I have application where there is chat page. On the page, I use ListView with DataTemplate to show incoming and outgoing message. Now the problem is when I click on Entry(Textbox) where user can write message, keyboard opens and my ListView keep space between last message and Entry.

I have read few blogs and example of chat but none having consistent behavior.

Code:

<ContentPage.Resources>
<ResourceDictionary>
  <local:MessageTemplateSelector x:Key="MessageTemplateSelector" />
</ResourceDictionary>
</ContentPage.Resources>
<ContentPage.Content>
    <StackLayout>
      <ListView x:Name="MessagesListView"
                ItemTemplate="{StaticResource MessageTemplateSelector}"
                ItemsSource="{Binding Messages}"
                HasUnevenRows="True"
                ItemSelected="MyListView_OnItemSelected"
                ItemTapped="MyListView_OnItemTapped"
                IsPullToRefreshEnabled="true"
                IsRefreshing="{Binding IsRefreshing}"
                RefreshCommand="{Binding RefreshCommand}"
                SeparatorVisibility="None"
                BackgroundColor="{DynamicResource d8GreyLight}"
                //RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent,Property=Height,Factor=1,Constant=0}"
        />

      <Grid x:Name="MessageControls" RowSpacing="1" ColumnSpacing="2" Padding="5"
            BackgroundColor="#EFEFF4"
            VerticalOptions="FillAndExpand"
            HorizontalOptions="FillAndExpand">
        <Grid.ColumnDefinitions>
          <ColumnDefinition Width="*" />
          <ColumnDefinition Width="Auto" />
        </Grid.ColumnDefinitions>

        <Entry x:Name="txtMessage" Grid.Column="0" HeightRequest="40" Placeholder="Message" Text="{Binding OutGoingText}" TextChanged="EnableSend"/>
        <Frame x:Name="SendButton">
          <Frame.GestureRecognizers>
            <TapGestureRecognizer Tapped="SendMessage_Click" NumberOfTapsRequired="1" />
          </Frame.GestureRecognizers>
          <Label Text="Send"/>
        </Frame>
      </Grid>
    </StackLayout>

</ContentPage.Content>

Way-1: KeyboardRendering for MessagePage: Keep Space between ListView last message and SendTextBox

using Project;
using Project.iOS;
using CoreGraphics;
using Foundation;
using System;
using UIKit;
using Xamarin.Forms;


[assembly: ExportRenderer(typeof(MessagePage), typeof(KeyboardAdaptedPageRenderer))]
namespace Project.iOS
{
    public class KeyboardAdaptedPageRenderer : ContentPageWithCustomBackButtonRenderer
    {
        //Way-1: Keep Space between ListView last message and SendTextBox
        public override void ViewWillAppear(bool animated)
        {
            base.ViewWillAppear(animated);

            Keyboard.WillShow += OnKeyboardWillShow;
            Keyboard.WillHide += OnKeyboardWillHide;
        }

        public override void ViewDidDisappear(bool animated)
        {
            base.ViewDidDisappear(animated);

            Keyboard.WillShow -= OnKeyboardWillShow;
            Keyboard.WillHide -= OnKeyboardWillHide;

            OnKeyboardWillHide(new KeyboardInfo()
            {
                AnimationDuration = 0,
                AnimatonOptions = UIViewAnimationOptions.TransitionNone
            });
        }

        protected override void Dispose(bool disposing)
        {
            base.Dispose(disposing);

            Keyboard.WillShow -= OnKeyboardWillShow;
            Keyboard.WillHide -= OnKeyboardWillHide;
        }

        private void OnKeyboardWillShow(KeyboardInfo info)
        {
            NSThread.SleepFor(1);
            if (info.SoftwareKeyboardIsVisible)
            {
                UIView.Animate(info.AnimationDuration, 0, info.AnimatonOptions, () =>
                {
                    var bounds = View.Bounds;
                    bounds.Y = info.BeginRect.Top - info.EndRect.Top; // iphone 4 and others
                    View.Bounds = bounds;
                }, null);
            }
        }

        private void OnKeyboardWillHide(KeyboardInfo info)
        {
            NSThread.SleepFor(1);

            UIView.Animate(info.AnimationDuration, 0, info.AnimatonOptions, () =>
            {
                var bounds = View.Bounds;
                bounds.Y = 0;
                View.Bounds = bounds;
            }, null);
        }
    }
}

Result

Way-2: KeyboardRendering for MessagePage: Design of SendTextBox issue when keyboard up and down

using Project;
using Project.iOS;
using CoreGraphics;
using Foundation;
using System;
using UIKit;
using Xamarin.Forms;


[assembly: ExportRenderer(typeof(MessagePage), typeof(KeyboardAdaptedPageRenderer))]
namespace Project.iOS
{
    public class KeyboardAdaptedPageRenderer : ContentPageWithCustomBackButtonRenderer
    {   
        //way-2 Error: Space issue is solved but not consistant in design of SendTextbox in         way-1
        NSObject observerHideKeyboard;
        NSObject observerShowKeyboard;


        public override void ViewDidLoad()
        {
            base.ViewDidLoad();

            var cp = Element as ConversationPage;
            if (cp != null && !cp.CancelsTouchesInView)
            {
                foreach (var g in View.GestureRecognizers)
                {
                    g.CancelsTouchesInView = false;
                }
            }
        }

        public override void ViewWillAppear(bool animated)
        {

            base.ViewWillAppear(animated);

            observerHideKeyboard = NSNotificationCenter.DefaultCenter.AddObserver(UIKeyboard.WillHideNotification, OnKeyboardNotification);
            observerShowKeyboard = NSNotificationCenter.DefaultCenter.AddObserver(UIKeyboard.WillShowNotification, OnKeyboardNotification);
        }

        public override void ViewWillDisappear(bool animated)
        {
            base.ViewWillDisappear(animated);

            NSNotificationCenter.DefaultCenter.RemoveObserver(observerHideKeyboard);
            NSNotificationCenter.DefaultCenter.RemoveObserver(observerShowKeyboard);
        }

        void OnKeyboardNotification(NSNotification notification)
        {
            if (!IsViewLoaded) return;

            var frameBegin = UIKeyboard.FrameBeginFromNotification(notification);
            var frameEnd = UIKeyboard.FrameEndFromNotification(notification);

            var page = Element as ContentPage;
            if (page != null && !(page.Content is ScrollView))
            {
                var padding = page.Padding;
                NSThread.SleepFor(1);
                page.Padding = new Thickness(padding.Left, padding.Top, padding.Right, padding.Bottom + (frameBegin.Top - frameEnd.Top));
            }
        }
    }
}

Result: