Windows Phone Programming Practice Sheet 2
CS387 Mobile Application Development
Windows Phone Programming Practice Sheet 2
Building a Persistent Count Application
Purpose:
To build a simple application that counts as you tap (press the left Mouse Button) and save the current value in isolated storage if you navigate away from the application. When you navigate back to the application, you continue based on the latest value of your count. To reset the count to zero, use a “Reset” button.
Interface:
You need three Grid Rows:
The top row for the application name and page title
The middle row for the count (use a huge font size)
The third row for the button
The following XAML code will help you achieve that:
<!--LayoutRoot is the root grid where all page content is placed-->
Grid x:Name="LayoutRoot" Background="Transparent">
Grid.RowDefinitions
RowDefinition Height="Auto"/>
RowDefinition Height="*"/>
RowDefinition Height="Auto"/>
</Grid.RowDefinitions
<!--TitlePanel contains the name of the application and page title-->
StackPanel x:Name="TitlePanel"Grid.Row="0" Margin="12,17,0,28">
TextBlock x:Name="ApplicationTitle" Text="Persistent Count"
Style="{StaticResourcePhoneTextNormalStyle}"/>
TextBlock x:Name="PageTitle" Text="Tap to Count" Margin="9,-7,0,0"
Style="{StaticResource PhoneTextTitle1Style}"/>
</StackPanel
<!-- Row 1: The text block containing the count -->
TextBlock x:Name="CountTextBlock"Grid.Row="1"TextAlignment="Center" Text="0"/>
<!-- Row 2: The reset button -->
Button x:Name="ResetButton"Grid.Row="2" Click="ResetButton_Click" Content="reset"/>
</Grid
Required Library Class:
Before you proceed to program the events, you need to place the following class in a shared folder. This is the class that will help you save the value of your count in isolated storage:
usingSystem.IO.IsolatedStorage;
namespaceWindowsPhoneApp
{
// Encapsulates a key/value pair stored in Isolated Storage ApplicationSettings
publicclassSetting<T>
{
string name;
T value;
T defaultValue;
boolhasValue;
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, outthis.value))
{
// It hasn't been set yet
this.value = this.defaultValue;
IsolatedStorageSettings.ApplicationSettings[this.name] =
this.value;
}
this.hasValue = true;
}
returnthis.value;
}
set
{
// Save the value to Isolated Storage
IsolatedStorageSettings.ApplicationSettings[this.name] = value;
this.value = value;
this.hasValue = true;
}
}
public T DefaultValue
{
get { returnthis.defaultValue; }
}
// "Clear" cached value:
publicvoidForceRefresh()
{
this.hasValue = false;
}
}
}
Programming the Events:
To count tap anywhere on the screen:
// Handle a tap anywhere on the page (other than the Button)
protectedoverridevoidOnMouseLeftButtonDown(MouseButtonEventArgs e)
{
base.OnMouseLeftButtonDown(e);
this.count++;
this.CountTextBlock.Text = this.count.ToString("N0");
}
To reset the count press the Reset Button:
privatevoidResetButton_Click(object sender, RoutedEventArgs e)
{
this.count = 0;
this.CountTextBlock.Text = this.count.ToString("N0");
}
If you navigate away from the application, the count will be saved in isolated storage:
protectedoverridevoidOnNavigatedFrom(NavigationEventArgs e)
{
base.OnNavigatedFrom(e);
// Persist state when leaving for any reason (Deactivated or Closing):
this.savedCount.Value = this.count;
}
If you navigate back to the application, the latest value of the count will be loaded from isolated storage:
protectedoverridevoidOnNavigatedFrom(NavigationEventArgs e)
{
base.OnNavigatedFrom(e);
// Persist state when leaving for any reason (Deactivated or Closing):
this.savedCount.Value = this.count;
}
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