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  • Determine Android phone's proximity to known point while conserving power

    - by ahsteele
    I am trying to determine if an Android user has had a close proximity to a list of predetermined locations. I'd like to do this with the least amount of drain on the phone's battery. The two mechanisms I see for accomplishing this are proximity alerts and requesting location updates. What are the pros and cons of the two methods? Will one have less affect on the battery than the other? In either case I would guess the specific location manager used would affect power usage (existing Stack Overflow answer).

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  • Best way to check for null values in Java?

    - by Arty-fishL
    I need to check whether the function of an object returns true or false in Java, but that object may be null, so obviously then the function would throw a NullPointerException. This means I need to check if the object is null before checking the value of the function. What is the best way to go about this? I've listed some methods I considered, I just want to know the most sensible one, the one that is best programming practice for Java (opinion?). // method 1 if (foo != null) { if (foo.bar()) { etc... } } // method 2 if (foo != null ? foo.bar() : false) { etc... } // method 3 try { if (foo.bar()) { etc... } } catch (NullPointerException e) { } // method 4 // would this work all the time, would it still call foo.bar()? if (foo != null && foo.bar()) { etc... }

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  • Android - Looking for an AOP solution

    - by Serj Lotutovici
    I'm writing an application that on the bottom line uses it's internal API for some manipulations. The problem is that to call any method provided by that class first I (or anybody who uses the API) have to call #prepare() and after that #cleanup(). It all worked fine until the application and the API started to grow. And the risk of not calling one of the supplied methods before or after the API is now to big to be ignored (which makes it a bug risky application). Searching for a solution I found this question. I use Google Guice in my app for other purposes, but Android doesn't support AOP, that's why a use only guice-no_aop-x.jar. So I end-up with two questions: Is there an AOP solution for android to implement the same approach that is shown in the link above? Or may be someone has an idea that will be suitable for my case? Thanks in advice!

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  • General zoom algorithm for drawing program

    - by Steven Sproat
    My GUI toolkit, wxPython provides some methods for implementing a user zoom factor, however the quality isn't too good. I'm looking for ideas on how to create a zooming feature, which I know is complicated. I have a bitmap representing my canvas which is drawn to. This is displayed inside a scrolled window. Problems I forsee: - performance when zoomed in and panning around the canvas - difficulties with "real" coordinates and zoomed in coordinates - image quality not degrading with the zoom Using wxPython's SetUserScale() on its device contexts presents image quality like this - this is with a 1px line, at 30% zoomed in. I'm just wondering the general steps I'll need to take and the challenges I'll encounter. Thanks for any suggestions

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  • Strange profiling results: definitely non-bottleneck method pops up

    - by jkff
    I'm profiling a program using sampling profiling in YourKit and JProfiler, and also "manually" (I launch it and press Ctrl-Break several times to get thread dumps). All three methods give me extremely strange results: some tens of percents of time spent in a 3-line method that does not even do any allocation or synchronization and doesn't have loops etc. Moreover, after I made this method into a NOP and even removed its invocation completely, the observable program performance didn't change at all (although it got a negligible memory leak, since it was a method for freeing a cheap resource). I'm thinking that this might be because of the constraints that JVM puts on the moments at which a thread's stacktrace may be taken, and it somehow turns out that in my program it is exactly the moments where this method is invoked, although there is absolutely nothing special about it or the context in which it is invoked. What can be the explanation for this phenomenon? What are the aforementioned constraints? What further measurements can I take to clarify the situation?

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  • Home Pages in ASP.NET MVC

    - by Maxim Z.
    I'm trying out ASP.NET MVC, but, after reading a huge tutorial, I'm slightly confused. I understand how Controllers have Actions that URLs are routed to, but how do home pages work? Is the home page its own controller (e.g. "Home") that has no actions? This sounds correct, but how is it functionality implemented without Actions (no Actions means no methods that call the View Engine)? In other words, my question is this: how are home pages implemented (in terms of Controllers and Views)? Could you please provide sample code?

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  • Twisted - how to create multi protocol process and send the data between the protocols

    - by SpankMe
    Hey, Im trying to write a program that would be listening for data (simple text messages) on some port (say tcp 6666) and then pass them to one or more different protocols - irc, xmpp and so on. I've tried many approaches and digged the Internet, but I cant find easy and working solution for such task. The code I am currently fighting with is here: http://pastebin.com/ri7caXih I would like to know how to from object like: ircf = ircFactory('asdfasdf', '#asdf666') get access to self protocol methods, because this: self.protocol.dupa1(msg) returns error about self not being passed to active protocol object. Or maybe there is other, better, easier and more kosher way to create single reactor with multiple protocols and have actions triggeres when a message arrives on any of them, and then pass that message to other protocols for handling/processing/sending? Any help will be highly appreciated!

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  • abstract class MouseAdapter vs. interface

    - by Stefano Borini
    I noted this (it's a java.awt.event class). public abstract class MouseAdapter implements MouseListener, MouseWheelListener, MouseMotionListener { .... } Then you are clearly forced to extend from this adapter public class MouseAdapterImpl extends MouseAdapter {} the class is abstract and implements no methods. Is this a strategy to combine different interfaces into a single "basically interface" ? I assume in java it's not possible to combine different interfaces into a single one without using this approach. In other words, it's not possible to do something like this in java public interface MouseAdapterIface extends MouseListener, MouseWheelListener, MouseMotionListener { } and then eventually public class MouseAdapterImpl implements MouseAdapterIface {} Is my understanding of the point correct ? what about C# ?

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  • The sieve of Eratosthenes in F#

    - by IVlad
    I am interested in an implementation of the sieve of eratosthenes in purely functional F#. I am interested in an implementation of the actual sieve, not the naive functional implementation that isn't really the sieve, so not something like this: let rec PseudoSieve list = match list with | hd::tl -> hd :: (PseudoSieve <| List.filter (fun x -> x % hd <> 0) tl) | [] -> [] The second link above briefly describes an algorithm that would require the use of a multimap, which isn't available in F# as far as I know. The Haskell implementation given uses a map that supports an insertWith method, which I haven't seen available in the F# functional map. Does anyone know a way to translate the given Haskell map code to F#, or perhaps knows of alternative implementation methods or sieving algorithms that are as efficient and better suited for a functional implementation or F#?

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  • How do I throttle my site's API users?

    - by scotts
    The legitimate users of my site occasionally hammer the server with API requests that cause undesirable results. I want to institute a limit of no more than say one API call every 5 seconds or n calls per minute (haven't figured out the exact limit yet). I could obviously log every API call in a DB and do the calculation on every request to see if they're over the limit, but all this extra overhead on EVERY request would be defeating the purpose. What are other less resource-intensive methods I could use to institute a limit? I'm using PHP/Apache/Linux, for what it's worth.

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  • abstract method signature, inheritance, and "Do" naming convention

    - by T. Webster
    I'm learning about design patterns and in examples of code I've seen a convention where the abstract class declares a method, for example: public abstract class ServiceBase { ... public virtual object GetSomething(); and then protected abstract object DoGetSomething(); My question is on why these two methods exist, since they appear to serve the same purpose. Is this so that the base class GetSomething() method logic cannot be overridden by inherited classes? But then again, the method is marked virtual, so it can be overridden anyway. What is the usefulness here in requiring derived class implementers to implement the abstract method when the virtual method can be called anyway?

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  • Interface and base class mix, the right way to implement this

    - by Lerxst
    I have some user controls which I want to specify properties and methods for. They inherit from a base class, because they all have properties such as "Foo" and "Bar", and the reason I used a base class is so that I dont have to manually implement all of these properties in each derived class. However, I want to have a method that is only in the derived classes, not in the base class, as the base class doesn't know how to "do" the method, so I am thinking of using an interface for this. If i put it in the base class, I have to define some body to return a value (which would be invalid), and always make sure that the overriding method is not calling the base. method Is the right way to go about this to use both the base class and an interface to expose the method? It seems very round-about, but every way i think about doing it seems wrong... Let me know if the question is not clear, it's probably a dumb question but I want to do this right.

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  • java: relationship of the Runnable and Thread interfaces

    - by Karl Patrick
    I realize that the method run() must be declared because its declared in the Runnable interface. But my question comes when this class runs how is the Thread object allowed if there is no import call to a particular package? how does runnable know anything about Thread or its methods? does the Runnable interface extend the Thread class? Obviously I don't understand interfaces very well. thanks in advance. class PrimeFinder implements Runnable{ public long target; public long prime; public boolean finished = false; public Thread runner; PrimeFinder(long inTarget){ target = inTarget; if(runner == null){ runner = new Thread(this); runner.start() } } public void run(){ } }

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  • Will there be IQueryable-like additions to IObservable? (.NET Rx)

    - by Jason
    The new IObservable/IObserver frameworks in the System.Reactive library coming in .NET 4.0 are very exciting (see this and this link). It may be too early to speculate, but will there also be a (for lack of a better term) IQueryable-like framework built for these new interfaces as well? One particular use case would be to assist in pre-processing events at the source, rather than in the chain of the receiving calls. For example, if you have a very 'chatty' event interface, using the Subscribe().Where(...) will receive all events through the pipeline and the client does the filtering. What I am wondering is if there will be something akin to IQueryableObservable, whereby these LINQ methods will be 'compiled' into some 'smart' Subscribe implementation in a source. I can imagine certain network server architectures that could use such a framework. Or how about an add-on to SQL Server (or any RDBMS for that matter) that would allow .NET code to receive new data notifications (triggers in code) and would need those notifications filtered server-side.

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  • What is the worst class/variable/function name you have ever encountered

    - by Chris Noe
    Naming things well is arguably Job 1 for professional programmers. Yet we have all suffered from some bad naming choices from time to time. So just to vent a little, what are some doozies that you may have run across? Just to get things started: One of our original developers wasn't sure what to call a secondary key - on what turned out to be a primary table for this app - so he called it: DL2WhateverTheHellThatIs. Unfortunately this system generates entity mappings from the XML, and attributes defined there result in classes, methods, and constants that are referenced through-out the app. To this day it is very hard to find a source file that does not reference this, er, thing! A few actual examples: DL2WhateverTheHellThatIsBean cos = (DL2WhateverTheHellThatIsBean)itr.next(); String code = getDL2WhateverTheHellThatIs().getCode(); From from = new From("DL2WhateverTheHellThatIs"); String filter = "_dL2WhateverTheHellThatIs._code"; (Very difficult to refactor)

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  • haml / rails: yield title with german umlauts

    - by Maxem
    Hi, I would like to do something like this in my application layout: %title= "#{yield(:sub_title)} - Page Name" and in a real view - content_for :sub_title do Übersicht # I tried &Uuml;bersicht, != "&Uuml;bersicht" and a bunch of other methods what happens is, I either get the black pound with the question mark in it - wrong encoding or the raw string (&UumI;bersicht). Does anyone know a way how to get this to work? Another requirement is that I'd like to show user generated content in the title and this content may or may not have umlauts in it. Used versions: Haml 3.0.11, Rails 3 beta4 and currently for development JRuby 1.5

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  • Is it possible to use flashvars with JBoss?

    - by Aikanaro
    Hi, I'm part of a team developing a product using JSF 2.0 and I was asked to investigate the possibility of including FusionCharts free in the app. I have tried different ways of inserting a simple chart in a JSF page but with no luck. On of the methods involves using the elements OBJECT and EMBED but hhen I try to use them I get a "null source" error from JBoss. From what I could find online (through Google), I am under the impression that 'flashvars' isn't quite compatible with JBoss. Is anyone here able to confirm this? If this is the case, what workaround would you suggest me? Other ways I also found online didn't show the chart not even an error message. Thanks in advance.

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  • Microsoft leaning support for VS2010

    - by John
    OK, I am a big fan of WPF, and while it is large area to fully understand, Microsoft has been great in posting loads of training video at http://windowsclient.net/learn/videos_wpf.aspx However with the release of 2010 it all seams to have gone very quite. I expected a lot of the support to be updated for 2010 and I also expected a lot of new videos on the best way to use the new features in 2010. Currently I find myself working through videos based on 2008 (or even 2005) and trying to apply them to 2010. Don't get me wrong it not that I mind doing this, it just that I fear I may be learning methods which have better or different solutions in 2010. It is just me expecting too much of Microsoft, or have I missed out on a new website?

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  • destroy an android service

    - by Jack Trowbridge
    I am using a service in my android app, which is called when an alarm is activated by a calander. When the service has been activated i want it to be destroyed by the OnStart() method once it has completed its code. My OnStart() method: @Override public void onStart(Intent intent, int startId) { super.onStart(intent, startId); Vibrator vi = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE); vi.vibrate(5000); Toast.makeText(this, "MyAlarmService.onStart()", Toast.LENGTH_LONG).show(); //CODE HERE TO DESTROY SERVICE?? } This bassically means when the service is called it runs the code in the OnStart() method and i want it to destroy itself. Any Ideas, methods that would do this?. Thanks, jack.

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  • WCF Service method synchronous/async

    - by Rafal
    Hi I have a problem with calling WCF Service methods with Silverlight 3. private bool usr_OK = false; clientService.CheckUserMailAsync(this.mailTF.Text); if (usr_OK == true) { isValidationOK = true; } else { isValidationOK = false; MessageBox.Show("User already exists.", "User registered succes!", MessageBoxButton.OK); } CheckUserMail should change usr_OK parameter. However it runs in other thread and it does not change the usr_OK param before IF block begins. I've tried thread.join byt the application freezed and i do not know what to do else. Please help me...how can i wait for WCF method to return param usr_OK.

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  • XML over HTTP with JMS and Spring

    - by Will Sumekar
    I have a legacy HTTP server where I need to send an XML file over HTTP request (POST) using Java (not browser) and the server will respond with another XML in its HTTP response. It is similar to Web Service but there's no WSDL and I have to follow the existing XML structure to construct my XML to be sent. I have done a research and found an example that matches my requirement here. The example uses HttpClient from Apache Commons. (There are also other examples I found but they use java.net networking package (like URLConnection) which is tedious so I don't want to use them). But it's also my requirement to use Spring and JMS. I know from Spring's reference that it's possible to combine HttpClient, JMS and Spring. My question is, how? Note that it's NOT in my requirement to use HttpClient. If you have a better suggestion, I'm welcome. Appreciate it. For your reference, here's the XML-over-HTTP example I've been talking about: /* * $Header: * $Revision$ * $Date$ * ==================================================================== * * Copyright 2002-2004 The Apache Software Foundation * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * ==================================================================== * * This software consists of voluntary contributions made by many * individuals on behalf of the Apache Software Foundation. For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * * [Additional notices, if required by prior licensing conditions] * */ import java.io.File; import java.io.FileInputStream; import org.apache.commons.httpclient.HttpClient; import org.apache.commons.httpclient.methods.InputStreamRequestEntity; import org.apache.commons.httpclient.methods.PostMethod; /** * * This is a sample application that demonstrates * how to use the Jakarta HttpClient API. * * This application sends an XML document * to a remote web server using HTTP POST * * @author Sean C. Sullivan * @author Ortwin Glück * @author Oleg Kalnichevski */ public class PostXML { /** * * Usage: * java PostXML http://mywebserver:80/ c:\foo.xml * * @param args command line arguments * Argument 0 is a URL to a web server * Argument 1 is a local filename * */ public static void main(String[] args) throws Exception { if (args.length != 2) { System.out.println( "Usage: java -classpath <classpath> [-Dorg.apache.commons."+ "logging.simplelog.defaultlog=<loglevel>]" + " PostXML <url> <filename>]"); System.out.println("<classpath> - must contain the "+ "commons-httpclient.jar and commons-logging.jar"); System.out.println("<loglevel> - one of error, "+ "warn, info, debug, trace"); System.out.println("<url> - the URL to post the file to"); System.out.println("<filename> - file to post to the URL"); System.out.println(); System.exit(1); } // Get target URL String strURL = args[0]; // Get file to be posted String strXMLFilename = args[1]; File input = new File(strXMLFilename); // Prepare HTTP post PostMethod post = new PostMethod(strURL); // Request content will be retrieved directly // from the input stream // Per default, the request content needs to be buffered // in order to determine its length. // Request body buffering can be avoided when // content length is explicitly specified post.setRequestEntity(new InputStreamRequestEntity( new FileInputStream(input), input.length())); // Specify content type and encoding // If content encoding is not explicitly specified // ISO-8859-1 is assumed post.setRequestHeader( "Content-type", "text/xml; charset=ISO-8859-1"); // Get HTTP client HttpClient httpclient = new HttpClient(); // Execute request try { int result = httpclient.executeMethod(post); // Display status code System.out.println("Response status code: " + result); // Display response System.out.println("Response body: "); System.out.println(post.getResponseBodyAsString()); } finally { // Release current connection to the connection pool // once you are done post.releaseConnection(); } } }

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  • Ruby class instance variables and inheritance

    - by rlandster
    I have a Ruby class called LibraryItem. I want to associate with every instance of this class an array of attributes. This array is long and looks something like ['title', 'authors', 'location', ...] Note that these attributes are not really supposed to be methods, just a list of attributes that a LibraryItem has. Next, I want to make a subclass of LibraryItem called LibraryBook that has an array of attributes that includes all the attributes of LibraryItem but will also include many more. Eventually I will want several subclasses of LibraryItem each with their own version of the array @attributes but each adding on to LibraryItem's @attributes (e.g., LibraryBook, LibraryDVD, LibraryMap, etc.). So, here is my attempt: class LibraryItem < Object class << self; attr_accessor :attributes; end @attributes = ['title', 'authors', 'location',] end class LibraryBook < LibraryItem @attributes.push('ISBN', 'pages'] end This does not work. I get the error undefined method `push' for nil:NilClass

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  • logging in scala

    - by IttayD
    In Java, the standard idiom for logging is to create a static variable for a logger object and use that in the various methods. In Scala, it looks like the idiom is to create a Logging trait with a logger member and mixin the trait in concrete classes. This means that each time an object is created it calls the logging framework to get a logger and also the object is bigger due to the additional reference. Is there an alternative that allows the ease of use of "with Logging" while still using a per-class logger instance? EDIT: My question is not about how one can write a logging framework in Scala, but rather how to use an existing one (log4j) without incurring an overhead of performance (getting a reference for each instance) or code complexity. Also, yes, I want to use log4j, simply because I'll use 3rd party libraries written in Java that are likely to use log4j.

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  • Stack trace for C++ using gcc

    - by dimba
    We use stack traces in proprietary assert like macro to catch developer mistakes - when error is caught, stack trace is printed. I find gcc's pair backtrace()/backtrace_symbols() methods insufficient: Names are mangled No line information 1st problem can be resolved by abi::__cxa_demangle. However 2nd problem s more tough. I found replacement for backtrace_symbols(). This is better than gcc's backtrace_symbols(), since it can retrieve line numbers (if compiled with -g) and you don't need to compile with -rdynamic. Hoverer the code is GNU licenced, so IMHO I can't use it in commercial code. Any proposals?

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  • Eclipse Class File Metadata

    - by Alex
    In Visual Studio, I can obtain a succinct list of public methods/members exposed in a class for which I do not have the source (i.e. bundled inside a DLL) by pressing F12 (GoToDefinition). Similarly, I am learning the Android API - in Eclipse. Jumping to an Android framework method definition produces decompilation output which is not intuitive to read, and is very verbose. To mimic results like Visual Studio, I am considering several options: How can I format the decompilation output to be 'cleaner' - I have looked through Eclipse's preferences menus and have not found a way to do this. How do I 'add corresponding source files' once Google provides it, so that jumping to definition yields the actual definition? Is there a plugin that does this already? I looked into Jadclipse, but that project has not been updated in several years, and is still a decompiler. Thank you in advance.

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