Merge pull request #453 from telerik/marchev/lv-auto-lod-command-raised-multiple-times

Marchev/lv auto lod command raised multiple times

Controls/Data.UWP/Data/IncrementalLoading/ManualBatchLoadingProvider.cs

@@ -5,6 +5,8 @@ namespace Telerik.Core.Data
     internal class ManualBatchLoadingProvider<T> : IDisposable, IBatchLoadingProvider
     {
         private ICollection<T> loadedItemsCollection;
+        private BatchLoadingStatus? status;
+
         public ManualBatchLoadingProvider(ICollection<T> loadedItemsCollection)
         {
             this.loadedItemsCollection = loadedItemsCollection;
@@ -15,6 +17,11 @@ namespace Telerik.Core.Data
 
         public bool ShouldRequestItems(int lastRequestedIndex, int bufferSize)
         {
+            if (this.status == BatchLoadingStatus.ItemsRequested)
+            {
+                return false;
+            }
+
             return lastRequestedIndex >= this.loadedItemsCollection.Count - bufferSize;
         }
 
@@ -28,6 +35,8 @@ namespace Telerik.Core.Data
 
         public void OnStatusChanged(BatchLoadingStatus status)
         {
+            this.status = status;
+
             var handler = this.StatusChanged;
             if (handler != null)
             {

Controls/DataControls/DataControls.UWP/ListView/Model/IListView.cs

@@ -19,5 +19,7 @@ namespace Telerik.UI.Xaml.Controls.Data
         void ScrollToTop();
 
         void SetScrollPosition(RadPoint point, bool updateUI, bool updateScrollViewer);
+
+        object GetDataContext();
     }
 }

Controls/DataControls/DataControls.UWP/ListView/Model/ListViewModel.cs

@@ -56,7 +56,8 @@ namespace Telerik.UI.Xaml.Controls.Data
                 {
                     if (this.DataLoadingMode == BatchLoadingMode.Explicit || this.GroupDescriptors.Count > 0)
                     {
-                        return this.View.CommandService.CanExecuteCommand(CommandId.LoadMoreData, new LoadMoreDataContext());
+                        LoadMoreDataContext context = new LoadMoreDataContext { View = this.View, DataContext = this.View.GetDataContext() };
+                        return this.View.CommandService.CanExecuteCommand(CommandId.LoadMoreData, context);
                     }
                 }
                 return false;
@@ -268,7 +269,8 @@ namespace Telerik.UI.Xaml.Controls.Data
 
             if (this.ShouldAutoRequestItems(null))
             {
-                this.View.CommandService.ExecuteCommand(CommandId.LoadMoreData, new LoadMoreDataContext());
+                LoadMoreDataContext context = new LoadMoreDataContext { View = this.View, DataContext = this.View.GetDataContext() };
+                this.View.CommandService.ExecuteCommand(CommandId.LoadMoreData, context);
             }
 
             // NOTE: If we decide that we won't zero the length of collapsed rows then this 'TotalLineCount - 1' will be incorrect.

Controls/DataControls/DataControls.UWP/ListView/View/Controls/ListViewLoadDataUICommand.cs

@@ -53,7 +53,9 @@ namespace Telerik.UI.Xaml.Controls.Data.ListView
         /// </param>
         public void Execute(object parameter)
         {
-            this.LoadDataControl.Owner.CommandService.ExecuteCommand(Commands.CommandId.LoadMoreData, new LoadMoreDataContext());
+            RadListView listView = this.LoadDataControl.Owner;
+            LoadMoreDataContext context = new LoadMoreDataContext { View = listView, DataContext = listView.DataContext };
+            listView.CommandService.ExecuteCommand(Commands.CommandId.LoadMoreData, context);
         }
     }
 }

Controls/DataControls/DataControls.UWP/ListView/View/RadListView.cs

@@ -978,6 +978,11 @@ namespace Telerik.UI.Xaml.Controls.Data
             }
         }
 
+        object IListView.GetDataContext()
+        {
+            return this.DataContext;
+        }
+
         internal void InvalidatePanelMeasure(RadSize radSize)
         {
             if (this.contentPanel != null)

Controls/DataControls/DataControls.UWP/ListView/View/Services/Commands/LoadMoreDataContext.cs

@@ -12,5 +12,15 @@
         /// </summary>
         /// <value>The size of the batch.</value>
         public uint? BatchSize { get; set; }
+
+        /// <summary>
+        /// Gets the underlying data context.
+        /// </summary>
+        public object DataContext { get; internal set; }
+
+        /// <summary>
+        /// Gets the view to which this context is associated with.
+        /// </summary>
+        public object View { get; internal set; }
     }
 }

SDKExamples.UWP/Data/Examples.xml

@@ -90,6 +90,7 @@
     <Example DisplayName="Reorder" ClassName="SDKExamples.UWP.Listview.Reorder" />
     <Example DisplayName="Reorder with Groups" ClassName="SDKExamples.UWP.Listview.ReorderWithGroups" />
     <Example DisplayName="Load on Demand" ClassName="SDKExamples.UWP.Listview.LoadOnDemand" />
+    <Example DisplayName="Load on Demand Command" ClassName="SDKExamples.UWP.Listview.LoadOnDemandCommand" />
     <Example DisplayName="Filtering" ClassName="SDKExamples.UWP.Listview.Filtering" />
     <Example DisplayName="Item Animations" ClassName="SDKExamples.UWP.Listview.ItemAnimations" />
     <Example DisplayName="Layouts" ClassName="SDKExamples.UWP.Listview.Layouts" />

SDKExamples.UWP/Examples/ListView/LoadOnDemandCommand.xaml

@@ -0,0 +1,46 @@
+<local:ExamplePageBase
+    x:Class="SDKExamples.UWP.Listview.LoadOnDemandCommand"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:SDKExamples.UWP"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:data="using:Telerik.UI.Xaml.Controls.Data"
+    mc:Ignorable="d" x:Name="page">
+
+    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+        <VisualStateManager.VisualStateGroups>
+            <VisualStateGroup>
+                <VisualState x:Name="Phone">
+                    <VisualState.StateTriggers>
+                        <AdaptiveTrigger MinWindowWidth="0" />
+                    </VisualState.StateTriggers>
+                    <VisualState.Setters>
+                        <Setter Target="loadingModeCombo.HorizontalAlignment" Value="Stretch" />
+                    </VisualState.Setters>
+                </VisualState>
+
+                <VisualState x:Name="Desktop">
+                    <VisualState.StateTriggers>
+                        <AdaptiveTrigger MinWindowWidth="640" />
+                    </VisualState.StateTriggers>
+                    <VisualState.Setters>
+                        <Setter Target="loadingModeCombo.HorizontalAlignment" Value="Left" />
+                    </VisualState.Setters>
+                </VisualState>
+            </VisualStateGroup>
+        </VisualStateManager.VisualStateGroups>
+
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto"/>
+            <RowDefinition Height="Auto"/>
+            <RowDefinition Height="*"/>
+        </Grid.RowDefinitions>
+
+        <TextBlock Text="{Binding Title, ElementName=page}" Style="{StaticResource ExampleHeaderTextBlockStyle}" />
+
+        <ComboBox Margin="10" Grid.Row="1" x:Name="loadingModeCombo" Header="Select IncrementalLoadingMode" SelectionChanged="SelectionChanged" />
+
+        <data:RadListView ItemsSource="{Binding Items}" Grid.Row="2" x:Name="ListView" />
+    </Grid>
+</local:ExamplePageBase>

SDKExamples.UWP/Examples/ListView/LoadOnDemandCommand.xaml.cs

@@ -0,0 +1,97 @@
+using System;
+using System.Collections.ObjectModel;
+using System.Threading.Tasks;
+using Telerik.Core.Data;
+using Telerik.UI.Xaml.Controls.Data.ListView.Commands;
+using Windows.UI.Xaml.Controls;
+
+namespace SDKExamples.UWP.Listview
+{
+    public sealed partial class LoadOnDemandCommand : ExamplePageBase
+    {
+        public LoadOnDemandCommand()
+        {
+            this.InitializeComponent();
+
+            this.loadingModeCombo.ItemsSource = Enum.GetValues(typeof(BatchLoadingMode));
+            this.loadingModeCombo.SelectedIndex = 0;
+
+            this.ListView.Commands.Add(new CustomLoadOnDemandCommand());
+
+            this.DataContext = new ViewModel();
+        }
+
+        public class ViewModel
+        {
+            public ViewModel()
+            {
+                this.Items = new ObservableCollection<int>();
+                this.AddItems(40);
+            }
+
+            public ObservableCollection<int> Items { get; }
+
+            public void AddItems(int count)
+            {
+                for (int i = 0; i < count; i++)
+                {
+                    this.Items.Add(this.Items.Count);
+                }
+            }
+        }
+
+        private void SelectionChanged(object sender, SelectionChangedEventArgs e)
+        {
+            ComboBox comboBox = (ComboBox)sender;
+            this.ListView.IncrementalLoadingMode = (BatchLoadingMode)comboBox.SelectedItem;
+        }
+    }
+
+    public class CustomLoadOnDemandCommand : LoadMoreDataCommand
+    {
+        private int lodCounter;
+
+        public CustomLoadOnDemandCommand()
+            :base()
+        {
+            this.Id = CommandId.LoadMoreData;
+        }
+
+        public override bool CanExecute(object parameter)
+        {
+            LoadMoreDataContext context = (LoadMoreDataContext)parameter;
+            LoadOnDemandCommand.ViewModel viewModel = (LoadOnDemandCommand.ViewModel)context.DataContext;
+
+            bool canExecute = viewModel.Items.Count < 100;
+            return canExecute;
+        }
+
+        public async override void Execute(object parameter)
+        {
+            base.Execute(parameter);
+
+            LoadMoreDataContext context = (LoadMoreDataContext)parameter;
+            LoadOnDemandCommand.ViewModel viewModel = (LoadOnDemandCommand.ViewModel)context.DataContext;
+            this.lodCounter++;
+
+            if (this.lodCounter % 3 == 0)
+            {
+                // If we do not need to get new data asynchronously, we can add the new items right away.
+                viewModel.AddItems(15);
+            }
+            else
+            {
+                // If we need to get new data asynchronously, we must manually update the loading status.
+
+                this.Owner.ChangeDataLoadingStatus(BatchLoadingStatus.ItemsRequested);
+
+                // Mimic getting data from server asynchronously.
+                await Task.Delay(2000);
+
+                viewModel.AddItems(15);
+
+                this.Owner.ChangeDataLoadingStatus(BatchLoadingStatus.ItemsLoaded);
+            }
+        }
+    }
+}

SDKExamples.UWP/SDKExamples.UWP.csproj

@@ -355,6 +355,9 @@
     <Compile Include="Examples\ListView\Layouts.xaml.cs">
       <DependentUpon>Layouts.xaml</DependentUpon>
     </Compile>
+    <Compile Include="Examples\ListView\LoadOnDemandCommand.xaml.cs">
+      <DependentUpon>LoadOnDemandCommand.xaml</DependentUpon>
+    </Compile>
     <Compile Include="Examples\ListView\LoadOnDemand.xaml.cs">
       <DependentUpon>LoadOnDemand.xaml</DependentUpon>
     </Compile>
@@ -799,6 +802,10 @@
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
     </Page>
+    <Page Include="Examples\ListView\LoadOnDemandCommand.xaml">
+      <Generator>MSBuild:Compile</Generator>
+      <SubType>Designer</SubType>
+    </Page>
     <Page Include="Examples\ListView\LoadOnDemand.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>