Prabhu Kumar

a tech twaddler..

Archive for the ‘Uncategorized’ Category

Learning By Slipping

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Here’s an old, but still relevant, post by Steven Sinofsky on shipping products,

http://blog.learningbyshipping.com/2013/05/01/learning-by-slipping/

Some excerpts,

“In order to slip you need to know the ship date. When people talk about projects shipping “first quarter” that is about 90 different dates and so that leaves everyone (on the team and elsewhere) guessing what the ship date might be.  A date is a date.  All projects should have a date.  While software itself is not launching to hit a Mars orbit, it is important that everyone agree on a single date.  Whether that date is public or not is a different question.”

“Interestingly, the error rate in short-term, continuous projects can often (in my experience) be much higher.  The view of continuously shipping can lead to a “project” lasting only a month or two.  The brain doesn’t think much of missing by a week or two, but that can be a 25 – 50% error rate.  On a 12 month project that can mean it would stretch to 15-18 months, which does sound like a disaster.”

“When a task cannot be partitioned because of sequential constraints, the application of more effort has no effect on schedule.  The bearing of a child takes nine months, no matter how many women are assigned. The Mythical Man-Month – Frederic P. Brooks

“Quality is the most difficult to manage and why the test leadership is such a critical part of the management structure of any project.  Quality is not something you think about at the end of the project nor is it particularly malleable.  While a great test manager knows quality is not binary at a global level, he/she knows that much like error bars in physics a little bit of sub-par quality across many parts of the project compounds and leads to a highly problematic, or buggy, product.  Quality is not just bugs but also includes scale, performance, reliability, security, and more.”

“Quality is difficult to manage because it is often where people want to cut corners.  A product might work for most cases but the boundary conditions or edge cases show much different results.  As we all know, you only get one chance to make a first impression.”

On the same topic, if you know that you suck at planning and factor this in next time, it might actually prove a little useful ;-)

Written by Prabhu Kumar

February 14th, 2014 at 6:16 pm

Posted in Uncategorized

Get ‘Programming Windows 6th Edition’ by Charles Petzold for $10!

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Programming Windows 6th Edition

O’Reilly has a special offer on the new book that Charles Petzold is working on, Programming Windows 6th Edition. This should be a great book covering Windows 8 app development in C# and XAML.

You can get this book for $10 now (offer lasts till 31st May), and future editions of this book, as and when new chapters are added, will be available to you for free.

Read more at Charles’ blog here: http://www.charlespetzold.com/blog/2012/05/An-Experiment-in-Book-Publishing.html

Shop at: http://shop.oreilly.com/product/0790145369079.do

Written by Prabhu Kumar

May 30th, 2012 at 8:37 pm

Posted in Uncategorized

‘CODE’ by Charles Petzold: An absolute must read

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You know how sometimes you come across a book and you go “I wish I had read this years ago!”. CODE is just that book. It’s a book about how computers work and the way in which Charles Petzold flows through the topics is pure artistry. Those electronics class lessons in college would have been much more interesting if I had read this book then ;)

The book starts off with two best friends trying to communicate from across the street using only flashlights. This is how the idea of ‘code’ is introduced. It then takes you through a journey involving Morse Code, Braille and how telegraphs and relays were used to send codes over long distances. For me, the most interesting part is when he starts building logic gates from relays and switches. This lays a solid foundation for things to come. These logic gates are then used to build half-adders, full-adders (using two half-adders), oscillators, flip-flops and latches; finally getting assembled into a unit of Random Access Memory. Towards the end, a simple computer with processing, input and output systems is designed. The book might be a little old but still very relevant.

The most amazing thing about this book? It teaches you concepts at such a fundamental level that your mind will be blown. And before you know it you will be building ripple counters from flip-flops! If you have anything to do with computers go read this book. You won’t be disappointed.

CODE on flipkart

CODE on Amazon

Written by Prabhu Kumar

November 15th, 2011 at 12:33 am

Posted in Uncategorized

Windows Phone 7: Building a simple dictionary web client

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Like I mentioned in this post a while back, I came across a dictionary web service called Aonaware that serves up word definitions from various dictionaries and is really easy to use. The services page on their website, http://services.aonaware.com/DictService/DictService.asmx, lists all the operations that are supported by the dictionary service. Here they are,

Word Dictionary Web Service

The following operations are supported. For a formal definition, please review the Service Description.

  • Define
    Define given word, returning definitions from all dictionaries
  • DefineInDict
    Define given word, returning definitions from specified dictionary
  • DictionaryInfo
    Show information about the specified dictionary
  • DictionaryList
    Returns a list of available dictionaries
  • DictionaryListExtended
    Returns a list of advanced dictionaries (e.g. translating dictionaries)
  • Match
    Look for matching words in all dictionaries using the given strategy
  • MatchInDict
    Look for matching words in the specified dictionary using the given strategy
  • ServerInfo
    Show remote server information
  • StrategyList
    Return list of all available strategies on the server

Follow the links above to get more information on each API.

In this post we will be building a simple windows phone 7 client which uses this service to get word definitions for words entered by the user. The application will also allow the user to select a dictionary from all the available ones and look up the word definition in that dictionary. So of all the apis above we will be using only two, DictionaryList() to get a list of all supported dictionaries and DefineInDict() to get the word definition from a particular dictionary.

Before we get started, a note to you all; I would have liked to implement this application using concepts from data binding, item templates, data templates etc. I have a basic understanding of what they are but, being a beginner, I am not very comfortable with those topics yet so I didn’t use them. I thought I’ll get this version out of the way and maybe in the next version I could give those a try.

A somewhat scary mock-up of the what the final application will look like,

AppMockup

Select Dictionary is a list picker control from the silverlight toolkit (you need to download and install the toolkit if you haven’t already). Below it is a textbox where the user can enter words to look up and a button beside it to fetch the word definition when clicked. Finally we have a textblock which occupies the remaining area and displays the word definition from the selected dictionary.

Create a silverlight application for windows phone 7, AonawareDictionaryClient, and add references to the silverlight toolkit and the web service. From the solution explorer right on References and select Microsoft.Phone.Controls.Toolkit from under the .NET tab,

adding-reference-sl-toolkit

Next, add a reference to the web service. Again right click on References and this time select Add Service Reference In the resulting dialog paste the service url in the Address field and press go, (url –> http://services.aonaware.com/DictService/DictService.asmx)

AddingReference

once the service is discovered, provide a name for the NameSpace, in this case I’ve called it AonawareDictionaryService. Press OK. You can now use the classes and functions that are generated in the AonawareDictionaryClient.AonawareDictionaryService namespace.

Let’s get the UI done now. In MainPage.xaml add a namespace declaration to use the toolkit controls,

xmlns:toolkit=”clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls.Toolkit”

the content of LayoutRoot is changed as follows, (sorry, no syntax highlighting in this post)

<StackPanel x:Name=”TitlePanel” Grid.Row=”0″ Margin=”12,5,0,5″>
<TextBlock x:Name=”ApplicationTitle” Text=”AONAWARE DICTIONARY CLIENT” Style=”{StaticResource PhoneTextNormalStyle}”/>
<!–<TextBlock x:Name=”PageTitle” Text=”page name” Margin=”9,-7,0,0″ Style=”{StaticResource PhoneTextTitle1Style}”/>–>
</StackPanel>

<!–ContentPanel – place additional content here–>
<Grid x:Name=”ContentPanel” Grid.Row=”1″ Margin=”12,0,12,0″>
<Grid.RowDefinitions>
<RowDefinition Height=”Auto”/>
<RowDefinition Height=”Auto”/>
<RowDefinition Height=”*”/>
</Grid.RowDefinitions>
<toolkit:ListPicker Grid.Row=”0″ x:Name=”listPickerDictionaryList”
Header=”Select Dictionary :”>
</toolkit:ListPicker>

<Grid Grid.Row=”1″ Margin=”0,5,0,0″>
<Grid.ColumnDefinitions>
<ColumnDefinition Width=”*”/>
<ColumnDefinition Width=”Auto” />
</Grid.ColumnDefinitions>

<TextBox x:Name=”txtboxInputWord” Grid.Column=”0″ GotFocus=”OnTextboxInputWordGotFocus” />
<Button x:Name=”btnGo” Grid.Column=”1″ Click=”OnButtonGoClick” >
<Button.Content>
<Image Source=”/images/button-go.png”/>
</Button.Content>
</Button>
</Grid>

<ScrollViewer Grid.Row=”2″ x:Name=”scrollViewer”>
<TextBlock  Margin=”12,5,12,5″  x:Name=”txtBlockWordMeaning” HorizontalAlignment=”Stretch”
VerticalAlignment=”Stretch” TextWrapping=”Wrap”
FontSize=”26″ />
</ScrollViewer>
</Grid>

I have commented out the PageTitle as it occupies too much valuable space, and the ContentPanel is changed to contain three rows. First row contains the list picker control, second row contains the textbox and the button, and the third row contains a textblock within a scroll viewer.

The designer will now be showing the final ui,

designerViewOfUI

Now go to MainPage.xaml.cs, and add the following namespace declarations,

using Microsoft.Phone.Controls;
using AonawareDictionaryClient.AonawareDictionaryService;
using System.IO.IsolatedStorage;

A class called DictServiceSoapClient would have been created for you in the background when you added a reference to the web service. This class functions as a wrapper to the services exported by the web service. All the web service functions that we saw at the start can be access through this class, or more precisely through an object of this class.

Create a data member of type DictServiceSoapClient in the Mainpage class, and a function which initializes it,

DictServiceSoapClient DictSvcClient = null;

private DictServiceSoapClient GetDictServiceSoapClient()
{
if (null == DictSvcClient)
{
DictSvcClient = new DictServiceSoapClient();
}

return DictSvcClient;
}

We have two major tasks remaining. First, when the application loads we need to populate the list picker with all the supported dictionaries and second, when the user enters a word and clicks on the arrow button we need to fetch the word’s meaning.


Populating the List Picker

In the OnNavigatingTo event of the MainPage, we call the DictionaryList() api. This can also be done in the OnLoading event handler of the MainPage; not sure if one has an advantage over the other. Here’s the code for OnNavigatedTo,

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
DictServiceSoapClient client = GetDictServiceSoapClient();

client.DictionaryListCompleted += new EventHandler<DictionaryListCompletedEventArgs>(OnGetDictionaryListCompleted);

client.DictionaryListAsync();

base.OnNavigatedTo(e);
}

Windows Phone 7 supports only async calls to web services. When we added a reference to the dictionary service, asynchronous versions of all the functions were generated automatically. So in the above function we register a handler to the DictionaryListCompleted event which will occur when the call to DictionaryList() gets a response from the server. Then we call the DictionaryListAsync() function which is the async version of the DictionaryList() api. The result of this api will be sent to the handler OnGetDictionaryListCompleted(),

void OnGetDictionaryListCompleted(object sender, DictionaryListCompletedEventArgs e)
{
IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;
Dictionary[] listOfDictionaries;

if (e.Error == null)
{
listOfDictionaries = e.Result;
PopulateListPicker(listOfDictionaries, settings);
}
else if (settings.Contains(“SavedDictionaryList”))
{
listOfDictionaries = settings["SavedDictionaryList"] as Dictionary[];
PopulateListPicker(listOfDictionaries, settings);
}
else
{
MessageBoxResult res = MessageBox.Show(“An error occured while retrieving dictionary list, do you want to try again?”, “Error”, MessageBoxButton.OKCancel);

if (MessageBoxResult.OK == res)
{
GetDictServiceSoapClient().DictionaryListAsync();
}
}

settings.Save();
}

I have used IsolatedStorageSettings to store a few things; the entire dictionary list and the dictionary that is selected when the user exits the application, so that the next time when the user starts the application the current dictionary is set to the last selected value. First we check if the api returned any error, if the error object is null e.Result will contain the list (actually array) of Dictionary type objects. If there was an error, we check the isolated storage settings to see if there is a dictionary list stored from a previous instance of the application and if so, we populate the list picker based on this saved list. Note that in this case there are chances that the dictionary list might be out of date if there have been changes on the server. Finally, if none of these cases are true, we display an error message to the user and try to fetch the list again.

PopulateListPicker() is passed the array of Dictionary objects and the settings object as well,

void PopulateListPicker(Dictionary[] listOfDictionaries, IsolatedStorageSettings settings)
{
listPickerDictionaryList.Items.Clear();

foreach (Dictionary dictionary in listOfDictionaries)
{
listPickerDictionaryList.Items.Add(dictionary.Name);
}

settings["SavedDictionaryList"] = listOfDictionaries;

string savedDictionaryName;
if (settings.Contains(“SavedDictionary”))
{
savedDictionaryName = settings["SavedDictionary"] as string;
}
else
{
savedDictionaryName = “WordNet (r) 2.0″; //default dictionary, wordnet
}

foreach (string dictName in listPickerDictionaryList.Items)
{
if (dictName == savedDictionaryName)
{
listPickerDictionaryList.SelectedItem = dictName;
break;
}
}

settings["SavedDictionary"] = listPickerDictionaryList.SelectedItem as string;
}

We first clear all the items from the list picker, add the dictionary names from the array and then create a key in the settings called SavedDictionaryList and store the dictionary list in it. We then check if there is saved dictionary available from a previous instance, if there is, we set it as the selected item in the list picker. And if not, we set “WordNet ® 2.0” as the default dictionary. Before returning, we save the selected dictionary in the “SavedDictionary” key of the isolated storage settings.
Fetching word definitions

Getting this part done is very similar to the above code. We get the input word from the textbox, call into DefineInDictAsync() to fetch the definition and when DefineInDictAsync completes, we get the result and display it in the textblock. Here is the handler for the button click,

private void OnButtonGoClick(object sender, RoutedEventArgs e)
{
txtBlockWordMeaning.Text = “Please wait..”;

IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;

if (txtboxInputWord.Text.Trim().Length <= 0)
{
MessageBox.Show(“Please enter a word in the textbox and press ‘Go’”);
}
else
{
Dictionary[] listOfDictionaries = settings["SavedDictionaryList"] as Dictionary[];
string selectedDictionary = listPickerDictionaryList.SelectedItem.ToString();

string dictId = “wn”; //default dictionary is wordnet (wn is the dict id)

foreach (Dictionary dict in listOfDictionaries)
{
if (dict.Name == selectedDictionary)
{
dictId = dict.Id;
break;
}
}

DictServiceSoapClient client = GetDictServiceSoapClient();

client.DefineInDictCompleted += new EventHandler<DefineInDictCompletedEventArgs>(OnDefineInDictCompleted);
client.DefineInDictAsync(dictId, txtboxInputWord.Text.Trim());
}
}

We validate the input and then select the dictionary id based on the currently selected dictionary. We need the dictionary id because the api DefineInDict() expects the dictionary identifier and not the dictionary name. We could very well have stored the dictionary id in isolated storage settings too. Again, same as before, we register a event handler for the DefineInDictCompleted event and call the DefineInDictAsync() method passing in the dictionary id and the input word.

void OnDefineInDictCompleted(object sender, DefineInDictCompletedEventArgs e)
{
WordDefinition wd = e.Result;

scrollViewer.ScrollToVerticalOffset(0.0f);

if (wd == null || e.Error != null || wd.Definitions.Length == 0)
{
txtBlockWordMeaning.Text = String.Format(“No definitions were found for ‘{0}’ in ‘{1}’”, txtboxInputWord.Text.Trim(), listPickerDictionaryList.SelectedItem.ToString().Trim());
}
else
{
foreach (Definition def in wd.Definitions)
{
string str = def.WordDefinition;
str = str.Replace(“  “, ” “); //some formatting
txtBlockWordMeaning.Text = str;
}
}
}

When the api completes, e.Result will contain a WordDefnition object. This class is also generated in the background while adding the service reference. We check the word definitions within this class to see if any results were returned, if not, we display a message to the user in the textblock. If a definition was found the text on the textblock is set to display the definition of the word.

Adding final touches, we now need to save the current dictionary when the application exits. A small but useful thing is selecting the entire word in the input textbox when the user selects it. This makes sure that if the user has looked up a definition for a really long word, he doesn’t have to press ‘clear’ too many times to enter the next word,

protected override void OnNavigatingFrom(System.Windows.Navigation.NavigatingCancelEventArgs e)
{
IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;

settings["SavedDictionary"] = listPickerDictionaryList.SelectedItem as string;

settings.Save();

base.OnNavigatingFrom(e);
}

private void OnTextboxInputWordGotFocus(object sender, RoutedEventArgs e)
{
TextBox txtbox = sender as TextBox;

if (txtbox.Text.Trim().Length > 0)
{
txtbox.SelectionStart = 0;
txtbox.SelectionLength = txtbox.Text.Length;
}
}

OnNavigatingFrom() is called whenever you navigate away from the MainPage, since our application contains only one page that would mean that it is exiting (or getting tombstoned).

I leave you with a short video of the application in action, but before that if you have any suggestions on how to make the code better and improve it please do leave a comment.

Until next time…

Written by Prabhu Kumar

December 30th, 2010 at 2:33 pm

Posted in Uncategorized

Windows Phone 7 : Dragging and flicking UI controls

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Who would want to flick and drag UI controls!? There might not be many use cases but I think some concepts here are worthy of a post.

So we will create a simple silverlight application for windows phone 7, containing a canvas element on which we’ll place a button control and an image and then, as the title says, drag and flick the controls. Here’s Mainpage.xaml,

  1. <Grid x:Name=”LayoutRoot” Background=”Transparent”>
  2. <Grid.RowDefinitions>
  3. <RowDefinition Height=”Auto”/>
  4. <RowDefinition Height=”*”/>
  5. </Grid.RowDefinitions>
  6. <!–TitlePanel contains the name of the application and page title–>
  7. <StackPanel x:Name=”TitlePanel” Grid.Row=”0″ Margin=”12,17,0,28″>
  8. <TextBlock x:Name=”ApplicationTitle” Text=”KINETICS” Style=”{StaticResource PhoneTextNormalStyle}”/>
  9. <TextBlock x:Name=”PageTitle” Text=”drag and flick” Margin=”9,-7,0,0″ Style=”{StaticResource PhoneTextTitle1Style}”/>
  10. </StackPanel>
  11. <!–ContentPanel – place additional content here–>
  12. <Grid x:Name=”ContentPanel” Grid.Row=”1″ >
  13. <Canvas x:Name=”MainCanvas” HorizontalAlignment=”Stretch” VerticalAlignment=”Stretch”>
  14. <Canvas.Background>
  15. <LinearGradientBrush StartPoint=”0 0″ EndPoint=”0 1″>
  16. <GradientStop Offset=”0″ Color=”Black”/>
  17. <GradientStop Offset=”1.5″ Color=”BlanchedAlmond”/>
  18. </LinearGradientBrush>
  19. </Canvas.Background>
  20. </Canvas>
  21. </Grid>
  22. </Grid>

the second row in the main grid contains a canvas element, MainCanvas, with its horizontal and vertical alignment set to stretch so that it occupies the entire grid. The canvas background is a linear gradient brush starting with Black and ending with BlanchedAlmond. We’ll add the button and image control to this canvas at run time.

Moving to Mainpage.xaml.cs the Mainpage class contains the following members,

  1. public partial class MainPage : PhoneApplicationPage
  2. {
  3. Button FlickButton;
  4. Image FlickImage;
  5. FrameworkElement ElemToMove = null;
  6. double ElemVelX, ElemVelY;
  7. const double SPEED_FACTOR = 60;
  8. DispatcherTimer timer;

FlickButton and FlickImage are the controls that we’ll add to the canvas. ElemToMove, ElemVelX and ElemVelY will be used by the timer callback to move the ui control. SPEED_FACTOR is used to scale the velocities of ui controls.

Here’s the Mainpage constructor,

  1. // Constructor
  2. public MainPage()
  3. {
  4. InitializeComponent();
  5. AddButtonToCanvas();
  6. AddImageToCanvas();
  7. timer = new DispatcherTimer();
  8. timer.Interval = TimeSpan.FromMilliseconds(35);
  9. timer.Tick += new EventHandler(OnTimerTick);
  10. }

We’ll look at those AddButton and AddImage functions in a moment. The constructor initializes a timer which fires every 35 milliseconds, this timer will be started after the flick gesture completes with some inertia.

Back to AddButton and AddImage functions,

  1. void AddButtonToCanvas()
  2. {
  3. LinearGradientBrush brush;
  4. GradientStop stop1, stop2;
  5. Random rand = new Random(DateTime.Now.Millisecond);
  6. FlickButton = new Button();
  7. FlickButton.Content = “”;
  8. FlickButton.Width = 100;
  9. FlickButton.Height = 100;
  10. brush = new LinearGradientBrush();
  11. brush.StartPoint = new Point(0, 0);
  12. brush.EndPoint = new Point(0, 1);
  13. stop1 = new GradientStop();
  14. stop1.Offset = 0;
  15. stop1.Color = Colors.White;
  16. stop2 = new GradientStop();
  17. stop2.Offset = 1;
  18. stop2.Color = (Application.Current.Resources["PhoneAccentBrush"] as SolidColorBrush).Color;
  19. brush.GradientStops.Add(stop1);
  20. brush.GradientStops.Add(stop2);
  21. FlickButton.Background = brush;
  22. Canvas.SetTop(FlickButton, rand.Next(0, 400));
  23. Canvas.SetLeft(FlickButton, rand.Next(0, 200));
  24. MainCanvas.Children.Add(FlickButton);
  25. //subscribe to events
  26. FlickButton.ManipulationDelta += new EventHandler<ManipulationDeltaEventArgs>(OnManipulationDelta);
  27. FlickButton.ManipulationCompleted += new EventHandler<ManipulationCompletedEventArgs>(OnManipulationCompleted);
  28. }

this function is basically glorifying a simple task. After creating the button and setting its height and width, its background is set to a linear gradient brush. The direction of the gradient is from top towards bottom and notice that the second stop color is the PhoneAccentColor, which changes along with the theme of the device. The line,

stop2.Color = (Application.Current.Resources["PhoneAccentBrush"] as SolidColorBrush).Color;

does the magic of extracting the PhoneAccentBrush from application’s resources, getting its color and assigning it to the gradient stop.

AddImage function is straight forward in comparison,

  1. void AddImageToCanvas()
  2. {
  3. Random rand = new Random(DateTime.Now.Millisecond);
  4. FlickImage = new Image();
  5. FlickImage.Source = new BitmapImage(new Uri(“/images/Marble.png”, UriKind.Relative));
  6. Canvas.SetTop(FlickImage, rand.Next(0, 400));
  7. Canvas.SetLeft(FlickImage, rand.Next(0, 200));
  8. MainCanvas.Children.Add(FlickImage);
  9. //subscribe to events
  10. FlickImage.ManipulationDelta += new EventHandler<ManipulationDeltaEventArgs>(OnManipulationDelta);
  11. FlickImage.ManipulationCompleted += new EventHandler<ManipulationCompletedEventArgs>(OnManipulationCompleted);
  12. }

The ManipulationDelta and ManipulationCompleted handlers are same for both the button and the image.

OnManipulationDelta() should look familiar, a similar implementation was used in the previous post,

  1. void OnManipulationDelta(object sender, ManipulationDeltaEventArgs args)
  2. {
  3. FrameworkElement Elem = sender as FrameworkElement;
  4. double Left = Canvas.GetLeft(Elem);
  5. double Top = Canvas.GetTop(Elem);
  6. Left += args.DeltaManipulation.Translation.X;
  7. Top += args.DeltaManipulation.Translation.Y;
  8. //check for bounds
  9. if (Left < 0)
  10. {
  11. Left = 0;
  12. }
  13. else if (Left > (MainCanvas.ActualWidth – Elem.ActualWidth))
  14. {
  15. Left = MainCanvas.ActualWidth – Elem.ActualWidth;
  16. }
  17. if (Top < 0)
  18. {
  19. Top = 0;
  20. }
  21. else if (Top > (MainCanvas.ActualHeight – Elem.ActualHeight))
  22. {
  23. Top = MainCanvas.ActualHeight – Elem.ActualHeight;
  24. }
  25. Canvas.SetLeft(Elem, Left);
  26. Canvas.SetTop(Elem, Top);
  27. }

all it does is calculate the control’s position, check for bounds and then set the top and left of the control.

OnManipulationCompleted() is more interesting because here we need to check if the gesture completed with any inertia and if it did, start the timer and continue to move the ui control until it comes to a halt slowly,

  1. void OnManipulationCompleted(object sender, ManipulationCompletedEventArgs args)
  2. {
  3. FrameworkElement Elem = sender as FrameworkElement;
  4. if (args.IsInertial)
  5. {
  6. ElemToMove = Elem;
  7. Debug.WriteLine(“Linear VelX:{0:0.00}  VelY:{1:0.00}”, args.FinalVelocities.LinearVelocity.X,
  8. args.FinalVelocities.LinearVelocity.Y);
  9. ElemVelX = args.FinalVelocities.LinearVelocity.X / SPEED_FACTOR;
  10. ElemVelY = args.FinalVelocities.LinearVelocity.Y / SPEED_FACTOR;
  11. timer.Start();
  12. }
  13. }

ManipulationCompletedEventArgs contains a member, IsInertial, which is set to true if the manipulation was completed with some inertia. args.FinalVelocities.LinearVelocity.X and .Y will contain the velocities along the X and Y axis. We need to scale down these values so they can be used to increment the ui control’s position sensibly. A reference to the ui control is stored in ElemToMove and the velocities are stored as well, these will be used in the timer callback to access the ui control. And finally, we start the timer.

The timer callback function is as follows,

  1. void OnTimerTick(object sender, EventArgs e)
  2. {
  3. if (null != ElemToMove)
  4. {
  5. double Left, Top;
  6. Left = Canvas.GetLeft(ElemToMove);
  7. Top = Canvas.GetTop(ElemToMove);
  8. Left += ElemVelX;
  9. Top += ElemVelY;
  10. //check for bounds
  11. if (Left < 0)
  12. {
  13. Left = 0;
  14. ElemVelX *= -1;
  15. }
  16. else if (Left > (MainCanvas.ActualWidth – ElemToMove.ActualWidth))
  17. {
  18. Left = MainCanvas.ActualWidth – ElemToMove.ActualWidth;
  19. ElemVelX *= -1;
  20. }
  21. if (Top < 0)
  22. {
  23. Top = 0;
  24. ElemVelY *= -1;
  25. }
  26. else if (Top > (MainCanvas.ActualHeight – ElemToMove.ActualHeight))
  27. {
  28. Top = MainCanvas.ActualHeight – ElemToMove.ActualHeight;
  29. ElemVelY *= -1;
  30. }
  31. Canvas.SetLeft(ElemToMove, Left);
  32. Canvas.SetTop(ElemToMove, Top);
  33. //reduce x,y velocities gradually
  34. ElemVelX *= 0.9;
  35. ElemVelY *= 0.9;
  36. //when velocities become too low, break
  37. if (Math.Abs(ElemVelX) < 1.0 && Math.Abs(ElemVelY) < 1.0)
  38. {
  39. timer.Stop();
  40. ElemToMove = null;
  41. }
  42. }
  43. }

if ElemToMove is not null, we get the top and left values of the control and increment the values with their X and Y velocities. Check for bounds, and if the control goes out of bounds we reverse its velocity. Towards the end, the velocities are reduced by 10% every time the timer callback is called, and if the velocities reach too low values the timer is stopped and ElemToMove is made null.

Here’s a short video of the program, the video is a little dodgy because my display driver refuses to run the animations smoothly. The flicks aren’t always recognised but the program should run well on an actual device (or a pc with better configuration),

You can download the source code from here: ButtonDragAndFlick.zip

Written by Prabhu Kumar

December 19th, 2010 at 2:35 pm

Posted in Uncategorized

Dictionary Web Service

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Today I came across this web service called aonaware which serves up word definitions from various dictionary databases, so I wrote up a quick windows phone 7 app to check it out and it’s kinda neat.

Here’s a video of the app running on the emulator, I’ll write a post soon.

Written by Prabhu Kumar

November 29th, 2010 at 2:36 pm

Posted in Uncategorized

Windows Phone 7 : UI Control Boundaries

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I was working on an application at work when I needed to figure out a really trivial case, well, trivial in theory at least. All I wanted to know was if a button was completely inside a rectangle. Could anything else be simpler you think. Just check the button bounds against the rectangle bounds,

pseudocode
if (Button.Top > Rectangle.Top &&
      Button.Left > Rectangle.Left &&
      Button.Right < Rectangle.Right &&
      Button.Bottom < Rectangle.Bottom)
{
    //Button is inside rectangle
}

the Right and Bottom of the Button and Rectangle can be calculated using the Width and the Height properties of each. You’d expect this to work correctly, but as far as Windows Phone 7 is concerned there is only one caveat.

I wrote up a simple application to illustrate this. Create a Windows Phone 7 Silverlight application and add the following to the ContentPanel grid in Mainpage.xaml,

  1. <Grid x:Name="ContentPanel" Grid.Row="1">
  2.     <Canvas x:Name="MainCanvas" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
  3.         <TextBlock x:Name="RectangleTop" Canvas.Top="0" />
  4.         <TextBlock x:Name="ButtonTop" Canvas.Top="30" />
  5.         <Rectangle x:Name="ColoredRectangle" Width="480" Height="150" Fill="Coral" Opacity="0.4" Canvas.Top="150" Canvas.Left="0"/>
  6.         <Button x:Name="MyButton" Content="Move Me" Canvas.Top="400" Canvas.Left="160" Background="Purple"/>
  7.     </Canvas>           
  8. </Grid>

the constructor of Mainpage looks like this,

  1. public MainPage()
  2. {
  3.     InitializeComponent();
  4.  
  5.     MyButton.ManipulationDelta += new EventHandler<ManipulationDeltaEventArgs>(OnMyButtonManipulationDelta);
  6.  
  7.     RectangleTop.Text = String.Format("Rectangle Top: {0}", Canvas.GetTop(ColoredRectangle));
  8.     ButtonTop.Text = String.Format("Button Top: {0}", Canvas.GetTop(MyButton));
  9. }

We register for the ManipulationDelta event on the button and update the Text on the two Textblocks to show the Top properties of the rectangle and the button, if you run the program this is how the application will look,

FirstScreen

The OnMyButtonManipulationDelta() function will be called whenever a ManipulationDelta event occurs on the MyButton control, which happens when the user clicks and drags the button around. Here we want to move the button along with the users drag,

  1. void OnMyButtonManipulationDelta(object sender, ManipulationDeltaEventArgs e)
  2. {
  3.     double deltaX = e.DeltaManipulation.Translation.X;
  4.     double deltaY = e.DeltaManipulation.Translation.Y;
  5.  
  6.     double btnX = Canvas.GetLeft(MyButton);
  7.     double btnY = Canvas.GetTop(MyButton);
  8.  
  9.     btnX += deltaX;
  10.     btnY += deltaY;
  11.  
  12.     Canvas.SetLeft(MyButton, btnX);
  13.     Canvas.SetTop(MyButton, btnY);
  14.  
  15.     ButtonTop.Text = String.Format("Button Top: {0}", Canvas.GetTop(MyButton));
  16. }

In this function we get the delta manipulation values along the X and Y axis and add it to the Buttons Left and Top property, this makes sure that the button control moves along with the users finger when he/she clicks and drags the button.

Now when we move the button and place it inside the rectangle the values on the textblocks update,

ButtonInsideRect

Things are fine till here, but they start getting interesting when you move the button to the top of the rectangle,

ButtonTopLessThanRectTop

the Button control appears to be well inside the Rectangle but the Top property of the button is 144 where as that of the Rectangle is 150. The values suggest that the button is outside the rectangle!

This happens because there is more to a button control than what meets the eyes. The button is not confined within the white rectangular boundary but is much bigger than that. When you drag and drop a button control using the visual editor in Visual Studio, the area of the button that is selected is bigger than the button itself, (see image below)

ButtonControlSelected

This is intentional and done to make sure that the target area for the user is a bit larger than the control itself so that the control can be selected easily without requiring too much precision. This, of course, is a nice feature (ask anyone who has tried using a Windows Mobile touch screen device with a finger ;)

Placing the Button control precisely on top of the rectangle like below,

ButtonOnTopOfRect

reveals that there are 12 extra pixels on all sides of the button control. (rectangle top = 150,  button top = 138)

So that is all in this post. In the next post we’ll see how easy it is to pick a button control and flick it, the button will bounce around the screen and come to a halt gradually. Refreshing old memories of marbles ;)

 

Post attachments
Source Code: ButtonBoundaries.zip

Update:
I forgot to add that the same case is also true for textbox and password box control

Update 2
I just recorded a short video of the application in action,

 

Written by Prabhu Kumar

November 22nd, 2010 at 2:46 pm

Posted in Uncategorized

Just another post

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angryBirdsIt’s been a while since my last post so I thought I’ll write a filler. Forgive me but I’m going to start off with some rant. My windows mobile marketplace account hasn’t been accessible for a couple of weeks now. Every time I try logging in I get this annoying error which says,

WE’RE SORRY. AN ERROR HAS OCCURRED.

We encountered an issue connecting your App Hub account with your Xbox Live Profile.
Please visit
Xbox.com and update your contact information.
After you have updated your contact information, please return to the App Hub (
https://users.create.msdn.com/Register) to continue.
View App Hub FAQ
A09/S3D4

The error code at the end keeps changing all the time, heck, I don’t even know if it’s an error code. As suggested, I updated my contact information on xbox.com, made sure that all the information at billing.microsoft.com was alright but still no luck. A little bit of searching on the help forums revealed that many other people were facing the same problem. And I thought Microsoft screwed up big time while migrating the mobile marketplace to the new and “improved” App Hub. What’s worse is that I can’t even see my existing app on the marketplace and I have no idea about the download figures, not that I am making thousands off it but still. And then yesterday I got the Windows Phone Newsletter for October, and it was reassuring in some ways. It said,

On October 11, we told you about App Hub, the single destination for both Windows Phone and Xbox Live indie developers. Although App Hub is now open for all developers to explore, only a small number of developers are currently able to submit Windows Phone 7 apps or games. On November 3, Windows Phone 7 app submission will be open to all registered Windows Phone Marketplace developers.” (emphasis mine)

Early October I had got a mail from Microsoft for early access to the App Hub. But I screwed it up by forgetting to attach the app screenshots (how difficult can mail attachments be!). Anyways, come November 3rd I hope all issues are resolved and access to marketplace is restored so that I can view the existing app and submit the new app I’ve been working on.

Update
Well, November 3rd has come and gone and nothing has changed. Still can’t access the Windows Phone 7 dashboard at AppHub. I have contributed to an existing thread showing my concern, here’s the link,
http://forums.create.msdn.com/forums/p/62093/397994.aspx#397994

Update 2
More forum threads here and here.

 

visualStudio In other news, the windows phone developer tools got an update, this October update includes,

  • A new Bing Maps Control that improves map performance during user gestures.
  • The Capability Detection Tool, which scans your application and reports on detected phone capabilities that will be applied during ingestion to marketplace.
  • The WP Connect Tool, with which you can create a connection between the Windows Phone and your PC without requiring Zune to be running, so you can debug media APIs.

You can download the update from here. Details about the Capability Detection Tool and the WP Connect Tool can be found here and here. I haven’t installed this update as I don’t see the need yet.

 

ProgWinPhone7 And finally, “Programming Windows Phone 7that Charles Petzold has been working on is now available for download and it’s free! You can download the pdf along with the sample code from here.

This is one book which I plan to read from start to end thoroughly. I have read the first two preview versions and highly recommend this to anyone serious about developing for Windows Phone 7. On being asked, Charles said that a print-on-demand soft cover version will be available soon which, of course, I plan to buy.

Written by Prabhu Kumar

October 31st, 2010 at 2:48 pm

Posted in Uncategorized

Windows Phone 7 : Final Release of Developer Tools!

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do-epic-shit-3 The official and the final bits of windows phone 7 developer tools are now available, go download them from here. The installer bundles everything you need to develop for windows phone 7 in a nice little package that includes,

- Visual Studio 2010 Express
- Silverlight for windows phone 7
- XNA Game Studio 4 for windows phone 7
- Expression Blend 4 for Windows Phone 7
- Windows Phone 7 emulator

You also get a phone registration and deployment tool which you can use to register and unlock a wp7 device, if you’re lucky enough to have one that is.The deployment tool works both on a physical device as well as the emulator and can be used to deploy your xap’s directly.

Another interesting bit of news today was the release of Windows Phone 7 Ads SDK, check it out here. I got really excited by this until I installed it and dug a little deeper. The documentation accompanying the install clearly says that, as of now at least, this can only be used by developers in the US,

Capture

disappointing, but hopefully it will be available for others outside of US soon. Off to installing the tools now, ciao.

Update: Forgot to mention about the Windows Phone 7 Training Kit. The samples have been updated to work with the RTM version of the tools and new tutorials have been added for pivot and panorama controls. You can download the kit from here.

Written by Prabhu Kumar

September 16th, 2010 at 2:49 pm

Posted in Uncategorized

Windows Mobile Marketplace: Getting started, App statistics and other details

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tempppppIf you follow me on twitter then this should not be news to you, the Mobile Minesweeper game that I’ve been working on (and off) forever has finally made it to marketplace and is available for download. There were a few surprises for me in store during the entire process. First, the amount of time it took for the app to be approved, one attempt and one working day! And second, the number of downloads! The app has been downloaded over 10,000 times since I made it available on the marketplace 10 days ago, even though the app is free I never expected so many downloads and it came as a pleasant shock. In this post I’ll share some resources that helped me to get started with marketplace and prepare for the entire process. And also some statistics related to my app.

Where do I begin?

To submit apps, you need to register for the marketplace and get a developer account. Go to http://developer.windowsphone.com and click on “Register for the marketplace”. Using this developer account you will also be able to submit apps for Windows Phone 7 when the marketplace opens for submissions early October. Here is a nice walk through the registration process,

Windows Marketplace for Mobile Developer Registration Walk Through

There are a few minor differences between the slides shown above and the present process, but it’s easy to figure out. So far, the marketplace experience for me has been really smooth. Apart from the initial hiccup during registration where my credit card wouldn’t work, app submission and an update have gone through without any problems.

Submitting apps to marketplace

Your application must meet all the application submission requirements and pass several test cases (like 2 hours of hopper test) to be certified. The Windows Mobile 6.5 Application Certification Requirements are available here (pdf) for download, and I suggest going through this document at least once. Here is a walk through the application submission process,

Windows Marketplace for Mobile Application Submission Walk Through

Another great resource is Joel’s article on marketplace, a must read;

http://www.codeproject.com/KB/windows/WiMoMarketPlc.aspx

App Statistics

From the start, I designed the app to support 3 resolutions 240×320, 240×400 and 480×800. I think that these are probably the most popular resolutions for windows mobile devices. The only other hardware requirement is that the device should have a touch screen. I had submitted the app for the US catalogue first, and after it passed certification I submitted the same for other English markets which include Australia, Canada, UK, India, and Singapore. Here are a few numbers,

EN-US Catalogue – available for 10 days

EN-US

 

AU, CA, UK, IN and SG Catalogue –available for 8 days

EN-AU

EN-CA

EN-GB

EN-IN

EN-SG

Clearly, US is by far the biggest market, no surprise really. If you happen to try out the app, do let me know what you think. Any suggestions or feedbacks are welcome. Goodbye. Until next time.

Written by Prabhu Kumar

September 5th, 2010 at 2:50 pm

Posted in Uncategorized