c#xamlmaui
Why does the listview display the items incorrectly after I remove them in .NET MAUI?
Firstscreen with all the notes.
After I deleted the first note!
I have recently started programming with .NET MAUI. The elements are correctly removed in the C# list. However, after deleting the remaining elements are only partially displayed. That means that only e.g. the 4th element is displayed. For the other elements only an empty bar is displayed.
My code so far: XAML:
<VerticalStackLayout>
<ScrollView>
<StackLayout>
<Grid>
<Grid.RowDefinitions>
<RowDefinition />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Image
Grid.Column="0"
Source="logo.png"
WidthRequest="150"
HorizontalOptions="Start"
VerticalOptions="Start"/>
<Label
TextColor="Black"
Grid.Column="1"
Text="TODO"
FontSize="35"
HorizontalOptions="Start"
VerticalOptions="Start"
Margin="23"/>
</Grid>
<Grid BackgroundColor="#24D4A3">
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<ListView
Grid.ColumnSpan="2"
Grid.RowSpan="2"
RowHeight="100"
x:Name="listview">
<ListView.ItemTemplate>
<DataTemplate >
<ViewCell >
<Grid BackgroundColor="#24D4A3">
<Grid.RowDefinitions>
<RowDefinition Height="auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="auto"/>
</Grid.ColumnDefinitions>
<Button BackgroundColor="#DEABF5"
Text="{Binding Title}"
Clicked="onNoteSelected"
BorderWidth="2"
TextColor="Black"
FontSize="28"
Margin="20"
CornerRadius="100"
WidthRequest="350"
HeightRequest="70"
HorizontalOptions="Center"
VerticalOptions="Start"/>
<Button
BindingContext="{Binding Id}"
Clicked="ToDoSolved"
BorderWidth="2"
BorderColor="Black"
BackgroundColor="White"
WidthRequest="45"
HeightRequest="45"
CornerRadius="35"
Margin="0,0,260,0"
/>
</Grid>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<ImageButton
Clicked="Settings"
Source="settings.png"
Grid.Row="0"
Grid.Column="2"
BorderColor="#2b3c3c"
BorderWidth="0"
BackgroundColor="#34A4EB"
CornerRadius="35"
HorizontalOptions="End"
WidthRequest="70"
HeightRequest="70"
Margin="0,10, 10, 0"
VerticalOptions="Start"/>
<ImageButton
Clicked="CreateNote"
Source="add.png"
Grid.Row="1"
Grid.Column="2"
BorderColor="#2b3c3c"
BorderWidth="0"
BackgroundColor="#34A4EB"
CornerRadius="35"
HorizontalOptions="End"
WidthRequest="70"
HeightRequest="70"
Margin="0,0,10,10"
Padding="2,0,0,0"/>
</Grid>
</StackLayout>
</ScrollView>
</VerticalStackLayout>
C#:
public partial class MainPage : ContentPage
{
private ObservableCollection<Note> notes = new ObservableCollection<Note>();
public ObservableCollection<Note> Notes
{
get { return notes; }
set { notes = value; }
}
public MainPage()
{
InitializeComponent();
notes.Add(new Note(1, "My Note1", "I'm ugly"));
notes.Add(new Note(2, "My Note2", "I'm short"));
notes.Add(new Note(3, "My Note3", "I'm smart"));
notes.Add(new Note(4, "My Note4", "I'm smart"));
//notes.Add(new Note(6, "My Note6", "I'm smart"));
//notes.Add(new Note(7, "My Note7", "I'm smart"));
//notes.Add(new Note(8, "My Note8", "I'm smart"));
//notes.Add(new Note(9, "My Note9", "I'm smart"));
this.BindingContext= Notes;
listview.ItemsSource= Notes;
}
private async void CreateNote(object sender, EventArgs e)
{
await Shell.Current.GoToAsync("//CreateNote");
}
private async void Settings(object sender, EventArgs e)
{
await Shell.Current.GoToAsync("//Settings");
}
private void ToDoSolved(object sender, EventArgs e)
{
Button button= (Button) sender ;
var id = (int)button.BindingContext;
var item = Notes.SingleOrDefault(x => x.Id == id);
if (item != null)
{
Notes.Remove(item);
Console.WriteLine(id);
}
}
async void onNoteSelected(object sender, EventArgs e)
{
Button button= (Button) sender ;
var id = (int)button.BindingContext;
//await Shell.Current.GoToAsync("NotePage" + id);
}
}
I would be grateful for any help :)
Solution
To delete the item, since you are using ListView, you can delete the via
Button click. However, you need to delete the item from bottom to top in order.
Code-behind:
public partial class MainPage : ContentPage
{
public ObservableCollection<Note> Notes { get; private set; } = new ObservableCollection<Note>();
public MainPage()
{
InitializeComponent();
AddNotes();
BindingContext = this;
}
private void AddNotes()
{
Notes.Add(new Note("0", "My Note1"));
Notes.Add(new Note("1", "My Note2"));
Notes.Add(new Note("2", "My Note3"));
Notes.Add(new Note("3", "My Note4"));
}
private void Button_Clicked(object sender, EventArgs e)
{
var note = (Button)sender;
Note listnote = (from itm in Notes
where itm.Id == note.CommandParameter.ToString()
select itm).FirstOrDefault<Note>();
Notes.Remove(listnote);
}
}
Xaml:
<VerticalStackLayout>
<ScrollView>
<StackLayout>
<Grid>
<Grid.RowDefinitions>
<RowDefinition />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Image
Grid.Column="0"
Source="logo.png"
WidthRequest="150"
HorizontalOptions="Start"
VerticalOptions="Start"
/>
<Label
TextColor="Black"
Grid.Column="1"
Text="TODO"
FontSize="35"
HorizontalOptions="Start"
VerticalOptions="Start"
Margin="23"
/>
</Grid>
<Grid BackgroundColor="#24D4A3">
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<ListView
Grid.ColumnSpan="2"
Grid.RowSpan="2"
RowHeight="100"
x:Name="listview"
ItemsSource="{Binding Notes}" >
<ListView.ItemTemplate>
<DataTemplate >
<ViewCell>
<Grid BackgroundColor="#24D4A3" >
<Grid.RowDefinitions>
<RowDefinition Height="auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="auto"/>
</Grid.ColumnDefinitions>
<Button BackgroundColor="#DEABF5"
Text="{Binding Title}"
BorderWidth="2"
TextColor="Black"
FontSize="28"
Margin="20"
CornerRadius="100"
WidthRequest="350"
HeightRequest="70"
HorizontalOptions="Center"
VerticalOptions="Start"/>
<Button
Text="Delete"
Clicked="Button_Clicked"
CommandParameter="{Binding Id}"
BorderWidth="2"
BorderColor="Black"
BackgroundColor="White"
WidthRequest="45"
HeightRequest="45"
CornerRadius="35"
Margin="0,0,260,0"
/>
</Grid>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</Grid>
</StackLayout>
</ScrollView>
</VerticalStackLayout>
Note:
public class Note
{
public string Id { get; set; }
public string Title { get; set; }
public Note(string id, string title)
{
Id = id;
Title = title;
}
}
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