Question

I’m porting an Android app to wp7 and I’m trying to do things the .net way, and I’m beginning to get my head wrapped around data binding, but I am lost when it comes to a few things.

My classes consist of the following:

• PickLeaf – the data representation of each item in the list
• PickLeafModel – the data representation of a collection of PickLeaf objects
• PickLeafCell – the user control for each item in the list
• PickLeafListView – derived version of ListBox
• PickLeafPage – the page that contains the list view and instantiates some of the controller objects and threads
• IPickLeafListener – an interface that the PickLeafPage implements and allows it to get notified when certain things occur regarding to the PickLeafCell (tap, context menu opened, scroll window changed)

Currently I am adding the PickLeafCell controls dynamically to PickLeafListView.Items, which kind of goes around data binding and perhaps is leading to some of the bugs I am seeing (such as updating it while its being scrolled causes scroll window to go berserk).

QUESTION: If I change it so that the PickLeafModel can be used as a DataSource, how do I pass the IPickLeafListener and PickLeaf references to the PickLeafCell using data binding?

Thanks!

Answer 1

It’s hard to understand your architecture, but I try.

First of all, bind your data to ListBox

listBox.ItemsSource = PickLeafModel;

Your ListBox should looks like:

 <ListBox x:Name="listBox" ...>
      <ListBox.ItemTemplate>
           <DataTemplate>
                <my:PickLeafCell DataContext={Binding} TapEvent="Tap" .../>
           </DataTemplate>
      </ListBox.ItemTemplate>
 </ListBox>

Two main thing happen here: PickLeafCell DataContext is bind to your data for each list item. And you subscribe to your PickLeafCell custom events.

When some event happens in PickLeafCell control, it raised custom event to which your main page is subscribed

 public class PickLeafCell...
 {
      public delegate void TapEventEventHandler(object sender, EventArgs e);
      public event TapEventEventHandler TapEvent;

      protected virtual void OnTap(EventArgs e) 
      {
           if (TapEvent != null)
                TapEvent(this, e);
      }

This is your C# main page code-behind where you have event handlers:

 private Tap(object sender, EventArgs e)
 {
      var item = (sender as FrameworkElement).DataContext as PickLeaf;
 }

And in PickLeafCell control you have DataContext already set to your PickLeaf, so you can easy bind to fields

 <TextBlock Text={Binding SomeFieldOfPickLeaf} />