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  • Sorting 1000-2000 elements with many cache misses

    - by Soylent Graham
    I have an array of 1000-2000 elements which are pointers to objects. I want to keep my array sorted and obviously I want to do this as quick as possible. They are sorted by a member and not allocated contiguously so assume a cache miss whenever I access the sort-by member. Currently I'm sorting on-demand rather than on-add, but because of the cache misses and [presumably] non-inlining of the member access the inner loop of my quick sort is slow. I'm doing tests and trying things now, (and see what the actual bottleneck is) but can anyone recommend a good alternative to speeding this up? Should I do an insert-sort instead of quicksorting on-demand, or should I try and change my model to make the elements contigious and reduce cache misses? OR, is there a sort algorithm I've not come accross which is good for data that is going to cache miss?

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  • Adding cancel ability and exception handling to async code.

    - by Rob
    I have this sample code for async operations (copied from the interwebs) public class LongRunningTask { public LongRunningTask() { //do nowt } public int FetchInt() { Thread.Sleep(2000); return 5; } } public delegate TOutput SomeMethod<TOutput>(); public class GoodPerformance { public void BeginFetchInt() { LongRunningTask lr = new LongRunningTask(); SomeMethod<int> method = new SomeMethod<int>(lr.FetchInt); // method is state object used to transfer result //of long running operation method.BeginInvoke(EndFetchInt, method); } public void EndFetchInt(IAsyncResult result) { SomeMethod<int> method = result.AsyncState as SomeMethod<int>; Value = method.EndInvoke(result); } public int Value { get; set; } } Other async approaches I tried required the aysnc page attribute, they also seemed to cancel if other page elements where actioned on (a button clicked), this approach just seemed to work. I’d like to add a cancel ability and exception handling for the longRunningTask class, but don’t erm, really know how.

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  • C++ Problem: Class Promotion using derived class

    - by Michael Fitzpatrick
    I have a class for Float32 that is derived from Float32_base class Float32_base { public: // Constructors Float32_base(float x) : value(x) {}; Float32_base(void) : value(0) {}; operator float32(void) {return value;}; Float32_base operator =(float x) {value = x; return *this;}; Float32_base operator +(float x) const { return value + x;}; protected: float value; } class Float32 : public Float32_base { public: float Tad() { return value + .01; } } int main() { Float32 x, y, z; x = 1; y = 2; // WILL NOT COMPILE! z = (x + y).Tad(); // COMPILES OK z = ((Float32)(x + y)).Tad(); } The issue is that the + operator returns a Float32_base and Tad() is not in that class. But 'x' and 'y' are Float32's. Is there a way that I can get the code in the first line to compile without having to resort to a typecast like I did on the next line?

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  • User switching without logging off

    - by mrh1967
    We need to switch users without logging off so we can remotely administrate a PC running with a limited user that will disconnect from the VPN if the user logs off. I've got this working by killing the explorer process and then running explorer.exe with the administrator user credentials as the following code shows: private void btnOk_Click(object sender, EventArgs e) { IntPtr tokenHandle = new IntPtr(0); if (LogonUser("administrator", Environment.UserDomainName, txtPassword.Text, 3, 0, ref tokenHandle)) { ProcessStartInfo psi = new ProcessStartInfo(@"C:\Windows\explorer.exe"); psi.UserName = "administrator"; char[] pword = txtPassword.Text.ToCharArray(); psi.Password = new System.Security.SecureString(); foreach (char c in pword) { psi.Password.AppendChar(c); } psi.UseShellExecute = false; psi.LoadUserProfile = true; restartExplorer(psi); this.Close(); } else { MessageBox.Show("Wrong password", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation); } } private void restartExplorer(ProcessStartInfo psi) { Process[] procs = System.Diagnostics.Process.GetProcesses(); foreach (Process p in procs) { if (p.ProcessName == "explorer") { p.Kill(); break; } } System.Diagnostics.Process.Start(psi); } [DllImport("advapi32.dll", SetLastError = true)] public extern static bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword, int dwLogonType, int dwLogonProvider, ref IntPtr phToken); This code and similar code that does the same but makes the ProcessStartInfo for the limited user works perfectly and allows changing between the limited and administrator accounts without disconnecting the VPN but it has one problem - If we use this to change to the administrator user, make some changes to the system, then change back to the limited user all works ok until the limited user logs off when a blank desktop is displayed until CTRL-ALT-DEL is pressed and the user is logged off again. Because we block CTRL-ALT-DEL the PC effectively hangs until it is powered off. Does anyone know how to stop this from happening so we can change users without the PC hanging when they log off?

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  • How can I prevent infinite recursion when using events to bind UI elements to fields?

    - by Billy ONeal
    The following seems to be a relatively common pattern (to me, not to the community at large) to bind a string variable to the contents of a TextBox. class MyBackEndClass { public event EventHandler DataChanged; string _Data; public string Data { get { return _Data; } set { _Data = value; //Fire the DataChanged event } } } class SomeForm : // Form stuff { MyBackEndClass mbe; TextBox someTextBox; SomeForm() { someTextBox.TextChanged += HandleTextBox(); mbe.DataChanged += HandleData(); } void HandleTextBox(Object sender, EventArgs e) { mbe.Data = ((TextBox)sender).Text; } void HandleData(Object sender, EventArgs e) { someTextBox.Text = ((MyBackEndClass) sender).Data; } } The problem is that changing the TextBox fires the changes the data value in the backend, which causes the textbox to change, etc. That runs forever. Is there a better design pattern (other than resorting to a nasty boolean flag) that handles this case correctly? EDIT: To be clear, in the real design the backend class is used to synchronize changes between multiple forms. Therefore I can't just use the SomeTextBox.Text property directly. Billy3

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  • Java constructor using generic types

    - by user37903
    I'm having a hard time wrapping my head around Java generic types. Here's a simple piece of code that in my mind should work, but I'm obviously doing something wrong. Eclipse reports this error in BreweryList.java: The method initBreweryFromObject() is undefined for the type <T> The idea is to fill a Vector with instances of objects that are a subclass of the Brewery class, so the invocation would be something like: BreweryList breweryList = new BreweryList(BrewerySubClass.class, list); BreweryList.java package com.beerme.test; import java.util.Vector; public class BreweryList<T extends Brewery> extends Vector<T> { public BreweryList(Class<T> c, Object[] j) { super(); for (int i = 0; i < j.length; i++) { T item = c.newInstance(); // initBreweryFromObject() is an instance method // of Brewery, of which <T> is a subclass (right?) c.initBreweryFromObject(); // "The method initBreweryFromObject() is undefined // for the type <T>" } } } Brewery.java package com.beerme.test; public class Brewery { public Brewery() { super(); } protected void breweryMethod() { } } BrewerySubClass.java package com.beerme.test; public class BrewerySubClass extends Brewery { public BrewerySubClass() { super(); } public void androidMethod() { } } I'm sure this is a complete-generics-noob question, but I'm stuck. Thanks for any tips!

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  • Rapid Web Application Development ASP.net vs. Open Source Platforms

    - by Yaaqov
    Good morning - I'm an intermediate-level developer who wants to build on online data-driven app (CRUD with a few calculations and basic HTML form inputs, nothing fancy) that keeps track of user sessions, and looks "professional" (or at least not "homemade"). I'm looking to development something with the look-and-feel that users get from sites like: http://www.datamasher.org/ http://www.thisweknow.org/ (About page says it was made with Ruby on Rails, which I'm unfamiliar with) (stackoverflow.com) Any pointers on whether I should just go the Miscrosoft route, and develop in ASP.net with WebForms, or if there's a quick qay to do this kind of development (with a WYSIWYG environment) on an open-source platform? I'm willing to learn, if it's somethat I can use to quickly drag/drop, add code, and publish online. Templates would be a plus, too. I apologize is the question seems a bit vague.

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  • Error compiling basic java code

    - by Michael Younani
    New to java. Practicing coding by following a book. Heres my code: class Motorcycle { //Three instance variables - make and color are strings. while a boolean refers to TRUE OR FLASE(in this case off or on) String make; String color; boolean engineState; void startEngine() { if (engineState == true) System.out.print("The engine is already on."); else { engineState = true; System.out.print("The engine is now on."); } void showAtts() { System.out.print("This motorcycle is a " + color + " " + make); if (engineState ==true) System.out.print("The engine is on."); else System.out.print("The engine is off."); } } } When I compile I get 2 errors: 1) illegal start of expression 2) ; expected I can't pin point the problem. If anyone can direct me or hint me please do.

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  • I have a question about variable release in global class.

    - by Beomseok
    + (void)findAndCopyOfDatabaseIfNeeded{ NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [path objectAtIndex:0]; NSFileManager *fileManager = [NSFileManager defaultManager]; NSString *databasePath = [documentsDirectory stringByAppendingPathComponent:@"DB"]; BOOL success = [fileManager fileExistsAtPath:databasePath]; if(!success){ NSString *resourcePath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"DB"]; [fileManager copyItemAtPath:resourcePath toPath:databasePath error:NULL]; } NSString *tracePath = [documentsDirectory stringByAppendingPathComponent:@"Trace"]; BOOL traceDir = [fileManager fileExistsAtPath:tracePath]; if(!traceDir){ NSString *resourcePath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"Trace"]; [fileManager copyItemAtPath:resourcePath toPath:tracePath error:NULL]; } NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init]; [dateFormatter setDateFormat:@"yyyy"]; NSDate *today = [[NSDate alloc]init]; NSString *resultYear = [dateFormatter stringFromDate:today]; NSString *traceYearPath = [tracePath stringByAppendingPathComponent:resultYear]; BOOL yearDir = [fileManager fileExistsAtPath:tracePath]; if (!yearDir) { [fileManager createDirectoryAtPath:traceYearPath attributes:nil]; } //[resultYear release]; ? //[today release]; ? //[dateFormatter release]; ? } I'm using global class like this [ + (void)findAndCopyOfDatabaseIfNeeded ]. hm,, I don't know NSArray, NSString and NSFileManager are released. Variable release or Not release ? please advice for me.

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  • Using an empty column as a divider in a JTable.

    - by Catalina Island
    I'm trying to use an empty column as a divider between pairs of columns in a JTable. Here's a picture and code for what I have so far. I know I can change the look using a custom TableCellRenderer. Before I go down that road, is there a better way to do this? Any ideas appreciated. import javax.swing.*; import javax.swing.table.*; public class TablePanel extends JPanel { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { JFrame f = new JFrame("TablePanel"); f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); f.add(new TablePanel()); f.pack(); f.setVisible(true); } }); } public TablePanel() { TableModel dataModel = new MyModel(); JTable table = new JTable(dataModel); table.getColumnModel().getColumn(MyModel.DIVIDER).setMaxWidth(0); JScrollPane jsp = new JScrollPane(table); jsp.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); this.add(jsp); } private static class MyModel extends AbstractTableModel { private static final int DIVIDER = 2; private final String[] names = { "A1", "A2", "", "B1", "B2" }; @Override public int getRowCount() { return 32; } @Override public int getColumnCount() { return names.length; } @Override public String getColumnName(int col) { if (col == DIVIDER) return ""; return names[col]; } @Override public Object getValueAt(int row, int col) { if (col == DIVIDER) return ""; return (row + 1) / 10.0; } @Override public Class<?> getColumnClass(int col) { if (col == DIVIDER) return String.class; return Number.class; } } }

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  • A Null Reference Exception

    - by Alex
    "Object reference not set to an instance of an object." using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.Graphics; namespace XNAdev { class Sprite { //The size of the Sprite public Rectangle Size; //Used to size the Sprite up or down from the original image public float Scale = 1.0f; //The current position of the Sprite public Vector2 Position = new Vector2(115, 0); //The texture object used when drawing the sprite private Texture2D mSpriteTexture; //Load the texture for the sprite using the Content Pipeline public void LoadContent(ContentManager theContentManager, string theAssetName) { mSpriteTexture = theContentManager.Load<Texture2D>(theAssetName); Size = new Rectangle(0, 0, (int)(mSpriteTexture.Width * Scale), (int)(mSpriteTexture.Height * Scale)); } //Draw the sprite to the screen public void Draw(SpriteBatch theSpriteBatch) { theSpriteBatch.Draw(mSpriteTexture, Position, new Rectangle(0, 0, mSpriteTexture.Width, mSpriteTexture.Height), Color.White, 0.0f, Vector2.Zero, Scale, SpriteEffects.None, 0); } } } I am very new at this C# so any help would be great. I have no idea what my error is.

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  • "Voice trigger" detection

    - by sehugg
    I have a voice application that would be much-improved if there was the ability to use a "trigger word" to start recording audio. I don't need a full speech-text engine, just the ability to reliably/efficiently detect the trigger word. I am wondering if there are any specialized speech engines that support this specific use case, or any libraries/methods to developing such a single-purpose detection engine. Ideally I'd like it to work in noisy environments, but it can be trained for a single user's voice. Pointers to research papers / topics would also be appreciated so I know what to ask for.

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  • Clear button at uisearchbar not working at all

    - by kevin.ng
    I created a search bar programmatically and added to my view using the codes below: - (void)viewDidLoad { searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake(xPositionForSearchBar, yPositionForSearchBar, widthForSearchBar, heightForSearchBar)]; UIView *bg = [[searchBar subviews] objectAtIndex:0]; searchBar.delegate = self; searchBar.placeholder = @"Search record"; for(UIView *view in searchBar.subviews){ if([view isKindOfClass:[UITextField class]]){ UITextField *tf = (UITextField *)view; tf.delegate = self; break; } } [bg removeFromSuperview]; [self.view addSubview: searchBar]; } The code is implemented with UISearchBarDelegate and UITextFieldDelegate. I have tried using - (void)searchBarCancelButtonClicked:(UISearchBar *)aSearchBar { NSLog(@"cancel clicked"); searchBar.text = @""; [aSearchBar resignFirstResponder]; } - (BOOL)textFieldShouldClear:(UITextField *)textField { NSLog(@"clear"); [self performSelector:@selector(searchBarCancelButtonClicked:) withObject:searchBar afterDelay: 0.1]; return YES; } and yet, the text inside the searchBar is not cleared at all when i click on the "clear button" - a circle with a "X" inside. The clear button works when I implemented it in IB. Wonder why? Kindly advice, many thanks.

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  • inserting datetimes into database using java

    - by gordatron
    Hi, I am wanting to insert a datetime into a MySql data base using Java and a prepared statement: Calendar cal = Calendar.getInstance(); PreparedStatement stmnt = db.PreparedStatement("INSERT INTO Run " + "(Time) VALUE (?) "); stmnt.setDate(1, new java.sql.Date(cal.getTime())); stmnt.executeQuery(); NOTE: thre is currently an error - cannot find symbol (java.sql.Date) line 4 here db is an instance of a sort of wrapper class that exposes what I need from java.sql - its just getting a prepared statement from my connection object here. Time (the column) is a date time in my database, and I can only see sedDate and setTime method but I want to store both - also my code does not work anyway ;-) if anyone could give me some pointers on inserting a combined date time (current time would be a great help as that's my first goal) into a MySql DB using a prepared statement I would be very grateful. Thanks

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  • Strange compilation error on reference passing argument to function

    - by Grewdrewgoo Goobergabbsoen
    Here's the code: #include <iostream> using namespace std; void mysize(int &size, int size2); int main() { int *p; int val; p = &val; cout << p; mysize(&val, 20); // Error is pointed here! } void mysize(int &size, int size2) { cout << sizeof(size); size2 = size2 + 6000; cout << size2; } Here's the error output from GCC: In function 'int main()': Line 10: error: invalid initialization of non-const reference of type 'int&' from a temporary of type 'int*' compilation terminated due to -Wfatal-errors. What does that imply? I do not understand the error message ... invalid initialization of a non-constant? I declared the prototype function above with two parameters to take, one a reference of an integer and one just an integer value itself. I passed the reference of the int (see line 10), yet this error keeps being thrown at me. What is the issue?

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  • Passing around objects to network packet handlers ?

    - by xeross
    Hey, I've been writing a networking server for a while now in C++ and have come to the stage to start looking for a way to properly and easily handle all packets. I am so far that I can figure out what kind of packet it is, but now I need to figure out how to get the needed data to the handler functions. I had the following in mind: Have a map of function pointers with the opcode as key and the function pointer as value Have all these functions have 2 arguments, packet and ObjectAccessor ObjectAccessor class contains various functions to fetch various items such as users and alike Perhaps pass the user's guid too so we can fetch it from the objectaccessor I'd like to know the various implementations others have come up with, so please comment on this idea and reply with your own implementations. Thanks, Xeross

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  • NSMutableArray for Object which has NSString property causes memory leak

    - by user262325
    Hello everyone I hope to add objects to a NSMutableArray "myArray", The NSMutableArray is the array for FileObj which has a NSString property "fileName" #import <UIKit/UIKit.h> @interface FileObj : NSObject { NSString *fileName; } -(void) setfileName:(NSString *)s ; -(NSString *) getfileName ; @end // // File.m// #import "File.h" @implementation FileObj -(void) setfileName:(NSString *)s ; { fileName=s; } -(NSString *) getfileName ; { return fileName; } @end I initialize the myArray here: NSMutableArray *temarray; temarray=[[NSMutableArray alloc] init]; self.myArray=temarray; [temarray release]; the codes to add object to myArray FileObj *newobj=[[FileObj alloc]init ]; NSString *fieldValue2 = [[NSString alloc] initWithUTF8String:@"aaaa"]; [newobj setfileName:fieldValue2]; [myArray addObject:newobj]; [fieldValue2 release]; //**if I enabled the line, it will cause crash** //**if I disable the line, it will cause memory leak** [newobj release]; Welcome any comment Thanks interdev

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  • Replacing the Import Table in PE file by standart LoadLibrary...

    - by user308368
    Hello. I have an executable (PE) file that load a dll file as represented in the Import table... let say: PEFile.exe Modules.dll my question is how can i remove Modules.dll's import_descriptor from the imports and do its work by loadLibrary without the rely on the import table and without destroy the file???... My bigger problem his i could not understand exactly how the Import thing works... after the loader read the information he needs to do the import's thing, i believe he use the LoadLibrary, GetProcAddress APIs... but i couldn't understated what he doing with the pointers he get... he putting them somewhere in memory... and then what just call them?!? all the papers i found in the net explain the structure of the import table, but i didn't found a paper that explain how it is really work and get used... i hope you cold understand my Gibberish English... Thank you!

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  • How can a class's memory-allocated address be determined from within the contructor?

    - by Jim Fell
    Is it possible to get the memory-allocated address of a newly instantiated class from within that class's constructor during execution of said constructor? I am developing a linked list wherein multiple classes have multiple pointers to like classes. Each time a new class instantiates, it needs to check its parent's list to make sure it is included. If I try to do something like this: MyClass() // contructor { extern MyClass * pParent; for ( int i = 0; i < max; i++ ) { pParent->rels[i] == &MyClass; // error } } I get this error: error C2275: 'namespace::MyClass' : illegal use of this type as an expression Any thoughts or suggestions would be appreciated. Thanks.

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  • how do i make the app take correct input..?

    - by user1824343
    This is my windows app's one layout which converts Celsius to Fahrenheit. The problem is that when I try to input the temperature it shows some junk(for eg: if i enter '3' it displayin '3.0000009') and sometimes its even showing stack overflow exception. The output is also not shown properly : cel.text is the textbox for celsius. fahre.text is the textbox for fahrenheit. namespace PanoramaApp1 { public partial class FahretoCel : PhoneApplicationPage { public FahretoCel() { InitializeComponent(); } private void fahre_TextChanged(object sender, TextChangedEventArgs e) { if (fahre.Text != "") { try { double F = Convert.ToDouble(fahre.Text); cel.Text = "" + ((5.0/9.0) * (F - 32)) ; //this is conversion expression } catch (FormatException) { fahre.Text = ""; cel.Text = ""; } } else { cel.Text = ""; } } private void cel_TextChanged(object sender, TextChangedEventArgs e) { if (cel.Text != "") { try { Double c = Convert.ToDouble(cel.Text); fahre.Text = "" + ((c *(9.0 / 5.0 )) + 32); } catch (FormatException) { fahre.Text = ""; cel.Text = ""; } } else { fahre.Text = ""; } } } }

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  • Is there a way of getting a file name and inserting into Matlab script?

    - by torr
    In a folder, I have both my .m file that contains the script and an imaging .dcm file that needs to be analyzed. Folder structure: Folder1/analysis.m Folder1/meas_dynamic_123.dcm My script (analysis.m) begins as follows: target =''; <== here should go the full path to the file + filename example: /Volumes/Data/Folder1/meas_dynamic_123.m txt = dir(target); // etc So I'm wondering if there is a way of when running analysis.m it will: automatically search the folder it's in, grab the full path + filename of file containing string dynamic in the name, insert its full path + name into target variable continue running the script Does anyone have any pointers on how to achieve this? Using ffpath?

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  • calling a function from a set of overloads depending on the dynamic type of an object

    - by Jasper
    I feel like the answer to this question is really simple, but I really am having trouble finding it. So here goes: Suppose you have the following classes: class Base; class Child : public Base; class Displayer { public: Displayer(Base* element); Displayer(Child* element); } Additionally, I have a Base* object which might point to either an instance of the class Base or an instance of the class Child. Now I want to create a Displayer based on the element pointed to by object, however, I want to pick the right version of the constructor. As I currently have it, this would accomplish just that (I am being a bit fuzzy with my C++ here, but I think this the clearest way) object->createDisplayer(); virtual void Base::createDisplayer() { new Displayer(this); } virtual void Child::createDisplayer() { new Displayer(this); } This works, however, there is a problem with this: Base and Child are part of the application system, while Displayer is part of the GUI system. I want to build the GUI system independently of the Application system, so that it is easy to replace the GUI. This means that Base and Child should not know about Displayer. However, I do not know how I can achieve this without letting the Application classes know about the GUI. Am I missing something very obvious or am I trying something that is not possible?

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  • OnClickListener cannot be resolved to a type

    - by Webnet
    I'm diving into Java (this is day 1) and I'm trying to create a button that will trigger a notification when I click it... This code is based off of the notification documentation here, and UI events documentation here package com.example.contactwidget; import android.app.Activity; import android.app.Notification; import android.app.NotificationManager; import android.app.PendingIntent; import android.content.Context; import android.content.Intent; import android.os.Bundle; import android.widget.Button; public class ContactWidget extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Button calc1 = (Button) findViewById(R.id.calc_button_1); calc1.setOnClickListener(buttonListener); setContentView(R.layout.main); } private static final int HELLO_ID = 1; //Error: OnClickListener cannot be resolved to a type private OnClickListener buttonListener = new OnClickListener() { public void onClick (View v) { String ns = Context.NOTIFICATION_SERVICE; NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns); int icon = R.drawable.icon; CharSequence ticketBrief = "Button Pressed Brief"; CharSequence ticketTitle = "Button pressed"; CharSequence ticketText = "You pressed button 1"; long when = System.currentTimeMillis(); Notification notification = new Notification(icon, ticketBrief, when); Intent notificationIntent = new Intent(this, ContactWidget.class); PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0); notification.setLatestEventInfo(getApplicationContext(), ticketTitle, ticketText, contentIntent); mNotificationManager.notify(HELLO_ID, notification); } } } I'm running into a problem: OnClickListener cannot be resolved to a type. The problem here is that I don't see any problems with my code in relation to the example I'm using

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  • Limiting object allocation over multiple threads

    - by John
    I have an application which retrieves and caches the results of a clients query. The client then requests different chunks of data and the application sends the relevant results and removes them from the cache. A new requirement for this application is that there needs to be a run-time configurable maximum number of results which may be cached. I've taken the naive approach and implemented this by using a counter under a lock which is incremented every time a result is cached and decremented whenever a result is removed from the cache. Unfortunately, this has drastically reduced the applications performance when processing a large number of concurrent requests. I have tried both a critical section lock and spin-lock; the performance improves a bit with a spin-lock, but is still unacceptably slow. Is there a better way to solve this problem which may improve performance? Right now I have a thread pool that services requests and each request is tied to a Request object which stores that cached results for that particular request. Here is a simplified pseudo code version of my current implementation: void ResultCallback( Result result, Request *request ) { lock totalResultsCached lock cachedLimit if( totalResultsCached + 1 > cachedLimit ) { unlock cachedLimit unlock totalResultsCached //cancel the request return; } ++totalResultsCached; unlock cachedLimit unlock totalResultsCached request.add(result) } void SendResults( int resultsToSend, Request *request ) { while ( resultsToSend > 0 ) { send(request.remove()) lock totalResultsCached --totalResultsCached unlock totalResultsCached --resultsToSend; } }

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  • Optimization of a c++ matrix/bitmap class

    - by Andrew
    I am searching a 2D matrix (or bitmap) class which is flexible but also fast element access. The contents A flexible class should allow you to choose dimensions during runtime, and would look something like this (simplified): class Matrix { public: Matrix(int w, int h) : data(new int[x*y]), width(w) {} void SetElement(int x, int y, int val) { data[x+y*width] = val; } // ... private: // symbols int width; int* data; }; A faster often proposed solution using templates is (simplified): template <int W, int H> class TMatrix { TMatrix() data(new int[W*H]) {} void SetElement(int x, int y, int val) { data[x+y*W] = val; } private: int* data; }; This is faster as the width can be "inlined" in the code. The first solution does not do this. However this is not very flexible anymore, as you can't change the size anymore at runtime. So my question is: Is there a possibility to tell the compiler to generate faster code (like when using the template solution), when the size in the code is fixed and generate flexible code when its runtime dependend? I tried to achieve this by writing "const" where ever possible. I tried it with gcc and VS2005, but no success. This kind of optimization would be useful for many other similar cases.

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