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techdugguDurgesh Khandal
techduggu
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Durgesh Khandal
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[Enhancement] ListView ScrollTo with empty groups - Android (#8310)f ixes #8279
* Fixed - 8279 - [Enhancement] ListView ScrollTo with empty groups * Added UI Tests for 8279 * Update Issue8279.cs * Fixed build error - finally * Added reset button to fix UI test * Added meaningful local variables for better code readability * Added meaningful names to local variables and removed unused condition Co-authored-by: Durgesh Khandal <[email protected]>
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‎Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue8279.cs

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using System;
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using System.Collections.Generic;
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using System.Collections.ObjectModel;
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using System.ComponentModel;
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using System.Linq;
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using Xamarin.Forms.CustomAttributes;
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using Xamarin.Forms.Internals;
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#if UITEST
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using Xamarin.Forms.Core.UITests;
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using Xamarin.UITest;
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using NUnit.Framework;
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#endif
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namespace Xamarin.Forms.Controls.Issues
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{
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[Preserve (AllMembers=true)]
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[Issue (IssueTracker.Github, 8279, "[Feature requested] ListView do not ScrollTo a group when there is no child of this group", PlatformAffected.Android)]
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public class Issue8279 : TestContentPage
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{
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public static ListView List { get; set; }
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public static List<MyGroup> Data { get; set; }
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const string ScrollWithNoItemButGroup = "ScrollWithNoItemButGroup";
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const string ScrollWithItemButNoGroup = "ScrollWithItemButNoGroup";
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const string ScrollWithItemWithGroup = "ScrollWithItemWithGroup";
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const string ScrollWithNoItemNoGroup = "ScrollWithNoItemNoGroup";
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const string ScrollWithNoItemEmptyGroup = "ScrollWithNoItemEmptyGroup";
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const string Reset = "Reset";
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protected override void Init()
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{
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}
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public Issue8279()
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{
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#if APP
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Data = new List<MyGroup>();
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Data.Add(new MyGroup(){Headertitle = "Header 1"});
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Data.First().Add(new MyData(){Title = "title 1"});
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Data.First().Add(new MyData() { Title = "title 2" });
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Data.First().Add(new MyData() { Title = "title 3" });
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Data.First().Add(new MyData() { Title = "title 4" });
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Data.First().Add(new MyData() { Title = "title 5" });
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Data.First().Add(new MyData() { Title = "title 6" });
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Data.First().Add(new MyData() { Title = "title 7" });
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Data.First().Add(new MyData() { Title = "title 8" });
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Data.Add(new MyGroup() { Headertitle = "Header 2" });
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Data.Add(new MyGroup() { Headertitle = "Header 3" });
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Data.Last().Add(new MyData() { Title = "title 3a" });
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Data.Last().Add(new MyData() { Title = "title 3b" });
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Data.Last().Add(new MyData() { Title = "title 3b" });
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Data.Last().Add(new MyData() { Title = "title 3b" });
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List = new ListView();
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List.HorizontalOptions = LayoutOptions.FillAndExpand;
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List.VerticalOptions = LayoutOptions.FillAndExpand;
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List.BackgroundColor = Color.Yellow;
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List.ItemTemplate = new DataTemplate(typeof (VCTest));
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List.GroupHeaderTemplate = new DataTemplate(typeof(VCHeader));
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List.IsGroupingEnabled = true;
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List.ItemsSource = Data;
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var lastGroup = Data.Last();
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var lastItem = lastGroup.First();
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var firstGroup = Data.First();
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var firstItem = firstGroup.First();
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var emptyGroup = Data[1];
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var button1 = new Button()
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{
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Text = "Scroll with no item but group",
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AutomationId = ScrollWithNoItemButGroup,
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Command = new Command(()=> List.ScrollTo(null, lastGroup, ScrollToPosition.MakeVisible, true))
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};
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var button2 = new Button()
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{
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Text = "Scroll with item but no group",
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AutomationId = ScrollWithItemButNoGroup,
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Command = new Command(() => List.ScrollTo(firstItem, ScrollToPosition.MakeVisible, true))
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};
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var button3 = new Button()
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{
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Text = "Scroll with item with group",
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AutomationId = ScrollWithItemWithGroup,
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Command = new Command(() => List.ScrollTo(firstItem, lastGroup, ScrollToPosition.MakeVisible, true))
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};
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var button4 = new Button()
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{
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Text = "Scroll with no item no group",
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AutomationId = ScrollWithNoItemNoGroup,
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Command = new Command(() => List.ScrollTo(null, null, ScrollToPosition.MakeVisible, true))
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};
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var button5 = new Button()
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{
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Text = "Scroll with no item but empty group",
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AutomationId = ScrollWithNoItemEmptyGroup,
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Command = new Command(() => List.ScrollTo(null, emptyGroup, ScrollToPosition.MakeVisible, true))
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};
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var resetButton = new Button()
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{
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Text = "Reset",
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AutomationId = Reset,
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Command = new Command(() => List.ScrollTo(null, firstGroup, ScrollToPosition.Center, true))
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};
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Content = new StackLayout () {
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VerticalOptions = LayoutOptions.StartAndExpand,
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HorizontalOptions = LayoutOptions.FillAndExpand,
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Children = { resetButton, button1, button2, button3, button4, button5, List },
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};
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#endif
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}
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#if UITEST
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[Test]
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public void ScrollWithNoItemButGroupTest()
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{
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RunningApp.WaitForElement(Reset);
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RunningApp.Tap(Reset);
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RunningApp.WaitForElement(ScrollWithNoItemButGroup);
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RunningApp.Tap(ScrollWithNoItemButGroup);
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// This will fail if the list didn't scroll. If it did scroll, it will succeed
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RunningApp.WaitForElement(q => q.Marked("Header 3"), timeout: TimeSpan.FromSeconds(2));
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}
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[Test]
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public void ScrollWithItemButNoGroupTest()
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{
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RunningApp.WaitForElement(Reset);
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RunningApp.Tap(Reset);
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RunningApp.WaitForElement(ScrollWithItemButNoGroup);
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RunningApp.Tap(ScrollWithItemButNoGroup);
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// This will fail if the list didn't scroll. If it did scroll, it will succeed
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RunningApp.WaitForElement(q => q.Marked("title 1"), timeout: TimeSpan.FromSeconds(2));
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}
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[Test]
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public void ScrollWithItemWithGroupTest()
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{
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RunningApp.WaitForElement(Reset);
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RunningApp.Tap(Reset);
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RunningApp.WaitForElement(ScrollWithItemWithGroup);
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RunningApp.Tap(ScrollWithItemWithGroup);
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// This will fail if the list didn't scroll. If it did scroll, it will succeed
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RunningApp.WaitForElement(q => q.Marked("Header 3"), timeout: TimeSpan.FromSeconds(2));
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}
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[Test]
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public void ScrollWithNoItemNoGroupTest()
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{
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RunningApp.WaitForElement(Reset);
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RunningApp.Tap(Reset);
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RunningApp.WaitForElement(ScrollWithNoItemNoGroup);
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RunningApp.Tap(ScrollWithNoItemNoGroup);
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// This will pass if the list didn't scroll and remain on the same state
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RunningApp.WaitForElement(q => q.Marked("Header 1"), timeout: TimeSpan.FromSeconds(2));
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}
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[Test]
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public void ScrollWithNoItemEmptyGroupTest()
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{
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RunningApp.WaitForElement(Reset);
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RunningApp.Tap(Reset);
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RunningApp.WaitForElement(ScrollWithNoItemEmptyGroup);
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RunningApp.Tap(ScrollWithNoItemEmptyGroup);
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// This will fail if the list didn't scroll. If it did scroll, it will succeed
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RunningApp.WaitForElement(q => q.Marked("Header 2"), timeout: TimeSpan.FromSeconds(2));
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}
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#endif
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[Preserve(AllMembers = true)]
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public class MyData : INotifyPropertyChanged
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{
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public event PropertyChangedEventHandler PropertyChanged;
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string _title;
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public const string PropTitle = "Title";
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public string Title
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{
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get { return _title; }
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set
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{
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if (value.Equals(_title, StringComparison.Ordinal))
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return;
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_title = value;
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OnPropertyChanged(new PropertyChangedEventArgs(PropTitle));
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}
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}
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public void OnPropertyChanged(PropertyChangedEventArgs e)
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{
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if (PropertyChanged != null)
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PropertyChanged(this, e);
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}
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}
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[Preserve(AllMembers = true)]
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public class MyGroup : ObservableCollection<MyData>, INotifyPropertyChanged
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{
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string _headertitle;
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public const string PropHeadertitle = "Headertitle";
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public string Headertitle
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{
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get { return _headertitle; }
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set
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{
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if (value.Equals(_headertitle, StringComparison.Ordinal))
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return;
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_headertitle = value;
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OnPropertyChanged(new PropertyChangedEventArgs(PropHeadertitle));
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}
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}
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}
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[Preserve(AllMembers = true)]
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internal class VCTest : ViewCell
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{
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public VCTest()
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{
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var label = new Label();
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label.SetBinding(Label.TextProperty, "Title");
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View = label;
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}
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}
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[Preserve(AllMembers = true)]
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internal class VCHeader : ViewCell
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{
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public VCHeader()
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{
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var label = new Label();
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label.SetBinding(Label.TextProperty, "Headertitle");
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View = label;
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}
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}
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}
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}

‎Xamarin.Forms.Platform.Android/Renderers/ListViewRenderer.cs

Lines changed: 21 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -273,32 +273,41 @@ void OnScrollToRequested(object sender, ScrollToRequestedEventArgs e)
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}
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Cell cell;
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int position;
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int scrollPosition;
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var scrollArgs = (ITemplatedItemsListScrollToRequestedEventArgs)e;
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var templatedItems = TemplatedItemsView.TemplatedItems;
280280
if (Element.IsGroupingEnabled)
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{
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var results = templatedItems.GetGroupAndIndexOfItem(scrollArgs.Group, scrollArgs.Item);
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if (results.Item1 == -1 || results.Item2 == -1)
283+
int indexOfGroup = results.Item1;
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int indexOfItem = results.Item2;
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286+
if (indexOfGroup == -1)
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return;
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286-
var group = templatedItems.GetGroup(results.Item1);
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cell = group[results.Item2];
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int itemIndex = indexOfItem == -1 ? 0 : indexOfItem;
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var group = templatedItems.GetGroup(indexOfGroup);
292+
if (group.Count == 0)
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cell = group.HeaderContent;
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else
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cell = group[itemIndex];
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289-
position = templatedItems.GetGlobalIndexForGroup(group) + results.Item2 + 1;
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//Increment Scroll Position by 1 when Grouping is enabled. Android offsets position of cells when using header.
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scrollPosition = templatedItems.GetGlobalIndexForGroup(group) + itemIndex + 1;
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}
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else
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{
293-
position = templatedItems.GetGlobalIndexOfItem(scrollArgs.Item);
294-
if (position == -1)
302+
scrollPosition = templatedItems.GetGlobalIndexOfItem(scrollArgs.Item);
303+
if (scrollPosition == -1)
295304
return;
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297-
cell = templatedItems[position];
306+
cell = templatedItems[scrollPosition];
298307
}
299308

300309
//Android offsets position of cells when using header
301-
int realPositionWithHeader = position + 1;
310+
int realPositionWithHeader = scrollPosition + 1;
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303312
if (e.Position == ScrollToPosition.MakeVisible)
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{
@@ -314,11 +323,11 @@ void OnScrollToRequested(object sender, ScrollToRequestedEventArgs e)
314323
if (cellHeight == -1)
315324
{
316325
int first = Control.FirstVisiblePosition;
317-
if (first <= position && position <= Control.LastVisiblePosition)
318-
cellHeight = Control.GetChildAt(position - first).Height;
326+
if (first <= scrollPosition && scrollPosition <= Control.LastVisiblePosition)
327+
cellHeight = Control.GetChildAt(scrollPosition - first).Height;
319328
else
320329
{
321-
AView view = _adapter.GetView(position, null, null);
330+
AView view = _adapter.GetView(scrollPosition, null, null);
322331
view.Measure(MeasureSpecFactory.MakeMeasureSpec(Control.Width, MeasureSpecMode.AtMost), MeasureSpecFactory.MakeMeasureSpec(0, MeasureSpecMode.Unspecified));
323332
cellHeight = view.MeasuredHeight;
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}

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