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  • can't connect Java client to C server.

    - by nexes
    I have a very simple server written in C and an equally simple client written in Java. When I run them both on the same computer everything works, but when I try to run the server on computer A and the client on computer B, I get the error IOException connection refused from the java client. I can't seem to find out whats happening, any thoughts? I've even turned off the firewalls but the problem still persists. server. #include <stdio.h> #include <unistd.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #define PORT 3557 #define BUF 256 int main(int argc, char *argv[]) { struct sockaddr_in host, remote; int host_fd, remote_fd; int size = sizeof(struct sockaddr);; char data[BUF]; host.sin_family = AF_INET; host.sin_addr.s_addr = htonl(INADDR_ANY); host.sin_port = htons(PORT); memset(&host.sin_zero, 0, sizeof(host.sin_zero)); host_fd = socket(AF_INET, SOCK_STREAM, 0); if(host_fd == -1) { printf("socket error %d\n", host_fd); return 1; } if(bind(host_fd, (struct sockaddr *)&host, size)) { printf("bind error\n"); return 1; } if(listen(host_fd, 5)) { printf("listen error"); return 1; } printf("Server setup, waiting for connection...\n"); remote_fd = accept(host_fd, (struct sockaddr *)&remote, &size); printf("connection made\n"); int read = recv(remote_fd, data, BUF, 0); data[read] = '\0'; printf("read = %d, data = %s\n", read, data); shutdown(remote_fd, SHUT_RDWR); close(remote_fd); return 0; } client. import java.net.*; import java.io.*; public class socket { public static void main(String[] argv) { DataOutputStream os = null; try { Socket socket = new Socket("192.168.1.103", 3557); os = new DataOutputStream(socket.getOutputStream()); os.writeBytes("phone 12"); os.close(); socket.close(); } catch (UnknownHostException e) { System.out.println("Unkonw exception " + e.getMessage()); } catch (IOException e) { System.out.println("IOException caught " + e.getMessage()); } } }

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  • Swing: How do I run a job from AWT thread, but after a window was layed out?

    - by java.is.for.desktop
    My complete GUI runs inside the AWT thread, because I start the main window using SwingUtilities.invokeAndWait(...). Now I have a JDialog which has just to display a JLabel, which indicates that a certain job is in progress, and close that dialog after the job was finished. The problem is: the label is not displayed. That job seems to be started before JDialog was fully layed-out. When I just let the dialog open without waiting for a job and closing, the label is displayed. The last thing the dialog does in its ctor is setVisible(true). Things such as revalidate(), repaint(), ... don't help either. Even when I start a thread for the monitored job, and wait for it using someThread.join() it doesn't help, because the current thread (which is the AWT thread) is blocked by join, I guess. Replacing JDialog with JFrame doesn't help either. So, is the concept wrong in general? Or can I manage it to do certain job after it is ensured that a JDialog (or JFrame) is fully layed-out? Simplified algorithm of what I'm trying to achieve: Create a subclass of JDialog Ensure that it and its contents are fully layed-out Start a process and wait for it to finish (threaded or not, doesn't matter) Close the dialog I managed to write a reproducible test case: EDIT Problem from an answer is now addressed: This use case does display the label, but it fails to close after the "simulated process", because of dialog's modality. import java.awt.*; import javax.swing.*; public class _DialogTest2 { public static void main(String[] args) throws Exception { SwingUtilities.invokeAndWait(new Runnable() { final JLabel jLabel = new JLabel("Please wait..."); @Override public void run() { JFrame myFrame = new JFrame("Main frame"); myFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); myFrame.setSize(750, 500); myFrame.setLocationRelativeTo(null); myFrame.setVisible(true); JDialog d = new JDialog(myFrame, "I'm waiting"); d.setModalityType(Dialog.ModalityType.APPLICATION_MODAL); d.add(jLabel); d.setSize(300, 200); d.setLocationRelativeTo(null); d.setVisible(true); SwingUtilities.invokeLater(new Runnable() { @Override public void run() { try { Thread.sleep(3000); // simulate process jLabel.setText("Done"); } catch (InterruptedException ex) { } } }); d.setVisible(false); d.dispose(); myFrame.setVisible(false); myFrame.dispose(); } }); } }

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  • Using PHP5s SOAP Client to send data to an ASP/.NET based SOAP server.

    - by user325143
    I am trying to write a snippet of PHP to connect to a third party's API via SOAP to enter some data into their database. The API requires me to pass several mandatory fields for every call (username, password, companyid, entitytype) in addition to the mandatory data fields. It also requires me to call the "ValidateEntity" funciton before calling the "CreateEntity" function. Documentation can be found here: http://wiki.agemni.com/Getting_Started/APIs/Database_API I have never worked with SOAP before, so I am very new to this. Here is what I have so far: error_reporting(E_ALL); ini_set('display_errors', '1'); $client = new SoapClient("http://agemni.com/AgemniWebservices/service1.asmx?WSDL", array('trace'=> true)); $options = array( 'username' => "myuser", 'password' => "mypassword", 'companyid' => myID, 'entitytype' => 2 ); $params = array( 'fname' => "John", 'lname' => "Doe", 'phone' => "859-333-3333", 'zip' => "40332", 'area id' => "12345", 'lead id' => "28222", 'contactdate' => "4/10/2010" ); $validate = $client->__soapCall("ValidateEntity", array($params), array($options)); $client->__soapCall("CreateEntity", array($params), array($options)); echo "<pre>"; var_dump($client-> __getLastRequestHeaders()); var_dump($client-> __getLastRequest()); var_dump($client-> __getLastResponseHeaders()); var_dump($client-> __getLastResponse()); var_dump($result); echo "</pre>"; Upon executing this code, I get the following error: Fatal error: Uncaught SoapFault exception: [Client] SOAP-ERROR: Encoding: object hasn't 'objecttype' property in /www/tmp/index-soap.php:24 Stack trace: #0 /www/tmp/index-soap.php(24): SoapClient->__soapCall('ValidateEntity', Array) #1 {main} thrown in /www/stealth/tmp/index-soap.php on line 24 I guess my question is.. am I even going about doing this the right way? I know this is a very broad question, but I appreciate any advice you can give me about making this work. Please let me know if you require more detail. Thanks!

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  • Dictionary w/ null key?

    - by Ralph
    Firstly, why doesn't Dictionary<TKey, TValue> support a single null key? Secondly, is there an existing dictionary-like collection that does? I want to store an "empty" or "missing" or "default" System.Type, thought null would work well for this. More specifically, I've written this class: class Switch { private Dictionary<Type, Action<object>> _dict; public Switch(params KeyValuePair<Type, Action<object>>[] cases) { _dict = new Dictionary<Type, Action<object>>(cases.Length); foreach (var entry in cases) _dict.Add(entry.Key, entry.Value); } public void Execute(object obj) { var type = obj.GetType(); if (_dict.ContainsKey(type)) _dict[type](obj); } public static void Execute(object obj, params KeyValuePair<Type, Action<object>>[] cases) { var type = obj.GetType(); foreach (var entry in cases) { if (entry.Key == null || type.IsAssignableFrom(entry.Key)) { entry.Value(obj); break; } } } public static KeyValuePair<Type, Action<object>> Case<T>(Action action) { return new KeyValuePair<Type, Action<object>>(typeof(T), x => action()); } public static KeyValuePair<Type, Action<object>> Case<T>(Action<T> action) { return new KeyValuePair<Type, Action<object>>(typeof(T), x => action((T)x)); } public static KeyValuePair<Type, Action<object>> Default(Action action) { return new KeyValuePair<Type, Action<object>>(null, x => action()); } } For switching on types. There are two ways to use it: Statically. Just call Switch.Execute(yourObject, Switch.Case<YourType>(x => x.Action())) Precompiled. Create a switch, and then use it later with switchInstance.Execute(yourObject) Works great except when you try to add a default case to the "precompiled" version (null argument exception).

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  • JPanel's child components paint/layout problem

    - by Tom Brito
    I'm having a problem that when my frame is shown (after a login dialog) the buttons are not on correct position, then in some miliseconds they go to the right position (the center of the panel with border layout). When I make a SSCCE, it works correct, but when I run my whole code I have this fast-miliseconds delay to the buttons to go to the correct place. Unfortunately, I can't post the whole code, but the method that shows the frame is: public void login(JComponent userView) { centerPanel.removeAll(); centerPanel.add(userView); centerPanel.revalidate(); centerPanel.repaint(); frame.setVisible(true); } What would cause this delay to the panel layout? (I'm running everything in the EDT) -- update In my machine, this SSCCE shows the layout problem in 2 of 10 times I run it: import java.awt.BorderLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.SwingUtilities; public class TEST { public static void main(String[] args) throws Exception { SwingUtilities.invokeAndWait(new Runnable() { @Override public void run() { System.out.println("Debug test..."); JPanel btnPnl = new JPanel(); btnPnl.add(new JButton("TEST")); JFrame f = new JFrame("TEST"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.getContentPane().setLayout(new BorderLayout()); f.getContentPane().add(btnPnl); f.pack(); f.setSize(800, 600); f.setVisible(true); System.out.println("End debug test!"); } }); } } The button first appers in the up-left, and then it goes to the center. Please, note that I'm understand, not just correct. Is it a java bug? --update OK, so the SSCCE don't show the problem with you that tried till now. Maybe it's my computer performance problem. But this don't answer the question, I still think Java Swing is creating new threads for make the layout behind the scenes.

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  • Is it thread safe to read a form controls value (but not change it) without using Invoke/BeginInvoke from another thread

    - by goku_da_master
    I know you can read a gui control from a worker thread without using Invoke/BeginInvoke because my app is doing it now. The cross thread exception error is not being thrown and my System.Timers.Timer thread is able to read gui control values just fine (unlike this guy: can a worker thread read a control in the GUI?) Question 1: Given the cardinal rule of threads, should I be using Invoke/BeginInvoke to read form control values? And does this make it more thread-safe? The background to this question stems from a problem my app is having. It seems to randomly corrupt form controls another thread is referencing. (see question 2) Question 2: I have a second thread that needs to update form control values so I Invoke/BeginInvoke to update those values. Well this same thread needs a reference to those controls so it can update them. It holds a list of these controls (say DataGridViewRow objects). Sometimes (not always), the DataGridViewRow reference gets "corrupt". What I mean by corrupt, is the reference is still valid, but some of the DataGridViewRow properties are null (ex: row.Cells). Is this caused by question 1 or can you give me any tips on why this might be happening? Here's some code (the last line has the problem): public partial class MyForm : Form { void Timer_Elapsed(object sender) { // we're on a new thread (this function gets called every few seconds) UpdateUiHelper updateUiHelper = new UpdateUiHelper(this); foreach (DataGridViewRow row in dataGridView1.Rows) { object[] values = GetValuesFromDb(); updateUiHelper.UpdateRowValues(row, values[0]); } // .. do other work here updateUiHelper.UpdateUi(); } } public class UpdateUiHelper { private readonly Form _form; private Dictionary<DataGridViewRow, object> _rows; private delegate void RowDelegate(DataGridViewRow row); private readonly object _lockObject = new object(); public UpdateUiHelper(Form form) { _form = form; _rows = new Dictionary<DataGridViewRow, object>(); } public void UpdateRowValues(DataGridViewRow row, object value) { if (_rows.ContainsKey(row)) _rows[row] = value; else { lock (_lockObject) { _rows.Add(row, value); } } } public void UpdateUi() { foreach (DataGridViewRow row in _rows.Keys) { SetRowValueThreadSafe(row); } } private void SetRowValueThreadSafe(DataGridViewRow row) { if (_form.InvokeRequired) { _form.Invoke(new RowDelegate(SetRowValueThreadSafe), new object[] { row }); return; } // now we're on the UI thread object newValue = _rows[row]; row.Cells[0].Value = newValue; // randomly errors here with NullReferenceException, but row is never null! }

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  • Template class + virtual function = must implement?

    - by sold
    This code: template <typename T> struct A { T t; void DoSomething() { t.SomeFunction(); } }; struct B { }; A<B> a; is easily compiled without any complaints, as long as I never call a.DoSomething(). However, if I define DoSomething as a virtual function, I will get a compile error saying that B doesn't declare SomeFunction. I can somewhat see why it happens (DoSomething should now have an entry in the vtable), but I can't help feeling that it's not really obligated. Plus it sucks. Is there any way to overcome this? EDIT 2: Okay. I hope this time it makes sence: Let's say I am doing intrusive ref count, so all entities must inherit from base class Object. How can I suuport primitive types too? I can define: template <typename T> class Primitive : public Object { T value; public: Primitive(const T &value=T()); operator T() const; Primitive<T> &operator =(const T &value); Primitive<T> &operator +=(const T &value); Primitive<T> &operator %=(const T &value); // And so on... }; so I can use Primitive<int>, Primitive<char>... But how about Primitive<float>? It seems like a problem, because floats don't have a %= operator. But actually, it isn't, since I'll never call operator %= on Primitive<float>. That's one of the deliberate features of templates. If, for some reason, I would define operator %= as virtual. Or, if i'll pre-export Primitive<float> from a dll to avoid link errors, the compiler will complain even if I never call operator %= on a Primitive<float>. If it would just have fill in a dummy value for operator %= in Primitive<float>'s vtable (that raises an exception?), everything would have been fine.

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  • How can i use the Orientation correct for images

    - by user3578109
    I´m learning android/java by myself @the moment and i have a problem with a part of my app i´m learning on. I made the code with help of the www and my problem is that if i open an image from the gallery it´s send to the edit activity but in the activity pictures what are made in portrait mode are displayed always wrong (90° to the right side).... The codes are Matrix private Bitmap rotateBitmapToOrientation(Bitmap b, int orientation){ Matrix matrix = new Matrix(); matrix.postRotate(orientation); Canvas offscreenCanvas = new Canvas(); offscreenCanvas.drawBitmap(b, matrix, null); return b; } and the other one @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); switch (requestCode) { case PICK_IMAGE_FROM_GALLERY: { if (resultCode == RESULT_OK) { Log.d(TAG, "Got Picture!"); Log.d(TAG,"File type - " + data.getType()); Uri photoUri = data.getData(); if (photoUri != null) { try { String[] filePathColumn = {MediaStore.Images.Media.DATA}; String[] orientationColumn = {MediaStore.Images.Media.ORIENTATION}; int orientation = -1; Cursor cursor = getContentResolver().query(photoUri, filePathColumn, null, null, null); cursor.moveToFirst(); int columnIndex = cursor.getColumnIndex(filePathColumn[0]); String filePath = cursor.getString(columnIndex); cursor.close(); cursor = getContentResolver().query(photoUri, orientationColumn, null, null, null); if(cursor != null && cursor.moveToFirst()){ orientation = cursor.getInt(cursor.getColumnIndex(orientationColumn[0])); } cursor.close(); HashMap<String, Integer> pRes = this.getImageResolutionSetting(); Bitmap shrunkenBitmap = FileUtilsHelper.shrinkBitmap(filePath, pRes.get("width"), pRes.get("height")); shrunkenBitmap = rotateBitmapToOrientation(shrunkenBitmap, orientation); String res = FileUtilsHelper.saveBitmapAsJpeg(shrunkenBitmap, this); Log.d(TAG,"File Path: " + res); shrunkenBitmap.recycle(); Intent editImage = new Intent(this, EditImage.class); editImage.addFlags(Intent.FLAG_ACTIVITY_FORWARD_RESULT); editImage.putExtra("stuff.path", res); startActivity(editImage); }catch(Exception e){ Toast.makeText(this, R.string.cant_save_image,Toast.LENGTH_SHORT).show(); } } } } break; } }} I don´t know what i´m doing wrong... I could really need a teacher on that :) Thx for your help dudes!!

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  • Command Not working in separate thread in J2me.

    - by RishiPatel
    I am creating a bluetooth application. I created a simple midlet with a exit command and i create a thread for finding the service and discovering the device. While doing so it displays a animated screen on which i added the parent commandListener for exit command. After successful connection both user is represented with greetings(Current screen calls the parent Display method setCurrent for displaying itself). This screen also have CommandListener set to the parent. Now i want to add few more commands. I Implemented the CommandLIstener Interface in this class, added few commands but the commands are not working. I dont whats wen wrong. I am giving u Code snippets to fully describle my issue : - package name Imports here public class MyMidlet extends MIDlet implements CommandListener { public CommandListener theListener; public Display theDisplay; public Command exitCommand; public MyMidlet() { // Retrieve the display for this MIDlet //Create the initial screen } public void startApp() throws MIDletStateChangeException { } public void pauseApp() { } public void destroyApp(boolean unconditional) { } public void commandAction(Command c, Displayable d) { // Determine if the exit command was selected if (c == exitCommand) { //End application here notifyDestroyed(); } else { //Start the new thread here } } } Now here is the code for the class which is invoked by the above midlet in a separate thread; package here; imports here public class MyService implements Runnable, CommandListener { private MyMidlet parent; private StreamConnection conn; private OutputStream output; private InputStream input; public Command sendCommand; private TextField messageToSend Form form; public BChatService(boolean isServer, BChatMidlet parent) { //some stuff here this.parent = parent; } public void run() { //functino for showing animation here try { input = conn.openInputStream(); output = conn.openOutputStream(); } catch (IOException e) { displayError("IO Error", "An error occurred while opening " + "the input and output streams" + "(IOException: " + e.getMessage() + ")"); try { conn.close(); } catch (Exception ex) { } return; } // Create the Form here when service is discoverd and greets the users Command sendCommand = new Command("Send", Command.ITEM, 2); exitCommand = new Command("Exit", Command.EXIT, 1); form.addCommand(exitCommand); form.addCommand(sendCommand); parent.theDisplay.setCurrent(form); form.setCommandListener(this); public void commandAction(Command c, Displayable d) { if (c == exitCommand) { // End the game parent.destroyApp(true); parent.notifyDestroyed(); } if(c == sendCommand) { form.append("SOme text here"); } } } When i select the Send command, the string doesnt append in form neither exit command works. What can be the possible cause for it?? I need to implement this functionality...Is there any other way to achieve this??

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  • C# - periodic data reading and Thread.Sleep()

    - by CaldonCZE
    Hello, my C# application reads data from special USB device. The data are read as so-called "messages", each of them having 24 bytes. The amount of messages that must be read per second may differ (maximal frequency is quite high, about 700 messages per second), but the application must read them all. The only way to read the messages is by calling function "ReadMessage", that returns one message read from the device. The function is from external DLL and I cannot modify it. My solution: I've got a seperate thread, that is running all the time during the program run and it's only job is to read the messages in cycle. The received messages are then processed in main application thread. The function executed in the "reading thread" is the following: private void ReadingThreadFunction() { int cycleCount; try { while (this.keepReceivingMessages) { cycleCount++; TRxMsg receivedMessage; ReadMessage(devHandle, out receivedMessage); //...do something with the message... } } catch { //... catch exception if reading failed... } } This solution works fine and all messages are correctly received. However, the application consumes too much resources, the CPU of my computer runs at more than 80%. Therefore I'd like to reduce it. Thanks to the "cycleCount" variable I know that the "cycling speed" of the thread is about 40 000 cycles per second. This is unnecessarily too much, since I need to receive maximum 700 messagges/sec. (and the device has buffer for about 100 messages, so the cycle speed can be even a little lower) I tried to reduce the cycle speed by suspending the thread for 1 ms by Thread.Sleep(1); command. Of course, this didn't work and the cycle speed became about 70 cycles/second which was not enough to read all messages. I know that this attempt was silly, that putting the thread to sleep and then waking him up takes much longer than 1 ms. However, I don't know what else to do: Is there some other way how to slow the thread execution down (to reduce CPU consumption) other than Thread.Sleep? Or am I completely wrong and should I use something different for this task instead of Thread, maybe Threading.Timer or ThreadPool? Thanks a lot in advance for all suggestions. This is my first question here and I'm a beginner at using threads, so please excuse me if it's not clear enough.

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  • Entity Framework: An object with the same key already exists in the objectstatemanager

    - by NealR
    I see that this question has been asked a lot, however I haven't found anything yet that solves the problem I'm having. Obviously i'm using the Entity Framework to perform an update to a record. Once the updates are complete, however, whenever I try to save I get the following error message: An object with the same key already exists in the objectstatemanager At first I was passing in a collection object from the view that contained a copy of the the ZipCodeTerritory model object zipToUpdate. I changed the code by pulling this object out and just sending in the relevant fields instead. However, I'm still getting the same error. What's also weird is the first time I run this code, it works fine. Any attempt after that I get the error. Controller Here is the code from the method calling the edit function public static string DescriptionOnly(ZipCodeIndex updateZip) { if (!string.IsNullOrWhiteSpace(updateZip.newEffectiveDate) || !string.IsNullOrWhiteSpace(updateZip.newEndDate)) { return "Neither effective or end date can be present if updating Territory Code only; "; } _updated = 0; foreach (var zipCode in updateZip.displayForPaging.Where(x => x.Update)) { ProcessAllChanges(zipCode, updateZip.newTerritory, updateZip.newStateCode, updateZip.newDescription, updateZip.newChannelCode); } _msg += _updated + " record(s) updated; "; return _msg; } And here is the method that actually does the updating. private static void ProcessAllChanges(ZipCodeTerritory zipToUpdate, string newTerritory, string newStateCode, string newDescription, string newChannelCode) { try { if (!string.IsNullOrWhiteSpace(newTerritory)) zipToUpdate.IndDistrnId = newTerritory; if (!string.IsNullOrWhiteSpace(newStateCode)) zipToUpdate.StateCode = newStateCode; if (!string.IsNullOrWhiteSpace(newDescription)) zipToUpdate.DrmTerrDesc = newDescription; if (!string.IsNullOrWhiteSpace(newChannelCode)) zipToUpdate.ChannelCode = newChannelCode; if (zipToUpdate.EndDate == DateTime.MinValue) zipToUpdate.EndDate = DateTime.MaxValue; _db.Entry(zipToUpdate).State = EntityState.Modified; _db.SaveChanges(); _updated++; } catch (DbEntityValidationException dbEx) { _msg += "Error during update; "; EventLog.WriteEntry("Monet", "Error during ProcessAllChanges: " + zipToUpdate.ToString() + " |EX| " + dbEx.Message); } catch (Exception ex) { _msg += "Error during update; "; EventLog.WriteEntry("Monet", "Error during ProcessAllChanges: " + zipToUpdate.ToString() + " |MESSAGE| " + ex.Message); } } EDIT The ZipCodeIndex object contains a list of ZipCodeTerritory model objects. These aren't being pulled from a linq query, but instead simply passed back to the controller from the view. Here is the signature of the controller method that starts the process: [HttpPost] public ActionResult Update(ZipCodeIndex updateZip, string button)

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  • Illegal Start of Expression

    - by Kraivyne
    Hello there, I have just started to learn the very basics of Java programming. Using a book entitled "Programming Video Games for the Evil Genius". I have had an Illegal Start of Expression error that I can't for the life of me get rid of. I have checked the sample code from the book and mine is identical. The error is coming from the for(int i = difficulty; i = 0; i- - ) line. Thanks for helping a newbie out. import javax.swing.*; public class S1P4 {public static void main(String[] args) throws Exception { int difficulty; difficulty = Integer.parseInt(JOptionPane.showInputDialog("How good are you?\n"+ "1 = Great\n"+"10 = Terrible")); boolean cont = false; do { cont = false; double num1 = (int)(Math.round(Math.random()*10)); double num2; do { num2 = (int)(Math.round(Math.random()*10)); } while(num2==0.0); int sign = (int)(Math.round(Math.random()*3)); double answer; System.out.println("\n\n*****"); if(sign==0) { System.out.println(num1+" times "+num2); answer = num1*num2; } else if(sign==1) { System.out.println(num1+" divided by"+num2); answer = num1/num2; } else if(sign==1) { System.out.println(num1+" plus "+num2); answer = num1+num2; } else if(sign==1) { System.out.println(num1+" minus "+num2); answer = num1-num2; } else { System.out.println(num1+" % "+num2); answer = num1%num2; } System.out.println("*****\n"); for(int i = difficulty; i >= 0; i- - ) { System.out.println(i+"..."); Thread.sleep(500); } System.out.println("ANSWER: "+answer); String again; again = JOptionPane.showInputDialog("Play again?"); if(again.equals("yes")) cont = true; } while(cont); } }

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  • C++: Why does gcc prefer non-const over const when accessing operator[]?

    - by JonasW
    This question might be more appropriately asked regarding C++ in general, but as I am using gcc on linux that's the context. Consider the following program: #include <iostream> #include <map> #include <string> using namespace std; template <typename TKey, typename TValue> class Dictionary{ public: map<TKey, TValue> internal; TValue & operator[](TKey const & key) { cout << "operator[] with key " << key << " called " << endl; return internal[key]; } TValue const & operator[](TKey const & key) const { cout << "operator[] const with key " << key << " called " << endl; return internal.at(key); } }; int main(int argc, char* argv[]) { Dictionary<string, string> dict; dict["1"] = "one"; cout << "first one: " << dict["1"] << endl; return 0; } When executing the program, the output is: operator[] with key 1 called operator[] with key 1 called first one: one What I would like is to have the compiler choose the operator[]const method instead in the second call. The reason is that without having used dict["1"] before, the call to operator[] causes the internal map to create the data that does not exist, even if the only thing I wanted was to do some debugging output, which of course is a fatal application error. The behaviour I am looking for would be something like the C# index operator which has a get and a set operation and where you could throw an exception if the getter tries to access something that doesn't exist: class MyDictionary<TKey, TVal> { private Dictionary<TKey, TVal> dict = new Dictionary<TKey, TVal>(); public TVal this[TKey idx] { get { if(!dict.ContainsKey(idx)) throw KeyNotFoundException("..."); return dict[idx]; } set { dict[idx] = value; } } } Thus, I wonder why the gcc prefers the non-const call over the const call when non-const access is not required.

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  • stringindexoutofbounds with currency converter java program

    - by user1795926
    I am have trouble with a summary not showing up. I am supposed to modify a previous Java assignment by by adding an array of objects. Within the loop, instantiate each individual object. Make sure the user cannot keep adding another Foreign conversion beyond your array size. After the user selects quit from the menu, prompt if the user want to display a summary report. If they select ‘Y’ then, using your array of objects, display the following report: Item Conversion Dollars Amount 1 Japanese Yen 100.00 32,000.00 2 Mexican Peso 400.00 56,000.00 3 Canadian Dollar 100.00 156.00 etc. Number of Conversions = 3 There are no errors when I compile..but when I run the program it is fine until I hit 0 to end the conversion and have it ask if i want to see a summary. This error displays: Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0 at java.lang.String.charAt(String.java:658) at Lab8.main(Lab8.java:43) my code: import java.util.Scanner; import java.text.DecimalFormat; public class Lab8 { public static void main(String[] args) { final int Max = 10; String a; char summary; int c = 0; Foreign[] Exchange = new Foreign[Max]; Scanner Keyboard = new Scanner(System.in); Foreign.opening(); do { Exchange[c] = new Foreign(); Exchange[c].getchoice(); Exchange[c].dollars(); Exchange[c].amount(); Exchange[c].vertical(); System.out.println("\n" + Exchange[c]); c++; System.out.println("\n" + "Please select 1 through 4, or 0 to quit" + >"\n"); c= Keyboard.nextInt(); } while (c != 0); System.out.print("\nWould you like a summary of your conversions? (Y/N): "); a = Keyboard.nextLine(); summary = a.charAt(0); summary = Character.toUpperCase(summary); if (summary == 'Y') { System.out.println("\nCountry\t\tRate\t\tDollars\t\tAmount"); System.out.println("========\t\t=======\t\t=======\t\t========="); for (int i=0; i < Exchange.length; i++) System.out.println(Exchange[i]); Foreign.counter(); } } } I looked at line 43 and its this line: summary = a.charAt(0); But I am not sure what's wrong with it, can anyone point it out? Thank you.

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  • program received signal SIGABRT (xcode)

    - by manish1990
    #import <UIKit/UIKit.h> @interface tableview : UIViewController<UITableViewDataSource> { NSArray *listOfItems; } @property(nonatomic,retain) NSArray *listOfItems; @end #import "tableview.h" @implementation tableview @synthesize listOfItems; - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier ]autorelease]; } //NSString *cellValue = [listOfItems objectAtIndex:indexPath.row]; cell.textLabel.text = [listOfItems objectAtIndex:indexPath.row]; return cell; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return 3; } - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; if (self) { // Custom initialization } return self; } - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. } #pragma mark - View lifecycle - (void)viewDidLoad { listOfItems = [[NSArray alloc] initWithObjects:@"first",@"second",@"third", nil]; //listOfItems = [[NSMutableArray alloc]init]; // [listOfItems addObject:@"first"]; //[listOfItems addObject:@"second"]; [super viewDidLoad]; // Do any additional setup after loading the view from its nib. } -(void)dealloc { [listOfItems release]; [super dealloc]; } @end GNU gdb 6.3.50-20050815 (Apple version gdb-1708) (Mon Aug 15 16:03:10 UTC 2011) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "x86_64-apple-darwin".sharedlibrary apply-load-rules all Attaching to process 438. 2012-04-27 13:33:23.276 tableview test[438:207] -[UIView tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x6855500 2012-04-27 13:33:23.362 tableview test[438:207] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIView tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x6855500' * First throw call stack: (0x13bb052 0x154cd0a 0x13bcced 0x1321f00 0x1321ce2 0x1ecf2b 0x1ef722 0x9f7c7 0x9f2c1 0xa228c 0xa6783 0x51322 0x13bce72 0x1d6592d 0x1d6f827 0x1cf5fa7 0x1cf7ea6 0x1d8330c 0x23530 0x138f9ce 0x1326670 0x12f24f6 0x12f1db4 0x12f1ccb 0x12a4879 0x12a493e 0x12a9b 0x2282 0x21f5) terminate called throwing an exceptionCurrent language: auto; currently objective-c (gdb)

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  • Asp.Net Scrapping Grid Pages

    - by SH
    I need cod in C#. Look, i am trying to post the search.aspx page which contains Asp.Net grid. When grid is rendered it loads very first page on the screen and then there are number of pages in the grid header. I scrap first page, and now i want to move on to the next page. All this is being done using following code: HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create("http://pubrec3.hillsclerk.com/oncore/search.aspx?" + param); myRequest.Method = "GET"; myRequest.KeepAlive = false; HttpWebResponse webresponse; try { webresponse = (HttpWebResponse)myRequest.GetResponse(); Encoding enc = System.Text.Encoding.GetEncoding(1252); StreamReader loResponseStream = new StreamReader(webresponse.GetResponseStream(), enc); string r = loResponseStream.ReadToEnd(); loResponseStream.Close(); webresponse.Close(); //if (GetRecordCount(r)) ExtractResultTable(bd, ed, r); } catch (Exception ex) { } The above code grabs first page... and now i have to move on to the next page. This is the link which produces a grid with 3 pages. http://pubrec3.hillsclerk.com/oncore/search.aspx?bd=01/01/2008&ed=12/31/2008&bt=O&lb=1000000&ub=1000000000&d=5/6/2010&pt=-1&dt=D,%20MTG&st=consideration Using above code i need to load the 2nd page with the same search criteria but the records found in 2nd page. and then so on. I know there is a trick to navigate through the grid pages. I used it but it did not work on this page. the trick is, you can pass __EVENTTARGET and __EVENTARGUMENT in query string to navigate through the gird but it does not work on this website. I am desperately searching a way, how to cope with this website. i really want this done. i do not want any code but a way to nevigate throgh the grid using query string if it does work. Otherwise please be specific to the problem.

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  • Python - 2 Questions: Editing a variable in a function and changing the order of if else statements

    - by Eric
    First of all, I should explain what I'm trying to do first. I'm creating a dungeon crawler-like game, and I'm trying to program the movement of computer characters/monsters in the map. The map is basically a Cartesian coordinate grid. The locations of characters are represented by tuples of the x and y values, (x,y). The game works by turns, and in a turn a character can only move up, down, left or right 1 space. I'm creating a very simple movement system where the character will simply make decisions to move on a turn by turn basis. Essentially a 'forgetful' movement system. A basic flow chart of what I'm intending to do: Find direction towards destination Make a priority list of movements to be done using the direction eg.('r','u','d','l') means it would try to move right first, then up, then down, then left. Try each of the possibilities following the priority order. If the first movement fails (blocked by obstacle etc.), then it would successively try the movements until the first one that is successful, then it would stop. At step 3, the way I'm trying to do it is like this: def move(direction,location): try: -snip- # Tries to move, raises the exception Movementerror if cannot move in the direction return 1 # Indicates movement successful except Movementerror: return 0 # Indicates movement unsuccessful (thus character has not moved yet) prioritylist = ('r','u','d','l') if move('r',location): pass elif move('u',location): pass elif move('d',location): pass elif move('l',location): pass else: pass In the if/else block, the program would try the first movement on the priority on the priority list. At the move function, the character would try to move. If the character is not blocked and does move, it returns 1, leading to the pass where it would stop. If the character is blocked, it returns 0, then it tries the next movement. However, this results in 2 problems: How do I edit a variable passed into a function inside the function itself, while returning if the edit is successful? I have been told that you can't edit a variable inside a function as it won't really change the value of the variable, it just makes the variable inside the function refer to something else while the original variable remain unchanged. So, the solution is to return the value and then assign the variable to the returned value. However, I want it to return another value indicating if this edit is successful, so I want to edit this variable inside the function itself. How do I do so? How do I change the order of the if/else statements to follow the order of the priority list? It needs to be able to change during runtime as the priority list can change resulting in a different order of movement to try.

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  • Android: Stopping method to be called twice if already running.

    - by user285831
    I'm trying to prevent my application to call the same method twice in the event of a double-click, or if the user presses different buttons quickly, almost at the same time. I have clickable Views, acting as buttons, that call the same method but passing different parameters. This is the call: startTheSearch(context, getState(), what, where); Inside this method I'm creating a new Thread, because it queries a web server for the result: new Thread(new Runnable() { public void run() { progDiag = ProgressDialog.show(ctx, null, "Searching", true); getServerXML(context, what, where, searchIsCustom, mOffset); handler.sendEmptyMessage(0); } }).start(); The problem is that upon two quick clicks, the method is fired twice, two threads are created, and consequently two new activities are created. That makes my app crash. When the methods are done, and we have the result from the server, we call the handler: private Handler handler = new Handler() { @Override public void handleMessage(Message msg) { super.handleMessage(msg); try { Intent i = new Intent(Golf.this, Result.class); Bundle b = new Bundle(); b.putString("what", mWhat); b.putString("where", mWhere); b.putInt("offset", mOffset); b.putBoolean("searchIsCustom", searchIsCustom); i.putExtras(b); startActivityForResult(i, Activity.RESULT_OK); progDiag.dismiss(); } catch (Exception e) { Alerts.generalDialogAlert("Error", "settings", ctx); } } }; I tried to have a global boolean variable called "blocked" initially set to false, creating a condition like: if(!blocked){ blocked = true; new Thread(new Runnable() { public void run() { But this only seems to work on slower phones like the G1, I tried on Nexus and before it set blocked = true, the second request has was granted. So is there any way I can block the method being called if it's already running, or if the thread has started so it wont create a new one? Please, I really need to fix this. I've been developing on Android for almost 2 months now, but I'm yet to tackle that bug. Thanks in advance.

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  • java nested for() loop throws ArrayIndexOutOfBoundsException

    - by Mike
    I'm working through a JPanel exercise in a Java book. I'm tasked with creating a 5x4 grid using GridLayout. When I loop through the container to add panels and buttons, the first add() throws the OOB exception. What am I doing wrong? package mineField; import java.awt.*; import javax.swing.*; @SuppressWarnings("serial") public class MineField extends JFrame { private final int WIDTH = 250; private final int HEIGHT = 120; private final int MAX_ROWS = 5; private final int MAX_COLUMNS = 4; public MineField() { super("Minefield"); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); Container mineFieldGrid = getContentPane(); mineFieldGrid.setLayout(new GridLayout(MAX_ROWS, MAX_COLUMNS)); // loop through arrays, add panels, then add buttons to panels. for (int i = 0; i < MAX_ROWS; i++) { JPanel[] rows = new JPanel[i]; mineFieldGrid.add(rows[i], rows[i].getName()); rows[i].setBackground(Color.blue); for (int j = 0; j < MAX_COLUMNS; j++) { JButton[] buttons = new JButton[i]; rows[i].add(buttons[j], buttons[j].getName()); } } mineFieldGrid.setSize(WIDTH, HEIGHT); mineFieldGrid.setVisible(true); } public int setRandomBomb(Container con) { int bombID; bombID = (int) (Math.random() * con.getComponentCount()); return bombID; } /** * @param args */ public static void main(String[] args) { //int randomBomb; //JButton bombLocation; MineField minePanel = new MineField(); //minePanel[randomBomb] = minePanel.setRandomBomb(minePanel); } } I'm sure I'm over-engineering a simple nested for loop. Since I'm new to Java, please be kind. I'm sure I'll return the favor some day.

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  • Can you get a Func<T> (or similar) from a MethodInfo object?

    - by Dan Tao
    I realize that, generally speaking, there are performance implications of using reflection. (I myself am not a fan of reflection at all, actually; this is a purely academic question.) Suppose there exists some class that looks like this: public class MyClass { public string GetName() { return "My Name"; } } Bear with me here. I know that if I have an instance of MyClass called x, I can call x.GetName(). Furthermore, I could set a Func<string> variable to x.GetName. Now here's my question. Let's say I don't know the above class is called MyClass; I've got some object, x, but I have no idea what it is. I could check to see if that object has a GetName method by doing this: MethodInfo getName = x.GetType().GetMethod("GetName"); Suppose getName is not null. Then couldn't I furthermore check if getName.ReturnType == typeof(string) and getName.GetParameters().Length == 0, and at this point, wouldn't I be quite certain that the method represented by my getName object could definitely be cast to a Func<string>, somehow? I realize there's a MethodInfo.Invoke, and I also realize I could always create a Func<string> like: Func<string> getNameFunc = () => getName.Invoke(x, null); I guess what I'm asking is if there's any way to go from a MethodInfo object to the actual method it represents, incurring the performance cost of reflection in the process, but after that point being able to call the method directly (via, e.g., a Func<string> or something similar) without a performance penalty. What I'm envisioning might look something like this: // obviously this would throw an exception if GetActualInstanceMethod returned // something that couldn't be cast to a Func<string> Func<string> getNameFunc = (Func<string>)getName.GetActualInstanceMethod(x); (I realize that doesn't exist; I'm wondering if there's anything like it.) If what I'm asking doesn't make sense, or if I'm being unclear, I'll be happy to attempt to clarify.

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  • VS 2010 IDE 2GB limt

    - by user561732
    I am using VS 2010 on a win 7 64 bit system with 8 GB of memory. My application is 32 bit. While in the VS 2010 .Net IDE, the app shows up in the Windows task manager as "MyApp.vshost.exe *32" while the VS IDE itself shows up as "devenv.exe *32". I checked and it appears that the VS 2010 IDE file (devenv.exe) is complied with the /LargeAddressAware flag. However, when debugging large models, the IDE fails with an Out of memory exception. In the Windows Task manager, the "MyApp.vshost.exe *32" process indicates about 1400 MB of memory usage (while the "devenv.exe *32" process is well under 500 MB). Is it possible to set the "MyApp.vshost.exe *32" process to be /LargeAddressAware in order to avoid this out of memory situation? If so, how can this be done in the IDE. While setting the final application binary to be /LargeAddressAware would work, I still need to be able to debug the app in the IDE with these type of large models. I should also note that my app has a deep object hierarchy with many collections that together required a lot of memory. However, my issue is not related to trying to create say 1 large array that requires greater then 2 GB of memory etc. I should note that I am able to run the same app in the VB6 IDE and not get an out of memory situation as long as the VB6 IDE is made /LargeAddressAware. In the case of VB6, the IDE and the app being debugged are part of the same process (and not split into 2 as is the case with VS 2010.) The VB6 process can be larger then 3 GB without running into out of memory issues. Ultimately, my objective is to have my app run completely in 64 bit to access more memory. I am hoping that in such cases, the IDE will allow the debugging process to exceed 2 GB without crashing (and certainly more then 1.4 GB as is the current case). However, for now, while 95% of my app is 64 bit, I am calling a legacy COM 32 bit DLL and as such, my entire app is forced to still run in 32 bit mode until I replace that DLL.

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  • Calling a webservice synchronously from a Silverlight 3 application?

    - by Lasse V. Karlsen
    I am trying to reuse some .NET code that performs some calls to a data-access-layer type service. I have managed to package up both the input to the method and the output from the method, but unfortunately the service is called from inside code that I really don't want to rewrite in order to be asynchronous. Unfortunately, the webservice code generated in Silverlight only produces asynchronous methods, so I was wondering if anyone had working code that managed to work around this? I tried the recipe found here: The Easy Way To Synchronously Call WCF Services In Silverlight, but unfortunately it times out and never completes the call. Or rather, what seems to happen is that the completed event handler is called, but only after the method returns. I am suspecting that the event handler is called from a dispatcher or similar, and since I'm blocking the main thread here, it never completes until the code is actually back into the GUI loop. Or something like that. Here's my own version that I wrote before I found the above recipe, but it suffers from the same problem: public static object ExecuteRequestOnServer(Type dalInterfaceType, string methodName, object[] arguments) { string securityToken = "DUMMYTOKEN"; string input = "DUMMYINPUT"; object result = null; Exception resultException = null; object evtLock = new object(); var evt = new System.Threading.ManualResetEvent(false); try { var client = new MinGatServices.DataAccessLayerServiceSoapClient(); client.ExecuteRequestCompleted += (s, e) => { resultException = e.Error; result = e.Result; lock (evtLock) { if (evt != null) evt.Set(); } }; client.ExecuteRequestAsync(securityToken, input); try { var didComplete = evt.WaitOne(10000); if (!didComplete) throw new TimeoutException("A data access layer web service request timed out (" + dalInterfaceType.Name + "." + methodName + ")"); } finally { client.CloseAsync(); } } finally { lock (evtLock) { evt.Close(); evt = null; } } if (resultException != null) throw resultException; else return result; } Basically, both recipes does this: Set up a ManualResetEvent Hook into the Completed event The event handler grabs the result from the service call, and signals the event The main thread now starts the web service call asynchronously It then waits for the event to become signalled However, the event handler is not called until the method above has returned, hence my code that checks for evt != null and such, to avoid TargetInvocationException from killing my program after the method has timed out. Does anyone know: ... if it is possible at all in Silverlight 3 ... what I have done wrong above?

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  • Thread too slow. Better way to execute code (Android AndEngine)?

    - by rphello101
    I'm developing a game where the user creates sprites with every touch. I then have a thread run to check to see if those sprites collide with any others. The problem is, if I tap too quickly, I cause a null pointer exception error. I believe it's because I'm tapping faster than my thread is running. This is the thread I have: public class grow implements Runnable{ public grow(Sprite sprite){ } @Override public void run() { float radf, rads; //fill radius/stationary radius float fx=0, fy=0, sx, sy; while(down){ if(spriteC[spriteNum].active){ spriteC[spriteNum].sprite.setScale(spriteC[spriteNum].scale += 0.001); if(spriteC[spriteNum].sprite.collidesWith(ground)||spriteC[spriteNum].sprite.collidesWith(roof)|| spriteC[spriteNum].sprite.collidesWith(left)||spriteC[spriteNum].sprite.collidesWith(right)){ down = false; spriteC[spriteNum].active=false; yourScene.unregisterTouchArea(spriteC[spriteNum].sprite); } fx = spriteC[spriteNum].sprite.getX(); fy = spriteC[spriteNum].sprite.getY(); radf=spriteC[spriteNum].sprite.getHeightScaled()/2; Log.e("F"+Float.toString(fx),Float.toString(fy)); if(spriteNum>0) for(int x=0;x<spriteNum;x++){ rads=spriteC[x].sprite.getHeightScaled()/2; sx = spriteC[x].body.getWorldCenter().x * 32; sy = spriteC[x].body.getWorldCenter().y * 32; Log.e("S"+Float.toString(sx),Float.toString(sy)); Log.e(Float.toString((float) Math.sqrt(Math.pow((fx-sx),2)+Math.pow((fy-sy),2))),Float.toString((radf+rads))); if(Math.sqrt(Math.pow((fx-sx),2)+Math.pow((fy-sy),2))<(radf+rads)){ down = false; spriteC[spriteNum].active=false; yourScene.unregisterTouchArea(spriteC[spriteNum].sprite); Log.e("Collided",Boolean.toString(down)); } } } } spriteC[spriteNum].body = PhysicsFactory.createCircleBody(mPhysicsWorld, spriteC[spriteNum].sprite, BodyType.DynamicBody, FIXTURE_DEF); mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(spriteC[spriteNum].sprite, spriteC[spriteNum].body, true, true)); } } Better solution anyone? I know there is something to do with a handler, but I don't exactly know what that is or how to use one.

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  • Cutting down repeating code in c# Class

    - by Tom Gullen
    This is a wrapper for an API I'm working on, am I doing it sort of right? I'm not particularly fond of all the repeating code in the constructor, if someone can show me if I can reduce that it would be very helpful! public class WebWizForumVersion { // Properties of returned data public string Software { get; private set; } public string Version { get; private set; } public string APIVersion { get; private set; } public string Copyright { get; private set; } public string BoardName { get; private set; } public string URL { get; private set; } public string Email { get; private set; } public string Database { get; private set; } public string InstallationID { get; private set; } public bool NewsPad { get; private set; } public string NewsPadURL { get; private set; } public WebWizForumVersion(XmlReader Data) { try { Data.ReadToFollowing("Software"); this.Software = Data.ReadElementContentAsString(); Data.ReadToFollowing("Version"); this.Version = Data.ReadElementContentAsString(); Data.ReadToFollowing("ApiVersion"); this.APIVersion = Data.ReadElementContentAsString(); Data.ReadToFollowing("Copyright"); this.Copyright = Data.ReadElementContentAsString(); Data.ReadToFollowing("BoardName"); this.BoardName = Data.ReadElementContentAsString(); Data.ReadToFollowing("URL"); this.URL = Data.ReadElementContentAsString(); Data.ReadToFollowing("Email"); this.Email = Data.ReadElementContentAsString(); Data.ReadToFollowing("Database"); this.Database = Data.ReadElementContentAsString(); Data.ReadToFollowing("InstallID"); this.InstallationID = Data.ReadElementContentAsString(); Data.ReadToFollowing("NewsPad"); this.NewsPad = bool.Parse(Data.ReadElementContentAsString()); Data.ReadToFollowing("NewsPadURL"); this.NewsPadURL = Data.ReadElementContentAsString(); } catch (Exception e) { } } }

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  • Encapsulating a Windows.Forms.Button

    - by devoured elysium
    I want to define a special kind of button that only allows two possible labels: "ON" and "OFF". I decided to inherit from a Windows.Forms.Button to implement this but now I don't know I how should enforce this rule. Should I just override the Text property like this? public override string Text { set { throw new InvalidOperationException("Invalid operation on StartStopButton!"); } } The problem I see with this is that I am breaking the contract that all buttons should have. If any code tries something like foreach (Button button in myForm) { button.Text = "123"; } they will get an Exception if I have any of my special buttons on the form, which is something that isn't expectable. First, because people think of properties just as "public" variables, not methods, second, because they are used to using and setting whatever they want to buttons without having to worry with Exceptions. Should I instead just make the set property do nothing? That could also lead to awkward results: myButton.Text = "abc"; MessageBox.Show(abc); //not "abc"! The general idea from the OO world is to in this kind of cases use Composition instead of inheritance. public class MySpecialButton : <Some class from System.Windows.Forms that already knows how to draw itself on forms> private Button button = new Button(); //I'd just draw this button on this class //and I'd then only show the fields I consider //relevant to the outside world. ... } But to make the Button "live" on a form it must inherit from some special class. I've looked on Control, but it seems to already have the Text property defined. I guess the ideal situation would be to inherit from some kind of class that wouldn't even have the Text property defined, but that'd have position, size, etc properties available. Upper in the hierarchy, after Control, we have Component, but that looks like a really raw class. Any clue about how to achieve this? I know this was a long post :( Thanks

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