Android :: Use Of Static Finals In Activity
Sep 8, 2010
Why is the use of static final variables encouraged to declare constants over just final variables? The use of static sounds logical when there will be many instances of a class but is this argument correct when used for a Android activity. In fact, since the Class instance will be around even after the activity finishes and is eventually garbage collected, it seems like all these constants will still be in memory until the class loader is around. Also, does the compiler inline non-static final variables(ints and String) just like it does for static final variables?
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Nov 17, 2010
Static Layout for whole app that must be in all Activity
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Jan 5, 2010
I am new to Android, and I haven't developed any app regarding databases on Android yet. So I have a few basic questions. I am after a good database class sample, that will let me to run the CRUD operations. I would like to use it as a static class
like: clsDB->Select("select * from clients");
or objClient->Delete(clientid);
I am wondering if someone, can share his database classes, if more people share the best. Also I have in mind to reuse this class in multiple ways, I will have services, activities etc...
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Jun 17, 2010
Since I seem to have caught two activity references in a heapdump, where the Activity is set to singleTask. Romain's advice on avoiding memory leaks includes: "Avoid non-static inner classes in an activity if you don't control their life cycle, use a static inner class and make a weak reference to the activity inside"
What does this mean exactly? I can't find any examples, positive, or negative for this rule. I do have some non static inner classes in my activity. Most of them are anonymous inner classes like this one. I see hundreds of them in the samples:....................
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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 26, 2010
I want to clear variable value when will i close activity.
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Jan 15, 2010
I wanted to create a static options menu for all my activity screens. I dont want to override onCreateOptionsMenu() in each activity. Since Menu class is an interface with a huge number of methods, its difficult to create a static object of the implementing class.
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Oct 28, 2009
I frequently run into the problem that I have to preserve state between several invocations of an activity (i.e. going through several onCreate()/onDelete() cycles). Unfortunately, Android's support for doing that is really poor. As an easy way to preserve state, I thought that since the class is only loaded once by the class loader, that it would be safe to store temporary data that's shared between several instances of an activity in a static Bundle field. However, occasionally, when instance A creates the static bundle and stores data in it, then gets destroyed, and instance B tries to read from it, the static field is suddenly NULL. Doesn't that mean that the class had been removed and reloaded by the classloader while the activity was going through a create/destroy cycle? How else could a static field suddenly become NULL when it was referencing an object before?
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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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Jun 17, 2010
I was just wondering if anyone knows of a way to watch the game on their Droid device. I have been able to see every game, but thanks to poor scheduling at my place of employment, I am not going to be able to see the game tonight. I have an app where I can listen to the game, but tonight is game 7 and I really don't want to miss watching it.
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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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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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Mar 26, 2010
Well after thousands of votes in the Android Tournament two phone have came out on top to this point....The Samsung Moment vs The Nexus One so now is your time to crown the king.Here is how the final four played out.The Samsung Moment vs The Motorola Droid.In a very exciting match-up the Motorola Droid was placed against the Samsung Moment and the voters came out in full force. The Samsung Moment came out to an early lead on day one and went up by 8% but by day two the Droid had cut the gap to 3%. On day four many people were surprised by the amazing comeback that Droid fans produced, Droid votes came from all forums and let the Droid taste its first day on the top of the poll but that would be its only time on top. Yesterday the Moment went on top in a big way and made sure it stayed that way.
The final score was: The Samsung Moment finished with 52% (968 votes) and The Motorola Droid finished with 48% (906 votes)The HTC MyTouch 3G vs The Nexus One.The other match-up between the Nexus One and the MyTouch 3G wasn't as exciting.The Nexus One took and huge lead early and cruised to victory. Here is the results:The final score was: The Nexus One finished with 64% (816 votes) and The MyTouch 3G finished with 36% (456 votes)
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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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Apr 2, 2010
They are at the final battle. It looks like we might have a fight on our hands since the Palm Pre just got the free hot-spot options from Verizon. March Smart Phone Madness Finals: Motorola Droid vs. Palm Pre Plus
The main points that I like to enjoy is: Droid beat out the phone that beat the iPhone, and the Droid got further in the brackets than any other Android OS phone Some of the progress is due to hardware, some due to following (over the Nexus'), but a lot due to the v2.01 (and now 2.1) version of the Android OS. Also, this poll is open ALL weekend - it does not close until April 5th, so we have tons of time...but then again, so does the Palm Pre. Let's have at 'em!
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Jan 4, 2010
Is there a way to get the current Context instance by using a static method? I'm looking for that way because i hate saving the context instance each time it changes.
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Sep 11, 2009
I was working on Freescale iMX31 board, I ported android and it was working fine , but when it came to integration of WiFi & Bluetooth, android forum recommended me to do static compilation for porting over android !
Can I know why some drivers have to be statically compiled before it is ported over android? It was not the case with other drivers which when integrated with android, they worked perfectly well like serial port, usb etc..
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Jul 29, 2009
I use a single static class in my code that defines a static field which I'm reusing between Activity onStop/onStart invocations. Here's a scenario:
User clicks on "Authorize" button (static data is initialized) Activity is stopped and web browser is called
Browser executes callback and Activity is restored (static data is reused)
At least one of my users reports the failure at step 3 which I cannot reproduce but which looks like reset of static data.
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Sep 30, 2010
I am creating an Android application which will have some embedded music inside of it ( ~ 80 MB ). I was planning on putting it in the res/raw folder.
Since android stores that all in it's internal memory, is this way too large? What are my options? I have come up with the following:
Copy resources out of internal storage and onto the SD card when application first starts. Afterwards remove from internal storage (is this possible?)
Download music from the web when the application first starts.
I would really prefer not to have to go with option 2 since I want the app to be entirely offline and the static music is not going to change (except between releases).
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Jun 3, 2009
As a first step toward a speech recognition project, we wrote a simple voice recording application based on the information in this thread:
http://groups.google.com/group/android-developers/browse_thread/threa...
It is working; however, the audio is extremely poor too static for our needs. As a comparison, we did a similar audio file captured with audacity on a PC and it was much better. Has anyone been able to record high quality audio with the android dev phone? According to the documentation of MediaRecorder, there is only one audio encoder "AMR (Narrowband) audio codec" and three output formats--3gpp, mpeg, and raw AMR:
http://developer.android.com/reference/android/media/MediaRecorder.html
According to wikipedia, AMR encoding is only 8hz. Is there a better option available perhaps a lower-level API compared to MediaRecorder? We are testing on Windows XP, with a Logitec USB microphone, eclipse ganymede, and we are using all the defaults for an android 1.5 app (no emulator command-line options. We defined the SD card in AVD manager).
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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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Apr 1, 2009
I have noticed in my application(s) that after a call to Activity.finish() that the static variables that I declared in my classes still hold the values that they were changed to during the activity's life cycle. Upon the re-launch of the activity, the program does not re-instantiate the variables as declared or set them to the default java behavior. Is there something that I can do to cause this to happen, other than re-setting every static variable in my application?
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Feb 15, 2010
I'm trying to handle exceptions at a global level. My understanding is that the only way to do this is with an UncaughtExceptionHandler. However, this reduces one to the primitive java file and network i/o packages. I'd like to be able to broadcast an intent or bind to a service. Is there some way to interact with the android packages to retrieve a context in a static manner? I could probably do some hack workaround with a thread local, weak-referenced context set at the time of the exception handler, but I'd rather avoid that nastiness.
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Jun 12, 2010
I have a ListView with several columns and I need a header row at the very top that labels each of these columns that *does not* scroll with the rest of the ListView. I am using addHeaderView right now, but I've ran into 2 problems:
1) The header scrolls. I need it outside of scrolling so that it's always "floating" on top.
2) Each column in the header isn't lining up with the columns in the listview. I can make the header columns and data columns all line up perfectly if they're all in one big TableLayout, but how would I get the header to be outside of the scrollview yet also stay uniform and inline with the data columns?
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Mar 19, 2010
In android, are using static variables a recommended practice?
E.g, implementing a Singleton pattern in Java, I usually do...
Also, when does this get cleaned up by the Android JVM?
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Sep 30, 2010
I use in the getView()-Method of this example a static function to download the source of an ImageView. Later there will be threading included. However, I like to know in general how save the use of static function is in this case.
Because I experienced, that in some cases (when I scroll really fast) the Images get mixed up.code...
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Jun 23, 2009
My application crashes after I try to use the static Bitmap createBitmap method to get a mutable bitmap in order to fill it later with data.
If I only create one 1024x1024 the application works just fine, but when I try to load the same image more than once (first making my object null in each round) my application crashes on my third or fourth try.
CODE:..........................
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Jul 28, 2010
I am currently developing a simple info app on various uni campuses. I want the app to operate predominantly in an offline state thus I want to store all my information locally. The data within the app will not be subject to any change thus I was wondering what the best (practice) method was to store such data? Basically should I be storing the info in a SQLite db, java file or xml?
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