I see a lot of Java code where android prefers to have developers use static inner classes. Particularly for patterns like the ViewHolder Pattern in custom ListAdapters. I'm not sure what the differences are between static and non-static classes. I've read about it but it doesn't seem to make sense when concerned with performance or memory-footprint.
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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:.............................
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:....................
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?
View 2 Replies View Relatedi 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();
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!
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.
Just a small discussion. Curious as to why people prefer Sense-less ROM's. Android is the best cell phone OS I have ever used, and I think the SenseUI only improves it, aesthetically(sp?) and socially speaking. The tiny lag my Hero suffers is worth it for all of the beautiful widgets, the launcher, the Facebook and Twitter integrations and did I mention. I have never described anything electronic as beautiful before! The stock Android look captivates me until I use it. It seems so bland and *ugh* to me. And as far as speed goes, the Senseless ROM's I have tried are no faster then the Fresh ROM I am running, and if it is it's completely unnoticed by me. But anyways I am just curious what reasons you have for using the SenseUI or stock Android OS, whether it be for apps to run more efficiently, speed, whatever. Just curious, might try a couple new ROM's soon.
View 8 Replies View RelatedI have multiple applications which use the same ContentProvider code for internal WebView to access local files (application private). Because the ContentProvider has the same code base (package name, content uri), this will cause problem when deployed 2 or more of my application in the same device? How do I make the contentProvider only accessible by its application and prefer a solution without code changes.
View 7 Replies View RelatedI 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
Does Android prefer a specific phone number formatting when syncing?
For example when entering in a contacts info in gmail should I be using dashes (1-666-555-7777) or just putting in 16665557777
I know this has probably been gone over before, but I'm still looking for an LED Flashlight for the HTC Incredible. Any word on if there is one or if there is one in the works? I'd prefer to not root my phone.
View 9 Replies View RelatedPlease answer the poll and state why your prefer the method you use.
View 21 Replies View RelatedWhy 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:.................
I hate soft keys. They're hard to see. It's hard to know whether I pressed them. I often press them accidentally. They add absolutely nothing to the phone. In short, soft keys suck.
View 18 Replies View RelatedHow can I set my Galaxy Nexus to prefer WiFi for data over the Mobile Network? I have to go to settings, turn off "enable data access over mobile network," then cycle WiFi on-off several times before the phone will connect to my home router. Router has two channels, both a WPA2 encrypted one, and a "home guest" (open) one. Both show up as disabled until I cycle the WiFi off and on several times. There must be a setting to tell the phone to prefer WiFi -- no?
View 12 Replies View RelatedI want to use the accessibility classes, but I'm a begginer in android programming and i can't understando how to use them. I don't find any example using these classes. Somebody can give me some use examples? Another thing Can I set enable the Accessility mode in the emulator?
View 2 Replies View RelatedI am writing a app, which has sort of plugin framework. public abstract class AbstractService {public abstract AbstractService getInstance(String name)..
View 2 Replies View RelatedI have an apk installed in /data/app. I want to use the class methods in there. Here is what I tried. code...
I got "ClassNotFoundException". By peeking into the apk, I don't see class files but classes.dex. I would assume SystemProperties class is in classes.dex. Why can I load it?
I am developing sample Video Recorder for Android.Following is My code snippet.
CODE:............
But when i am trying to run in eclipse,am getting following errors. MediaRecorder.VideoSource can't be resolved. MediaRecorder.VideoEncoder can't be resolved.
I am using android-sdk-windows-1.1_r1 as my android SDK,and didn update this from 1.0 instead i installed it freshly.
I guess there might be some problem with the SDK.
I am looking for the implementation of the IAlarmManager.I am interested in the scheduling done by the AlarmManager.setInexactRepeating method and so I started looking for the implementation but I haven't been able to find anything.Internally to AlarmManager, I can see that the actual work is being done by an android.app.IAlarmManager interface.After googling around for a bit there seems to reference to an implementing class called android.app.IAlarmManager.Stub but that is as far I get.I am working with Android 1.6.
View 1 Replies View RelatedI have an app I am working on and being new to Android Dev I am running into a situation. I have a Scores class not extended from anything (Activity,Service, etc) but in the same package that needs to access SharedPreferences
public class Scores {
Context ctcx;
public Scores(Context context) { ctcx = context;
}
I am trying to determine how to structure the code of a simple android game I am writing. I am focused on the UI portion. The behind the scenes portion (like a pause/restart/switching/etc) does not concern me. The Android demo games source code already do a great job with this. Essentially my game will need a UI with a series of objects on the screen (roughly 100 or 10x10) that the user can interact with. I need to supply an image for each object as well as implement the touch events and animation events for each object. What I am wondering is what type of class do I use for each object so that I can successfully implement these methods and how do I implement that particular class. Note that this game only executes on a user interaction with one of these objects, meaning I don't need a "real-time" implementation.....
View 2 Replies View RelatedI have read the Backward Compatibility Article, and I don't full understand how (or if I can) make a program backwards compatible if I want to use a class introduced in later versions. For example, I want to use WallpaperManager for apis 5+, but make the app as a whole compatible with api 3+. Is this possible?
View 14 Replies View RelatedSince i'm still new on Android programming, I have some problems on some issues. I have a QuadTree data structure implementation in 3 seperated Java files and i would like to use this data structure in my application. But i don't know how to use this .java files in an Android project. I tried to put them in a new Android project, just for testing, but I get lots of errors. Could anyone help me about using this java classes in my Application?
View 3 Replies View RelatedI have a class2 which is involved by class1 when clicks are made. I have to pass some parameters/objects from class1 to class2. I only know the standard way which does not have an option of passing parameters.
CODE:.................
How can I install java classes not included with android ?
Is it possible to add java.awt.image package into android?
Where can I find above package jar file?
This is a very weird problem. My app that runs just fine but somehow if I leave my phone for an hour or two while my app is running, I get the following error when I come back to it later:
CODE:................
I know for a fact that my yoga.database.Manager class was loaded at the time when the app was launched, but somehow the class must have been unloaded by the system as I left the phone.
Does Android unload classes automatically after certain periods? What can I do when my class gets unloaded? The above error causes my app to crash, but I can easily re-launch it and it runs just fine. The problem occurs mostly on my HTC Magic phone running Android 1.6.
I have a couple of third party classes which serve as a library I can build my application upon. They are contained in a folder which was added Java Build Path -> Libraries (in Eclipse) with "Add Class Folder". It works fine so far an my app compiles. But the produced .apk contains only my classes and therefore the application does not run. How can I tell Eclipse to package the third party classes into the .apk as well?
View 1 Replies View RelatedI have a bunch of objects that implement Serializable that I want to store in a SQL database.
I have two questions:
Is there a way to serialize the object directly into the database. Is that the best way to do it or should I Write the object out to a formatting String and put it in the database that way and then parse it back out
Write each member to the database with a field that is unique to each object.