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POMisbehaviour in LoadState using SplitPage
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  1. POMisbehaviour in LoadState using SplitPage
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    copied!<p>I am working on a Windows 8 Metro Newsreader-App (with C# and XAML). I show the feed-items on a <code>Grouped Items Page</code> (template). A click forwards the user to a detail-page, which I implemented as a <code>Split Page</code>. Therefore, I have an Image-Gallery where the user can navigate from this DetailPage (and back). This works fine. On the ItemDetailPage I have to assign the Data in the <code>LoadState</code> function. The template offers me the following solution:</p> <pre><code>protected override void LoadState(Object navigationParameter, Dictionary&lt;String, Object&gt; pageState) { // TODO: Assign a bindable group to this.DefaultViewModel["Group"] // TODO: Assign a collection of bindable items to this.DefaultViewModel["Items"] if (pageState == null) { // When this is a new page, select the first item automatically unless logical page // navigation is being used (see the logical page navigation #region below.) if (!this.UsingLogicalPageNavigation() &amp;&amp; this.itemsViewSource.View != null) { this.itemsViewSource.View.MoveCurrentToFirst(); } } else { // Restore the previously saved state associated with this page if (pageState.ContainsKey("SelectedItem") &amp;&amp; this.itemsViewSource.View != null) { // TODO: Invoke this.itemsViewSource.View.MoveCurrentTo() with the selected // item as specified by the value of pageState["SelectedItem"] } } } </code></pre> <p>What I did was the following:</p> <pre><code>protected override void LoadState(Object navigationParameter, Dictionary&lt;String, Object&gt; pageState) { if (pageState == null) { // When this is a new page, select the first item automatically unless logical page // navigation is being used (see the logical page navigation #region below.) if (!this.UsingLogicalPageNavigation() &amp;&amp; this.itemsViewSource.View != null) { this.itemsViewSource.View.MoveCurrentToFirst(); } } else { // Restore the previously saved state associated with this page if (pageState.ContainsKey("SelectedItem") &amp;&amp; this.itemsViewSource.View != null) { this.itemsViewSource.View.MoveCurrentTo(pageState["SelectedItem"]); } } var item = ArticleDataSource.GetItem((int)navigationParameter); if (item != null) { this.DefaultViewModel["Group"] = item.Group; this.DefaultViewModel["Items"] = item.Group.Items; if (this.itemsViewSource.View != null) this.itemsViewSource.View.MoveCurrentTo(item); // remove? // Register this page as a share source. this.dataTransferManager = DataTransferManager.GetForCurrentView(); this.dataTransferManager.DataRequested += new TypedEventHandler&lt;DataTransferManager, DataRequestedEventArgs&gt;(this.OnDataRequested); } } </code></pre> <ol> <li>If I navigate from the OverviewPage to the DetailsPage the selected item (A) is shown.</li> <li>I select an other item (from the list) and the correct details (B) are shown.</li> <li>If I navigate from the DetailsPage to the GalleryPage the images of the correct item (B) are shown.</li> <li>If I now navigate back (to the DetailsPage) not the last selected item (B) but the item I selected (A) to enter DetailsPage is shown.</li> </ol> <p>I am aware of the fact that I changed the order (proposed by the template) and I added <code>if (this.itemsViewSource.View != null) this.itemsViewSource.View.MoveCurrentTo(item);</code> that I'd probably better remove.</p> <p>I think that the problem (described in step 4) is, that <code>this.itemsViewSource.View</code> is null and therefore (logically) <code>this.itemsViewSource.View.MoveCurrentTo(pageState["SelectedItem"])</code> doesn't get executed. Unfortunately, I was unable to find out why or if this is the bug.</p> <p>Any help or link to a tutorial (which could solve my problem) are really much appreciated! thanks.</p>
 

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