Develop Reference

Xamarin Forms Collectionview not updating when observable collection is updated

I have been stuck with this issue for quite sometime now. It might be quite simple for you guys.
I have a collection view which has its item source that shows an observable collection. It shows messages from users when the app starts and then as a new message comes, I want to add the new message as the 1st element in the collectionview but it gets distorted and removes the prior items (only from the UI and not the actual observable collection data) and only shows 1 item. And when I navigate to other page and come back it shows correctly. Could someone please help me with this.
Xaml
<CollectionView Grid.Row="1" x:Name="myMessagesCV" SelectionMode="Single" SelectionChanged="MyMessagesCV_SelectionChanged" RemainingItemsThresholdReached="MyMessagesCV_RemainingItemsThresholdReached" RemainingItemsThreshold="5">
<CollectionView.ItemTemplate>
<DataTemplate>
<StackLayout Padding="8, 8, 8, 0">
<Grid Padding="0" ColumnSpacing="0" RowSpacing="0" Margin="2">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="75"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<ffimageloading:CachedImage x:Name="userImage" Source="{Binding userImage}" Aspect="AspectFill" HeightRequest="75" Grid.Row="0" Grid.Column="0" CacheType="All" DownsampleToViewSize="True">
<ffimageloading:CachedImage.Transformations>
<transformations:CircleTransformation/>
</ffimageloading:CachedImage.Transformations>
</ffimageloading:CachedImage>
<Grid Grid.Row="0" Grid.Column="1" Padding="5">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Label Padding="10, 0, 0, 5" Text="{Binding userName}" LineBreakMode="TailTruncation" TextColor="Black" FontSize="Medium" Grid.Row="0" Grid.Column="0"/>
<Label Padding="10, 0, 0, 5" Text="{Binding message}" FontAttributes="{Binding newMessage}" FontSize="Small" TextColor="Black" Grid.Row="1" Grid.Column="0" HorizontalOptions="StartAndExpand" />
<Image Grid.Row="0" Grid.Column="1" Grid.RowSpan="2" Source="dot.png" Aspect="AspectFill" WidthRequest="10" IsVisible="{Binding IsNewMessage}" HorizontalOptions="Center" VerticalOptions="Center"/>
</Grid>
<BoxView BackgroundColor="LightGray" HeightRequest="1" Grid.Row="1" Grid.Column="1"/>
</Grid>
</StackLayout>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
Code Behind Page
public ObservableCollection<Messages> MyMessagesList = new ObservableCollection<Messages>();
public async void GetMyMessages()
{
if (IsBusy)
return;
IsBusy = true;
var messages = await FirebaseDataHelper.GetMyMessages(uid);
var allmyMessages = await Task.WhenAll(FirebaseDataHelper.GetUserMessagesDetail(messages));
myunreadmsg = 0;
allmyMessagesCount = messages.Count;
IsSubscribe = false;
foreach (var message in allmyMessages)
{
if (message.Count > 0)
{
for (int i = 0; i < message.Count; i++)
{
if (message[i].status == "Delivered" && message[i].senderId != uid)
{
message[i].newMessage = FontAttributes.Bold;
message[i].IsNewMessage = true;
myunreadmsg++;
}
if (!MyMessagesList.Any(m => m.otheruserId == message[i].otheruserId) && message[i].message != null)
MyMessagesList.Add(message[i]);
}
}
}
myMessagesCV.ItemsSource = MyMessagesList;
}
public void GetMyNewMessages(Messages messageData)
{
IsSubscribe = false;
myunreadmsg = 0;
Messages newMessageData = new Messages();
if (messageData.status == "Delivered" && messageData.senderId != uid)
{
newMessageData.newMessage = FontAttributes.Bold;
newMessageData.IsNewMessage = true;
newMessageData.otheruserId = messageData.otheruserId;
newMessageData.senderId = messageData.senderId;
newMessageData.sellerId = messageData.sellerId;
myunreadmsg++;
}
else
{
newMessageData.newMessage = FontAttributes.None;
}
for (int i = 0; i < MyMessagesList.Count; i++)
{
if (MyMessagesList[i].otheruserId == messageData.otheruserId)
{
if (i == 0)
{
MyMessagesList[i].message = messageData.message;
if (myunreadmsg > 0)
{
MyMessagesList[i].IsNewMessage = true;
MyMessagesList[i].newMessage = FontAttributes.Bold;
}
break;
}
else
{
newMessageData.userName = MyMessagesList[i].userName;
newMessageData.userImage = MyMessagesList[i].userImage;
newMessageData.message = messageData.message;
newMessageData.time = messageData.time;
newMessageData.messageId = messageData.messageId;
MyMessagesList.Remove(MyMessagesList[i]);
MyMessagesList.Insert(0, newMessageData);
break;
}
}
}
myMessagesCV.ItemsSource = MyMessagesList;
}
Thank you guys. Hope I can solve this.

When your new message arrives, don't set ItemSource again like you do it in your GetMyNewMessages method:
myMessagesCV.ItemsSource = MyMessagesList;
Just insert your new message into MyMessagesList ObservableCollection.
MyMessagesList.Insert(0, newMessageData);
I made a simple project where it is demonstrated.
Here is xaml:
<ContentPage
x:Class="Search.MainPage"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
BackgroundColor="White">
<Grid Margin="15">
<CollectionView
x:Name="CollectionView"
HorizontalOptions="FillAndExpand"
VerticalOptions="FillAndExpand">
<CollectionView.ItemTemplate>
<DataTemplate>
<Label Text="{Binding}" TextColor="Red" />
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
</Grid>
</ContentPage>
And here is code behind of this page:
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
}
public ObservableCollection<int> Data { get; set; } = new ObservableCollection<int>(Enumerable.Range(1, 10));
protected override void OnAppearing()
{
base.OnAppearing();
Device.StartTimer(TimeSpan.FromSeconds(3), () =>
{
Data.Insert(0, new Random().Next(1, 1000));
return true;
});
CollectionView.ItemsSource = Data;
}
}

UWP: Adjusting InkCanvas size when writing/drawing

I'm learning how to develop UWP apps and I'm using Microsoft's documentation as tutorials/research.
I want to have an InkCanvas design similar to OneNote where the InkCanvas height and width can expand (as you're writing/drawing and reach the end of the window size) and can shrink (when you erase ink strokes and the extra size can decrease based on the position of the ink strokes until you get back to the original size).
I'm able to increase the InkCanvas width and height, but can't decrease when erasing ink strokes.
Here is a MainPage.xaml code:
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<TextBlock Text="Heading"
FontSize="36"
FontWeight="Bold"
Margin="10"
Grid.Column="0"
Grid.Row="0"/>
<Grid BorderBrush="Red"
BorderThickness="2"
Margin="10"
Grid.Column="0"
Grid.Row="1">
<ScrollViewer HorizontalScrollBarVisibility="Auto"
HorizontalScrollMode="Enabled"
VerticalScrollBarVisibility="Auto"
VerticalScrollMode="Enabled" >
<Grid BorderBrush="Blue"
BorderThickness="2"
Margin="1">
<InkCanvas Name="inkCanvas"/>
</Grid>
</ScrollViewer>
</Grid>
And the MainPage.cs code:
public MainPage()
{
this.InitializeComponent();
nkCanvas.InkPresenter.StrokeInput.StrokeEnded += adjustInkCanvasSize;
}
private async void adjustInkCanvasSize(InkStrokeInput sender, PointerEventArgs args)
{
await Task.Delay(100);
var XBound = inkCanvas.InkPresenter.StrokeContainer.BoundingRect.Bottom;
if (XBound > inkCanvas.ActualHeight - 200)
inkCanvas.Height = XBound + 200;
var YBound = inkCanvas.InkPresenter.StrokeContainer.BoundingRect.Right;
if (YBound > inkCanvas.ActualWidth - 200)
inkCanvas.Width = YBound + 200;
}
The c# code also came from another stackoverflow solution, but not able to figure out the "decrease" part.
Any help would be much appreciated. Thanks

If you want the InkCanvas control to shrink when you erase ink strokes and the extra size can decrease based on the position of the ink strokes until the original size, you need to add the InkPresenter.StrokesErased event to manage the size of the InkCanvas control. For example:
Here is a MainPage.xaml code( To facilitate testing, I added the mouse support):
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<TextBlock Text="Heading"
FontSize="36"
FontWeight="Bold"
Margin="10"
Grid.Column="0"
Grid.Row="0"/>
<Grid BorderBrush="Red"
BorderThickness="2"
Margin="10"
Grid.Column="0"
Grid.Row="1">
<Grid.RowDefinitions>
<RowDefinition Height="auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<InkToolbar x:Name="inkToolbar" VerticalAlignment="Top" Margin="10,0,10,0"
TargetInkCanvas="{x:Bind inkCanvas}" Grid.Row="0"/>
<ScrollViewer HorizontalScrollBarVisibility="Auto"
HorizontalScrollMode="Enabled" Grid.Row="1"
VerticalScrollBarVisibility="Auto"
VerticalScrollMode="Enabled" >
<Grid BorderBrush="Blue"
BorderThickness="2"
Margin="1">
<InkCanvas Name="inkCanvas" />
</Grid>
</ScrollViewer>
</Grid>
</Grid>
And the MainPage.cs code:
public sealed partial class MainPage : Page
{
private double originalX; //The original size
private double originalY;
private double maxX=0.0;
private double maxY=0.0;
private bool flag = true;
public MainPage()
{
this.InitializeComponent();
inkCanvas.InkPresenter.InputDeviceTypes = CoreInputDeviceTypes.Mouse | CoreInputDeviceTypes.Touch |
CoreInputDeviceTypes.Pen;
inkCanvas.InkPresenter.StrokeInput.StrokeEnded += adjustInkCanvasSize;
inkCanvas.InkPresenter.StrokesErased += InkPresenter_StrokesErased;
}
private async void InkPresenter_StrokesErased(InkPresenter sender, InkStrokesErasedEventArgs args)
{
await Task.Delay(100);
//The coordinate of the lower right corner of the erased ink stoke
var erasedInkX= args.Strokes.ElementAt(0).BoundingRect.Bottom;
var erasedInkY = args.Strokes.ElementAt(0).BoundingRect.Right;
var XBound = inkCanvas.InkPresenter.StrokeContainer.BoundingRect.Bottom;
if (erasedInkX >=maxX&&XBound < inkCanvas.ActualHeight + 100)
{
if (XBound - 100 > originalX)
inkCanvas.Height = XBound - 100;
else
inkCanvas.Height = originalX; //The size of InkCanvas shrinks to the original size.
maxX = inkCanvas.Height;
}
var YBound = inkCanvas.InkPresenter.StrokeContainer.BoundingRect.Right;
if (erasedInkY>=maxY&&YBound < inkCanvas.ActualWidth + 100)
{
if (YBound - 100 > originalY)
{
inkCanvas.Width = YBound - 100;
}
else
inkCanvas.Width = originalY;
maxY = inkCanvas.Width;
}
}
private async void adjustInkCanvasSize(InkStrokeInput sender, PointerEventArgs args)
{
await Task.Delay(100);
if(flag)
{
flag = false;
originalX = inkCanvas.ActualHeight; //Get the original size
originalY = inkCanvas.ActualWidth;
}
var XBound = inkCanvas.InkPresenter.StrokeContainer.BoundingRect.Bottom;
if (XBound > maxX)
maxX = XBound; //maxX and maxY always hold the maximum size of StrokeContainer
if (XBound > inkCanvas.ActualHeight - 200)
inkCanvas.Height = XBound + 200;
var YBound = inkCanvas.InkPresenter.StrokeContainer.BoundingRect.Right;
if (YBound > maxY)
maxY = YBound;
if (YBound > inkCanvas.ActualWidth - 200)
inkCanvas.Width = YBound + 200;
}
}

EllipseGeometry Shrink & Fade Without Exceeding Canvas Bounds in C# WPF

How to make animation stay within the canvas at bigger sizes when the user clicks around the edge of the canvas? Currently, if sizes are too big and if user clicks near the edge of the canvas, the ellipse will grow outside of the canvas to cover the buttons. I need the animation to stay within the canvas to make it look like a slice of pizza essentially.
Should look like this:
Size 50 where user clicks near top left of canvas
Currently looks like this:
Size 50 where user clicks near top left of canvas
Xaml:
<Window.Resources>
<Storyboard x:Key="anim">
<DoubleAnimation
Storyboard.TargetName="myCircle"
Storyboard.TargetProperty="RadiusX"
AutoReverse="True"/>
<DoubleAnimation
Storyboard.TargetName="myCircle"
Storyboard.TargetProperty="RadiusY"
AutoReverse="True"/>
<DoubleAnimation
Storyboard.TargetName="path"
Storyboard.TargetProperty="Opacity"
AutoReverse="True"/>
</Storyboard>
</Window.Resources>
<Grid HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<Grid.RowDefinitions>
<RowDefinition Height="23"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<DockPanel HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Row="0" Margin="0,0,0,1">
<Menu DockPanel.Dock="Top" Height="23">
<MenuItem Header="Main" RenderTransformOrigin="-1.896,0.643" HorizontalAlignment="Left" Width="39" Height="23">
<MenuItem Header="Exit, Esc" Click="MenuItem_Click_Exit"/>
</MenuItem>
</Menu>
</DockPanel>
<Grid HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Row="1" Name="pane">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="150"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Column="0" Name="pane2">
<Grid.RowDefinitions>
<RowDefinition Height="35"/>
<RowDefinition Height="35"/>
<RowDefinition Height="35"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="100"/>
<ColumnDefinition Width="50"/>
</Grid.ColumnDefinitions>
<Label Content="Size" Grid.Row="0" Grid.Column="0" Height="25" VerticalAlignment="Stretch"/>
<Label Content="Fill Color" Grid.Row="1" Grid.Column="0" Height="25" VerticalAlignment="Stretch"/>
<Label Content="Stroke Thickness" Grid.Row="2" Grid.Column="0" Height="25" VerticalAlignment="Stretch"/>
<Label Content="Stroke Color" Grid.Row="3" Grid.Column="0" VerticalAlignment="Top" Height="25"/>
<Slider x:Name="Slider_Size" Grid.Row="0" Grid.Column="1" Height="20" Width="45"
Minimum="5" Maximum="50"
AutoToolTipPlacement="BottomRight"
TickFrequency="1"
IsSnapToTickEnabled="True"
PreviewMouseUp="Slider_Size_PreviewMouseUp"/>
<Label Name="tempSize" Content="{Binding Path=Value, ElementName=Slider_Size}" Margin="0,25,0,131" Grid.Row="3" Visibility="Hidden"/>
<ComboBox Name="ComboBox_FillColor" Grid.Row="1" Grid.Column="1" Height="20" Width="45" SelectionChanged="ComboBox_FillColor_Selected"/>
<TextBox Name="textBox" Grid.Row="2" Grid.Column="1" Height="20" Width="45" TextChanged="textBox_TextChanged"/>
<ComboBox Name="ComboBox_StrokeColor" Grid.Row="3" Grid.Column="1" VerticalAlignment="Top" Height="20" Width="45" SelectionChanged="ComboBox_StrokeColor_Selected"/>
</Grid>
<Border Name ="border" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" BorderBrush="Black" Grid.Column="1" BorderThickness="2">
<Canvas Name="canvas" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" MouseDown="Canvas_MouseDown">
<Path x:Name="path">
<Path.Data>
<EllipseGeometry x:Name="myCircle"/>
</Path.Data>
</Path>
<Canvas.Background>
<SolidColorBrush Color="White" Opacity="0"/>
</Canvas.Background>
</Canvas>
</Border>
</Grid>
</Grid>
C#:
public partial class MainWindow : Window
{
private int size;
private SolidColorBrush fillColor;
private SolidColorBrush strokeColor;
private List<SolidColorBrush> colors;
private int fillIndex;
private int strokeIndex;
private int strokeThickness = 1;
private int fillColorDefault;
private int strokeColorDefault;
private Point? _start = null;
public MainWindow()
{
InitializeComponent();
addColors();
textBox.Text = strokeThickness.ToString();
parse();
}
private void MenuItem_Click_Exit(object sender, RoutedEventArgs e) { Environment.Exit(1); }
private void Window_KeyUp_ESC(object sender, KeyEventArgs e)
{
if (Key.Escape == e.Key)
MenuItem_Click_Exit(sender, e);
}
private void addColors()
{
colors = typeof(Brushes).GetProperties().Select(p => p.GetValue(null, null) as SolidColorBrush).ToList();
int count = 0;
foreach (SolidColorBrush color in colors)
{
ComboBox_FillColor.Items.Add(new Rectangle() { Height = 12, Width = 17.5, Fill = color });
ComboBox_StrokeColor.Items.Add(new Rectangle() { Height = 12, Width = 17.5, Fill = color });
if (color.Color == Colors.Red)
{
fillIndex = count;
fillColor = colors[fillIndex];
ComboBox_FillColor.SelectedIndex = count;
fillColorDefault = count;
}
if (color.Color == Colors.Black)
{
strokeIndex = count;
strokeColor = colors[strokeIndex];
ComboBox_StrokeColor.SelectedIndex = count;
strokeColorDefault = count;
}
count++;
}
}
private void ComboBox_FillColor_Selected(object sender, RoutedEventArgs e) { fillIndex = ComboBox_FillColor.SelectedIndex; fillColor = colors[fillIndex]; }
private void ComboBox_StrokeColor_Selected(object sender, RoutedEventArgs e) { strokeIndex = ComboBox_StrokeColor.SelectedIndex; strokeColor = colors[strokeIndex]; }
private void Canvas_MouseDown(object sender, MouseButtonEventArgs e)
{
path.Stroke = strokeColor;
path.StrokeThickness = strokeThickness;
path.Fill = fillColor;
path.HorizontalAlignment = HorizontalAlignment.Stretch;
path.VerticalAlignment = VerticalAlignment.Stretch;
path.Stretch = Stretch.None;
path.SetValue(Grid.ColumnProperty, 1);
_start = Mouse.GetPosition((UIElement)sender);
myCircle.Center = (Point)_start;
var sb = FindResource("anim") as Storyboard;
var x = sb.Children.First() as DoubleAnimation;
x.To = 2 * size;
x.Duration = new Duration(TimeSpan.FromSeconds(0.5));
var y = sb.Children.ElementAt(1) as DoubleAnimation;
y.To = 2 * size;
y.Duration = new Duration(TimeSpan.FromSeconds(0.5));
var z = sb.Children.Last() as DoubleAnimation;
z.From = 0.0;
z.To = 1.0;
z.Duration = new Duration(TimeSpan.FromSeconds(0.5));
sb.Begin(path);
}
private void textBox_TextChanged(object sender, TextChangedEventArgs e)
{
//regex where any string of chars besides numbers
Regex pattern = new Regex(#"^([^0-9]*)$", RegexOptions.Compiled);
Match result = pattern.Match(textBox.Text);
if (textBox.Text.ToString() == string.Empty)
return;
else if (result.Success)
{
MessageBox.Show("Invalid character entered. Integer numbers only. Stroke Thickness will be reseted to a default of 1.");
strokeThickness = 1;
textBox.Text = strokeThickness.ToString();
textBox.SelectAll();
}
else
{
int x;
if (int.TryParse(textBox.Text, out x))
strokeThickness = int.Parse(textBox.Text);
}
}
private void Slider_Size_PreviewMouseUp(object sender, MouseButtonEventArgs e)
{
parse();
}
private void parse()
{
int x;
if (int.TryParse(tempSize.Content.ToString(), out x))
size = x;
}
}
}

So you don't need the ellipse to stay within the Canvas, but you want to clip away the parts leaving it, right? Just set ClipToBounds (of Canvas) to true (can be done in Xaml).

Grid or border not allowing drop

I have to do a drag and drop application listView to code-generated grid.
So I have done a test program and that works
here is the xaml
<Grid Margin="0,0,-61.6,0.4">
<ListView x:Name="lwOne" PreviewMouseLeftButtonDown="ListBox_PreviewMouseLeftButtonDown" Background="Bisque" Margin="16,65,340.2,22">
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Horizontal" Width="250" VerticalAlignment="Top"></WrapPanel>
</ItemsPanelTemplate>
</ListView.ItemsPanel>
</ListView>
<Grid Name="grdMain" Drop="Grid_Drop" Background="AliceBlue" AllowDrop="True" Margin="380,65,81.2,62"/>
Now I have to migrate all this to my real application Which looks like that
So from how the cursor looks like i can see that the drag and drop is not allowed on the grid but it is on the tiny border of each cell.
So the problem is not doing d&d but ALLOWING to it
here is the xaml. The source listView is lvAllowedPPtab2, the destination grid is grdPalletTab2
<TabItem Name="tabItem2" HorizontalAlignment="Center" Height="80" MouseLeftButtonUp="TabItem_MouseLeftButtonUp" FontSize="{StaticResource TOOLTIP_FONTSIZE}" IsSelected="false" >
<TabItem.Header>
<StackPanel>
<TextBlock Text="" FontSize="{StaticResource TAB_FONTSIZE}"/>
<TextBlock Name="tbTab2" Visibility="Hidden" FontSize="{StaticResource BUTTON_FONTSIZE}" />
</StackPanel>
</TabItem.Header>
<TabItem.Background>
<ImageBrush/>
</TabItem.Background>
<Grid >
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Border x:Name="Border1Tab2" BorderBrush="Gainsboro" BorderThickness="5" Width="200" Margin="10,10,10,10" >
<StackPanel Margin="-1.8,-0.8,2.2,1.4">
<ListBox x:Name="lbxPalletsTab2" Background="{x:Null}" BorderBrush="{x:Null}" Height="600" SelectionChanged="ListBox_SelectionChanged" Margin="12,10.2,8.4,10.4" />
</StackPanel>
</Border>
<Border x:Name="Border2Tab2" BorderBrush="Gainsboro" MinWidth="150" BorderThickness="5" Grid.Column="1" Margin="10,10,10,10">
<Grid >
<Grid.ColumnDefinitions>
<ColumnDefinition Width="300px"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid HorizontalAlignment="Stretch" Grid.Column="0">
<Grid.RowDefinitions>
<RowDefinition Height="50px"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock Name="tbkPPtab2" Grid.Row="0" FontSize="22" Background="{x:Null}" FontWeight="Black" Text="---" HorizontalAlignment="Center" VerticalAlignment="Bottom"></TextBlock>
<ListView x:Name="lvAllowedPPtab2" Grid.Row="1" FontSize="12" Background="{x:Null}" BorderBrush="Gainsboro" BorderThickness="5" Margin="10" VerticalAlignment="Stretch" PreviewMouseLeftButtonDown="ListBox_PreviewMouseLeftButtonDown">
<ListView.ItemsPanel >
<ItemsPanelTemplate >
<WrapPanel Orientation="Horizontal" Width="250" Background="{x:Null}" VerticalAlignment="Top"></WrapPanel>
</ItemsPanelTemplate>
</ListView.ItemsPanel>
</ListView>
</Grid>
<Border Grid.Column="1" BorderBrush="Gainsboro" BorderThickness="5" Margin="10,60,10,10">
<Grid Name="grdPalletTab2" AllowDrop="True" Drop="Grid_Drop"/>
</Border>
</Grid>
</Border>
</Grid>
</TabItem>
the grid is formed through
PalletWindow.PalletWindow.SetPalletGrid(numRows, numColumns,ref grdPalletTab2);
whose code is:
public static bool SetPalletGrid(int numRows, int numColumns, ref Grid grd)
{
try
{
grd.Children.Clear();
grd.RowDefinitions.Clear();
grd.ColumnDefinitions.Clear();
grd.AllowDrop = true;
for (int row = 0; row < numRows; row++)
{
var rd = new RowDefinition();
rd.AllowDrop = true;
rd.Height = new GridLength(1.0, GridUnitType.Star);
grd.RowDefinitions.Add(rd);
}
for (int column = 0; column < numColumns; column++)
{
var cd = new ColumnDefinition();
cd.AllowDrop = true;
cd.Width = new GridLength(1.0, GridUnitType.Star);
grd.ColumnDefinitions.Add(cd);
}
for (int row = 0; row < numRows; row++)
{
for (int column = 0; column < numColumns; column++)
{
var borderImage = new Border();
borderImage.AllowDrop = true;
borderImage.BorderThickness = new Thickness(2);
borderImage.BorderBrush = new SolidColorBrush(Colors.Black);
borderImage.Name = "BRD_" + row + "_" + column;
borderImage.Effect = new DropShadowEffect
{
Color = new Color { R = 255, G = 255, B = 255 },
Direction = 320,
ShadowDepth = 5,
Opacity = 0.95
};
Grid.SetRow(borderImage, row);
Grid.SetColumn(borderImage, column);
grd.Children.Add(borderImage);
}
}
return true;
}
catch// (Exception exc)
{
return false;
}
}
thanks for any help
Patrick

To make d&d work you have to set the background of the target element (don't know why). In your case set borderImage = new SolidColorBrush(Colors.Transparent);

get every textblock from listview

I'm building a UWP app and I'm trying to get every textblock from my listview.
This is my listview:
<ListView Grid.Row="1" BorderBrush="#0062AD" BorderThickness="1" ItemsSource="{Binding BusRoutes}" x:Name="Routes1" SelectionMode="None" IsItemClickEnabled="False" Padding="0 10 0 0">
<ListView.ItemTemplate>
<DataTemplate>
<Grid Width="400">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock x:Name="startingPoint" Grid.Row="0" Grid.Column="0" Padding="0 10 0 10" TextAlignment="Center" HorizontalAlignment="Center" Text="{Binding hours}"/>
<TextBlock TextAlignment="Center" Grid.Row="0" Grid.Column="1" Padding="0 10 0 10" x:Name="endingPoint" HorizontalAlignment="Center" Text="{Binding hours2}" />
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
And this is my attempt of doing this:
public T FindElementByName<T>(DependencyObject element, string sChildName) where T : FrameworkElement
{
T childElement = null;
var nChildCount = VisualTreeHelper.GetChildrenCount(element);
for (int i = 0; i < nChildCount; i++)
{
FrameworkElement child = VisualTreeHelper.GetChild(element, i) as FrameworkElement;
if (child == null)
continue;
if (child is T && child.Name.Equals(sChildName))
{
childElement = (T)child;
break;
}
childElement = FindElementByName<T>(child, sChildName);
if (childElement != null)
break;
}
return childElement;
}
And in my ItemClick event I did this:
this.UpdateLayout();
for (int i = 0; i < Routes1.Items.Count; i++)
{
var container = this.Routes1.ContainerFromIndex(i);
TextBlock endingPoint = FindElementByName<TextBlock>(container, "endingPoint");
endingPoint.Visibility = Visibility.Collapsed;
}
for (int i = 0; i < Routes1.Items.Count; i++)
{
var container = this.Routes1.ContainerFromIndex(i);
TextBlock startingPoint = FindElementByName<TextBlock>(container, "startingPoint");
startingPoint.SetValue(Grid.ColumnSpanProperty, 2);
}
and I'm getting System.ArgumentException. The weird thing is that when I'm trying to take one textblock eg var container = this.Routes1.ContainerFromIndex(0);
I can get the first textblock normally. Why is this happening?
I forgot to mention that the exception blows up at this line:
var nChildCount = VisualTreeHelper.GetChildrenCount(element);