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Passing data from viewmodel to viewmodel and use it .Net maui

How to use viewmodel get data and draw graphic,Can I send data from mainpageviewmodel to use on graphicviewmodel and show on graphicpage
MainPage.xaml
<CollectionView
BackgroundColor="Transparent"
ItemsSource="{Binding graphiclist}"
SelectionMode="None">
<CollectionView.ItemTemplate>
<DataTemplate x:DataType="model:GRAPHICModel">
<Grid Padding="0">
<Frame HeightRequest="100">
<Frame.GestureRecognizers>
<TapGestureRecognizer Command="{Binding Source={RelativeSource AncestorType={x:Type viewmodel:MainViewModel}}, Path=DrawGRAPHCommand}" CommandParameter="{Binding .}" />
</Frame.GestureRecognizers>
<Grid Padding="0">
<VerticalStackLayout>
<Label Style="{StaticResource BoldLabel}" Text="{Binding GraphicNamae}" />
</VerticalStackLayout>
</Grid>
</Frame>
</Grid>
</DataTemplate>
</CollectionView.ItemTemplate>
mainpageviewmodel.cs
public partial class MainpageViewModel : ObservableObject
{
public ObservableCollection<GRAPHICModel> graphiclist { get; set; }
public MainpageViewModel()
{
graphiclist = new ObservableCollection<GRAPHICModel>
{
new GRAPHICModel { GraphicName= "Name1", Path = "somecoordinate" },
new GRAPHICModel { GraphicName= "Name2", Path = "somecoordinate" },
new GRAPHICModel { GraphicName= "Name3", Path = "somecoordinate" },
new GRAPHICModel { GraphicName= "Name4", Path = "somecoordinate" }
};
}
[ICommand]
async Task DrawGRAPHCommand(GRAPHICModel glist)
{
await Shell.Current.GoToAsync(nameof(DrawPage), true, new Dictionary<string, object>
{
["GRAPHICModel"] = glist
});
}
}
graphicpage.xaml
<VerticalStackLayout>
<Label Text="{Binding Graphiclist.GraphicName}" />
<FlexLayout
AlignItems="Center"
Direction="Column"
JustifyContent="SpaceEvenly">
<VerticalStackLayout>
<GraphicsView
Drawable="{StaticResource drawable}"
HeightRequest="1000"
WidthRequest="1000" />
</VerticalStackLayout>
</FlexLayout>
</VerticalStackLayout>
graphicviewmodel.cs
[QueryProperty(nameof(Graphiclist), "GRAPHICModel")]
public partial class GraphicViewModel : ObservableObject, IDrawable
{
[ObservableProperty]
GRAPHICModel graphiclist;
public void Draw(ICanvas canvas, RectF dirtyRect)
{
something.load(graphiclist.Path)
canvas.StrokeColor = Colors.Red;
canvas.StrokeSize = 4;
canvas.DrawPath();
}
}
After tap , can not get graphiclist.path for canvas.DrawPath(-somepoint-); after tap
but can show <Label Text="{Binding Graphiclist.GraphicName}" />

In MVVM for communication between View Models common practice is to use Mediator Design Pattern !! There are a lot articles around it as much as yt videos.

Xamarin Forms TapGestureRecognizer Is not issuing command

So I have a xamarin forms app that currently only implemented for android. I am attempting to implement a tap event. When tapped though this never hits the command in the ViewModel. I'm not sure if I have something the matter with my code or I am just implementing it wrong.
ViewModel Code:
private RelayCommand<object> _OnClickableLabel;
public RelayCommand<object> OnClickableLabel
{
get { return _OnClickableLabel ?? (_OnClickableLabel = new RelayCommand<object>((currentObject) => Test(currentObject))); }
}
private void Test(object currentObject)
{
Application.Current.MainPage.DisplayAlert("Alert", "were going down cap", "OK");
}
Page Xaml:
<ListView Grid.Row="1" ItemsSource="{Binding Notifications}" RowHeight="100">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<StackLayout Orientation="Vertical" BackgroundColor="{Binding BackgroundColor}">
<StackLayout.GestureRecognizers>
<TapGestureRecognizer Command="{Binding OnClickableLabel }" />
</StackLayout.GestureRecognizers>
<Label FontSize="Large" Text="{Binding Title}"></Label>
<Label FontSize="Small" Text="{Binding Text}"></Label>
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
I have tested it using a method in the page's cs code and that works fine but it has to be implemented in the ViewModel because it affects that data.

From your description, you want to add a tap gesture recognizer in ListView, and want to pass ListView current row data to TapGestureRecognizer event, am I right?
If yes, as Jason's opinion, you need to take a look Xamarin.Forms Relative Bindings firstly,name ListView as listview1, then take a look the following code:
<ListView
x:Name="listview1"
Grid.Row="1"
ItemsSource="{Binding Notifications}"
RowHeight="100">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<StackLayout BackgroundColor="{Binding BackgroundColor}" Orientation="Vertical">
<StackLayout.GestureRecognizers>
<TapGestureRecognizer Command="{Binding BindingContext.OnClickableLabel, Source={x:Reference listview1}}" CommandParameter="{Binding .}" />
</StackLayout.GestureRecognizers>
<Label FontSize="Large" Text="{Binding Title}" />
<Label FontSize="Small" Text="{Binding Text}" />
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
public partial class Page16 : ContentPage
{
public ObservableCollection<Notclass> Notifications { get; set; }
public ICommand OnClickableLabel { get; set; }
public Page16()
{
InitializeComponent();
Notifications = new ObservableCollection<Notclass>()
{
new Notclass(){Title="title 1",Text="notification 1"},
new Notclass(){Title="title 2",Text="notification 2"},
new Notclass(){Title="title 3",Text="notification 3"},
new Notclass(){Title="title 4",Text="notification 4"},
new Notclass(){Title="title 5",Text="notification 5"}
};
OnClickableLabel = new Command(n=> {
var vm = (Notclass)n;
Application.Current.MainPage.DisplayAlert("Alert",vm.Title , "OK");
});
this.BindingContext = this;
}
}
public class Notclass
{
public string Title { get; set; }
public string Text { get; set; }
public Color BackgroundColor { get; set; } = Color.White;
}

How to get indexes of Xamarin CollectionView Items?

I have a CollectionView:
<CollectionView Grid.Row="10" Grid.Column="0" Grid.ColumnSpan="1" x:Name="SomeCollection"
ItemsLayout="VerticalList">
<CollectionView.ItemTemplate>
<DataTemplate>
<StackLayout Orientation="Horizontal" Padding="3" Spacing="0">
<Label WidthRequest="90" HeightRequest="20" Text="{Binding SomeItemText}" BackgroundColor="Black" TextColor="White"
VerticalTextAlignment="Center" HorizontalTextAlignment="Center" />
<Button WidthRequest="36" HeightRequest="36" CornerRadius="0" ImageSource="plus_thick.xml" BackgroundColor="Green"
Clicked="Duplicate_Clicked" />
<Button WidthRequest="36" HeightRequest="36" CornerRadius="0" ImageSource="close_thick.xml" BackgroundColor="Red"
Clicked="Remove_Clicked" />
</StackLayout>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
Every item in the collection has a duplicate and a remove button. By clicking the button I would like to duplicate/remove the item, but CollectionView doesn't have indexes on items.
Could you help me with a custom renderer or even something shorter and simpler?

About getting current collectionview item index by Button command, I do one sample that you can take a look:
<StackLayout>
<CollectionView
x:Name="SomeCollection"
ItemsLayout="VerticalList"
ItemsSource="{Binding items}">
<CollectionView.ItemTemplate>
<DataTemplate>
<StackLayout
Padding="3"
Orientation="Horizontal"
Spacing="0">
<Label
BackgroundColor="Black"
HeightRequest="20"
HorizontalTextAlignment="Center"
Text="{Binding SomeItemText}"
TextColor="White"
VerticalTextAlignment="Center"
WidthRequest="90" />
<Button
BackgroundColor="Green"
Command="{Binding BindingContext.duplicatecommand, Source={x:Reference SomeCollection}}"
CommandParameter="{Binding}"
CornerRadius="0"
HeightRequest="36"
Text="duplicate item"
WidthRequest="36" />
</StackLayout>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
</StackLayout>
public partial class Page13 : ContentPage
{
public ObservableCollection<someitems> items { get; set; }
public ICommand duplicatecommand { get; set; }
public Page13()
{
InitializeComponent();
items = new ObservableCollection<someitems>()
{
new someitems(){SomeItemText="test 1"},
new someitems(){SomeItemText="test 2"},
new someitems(){SomeItemText="test 3"},
new someitems(){SomeItemText="test 4"},
new someitems(){SomeItemText="test 5"},
new someitems(){SomeItemText="test 6"}
};
duplicatecommand = new Command<someitems>(getindexfun);
this.BindingContext = this;
}
private void getindexfun(someitems item)
{
int index = items.IndexOf(item);
}
}
public class someitems
{
public string SomeItemText { get; set; }
}

Instead of using click events, I would bind the buttons to a Command<T>.
This way in the ViewModel where you have your ItemsSource, you can just check what the index is of the Item ViewModel you are passing into the command as parameter. So in the ViewModel add something like this:
public Command<ItemViewModel> RemoveItemCommand { get; }
ctor() // this is the ViewModel constructor
{
RemoveItemCommand = new Command<ItemViewModel>(DoRemoveItemCommand);
}
private void DoRemoveItemCommand(ItemViewModel model)
{
// do stuff to remove
// probably something like:
Items.Remove(model);
// or get the index like:
var index = Items.IndexOf(model);
}
Then you can bind this command like so:
<Button
WidthRequest="36"
HeightRequest="36"
CornerRadius="0"
ImageSource="close_thick.xml"
BackgroundColor="Red"
Command="{Binding Source={RelativeSource AncestorType={x:Type local:ItemViewModel}}, Path=RemoveItemCommand}"
CommandParameter="{Binding}" />

How To Get Value Of SelectedItem In List

I would like to get the value of a selectedItem in A listView,this is my code.
public class BlogClass{
public string NewId;
public BlogClass()
{
additem();
}
public class BlogViews
{
public string id { get; set; }
public string DisplayTopic { get; set; }
public string DisplayMain { get; set; }
public ImageSource BlogImageSource { get; set; }
}
public List<BlogViews> BlogList1 = new List<BlogViews>();
public void additem()
{
BlogList1.Add(new BlogViews { id = "1", DisplayMain = "Margret", DisplayTopic = "Mensah" });
BlogList1.Add(new BlogViews { id = "2", DisplayMain = "Maet", DisplayTopic = "Meah" });
BlogList1.Add(new BlogViews { id = "3", DisplayMain = "dargret", DisplayTopic = "sah" });
BlogList1.Add(new BlogViews { id = "4", DisplayMain = "gret", DisplayTopic = "Meh" });
BlogListView.ItemsSource = BlogList1;
}
}
<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="demoListView.ImageCellPage">
<ContentPage.Content>
<ListView x:Name="BloglistView">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<StackLayout BackgroundColor="#eee"
Orientation="Vertical">
<StackLayout Orientation="Horizontal">
<Image Source="{Binding BlogImageSource}" />
<Label Text="{Binding id}"
TextColor="#f35e20" />
<Label Text="{Binding DisplayTopic}"
HorizontalOptions="EndAndExpand"
TextColor="#503026" />
<Label Text="{Binding DisplayMain}"
HorizontalOptions="EndAndExpand"
TextColor="#503026" />
</StackLayout>
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentPage.Content>
</ContentPage>
Question
Now When i select an item on BlogListView I want to set the Value of NewId to that of id according to the selecteditem.Hence gatting the value of id

You just need to add ItemTapped event for the listview:
XAML:
<ListView x:Name="BloglistView" ItemTapped="Handle_ItemTapped">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<StackLayout BackgroundColor="#eee"
Orientation="Vertical">
<StackLayout Orientation="Horizontal">
<Image Source="{Binding BlogImageSource}" />
<Label Text="{Binding id}"
TextColor="#f35e20" />
<Label Text="{Binding DisplayTopic}"
HorizontalOptions="EndAndExpand"
TextColor="#503026" />
<Label Text="{Binding DisplayMain}"
HorizontalOptions="EndAndExpand"
TextColor="#503026" />
</StackLayout>
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
Code Behind:
void Handle_ItemTapped(object sender, Xamarin.Forms.ItemTappedEventArgs e)
{
var selectedItem = e.Item as BlogViews;
NewId = selectedItem.id;
}

Databinding ListView with Custom Class

I would like to databind a custom class when displayed in xmal, but I'm getting nothing displayed in the list view. Any pointers to what I'm missing would be much appreciated.
public Transactional()
{
string oCustomerLoggedIn = Preferences.Get("uLoginUsername", "default_value");
int oCustomerLoggedInId = GetCustomerId(oCustomerLoggedIn);
List<TransactionsList> custTransactions = ViewCustomerTransactions(oCustomerLoggedInId);
InitializeComponent();
listView.SetBinding(ListView.ItemsSourceProperty, new Binding("."));
listView.BindingContext = custTransactions;
}
<ListView x:Name="listView" ItemSelected="OnItemSelected">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<ViewCell.ContextActions>
<MenuItem Clicked="OnMore" CommandParameter="{Binding .}" Text="More" />
<MenuItem Clicked="OnDelete" CommandParameter="{Binding .}" Text="Delete" IsDestructive="True" />
</ViewCell.ContextActions>
<StackLayout HorizontalOptions="StartAndExpand" Orientation="Horizontal">
<StackLayout Padding="5,0,0,0" VerticalOptions="StartAndExpand" Orientation="Vertical">
<Label Text="{Binding .}" VerticalTextAlignment="Center" FontSize="Medium" />
</StackLayout>
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>

Try this, refactor and modify where appropriate ...
List Item Model ...
using System;
namespace Playpen
{
public class ListItem
{
public string Text { get; set; }
public string SubText { get; set; }
}
}
XAML ...
<?xml version="1.0" encoding="utf-8"?>
<ContentPage
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:Playpen"
x:Class="Playpen.MainPage">
<StackLayout VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand">
<ListView
ItemsSource="{Binding DataSource}"
HasUnevenRows="true"
HorizontalOptions="FillAndExpand"
VerticalOptions="FillAndExpand"
SeparatorColor="Silver">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<StackLayout VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand" Padding="10">
<Label Text="{Binding Text}" FontSize="Medium" FontAttributes="Bold" LineBreakMode="TailTruncation"
TextColor="Black" VerticalOptions="Start" HorizontalOptions="StartAndExpand" />
<Label Text="{Binding SubText}" FontSize="Small" Margin="0, 5, 0, 0" LineBreakMode="TailTruncation"
TextColor="Gray" VerticalOptions="Start" HorizontalOptions="StartAndExpand" />
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackLayout>
</ContentPage>
Page Code Behind (you can refactor to MVVM as you need) ...
using System;
using System.Collections.ObjectModel;
using Xamarin.Forms;
namespace Playpen
{
public partial class MainPage : ContentPage
{
public ObservableCollection<ListItem> DataSource { get; set; }
public MainPage()
{
this.BindingContext = this;
DataSource = new ObservableCollection<ListItem>();
DataSource.Add(new ListItem() { Text = "Item 1", SubText = "Sub Item Text 1" });
DataSource.Add(new ListItem() { Text = "Item 2", SubText = "Sub Item Text 2" });
DataSource.Add(new ListItem() { Text = "Item 3", SubText = "Sub Item Text 3" });
InitializeComponent();
}
}
}