[android-developers] Singletons in Android .... Final solution?
I have been testing and experimenting with android low end devices and trying to find a consistent solution for singletons in android. I beleive I have gone through most posts addressing this issue and I am pretty sure that I have a good solution. http://www.devahead.com/blog/2011/06/extending-the-android-application-class-and-dealing-with-singleton/ I found that *sometimes some static variables bound to activities happened to be uninitialized even though they’ve previously been initialized!* I thought that when a static variable is initialized it stays so for the entire life of the application, but this doesn’t seem to be the case. Among all the information I found on the web, I tried to find out a *safe and reliable way to initialize static variables* (and you know that the singleton design pattern requires the use of a static variable). The explanation of the weird behavior I saw that makes more sense to me is that *the static variables instances are bound to the class loader of the class that first initialized them*. So what does this mean? This means that if a static variable inside any class has been initialized by an activity, when that activity is destroyed also its class might be unloaded and so the variable becomes uninitialized again! While if the variable is initialized by the application class, it’s life is the same as the application process so we’re sure that it will never become uninitialized again. That’s why I chose to initialize all the singletons in the *MyApplication* class. I want experts to look into this and confirm that this dosent has any serious drawbacks. I am opposing this solution as previously discussed in this same group https://groups.google.com/forum/?fromgroups#!topic/android-developers/2i82mjoM46M/overview Anxious. -- 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+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
Re: [android-developers] Singletons in Android .... Final solution?
I think I got my bit to research further more into it! But just look at this one final argument. I am not telling the solution in my above mentioned post is correct. But the only solution that ensured that my static data was consistent was to convert it from static data to an object of Application class. (The solution that is mentioned in the blog post). Consider this scenario 1) Activity A(SingleTask) launches Activity B 2) Activity B uses static Data containing boolean, int and arraylist. 3) send it to background, and return after 45 mins. Returned to Activity A . 4) Check static Data. int initialized to garbage. Boolean to false. arraylist to null. No, the application wasn't killed or restarted, my logs also show the PID(dosen't change). I am performing absolutely nothing when the app is in background so I am giving android no reason to clear memory or close activity. Convert static data to a object of application class and no logical change at all(I did a Tit for Tat). This issue is fixed. If you think this bit I mentioned is impossible just direct me to a resource/book that makes me design more definite tests to prove this or gives me an insight to static data handling inside the DVM, JVM etc. It cant be possible Mobile OS that has cases of sleep, hibernate, lock and low memory conditions will just make sure that static data stays there. Even if the application is marked as always running. Appreciate your time. On Thursday, 3 May 2012 16:02:37 UTC+5, Mark Murphy (a Commons Guy) wrote: AFAIK, the quoted passage is mostly incorrect. Classes are not unloaded once loaded. There can be issues with static data members if you use multiple ClassLoaders -- AFAIK, you get the same effect in traditional Java. However, you should only encounter that when you create your own ClassLoader for one reason or another. And, of course, when the process goes away, static data members go away, but so do custom Application subclasses. If you examine the Android frameworks' source code, it is littered with static data members. Furthermore, based on a quick survey, only about half of the AOSP apps have a custom Application subclass, and half of those simply use it to initialize static data members. On Thu, May 3, 2012 at 2:01 AM, DebUggEr sjkliteral.w...@gmail.com wrote: I have been testing and experimenting with android low end devices and trying to find a consistent solution for singletons in android. I beleive I have gone through most posts addressing this issue and I am pretty sure that I have a good solution. http://www.devahead.com/blog/2011/06/extending-the-android-application-class-and-dealing-with-singleton/ I found that sometimes some static variables bound to activities happened to be uninitialized even though they’ve previously been initialized! I thought that when a static variable is initialized it stays so for the entire life of the application, but this doesn’t seem to be the case. Among all the information I found on the web, I tried to find out a safe and reliable way to initialize static variables (and you know that the singleton design pattern requires the use of a static variable). The explanation of the weird behavior I saw that makes more sense to me is that the static variables instances are bound to the class loader of the class that first initialized them. So what does this mean? This means that if a static variable inside any class has been initialized by an activity, when that activity is destroyed also its class might be unloaded and so the variable becomes uninitialized again! While if the variable is initialized by the application class, it’s life is the same as the application process so we’re sure that it will never become uninitialized again. That’s why I chose to initialize all the singletons in the MyApplication class. I want experts to look into this and confirm that this dosent has any serious drawbacks. I am opposing this solution as previously discussed in this same group https://groups.google.com/forum/?fromgroups#!topic/android-developers/2i82mjoM46M/overview; Anxious. -- 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+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -- Mark Murphy (a Commons Guy) http://commonsware.com | http://github.com/commonsguy http://commonsware.com/blog | http://twitter.com/commonsguy Android Training...At Your Office: http://commonsware.com/training -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send
[android-developers] Re: Singletons in Android .... Final solution?
I will get back with a test that can prove this, as soon as I lose Codejam :) Thanks for all your time. On Thursday, 3 May 2012 11:01:37 UTC+5, DebUggEr wrote: I have been testing and experimenting with android low end devices and trying to find a consistent solution for singletons in android. I beleive I have gone through most posts addressing this issue and I am pretty sure that I have a good solution. http://www.devahead.com/blog/2011/06/extending-the-android-application-class-and-dealing-with-singleton/ I found that *sometimes some static variables bound to activities happened to be uninitialized even though they’ve previously been initialized!* I thought that when a static variable is initialized it stays so for the entire life of the application, but this doesn’t seem to be the case. Among all the information I found on the web, I tried to find out a *safe and reliable way to initialize static variables* (and you know that the singleton design pattern requires the use of a static variable). The explanation of the weird behavior I saw that makes more sense to me is that *the static variables instances are bound to the class loader of the class that first initialized them*. So what does this mean? This means that if a static variable inside any class has been initialized by an activity, when that activity is destroyed also its class might be unloaded and so the variable becomes uninitialized again! While if the variable is initialized by the application class, it’s life is the same as the application process so we’re sure that it will never become uninitialized again. That’s why I chose to initialize all the singletons in the *MyApplication* class. I want experts to look into this and confirm that this dosent has any serious drawbacks. I am opposing this solution as previously discussed in this same group https://groups.google.com/forum/?fromgroups#!topic/android-developers/2i82mjoM46M/overview Anxious. On Thursday, 3 May 2012 11:01:37 UTC+5, DebUggEr wrote: I have been testing and experimenting with android low end devices and trying to find a consistent solution for singletons in android. I beleive I have gone through most posts addressing this issue and I am pretty sure that I have a good solution. http://www.devahead.com/blog/2011/06/extending-the-android-application-class-and-dealing-with-singleton/ I found that *sometimes some static variables bound to activities happened to be uninitialized even though they’ve previously been initialized!* I thought that when a static variable is initialized it stays so for the entire life of the application, but this doesn’t seem to be the case. Among all the information I found on the web, I tried to find out a *safe and reliable way to initialize static variables* (and you know that the singleton design pattern requires the use of a static variable). The explanation of the weird behavior I saw that makes more sense to me is that *the static variables instances are bound to the class loader of the class that first initialized them*. So what does this mean? This means that if a static variable inside any class has been initialized by an activity, when that activity is destroyed also its class might be unloaded and so the variable becomes uninitialized again! While if the variable is initialized by the application class, it’s life is the same as the application process so we’re sure that it will never become uninitialized again. That’s why I chose to initialize all the singletons in the *MyApplication* class. I want experts to look into this and confirm that this dosent has any serious drawbacks. I am opposing this solution as previously discussed in this same group https://groups.google.com/forum/?fromgroups#!topic/android-developers/2i82mjoM46M/overview Anxious. -- 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+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
Re: [android-developers] Re: PDF Reader in Android OS
Khanh, Please search code.google.com for droid reader. It is full implementation for you. Of course if you are a beginner you will need someone to guide you how to understand it. Also, try to put more understanding to your questions. Sincerely, Jehandad -- 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+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
Re: [android-developers] Re: PDF Reader in Android OS
Thats what droid reader and pdf readers do, they use c library in jni folder of their source. Can you show me how to solve this one? I believe you dont understand the full scale of this project. Its time taking and cant be done through emails or even skype. I also have a hint that you are requiring a single file to be output as executable in android rather than a full pdf reader. Then you can convert them to images and put them in Image view. If not then you are looking for a integration like in windows but thing like that isnt possible without a viewer. So it wont speed up. On Sunday, May 22, 2011 6:00:33 AM UTC+5, khanh le wrote: To be specific, I need a lib to read pdf files and the output of each page will be an image stream. On Sun, May 22, 2011 at 7:55 AM, khanh_qhi™ khanhq...@gmail.com wrote: Hi, My problem is that I want to read an ebook file(PDF extension), but not depend on and pdf viewer app(because it may be slow down program). So, I need an open source to view it, I think it will faster than I use on pdf viewer application. Can you show me how to solve this one? On Sat, May 21, 2011 at 10:45 PM, DebUggEr sjklite...@gmail.com wrote: Khanh, Please search code.google.com for droid reader. It is full implementation for you. Of course if you are a beginner you will need someone to guide you how to understand it. Also, try to put more understanding to your questions. Sincerely, Jehandad -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-d...@googlegroups.com To unsubscribe from this group, send email to android-develop...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -- Regards, Khanh. -- Regards, Khanh. -- 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+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: Sharing data across Activities
Seems like heres the answer. I am not an expert but do consider and let me know too. ANDROID.APP.APPLICATION CLASS Each Android application can have at most one android.app.Applicationassociated with it. You are responsible for sub-classing the Application Class, and it is used to maintain a global state of the application across all Activites. Conceptually, you can think of it as a non-static singleton its life cycle being managed by Android OS. *Benefits:* - Gives you complete control over the management of application life-cycle, so resources can be properly initialised and disposed of. - Provides a single entry point where *any* Activity or Service within the application can gain access to the desired object *Drawbacks:* - Can only expose information to Activities and Services within the application -- 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+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: onBufferingUpdate What is the progress argument
That is a good guess. I will experiment it. -- 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+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: onBufferingUpdate What is the progress argument
I myself dont get what the situation is, the mediaplayer isnt seeking correctly because of it. -- 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+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Answer Incoming call automatically.
Well I need to do to things, 1. automatically answer the calls which are in the blacklist 2. Receive all other calls through the usual android call receiver. I know the first thing is to register intent, but since no activity can handle it, I need to use services and a media recorder somehow in conjunction. Any ideas?? -- 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+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
