This document provides an overview of key concepts for building apps for Windows Phone 8.1, including navigation, view models, data binding, and more. It discusses using frames to navigate between pages, passing parameters between pages, handling the back button, and caching pages. It also covers implementing INotifyPropertyChanged for view models, binding to view models, and using fallback values and modes in bindings.

1. WinRT Apps
29 April 2014
Building Apps for Windows Phone 8.1 Jump Start

4. Window
Frame
Page
Window

5. protected override void OnLaunched(LaunchActivatedEventArgs e)
{
Frame rootFrame = Window.Current.Content as Frame;
// Do not repeat app initialization when the Window already has
// content, just ensure that the window is active
if (rootFrame == null)
{
// Create a Frame to act as the navigation context and navigate
// to the first page
rootFrame = new Frame();
...
// Place the frame in the current Window
Window.Current.Content = rootFrame;
}
if (rootFrame.Content == null)
{
// Navigate to the first page
rootFrame.Navigate(typeof(MainPage), e.Arguments);
}
// Ensure the current window is active
Window.Current.Activate();
}

6. private void itemListView_ItemClick(object sender, ItemClickEventArgs e)
{
// Navigate to the appropriate destination page, configuring the new page
// by passing required information as a navigation parameter
var itemId = ((MyListViewItem)e.ClickedItem).UniqueId;
Frame.Navigate(typeof(MyDetailPage), itemId);
}
You are responsible for context
When navigating to a page, you are responsible for providing any parameters/data using the
“parameter” parameter of the Navigate method.

7. private void btnGoBack_Click(
object sender, RoutedEventArgs e)
{
if (this.Frame.CanGoBack)
this.Frame.GoBack();
}

8. In Windows Phone Store apps, you must include code to
override this to cause a backwards navigation within the app
Differs from Windows Phone Silverlight – within an app,
backwards page navigation is default for that framework
Differs from Windows Phone Silverlight – Closes the current
app in that framework

10. public sealed partial class SecondPage : Page
{
...
protected override void OnNavigatedTo(NavigationEventArgs e)
{
Windows.Phone.UI.Input.HardwareButtons.BackPressed += HardwareButtons_BackPressed;
}
protected override void OnNavigatedFrom(NavigationEventArgs e)
{
Windows.Phone.UI.Input.HardwareButtons.BackPressed -= HardwareButtons_BackPressed;
}
async void HardwareButtons_BackPressed(object sender, Windows.Phone.UI.Input.BackPressedEventArgs e)
{
e.Handled = true; // We've handled this button press
// If the secondary UI is visible, hide it
if (SecondaryUI.Visibility == Visibility.Visible )
{
FadeOutSecondaryStoryboard.Begin();
}
else
{
// Standard page backward navigation
if (Frame.CanGoBack)
Frame.GoBack();
}
}

12. NavigationCacheMode
NavigationCacheMode.Disabled
NavigationCacheMode.Enabled
NavigationCacheMode.Required

14. NavigationCacheMode.Disabled
NavigationCacheMode.Enabled Required
Page 1 Page 2 Page 3
new new
?

20. Or
<TextBlock x:Name="DirectionsTextBlock" TextWrapping="Wrap"
Margin="12,0,0,0" Text="{Binding Directions}" />

21. <TextBlock x:Name="DirectionsTextBlock" TextWrapping="Wrap"
Margin="12,0,0,0" Text="{Binding Directions, Mode=OneWay}" />

22. public class ItemViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
…
}

23. Subscribes to

24. public class ItemViewModel : INotifyPropertyChanged
{
private string _id;
/// Sample ViewModel property;
public string ID
{
get { return _id; }
set {
if (value != _id) {
_id = value;
NotifyPropertyChanged("ID"); }
} }
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
handler(this, new PropertyChangedEventArgs(propertyName));
}
}

25. public class ItemViewModel : INotifyPropertyChanged {
// Properties
private string _id;
public string ID
{
get { return _id; }
set { this.SetProperty(ref this._id, value); }
}
// Property Change logic
public event PropertyChangedEventHandler PropertyChanged;
protected bool SetProperty<T>(ref T storage, T value, [CallerMemberName] String propertyName = null)
{
if (object.Equals(storage, value)) return false;
storage = value;
this.OnPropertyChanged(propertyName);
return true;
}
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var eventHandler = this.PropertyChanged;
if (eventHandler != null)
eventHandler(this, new PropertyChangedEventArgs(propertyName));
}
}

26. <ListView x:Name="IngredientsLIstBox"
ItemTemplate="{StaticResource MyDataTemplate}"
DataContext="{StaticResource RecipeViewModel}"/>
ItemsSource="{Binding Ingredients}"/>

27. public class RecipeDetails : INotifyPropertyChanged
{
/// <summary>
/// A collection for ItemViewModel objects.
/// </summary>
public ObservableCollection<ItemViewModel> Items { get; private set; }
public void LoadData()
{
this.Items.Add(new ItemViewModel() { ID = "0", LineOne = "runtime one", LineTwo = ... });
this.Items.Add(new ItemViewModel() { ID = "1", LineOne = "runtime two", LineTwo = ... });
this.Items.Add(new ItemViewModel() { ID = "2", LineOne = "runtime three", LineTwo =...});
}
...
}

28. <Button Content="{Binding Path=NextItem, Mode=OneWay,
TargetNullValue={Binding Path=NullValue}}" />
<TextBlock Text="{Binding Path=badPath,
FallbackValue='this is a fallback value'}"
Grid.Column="1"> </TextBlock>

29. http://msdn.microsoft.com/en-us/library/hh821028.aspx

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