protected override void OnNavigatingFrom(NavigatingCancelEventArgs e)
{
// Before we navigate away from the page, we want to generate a new _persistedPosition string. This string contains the key of the item at the top of the
// viewing window (generated by the function GetKey) and the offset of that item.
RestoreScrollPositionSample._persistedPosition = ListViewPersistenceHelper.GetRelativeScrollPosition(this.ItemsListView, this.GetKey);
base.OnNavigatingFrom(e);
}
private async void RestoreScrollPosition()
{
if (this.savedScrollPosition != null)
{
await ListViewPersistenceHelper.SetRelativeScrollPositionAsync(BottomUpList, this.savedScrollPosition, (s) => Task.FromResult((object)s).AsAsyncOperation());
}
}
private void Page_Loaded(object sender, RoutedEventArgs e)
{
if (!string.IsNullOrEmpty(_persistedPosition))
{
_ = ListViewPersistenceHelper.SetRelativeScrollPositionAsync(itemGridView, _persistedPosition, GetItem);
}
}
private async void Page_Loaded(object sender, RoutedEventArgs e)
{
if (!string.IsNullOrEmpty(_persistedPosition))
{
await ListViewPersistenceHelper.SetRelativeScrollPositionAsync(this.DuanListView, _persistedPosition, this.GetItem);
}
}
private async void Page_Loaded(object sender, RoutedEventArgs e)
{
if (!string.IsNullOrEmpty(RestoreScrollPositionSample._persistedPosition))
{
// Here we kick off the async function to use the saved string _persistedPosition and the function GetItem to restore the scroll posistion
await ListViewPersistenceHelper.SetRelativeScrollPositionAsync(this.ItemsListView, RestoreScrollPositionSample._persistedPosition, this.GetItem);
}
}
protected override void OnNavigatingFrom(NavigatingCancelEventArgs e)
{
_persistedPosition = ListViewPersistenceHelper.GetRelativeScrollPosition(itemGridView, GetKey);
base.OnNavigatingFrom(e);
if (e.Cancel)
{
return;
}
if (e.NavigationMode == NavigationMode.Back)
{
_persistedPosition = null;
var animation = ConnectedAnimationService.GetForCurrentView()
.PrepareToAnimate(CONNECTED_ANIMATION_HOSTED_CONFIG_NAME, hostedConfigNameTextBlock);
if (ApiInformation.IsTypePresent("Windows.UI.Xaml.Media.Animation.DirectConnectedAnimationConfiguration"))
{
animation.Configuration = new DirectConnectedAnimationConfiguration();
}
}
}
private void PersistControlsState()
{
try
{
TempSettingsUtils.Set(Constants.TEMP_PIVOT_STATE, MainPivot.SelectedIndex);
if (this.SurahListView.ItemsPanelRoot != null)
{
TempSettingsUtils.Set(Constants.TEMP_SURAH_LIST_STATE, ListViewPersistenceHelper.GetRelativeScrollPosition(this.SurahListView, this.GetKeyFromListView));
}
if (this.JuzListView.ItemsPanelRoot != null)
{
TempSettingsUtils.Set(Constants.TEMP_JUZ_LIST_STATE, ListViewPersistenceHelper.GetRelativeScrollPosition(this.JuzListView, this.GetKeyFromListView));
}
}
catch (Exception ex)
{
telemetry.TrackException(ex, new Dictionary <string, string> {
{ "Scenario", "PersistControlsState" }
});
}
}
private async void RestoreControlsState()
{
try
{
var pivotState = TempSettingsUtils.Get <int>(Constants.TEMP_PIVOT_STATE);
if (pivotState >= 0)
{
MainPivot.SelectedIndex = pivotState;
}
var surahListViewState = TempSettingsUtils.Get <string>(Constants.TEMP_SURAH_LIST_STATE);
if (surahListViewState != null)
{
await ListViewPersistenceHelper.SetRelativeScrollPositionAsync(this.SurahListView, surahListViewState, key =>
{
return(Task.Run(() =>
{
return (object)ViewModel.Surahs.FirstOrDefault(s => s.Id == key);
}).AsAsyncOperation());
});
}
var juzListViewState = TempSettingsUtils.Get <string>(Constants.TEMP_JUZ_LIST_STATE);
if (juzListViewState != null)
{
await ListViewPersistenceHelper.SetRelativeScrollPositionAsync(this.JuzListView, juzListViewState, key =>
{
return(Task.Run(() =>
{
return (object)ViewModel.Juz.FirstOrDefault(s => s.Id == key);
}).AsAsyncOperation());
});
}
}
catch (Exception ex)
{
telemetry.TrackException(ex, new Dictionary <string, string> {
{ "Scenario", "RestoreControlsState" }
});
}
}
public String GetState(Func <Object, String> itemToKeyFunction)
{
var itemToKeyHandler = (ListViewItemToKeyHandler)((item) => itemToKeyFunction.Invoke(item));
return(ListViewPersistenceHelper.GetRelativeScrollPosition(this, itemToKeyHandler));
}
public Task SetStateAsync(String state, Func <String, Object> keyToItemFunction)
{
ListViewKeyToItemHandler keyToItemHandler = (key) => LoadedStateAwaiter.Task.ContinueWith(t => String.IsNullOrEmpty(key) ? null : keyToItemFunction.Invoke(key)).AsAsyncOperation();
return(ListViewPersistenceHelper.SetRelativeScrollPositionAsync(this, state, keyToItemHandler).AsTask());
}
private void SaveScrollPosition()
{
// We let the item be its own key. In a more general program, the item would have
// a unique ID that identifies it in the list.
this.savedScrollPosition = ListViewPersistenceHelper.GetRelativeScrollPosition(BottomUpList, (o) => o.ToString());
}
protected override void OnNavigatingFrom(NavigatingCancelEventArgs e)
{
_persistedPosition = ListViewPersistenceHelper.GetRelativeScrollPosition(DuanListView, GetKey);
base.OnNavigatingFrom(e);
}
