Prince Sultan University
College of Computer & Information Sciences
Department of Computer Science
CS387: Mobile Applications Development
Win phone 7: Practice Sheet 3
Building a Simple FlashLight Application
Purpose:
The main purpose of this sheet is to build a simple flash light application that generates a
pattern of light signals using a timer, Two types of signal patterns will be generated: SOS
(base on Morse code) and a continuous strobe patterns. The user may switch between the
two using a couple of application bar buttons.
Include Namespaces:
using System.Reflection;
using System.Windows.Threading;
using Microsoft.Phone.Shell;
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The Setting Class again and the images:
The Setting Class Again:
using System.IO.IsolatedStorage;
namespace FlashLight2
{
// Encapsulates a key/value pair stored in Isolated Storage
ApplicationSettings
public class Setting<T>
{
string name;
T value;
T defaultValue;
bool hasValue;
public Setting(string name, T defaultValue)
{
this.name = name;
this.defaultValue = defaultValue;
}
public T Value
{
get
{
// Check for the cached value
if (!this.hasValue)
{
// Try to get the value from Isolated Storage
if (!IsolatedStorageSettings.ApplicationSettings.TryGetValue(
this.name, out this.value))
{
// It hasn't been set yet
this.value = this.defaultValue;
IsolatedStorageSettings.ApplicationSettings[this.name] =
this.value;
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}
this.hasValue = true;
}
return this.value;
}
set
{
// Save the value to Isolated Storage
IsolatedStorageSettings.ApplicationSettings[this.name] = value;
this.value = value;
this.hasValue = true;
}
}
public T DefaultValue
{
get { return this.defaultValue; }
}
// "Clear" cached value:
public void ForceRefresh()
{
this.hasValue = false;
}
}
}
The main interface:
The following XAML code describes the main interface. As clear from the code, the
interface consists of an application bar with two buttons and a Menu Item List.
<phone:PhoneApplicationPage.ApplicationBar>
<!-- The ApplicationBar object: -->
<shell:ApplicationBar Opacity=".5">
<!-- Two buttons: -->
<shell:ApplicationBarIconButton Text="sos" IconUri="Images/sos.png"
Click="SosButton_Click"/>
<shell:ApplicationBarIconButton Text="strobe"
IconUri="Images/strobe.png" Click="StrobeButton_Click"/>
<!-- Eight menu items: -->
<shell:ApplicationBar.MenuItems>
<shell:ApplicationBarMenuItem Text="red"/>
<shell:ApplicationBarMenuItem Text="orange"/>
<shell:ApplicationBarMenuItem Text="yellow"/>
<shell:ApplicationBarMenuItem Text="green"/>
<shell:ApplicationBarMenuItem Text="cyan"/>
<shell:ApplicationBarMenuItem Text="purple"/>
<shell:ApplicationBarMenuItem Text="gray"/>
<shell:ApplicationBarMenuItem Text="white"/>
</shell:ApplicationBar.MenuItems>
</shell:ApplicationBar>
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</phone:PhoneApplicationPage.ApplicationBar>
<!-- No content other than a solid background: -->
<Grid x:Name="BackgroundGrid" Background="White"/>
The main resources (three icon images):
The icon images for three application bar buttons are provided for your convenience.
These are:
Cancel.png
SOS.png
Strobe.png
They should be placed in a subdirectory within the solution explorer
Declaring Top-Level Member variables and objects:
// All three modes
enum FlashlightMode
{
Solid,
Sos,
Strobe
}
The application bar buttons are a special type of buttons that should be declared directly
in your code.
Note that we declare two timers for the signaling process:
// Members for the two application bar buttons:
IApplicationBarIconButton sosButton;
IApplicationBarIconButton strobeButton;
// For the two special modes:
SolidColorBrush onBrush;
SolidColorBrush offBrush = new SolidColorBrush(Colors.Black);
DispatcherTimer strobeTimer = new DispatcherTimer();
DispatcherTimer sosTimer = new DispatcherTimer();
int sosStep;
// Remember the chosen color, for future app activations or launches:
Setting<Color> savedColor = new Setting<Color>("SavedColor", Colors.White);
// The current mode (Solid, Sos, or Strobe)
FlashlightMode mode = FlashlightMode.Solid;
Initialization (Constructor):
As usual, the initialization is performed within the constructor:
public MainPage()
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{
InitializeComponent();
// Assign application bar buttons to member fields, because this cannot be
// done by InitializeComponent:
this.sosButton = this.ApplicationBar.Buttons[0]
as IApplicationBarIconButton;
this.strobeButton = this.ApplicationBar.Buttons[1]
as IApplicationBarIconButton;
// Initialize the timer for strobe mode
this.strobeTimer.Interval = TimeSpan.FromSeconds(.1); // Not too fast!
this.strobeTimer.Tick += StrobeTimer_Tick;
// Initialize the timer for SOS mode
this.sosTimer.Interval = TimeSpan.Zero;
this.sosTimer.Tick += SosTimer_Tick;
// Attach the same Click handler to all menu items in the application bar
foreach (IApplicationBarMenuItem menuItem in this.ApplicationBar.MenuItems)
menuItem.Click += MenuItem_Click;
// Restore persisted color
this.onBrush = new SolidColorBrush(this.savedColor.Value);
this.BackgroundGrid.Background = onBrush;
}
Programming the SOS Timer Event:
void SosTimer_Tick(object sender, EventArgs e)
{
// Toggle the background, but also adjust the time between each tick in
// order to make the dot-dot-dot-dash-dash-dash-dot-dot-dot pattern
switch (this.sosStep)
{
case 1: case 3: case 5:
// Each dot in the first S
case 13: case 15: case 17:
// Each dot in the second S
this.BackgroundGrid.Background = this.onBrush;
this.sosTimer.Interval = TimeSpan.FromSeconds(.2); // A short value
break;
case 7: case 9: case 11:
// Each dash in the O
this.BackgroundGrid.Background = this.onBrush;
this.sosTimer.Interval = TimeSpan.FromSeconds(1); // A long value
break;
case 18:
// The space between the end of one SOS
// and the beginning of the next one
this.BackgroundGrid.Background = this.offBrush;
this.sosTimer.Interval = TimeSpan.FromSeconds(1);
break;
default:
// The space between each dot/dash
this.BackgroundGrid.Background = this.offBrush;
this.sosTimer.Interval = TimeSpan.FromSeconds(.2);
break;
}
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// Cycle from 0 - 18
this.sosStep = (this.sosStep + 1) % 19;
}
The Strobe Timer Event:
void StrobeTimer_Tick(object sender, EventArgs e)
{
// Toggle the background on every tick
if (this.BackgroundGrid.Background == this.onBrush)
this.BackgroundGrid.Background = this.offBrush;
else
this.BackgroundGrid.Background = this.onBrush;
}
The SOS Button Click Event:
// The Click handler for the SOS button
void SosButton_Click(object sender, EventArgs e)
{
// First, reset the current state to solid mode
FlashlightMode mode = this.mode;
RestoreSolidMode();
// If we were already in SOS mode, then this click
// cancels it and we are done
if (mode == FlashlightMode.Sos)
return;
// Change to SOS mode
// Change the button icon, the mode, a counter, and start the timer
(sender as IApplicationBarIconButton).IconUri =
new Uri("Images/cancel.png", UriKind.Relative);
this.mode = FlashlightMode.Sos;
this.sosStep = 0;
this.sosTimer.Start();
}
The Strobe-Button Click Event:
// The Click handler for the strobe button
void StrobeButton_Click(object sender, EventArgs e)
{
// First, reset the current state to solid mode
FlashlightMode mode = this.mode;
RestoreSolidMode();
// If we were already in strobe mode, then this click
// cancels it and we are done
if (mode == FlashlightMode.Strobe)
return;
// Show a warning
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MessageBoxResult result = MessageBox.Show("Strobe lights can trigger " +
"seizures for people with photosensitive epilepsy. " +
"Are you sure you want to start the strobe light?",
"Warning!", MessageBoxButton.OKCancel);
// If the user agreed, change to strobe mode
if (result == MessageBoxResult.OK)
{
// Change the button icon, the mode, and start the timer
(sender as IApplicationBarIconButton).IconUri =
new Uri("Images/cancel.png", UriKind.Relative);
this.mode = FlashlightMode.Strobe;
this.strobeTimer.Start();
}
}
The Menu Item Click Events:
// The menu item Click handler that changes the flashlight color
void MenuItem_Click(object sender, EventArgs e)
{
// Grab the text from the menu item to determine the desired color
string chosenColor = (sender as IApplicationBarMenuItem).Text;
// Use reflection to turn the color name (e.g. "red") into an actual Color
Color c = (Color)typeof(Colors).GetProperty(chosenColor,
BindingFlags.Public | BindingFlags.Static | BindingFlags.IgnoreCase).
GetValue(null, null);
// Persist this choice and set the background color
this.savedColor.Value = c;
this.onBrush = new SolidColorBrush(this.savedColor.Value);
this.BackgroundGrid.Background = onBrush;
}
Reset Solid Mode:
// Reset the state associated with mode switches
void RestoreSolidMode()
{
this.strobeTimer.Stop();
this.sosTimer.Stop();
this.BackgroundGrid.Background = onBrush;
this.sosButton.IconUri = new Uri("Images/sos.png", UriKind.Relative);
this.strobeButton.IconUri = new Uri("Images/strobe.png", UriKind.Relative);
this.mode = FlashlightMode.Solid;
}
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