that has far more complex things in it with half the code that I've seen for the examples of the two line lists.
I tried on my own to figure it out (I am decent with C# and vaguely familiar with Java, self taught, and programming for some other systems like Python, again all self-taught), but like ALL coding references, they're organised by the actual code you implement (that you don't know) instead of by what you want it to do (so you have to search the whole code base to find something that you don't know what it's called but know what it does). >:C
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Sep 21, 2009
I have an Activity that running on system. I can get the Intent that is used to start the activity. But i don't know how to get the Activity object from the Intent object or something else. Can anyone tell me how to do this??? Note that, I don't use Instrumentation object.
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Apr 5, 2010
In my application I have several activities, the main screen has 4 buttons that each start a different activity. So one of them is a search activity, once it searches it shows you a result activity. This result activity can be reached from other activities, so in general something like this:
Main activity -> Search activity -> Result activity
Main acitivty -> someother activity -> Result activity
Now, if I have reached this result activity and press back once or twice, and after that press the Home key it will show the Home screen. But if I want to get back to my application by holding the Home button and clicking on my app it will always go back to the Result activity, no matter which activity was the last one I was using. And if I press again back it will take me back to the Home screen.
If I try it again it will take me again to the Result activity. The only way to avoid this is to start the application by clicking on the app's icon. And this takes me to the last activity I was using and it remembers the state so if I press back again it doesn't take me to the Home screen, instead to the activity before it. To illustrate this:
Main activity -> Search activity -> result activity --back--> Search activity --Home Button--> Home Screen --Hold Home and select the app --> Result activity --back--> Home Screen
--Click application icon--> Search activity --back--> Main activity
Another thing that happens is that if I press the Home button while on the Result activity, and start the app by clicking the icon, it will take me to the activity prior the the Result one.
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Sep 10, 2010
There's a decent amount of information out there on the Activity lifecycle. But I'm surprised how difficult it is to find a comprehensive description of the rendering lifecycle. By that I mean the order and rules by which a tree of nested activities, views, and drawables get to be sized and drawn to the screen, and the points at which a developer can modify rendering behavior.
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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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Feb 7, 2010
I am having difficulties with the lifecycle of the opengl context. While rendering my scene and the user hits the back button, home button or another application opens in front of my application, my app is still running in the background.
So when my application comes to the foreground later on (user relaunches it or the app that was opened on top of it finishes), my application crashes and leaves me nothing but a GL stack trace which i can't properly decipher.
For rendering i use the GLSurfaceView and therefore delegate the onPause and onResume. The crash happens on the first call to glDrawElements(..).
I have tried to reload my resource (geometry/textures etc.) on onSurfaceChanged but with or without reloading... The problem persists.
This behavior can be observed on all AVD versions of the emulator as well as on the G1.
Here is the gl stacktrace i get.
CODE:.............
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Jul 8, 2010
I am trying to create a Servicefor my application which will negotiate Bluetooth connections and data. I want this service's lifecycle to start and end with the Application, but still be able to have specific Activities listen for events that occur within this service (in addition an Activty should be able to call specific methods of the Service to write data or query connection state).
I started by creating AIDL interfaces for my callbacks and service, but I can't figure out exactly what I'm doing.
How is the best way to go about this? EDIT: To be clear, I do not specifically need (or want) more than one process for my application. Right now I don't have more than one; I'm just using AIDL because it is the only way I know of for a Service to communicate with an Activity.
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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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Apr 19, 2010
I slapped together a simple test application that has a button, and makes a noise when the user clicks on it.
Here are it's method:
CODE:..................
My question is, why is onCreate acting like it's in a while loop? I can click on the button whenever, and it makes the sound. I might think it was just a property of listeners, but the Button object wasn't a member variable. I thought that Android would just go through onCreate onse, and proceed onto the next lifecycle method. Also, I know that my current way of seeing if the sound is playing is crap...I'll get to that later.
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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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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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Feb 6, 2010
I've an App which performs a potentially large download in background thread. When the orientation changes or the keyboard is opened the App lifecycle system invokes the start/stop/pause/resume etc calls - is there any strategy available to resume the download rather than just set a flag so the new onCreate() knows it was interrupted and has to start it again?
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Sep 15, 2010
Why should a static method in java accept only final or non final variables within its method, but not static?
For example I have the following method:
CODE:.................
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Feb 18, 2009
I am trying to get a FileInputStream object on an image that the user selects from the picture gallery.
This is the android URI returned by android.provider.MediaStore.Images.Media.INTERNAL_CONTENT_URI content://media/external/images/media/3
When I try to construct a java URI object from this object, I get an IllegalArgumentException with the exception description Expected file scheme in URI: content://media/external/images/media/3 whereas the android URI shows the scheme as content
Never found a solution for the original question. But if you want the byte stream of an image in the pictures gallery, this piece of code will do that.
CODE:...................
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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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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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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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