I have a list of items - when one is selected, I'd like to slide the appbar up. This is what I have so far:
<AppBar IsOpen="{Binding BookIsSelected}">
<Grid>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
<AppBarButton Icon="Remove" Label="Remove Book" Command="{Binding RemoveBook}" Visibility="{Binding BookIsSelected, Mode=TwoWay, Converter={StaticResource BooleanToVisibilityConverter}}" />
</StackPanel>
</Grid>
</AppBar>
In the gridview of books, I have this:
SelectedItem ="{Binding SelectedBook, Mode = TwoWay}" />
BookIsSelected:
private bool _bookSelected;
public bool BookIsSelected {
get {
return _bookSelected;
}
set {
SetProperty(ref _bookSelected, value);
}
}
I can see the get/set hit when I select a book, but the appbar never flies out. What am I doing wrong?
I can't see any obvious problems with the code that you've shown so far. However, you haven't shown the code for the SelectedBook property or SetProperty method, so perhaps your problem lies there? Your SelectedBook property should look something like this, setting BookIsSelected to true:
private YourDataType _selectedBook;
public YourDataType SelectedBook{
get {
return _selectedBook;
}
set {
SetProperty(ref _selectedBook, value);
BookIsSelected = true;
}
}
However, unless you set the BookIsSelected property back to false at some stage, this will only work once. Your SetProperty method should notify the INotifyPropertyChanged interface of property changes, as #Amer mentioned in the comments. It should look something like this example from the linked page:
private void SetProperty([CallerMemberName] String propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
Related
I have this strange problem, where the binding seems completely ignored.
my xaml
<Button IsEnabled="{Binding ButtonEnabled}" x:Name="ButtonOK" BackgroundColor="Green" TextColor="White" Text="OK"/>
my C#
private bool _buttonEnabled = false;
public bool ButtonEnabled
{
get
{
// breakpoint 1, which never hits with value = false
return _buttonEnabled;
}
set
{
// breakpoint 2, which hits
_buttonEnabled = value;
OnPropertyChanged(nameof(ButtonEnabled));
}
}
private void ChassisEntry_TextChanged(object sender, TextChangedEventArgs e)
{
ButtonEnabled = ChassisEntry.Text != "";
}
private void PageScan_Appearing(object sender, EventArgs e)
{
ChassisEntry.Text = "";
}
I expect that when this page opens that ButtonOK is disabled, but it is not.
When I set breakpoints then breakpoint 1 (in the getter) never hits, its like if the xaml IsEnabled="{Binding ButtonEnabled}" is ignored.
The breakpoint 2 does hits, with value = false
What am I missing here ?
I googled this problem and found many similar questions, but all solutions given do not help with my problem.
Button IsEnabled binding not working properly
How to disable a button until all entries are filled?
Disable/Enable save button based on the mandatory field being null or empty using Behaviors
and many more
I am guessing you are using the xaml.cs page for holding your Bindings and hence if you are doing that there are two ways to do this
Set the BindingContext to the current class in the constructor before or right after InitializeComponent
BindingContext= this;
Or In your XAML
<ContentPage
....
x:Name="currentPage">
And in your button
<Button IsEnabled="{Binding ButtonEnabled, Source={x:Reference currentPage}}"
I would go with this: Set my Button in my XAML disabled.
<Button IsEnabled="False" x:Name="ButtonOK" BackgroundColor="Green" TextColor="White" Text="OK"/>
Then on my Entry control i would add the property TextChanged.
<Entry x:Name="ChassisEntry"
PlaceholderColor="DarkGray"
TextChanged="ChassisEntryChanged">
On xaml.cs file:
private void ChassisEntryChanged(object sender, TextChangedEventArgs e)
{
if (e.NewTextValue.Text != "")
{
ButtonOK.IsEnabled = true;
}
else
{
ButtonOK.IsEnabled = false;
}
}
I want to show a label when i click on my item in my listview.
The real problem i don't know how to link between my viewmodel and my views
I want modify my label in viewmodel but I don't know if its possible currently.
My xaml :
<StackLayout>
<Label x:Name="labelperso"
Text="{Binding newProduct}"
IsVisible="{Binding Addproduct}"
VerticalTextAlignment="Center"
HorizontalTextAlignment="Center"
BackgroundColor="#000000"
FontSize="20"
Opacity="0"/>
<ListView ItemsSource="{Binding Products}" CachingStrategy="RecycleElement" RowHeight="50" >
<ListView.ItemTemplate>
<DataTemplate>
<TextCell Text="{Binding CodeReferenceLibelle}" TextColor="Black"/>
</DataTemplate>
</ListView.ItemTemplate>
<ListView.Behaviors>
<b:EventToCommandBehavior EventName="ItemSelected" Command="{Binding
SelectCommand}" Converter="{StaticResource SelectedItemConverter}"/>
</ListView.Behaviors>
my viewmodel :
#region labelperso property
private string _newProduct;
public string newProduct
{
get { return _newProduct; }
set { SetProperty(ref _newProduct, value); }
}
#endregion
#region Addproduct property
private bool _Addproduct;
public bool Addproduct
{
get { return _Addproduct; }
set { SetProperty(ref _Addproduct, value); }
}
#endregion
when I click on my item :
async Task Select()
{
newProduct = "Produit ajouté !";
basketManager.AddProductSkuAsync(sku);
newProduct = "";
await Task.Run(() => ShowText());
}
//I have tried this but I can't use my label in my view
async Task ShowText()
{
await labelperso.FadeTo(1);
await Task.Delay(1000);
await labelperso.FadeTo(0);
}
Why are you want to take the label "labelperso" in VM ? you can use it in xaml.cs instead.
You just need to add the event ItemSelected like this:
<ListView ItemsSource="{Binding Products}" ItemSelected="OnSelection">
In xaml.cs
void OnSelection(object sender, SelectedItemChangedEventArgs e)
{
if (e.SelectedItem == null)
{
return;
}
//suppose the binding Object is Product
Product product = (Product)e.SelectedItem;
//labelperso.Text = "name = " + product.Name;
labelperso.FadeTo(1);
Task.Delay(1000);
labelperso.FadeTo(0);
}
Normally, VM are unrelated to Xaml, and we should not get labels from VM.
And we don't recommend it.But if you must, you can pass the Label in from the xaml.cs file like this:
You can define a variable in yourpage.xaml.cs:
public Label pageLabel;
and initial like this:
pageLabel = labelperso;
BindingContext = new YourViewmodel(this);
And in YourViewmodel.cs:
public Label ss;
public YourViewmodel(ContentPage parentPage)
{// here HomePage is your contentPage name of the page`
ss = ((HomePage)parentPage).pageLabel;//after this you can use it
}
You need to add a SelectedProduct property to your VM.
private string _SelectedProduct;
public string SelectedProduct
{
get { return _SelectedProduct; }
set { SetProperty(ref _SelectedProduct, value); }
}
You can then bind your ListView's SelectedItem to it
<ListView ItemsSource="{Binding Products}"
SelectedItem="{Binding SelectedProduct}"
CachingStrategy="RecycleElement"
RowHeight="50" >
You can then control the visibility of your label by binding to SelectedProduct via a "nullToVisibility" converter, or by using triggers etc.
You should try to use MVVM pattern rather than hacking with code behind.
Using MVVM you can add a Visible property to your viewmodel and bind the IsVisible property of the label to it.
Code will be much easy to read and maintain.
I am new to silverlight. I am trying to generate a list of checkboxes(with content). The idea is that the user will select some of these checkboxes and will press a button. Then we try to read the content of selected checkboxes for further processing. I don't know how many number of checkboxes will be there and therefore I can't use bindings.
This is the code snippet in the .xaml file.
<StackPanel Grid.Row="21" Grid.Column="1" Margin="5" VerticalAlignment="Center">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<ItemsControl Name="infoPairItems" ItemsSource="{Binding InfoPair}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox Grid.Column="0" Name="infoPairSelectBox" IsEnabled="True" IsThreeState="False"
Margin="0,5" FontSize="12" IsChecked="bool"
Content="{Binding Converter={StaticResource infoPairToStringValueConverter}}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
</StackPanel>
I am trying to access these checkboxes in the .xaml.cs file like this.
foreach(var infoPairItem in infoPairItems.Items)
{
ContentPresenter container = infoPairItems.ItemContainerGenerator.ContainerFromItem(infoPairItem) as ContentPresenter;
if(container == null)
{
DebugLog.Log("container is null ");
}
DataTemplate dataTemplate = container.ContentTemplate;
CheckBox checkBox = (CheckBox)dataTemplate.LoadContent();
if (checkBox == null)
{
DebugLog.Log("checkBox is null !!!");
return;
}
if (checkBox.IsChecked.HasValue)
{
if (checkBox.IsChecked.Value)
{
DebugLog.Log("checkbox value true");
}
else
{
DebugLog.Log("checkbox value false");
}
}
}
The log 'checkbox value false' is always getting printed for all the checkboxes even when some of them are selected. I tried to use the debugger. It looks like that variable container is getting loaded with the correct value. Either the method LoadContent() is not working or I am using the wrong method.
I apologize beforehand if it is a repeat question. I tried to look into the previous questions on stackoverflow but could not find any answer. Please guide me in correct direction.
I will explain what happens and how to solve:
1.- You are getting the datatemplate not instances of the datatemplate, in case you want to manage the instances you can do by using the Loaded Event to add items to the List to create and update for instance a List.
2.- What makes all of these events a really complex code to manage is easier if you create the following:
2.1 A class for instance that has a bool and a string for the content with INotifyPropertyChanged:
public class InfoSelection : Model
{
Property bool for Selected
Property string for Info, or whatever and the converter
}
2.2 A list with the items you need of the type of that class in the DataContext
public List<InfoSelection> {get;set;}
(If you initialize just once in the constructor for instance, you do not need to implement INotiyPropertyChanged, just clear or removeitems, never reassign)
2.3 In the Xaml binding change to the following:
<CheckBox Grid.Column="0"
Name="infoPairSelectBox"
IsEnabled="True"
IsThreeState="False"
Margin="0,5"
FontSize="12"
IsChecked="{Binding Selected, Mode=TwoWay}"
Content="{Binding Info}"/>
I don't know how many number of checkboxes will be there and therefore I can't use bindings.
Incorrect.
To Visually display two levels of data generically, the use of a ItemsControl with individual DataTemplate`s for the parent items and their child items can be done.
Then to allow for the editing (your deletion operation) one needs to identify who the parent node is from the child nodes, along with getting the state of the checkbox.
That identification requires us to project the initial data into a wrapper class to facilitate binding/identification.
Let me explain.
Say our data displays a top level last name and all first names associated with the last name.
The above simulates a top level checkbox (to delete all) and children checkbox (to delete an individual item) for the following data class retrieved from the database:
public class VectorStrings
{
public int Id { get; set; }
public string LastName { get; set; }
public List<string> FirstNames { get; set; }
}
With simulated data loaded as such:
LastNames = new List<VectorStrings>()
{
new VectorStrings() { Id=9, LastName="Smith", FirstNames = new List<string>() { "Bob", "Victoria" } },
new VectorStrings() { Id=12, LastName="Jones", FirstNames = new List<string>() { "Peter", "Paul", "Mary" } },
};
Now for display I can generically display those items to the above data, but because we need to operate on the child data, we need to project that information into a holding wrapper class.
public class VectorCheckbox
{
public int Id { get; set; }
public int ParentId { get; set; }
public string DisplayName { get; set; }
public List<VectorCheckbox> Children { get; set; }
public object Tag { get; set; } // Same concept as a visual control property 'Tag'
}
so our code to project the original data looks like this:
CheckBoxData =
LastNames.Select(ln => new VectorCheckbox()
{
DisplayName = ln.LastName,
Id = ln.Id,
Tag = ln,
Children = ln.FirstNames.Select((fn, index) => new VectorCheckbox()
{
Id = index,
ParentId = ln.Id,
DisplayName = fn,
Tag = ln.Id // Hold the parent Id for identification
}).ToList()
})
.ToList();
Sweet! Now we just need nested ItemControl classes to display our data:
<ItemsControl ItemsSource="{Binding CheckBoxData}">
<ItemsControl.Resources>
<system:String x:Key="Format">Delete All for ID: '{0}' </system:String>
</ItemsControl.Resources>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Vertical" Margin="10" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" Margin="6,0,0,0">
<CheckBox Tag="{Binding Id}" Margin="0,0,0,10" Click="DeleteAll_Click">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Id, StringFormat={StaticResource Format}}"/>
<TextBlock Text="{Binding DisplayName}" Margin="4,0,6,0"/>
<ItemsControl ItemsSource="{Binding Children}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox Tag="{Binding Tag}"
Content="{Binding DisplayName}"
Click="DeleteIndividual_Click"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</StackPanel>
</CheckBox>
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
Now in code behind we subscribe to the click events. I use a message box to show that I have identified the right items. For example if one clicks on a delete all check box, it identifies the children and the state of the checkbox, and if I click on a child it identifies its parent and itself.
Parent Click
private void DeleteAll_Click(object sender, RoutedEventArgs e)
{
var cb = sender as CheckBox;
if (cb != null)
{
var id = (int)cb.Tag;
var nameInstance = ViewModel.LastNames.FirstOrDefault(nm => nm.Id == id);
if (nameInstance != null)
MessageBox.Show(string.Format("Delete all for {0} of names {1} (Status {2})",
nameInstance.LastName,
string.Join(",", nameInstance.FirstNames),
((cb.IsChecked ?? false) ? "Checked" : "UnChecked")
));
}
}
Child Click
private void DeleteIndividual_Click(object sender, RoutedEventArgs e)
{
var cb = sender as CheckBox;
if (cb != null)
{
var parentId = (int)cb.Tag; // Parent Id
var nameInstance = ViewModel.LastNames.FirstOrDefault(nm => nm.Id == parentId);
if (nameInstance != null)
MessageBox.Show(string.Format("Delete individual for {0} of name {1} (Status {2})",
nameInstance.LastName,
cb.Content,
((cb.IsChecked ?? false) ? "Checked" : "UnChecked")
));
}
}
So from that I have identified the checkbox state along with the target original items. This code simulates ultimately what you want to do. I leave the actual plumbing of the observable collection remove items up to you. But this gets the idea across.
I recommend that you experiment in WPF then take it to Silverlight, for the concepts are the same, but its easier/faster to test out in WPF.
In my Xaml I have this listview:
<ListView HorizontalAlignment="Left"
Height="355"
Margin="144,373,0,0"
VerticalAlignment="Top"
Width="154"
ItemsSource="{Binding People}"
SelectedItem="{Binding SelectedItem}"
ItemTemplate="{StaticResource Standard310x260ItemTemplate}"/>
And on my VM i have this property:
private Person _selectedItem;
public Person SelectedItem
{
get
{
return _selectedItem;
}
set
{
if (_selectedItem == value || value == null)
{
return;
}
var oldValue = _selectedItem;
_selectedItem = value;
// Update bindings, no broadcast
RaisePropertyChanged("SelectedItem");
}
}
What im hoping for is that the SelectedItem-property on my VM would get updated whenever I click an item in the listview. Can someone see what I am missing here?
Try with
<ListView SelectedItem="{Binding SelectedItem, Mode=TwoWay}" />
If it doesn't work, in page constructor add:
this.DataContext = this;
It should work now.
Hope it helps :)
Try adding IsSynchronizedWithCurrentItem:
MSDN
I've searched a bit, but the info I've found isn't what I need. So I decided to ask you all - I'm sure it's a newbie question but i really don't get it.
Let's start:
I have a DataSource which is a grouped observable collection. At the moment I've 2 groups with a different count of items. The two groups and the items belong to the same common base:
public DataCommon(String uniqueId, String title, String subtitle, String imagePath, String description)
{
this._uniqueId = uniqueId;
this._title = title;
this._subtitle = subtitle;
this._description = description;
this._imagePath = imagePath;
}
This is the constructor of the model.
In the ViewModel I fill it.
Now I would like bind the ItemClick with a Command to my ViewModel. I do like this (only a short part):
<GridView
x:Name="itemGridView"
AutomationProperties.AutomationId="ItemGridView"
AutomationProperties.Name="Grouped Items"
Grid.RowSpan="2"
Padding="116,137,40,46"
ItemsSource="{Binding Source={StaticResource groupedItemsViewSource}}"
ItemTemplate="{StaticResource Standard250x250ItemTemplate}"
SelectionMode="None"
IsSwipeEnabled="false"
IsItemClickEnabled="True"
>
<WinRtBehaviors:Interaction.Behaviors>
<Win8nl_Behavior:EventToCommandBehavior Event="ItemClick" Command="ItemClickCommand" CommandParameter="{Binding UniqueId}"/>
</WinRtBehaviors:Interaction.Behaviors>
But now the problem. At the "Binding UniqueId" it's saying the DataContext is my ViewModel, so i can't connect it to the properties of the Model. Looked at the Page.DataContext i told XAML tu use my ViewModel as DataContext. I guess this was correct. But how can I access the Model-properties?
I've tried to do it like this (defined my Model as DataModel):
<WinRtBehaviors:Interaction.Behaviors>
<Win8nl_Behavior:EventToCommandBehavior Event="ItemClick" Command="ItemClickCommand" CommandParameter="{Binding DataModel:SampleDataCommon.UniqueId}"/>
</WinRtBehaviors:Interaction.Behaviors>
but as I guessed beforehand it didn't work - as parameter i get null.
I would be thankful for any help, because as i said at the beginning of the post: I really don't get it...
You can't use EventToCommandBehavior in this way - this was also stated by its author in the comments.
I'm using the following attached property in such cases:
public static class ItemClickBehavior
{
public static DependencyProperty ItemClickCommandProperty = DependencyProperty.RegisterAttached("ItemClickCommand",
typeof(ICommand),
typeof(ItemClickBehavior),
new PropertyMetadata(null, OnItemClickCommandChanged));
public static void SetItemClickCommand(DependencyObject target, ICommand value)
{
target.SetValue(ItemClickCommandProperty, value);
}
public static ICommand GetItemClickCommand(DependencyObject target)
{
return (ICommand)target.GetValue(ItemClickCommandProperty);
}
private static void OnItemClickCommandChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)
{
var element = target as ListViewBase;
if (element != null)
{
// If we're putting in a new command and there wasn't one already
// hook the event
if ((e.NewValue != null) && (e.OldValue == null))
{
element.ItemClick += OnItemClick;
}
// If we're clearing the command and it wasn't already null
// unhook the event
else if ((e.NewValue == null) && (e.OldValue != null))
{
element.ItemClick -= OnItemClick;
}
}
}
static void OnItemClick(object sender, ItemClickEventArgs e)
{
GetItemClickCommand(sender as ListViewBase).Execute(e.ClickedItem);
}
}
This is how you would bind a command to it:
<GridView
x:Name="itemGridView"
AutomationProperties.AutomationId="ItemGridView"
AutomationProperties.Name="Grouped Items"
Grid.RowSpan="2"
Padding="116,137,40,46"
ItemsSource="{Binding Source={StaticResource groupedItemsViewSource}}"
ItemTemplate="{StaticResource Standard250x250ItemTemplate}"
SelectionMode="None"
IsSwipeEnabled="false"
IsItemClickEnabled="True"
itbmb:ItemClickBehavior.ItemClickCommand="{Binding ItemClickCommand}"
>
I guess it wouldn't be all that difficult to create a behavior from the attached property if you really wanted to.