private async Task DoLoadAsync()
{
IsBusy = true;
bool couldLoad = false;
try
{
// Need to define the action to call
var data = await LoadPageFromNetworkAsync();
foreach (T item in data)
{
AllItems.Add(item);
}
couldLoad = true;
DataLocation = DataLoadLocation.RemoteService;
}
catch (Exception e)
{
HandleLoadException(e);
couldLoad = false;
}
if (!couldLoad)
{
DataLocation = DataLoadLocation.Cache;
try
{
AllItems.Clear();
var data = await LoadDataFromCacheAsync();
foreach (T item in data)
{
AllItems.Add(item);
}
HasMoreData = false;
}
catch (Exception e)
{
HandleLoadException(e);
}
DataLocation = DataLoadLocation.Cache;
}
UpdateOfflineIndicator();
IsBusy = false;
IsLoading = false;
}
protected IncrementalSearchPage()
{
RowsBeforeTheEndToLoad = 10;
LastSearch = String.Empty;
DataLocation = DataLoadLocation.None;
AllItems = new ObservableCollection <T>();
SearchBar = new SearchBar {
Placeholder = "Search for..."
};
SearchBar.SearchButtonPressed += async(sender, args) => await LoadItemsAsync(SearchBar.Text);
ActivityView = new ActivityMessageView {
IsVisible = false
};
ActivityView.SetBinding(ActivityMessageView.IsShowingProperty,
new Binding("IsBusy", source: this));
OfflineIndicator = new FramedLabel {
IsVisible = false,
Text = "Currently offline - using cached data"
};
this.ListView = new ListView(ListViewCachingStrategy.RecycleElement)
{
ItemsSource = AllItems,
ItemTemplate = new DataTemplate(typeof(TextCell))
};
this.ListView.ItemTapped += async(s, e) => {
var item = e.Item as T;
this.ListView.SelectedItem = null;
await ItemSelectedAsync(item);
};
// Provide Access for infinite scrolling by loading more data
// when you are at the last record
this.ListView.ItemAppearing += async(sender, e) => {
if (HasMoreData && !IsLoading)
{
var foundIndex = AllItems.IndexOf(e.Item as T);
if (foundIndex == AllItems.Count - RowsBeforeTheEndToLoad)
{
await LoadNextPageAsync();
}
}
};
this.ListView.IsPullToRefreshEnabled = true;
this.ListView.Refreshing += async(sender, e) => {
await LoadItemsAsync(LastSearch);
this.ListView.IsRefreshing = false;
};
var layout = new RelativeLayout();
layout.Children.Add(
SearchBar,
Constraint.Constant(0),
Constraint.Constant(0),
Constraint.RelativeToParent(p => p.Width),
Constraint.Constant(50)
);
layout.Children.Add(
this.ListView,
Constraint.Constant(0),
Constraint.Constant(50),
Constraint.RelativeToParent(p => p.Width),
Constraint.RelativeToParent(p => p.Height - 50)
);
layout.Children.Add(
OfflineIndicator,
Constraint.Constant(0),
Constraint.RelativeToParent(p => p.Height - 45),
Constraint.RelativeToParent(p => p.Width),
Constraint.Constant(45)
);
layout.Children.Add(
ActivityView,
Constraint.RelativeToParent(p => p.Width - 100),
Constraint.RelativeToParent(p => p.Height - 100),
Constraint.Constant(90),
Constraint.Constant(90)
);
Content = layout;
}