I'm seeing an error trying to use a custom converter in my WP8 app.
I defined my converter in a namespace: standrighthere.Utilities:
namespace standrighthere.Utilities
{
public class NonNullVisibilityConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return value == null ? Visibility.Collapsed : Visibility.Visible;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
I then included it in the App.xaml manifest as so:
<Application.Resources>
<utilities:NonNullVisibilityConverter x:Key="NonNullVisibiltyConverter" />
</Application.Resources>
I then tried to use it in my phone application page like this:
<Button Visibility="{Binding Source={Binding User}, Converter={StaticResource ResourceKey=NonNullVisibilityConverter}}" />
However, it keeps giving the error:
Error 1 The resource "NonNonNullVisibilityConverter" could not be resolved.
I feel like I must be missing something really obvious here.
Looks like a simple typo. You called your converter "NonNullVisibiltyConverter" in the resources and NonNonNullVisibil*i*tyConverter in the binding.
Related
I am trying to access to method class from XAML file.
My class is on folder: project.Utils.
Adding on xaml Content Page:
xmlns:local="project.Utils"
I try to use myConverterMethod class inside Utils folder and use it as:
Converter={StaticResource myConverterMethod}
but error Type myConverterMethod not found in xmlns project.Utils.
Where is my fault?
You can use
xmlns:local="clr-namespace:project.Utils;assembly=project"
It is not possible to refer to a Method within a specific class but to a IValueConverter.
In order to achieve what you want, you need to define a class that implements IValueConverter:
public class IntToBoolConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return (int)value != 0;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return (bool)value ? 1 : 0;
}
}
Define the created converter in accessible scope: Page/View or Application. By scope I mean resources:
<ContentPage.Resources>
<ResourceDictionary>
<local:IntToBoolConverter x:Key="intToBool" />
</ResourceDictionary>
</ContentPage.Resources>
and finally consume the converter in the next way:
<Button Text="Search"
HorizontalOptions="Center"
VerticalOptions="CenterAndExpand"
IsEnabled="{Binding Source={x:Reference entry1},
Path=Text.Length,
Converter={StaticResource intToBool}}" />
Xamarin has a very nice documentation that will answer all your questions and it usually has a good code samples.
would it be possible to databind a static resource in Xamarin Forms?
Something like
Style="{StaticResource {Binding foo, StringFormat='SomeStyle{0}'}}"
Thanks
What you probably want is a Value Converter that handles locating the StaticResource for you. Full Microsoft Documentation here.
On your XAML element, you'd do something like this:
<Entry Style="{Binding foo, Converter={StaticResource FooToStyleConverter}}"/>
Your converter would work something like this:
public class FooToStyleConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var someValue = (string)value; // Convert 'object' to whatever type you are expecting
// evaluate the converted value
if (someValue != null && someValue == "bar")
return (Style)App.Current.Resources["StyleOne"]; // return the desired style
return (Style)App.Current.Resources["StyleTwo"];
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
// Usually unused, but inverse the above logic if needed
throw new NotImplementedException();
}
}
Lastly, set up your converter as a Static Resource in App.xaml (or as a local resource on the page) so your page can properly reference it
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:DataBindingDemos">
<ContentPage.Resources>
<ResourceDictionary>
<local:FooToStyleConverter x:Key="FooToStyleConverter" />
....
I have a simple XAML:
<CheckBox x:Name="chkShowGrid" IsThreeState="False" IsChecked="False">Show content</CheckBox>
<Grid Visibility="{Binding IsChecked, ElementName=chkShowGrid}">
<TextBlock>Some content goes here</TextBlock>
</Grid>
This XAML works well in WinRT Windows 8.1 application. When I trying it in WP8.1 application it works in designer (shows or hides grid depend of checkbox value), but not on the phone. Why?
UPDATE:
I have universal 8.1 app and if use converter then shows me exception:
error CS0012: The type 'Type' is defined in an assembly that is not
referenced. You must add a reference to assembly 'System.Runtime,
Version=4.0.10.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
Converter code:
class BoolConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, string language)
{
if (value == null) return false;
return (bool)value;
}
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
throw new NotImplementedException();
}
}
In XAML
<Page.Resources>
<local:BoolConverter x:Name="ThatsMyConverter"/>
</Page.Resources>
........
<Grid Visibility="{Binding IsChecked, ElementName=chkShowSettings,Converter={StaticResource ThatsMyConverter}}">
Your converter returns a boolean value and you are trying to assign a bool to Visibility which can only take Visible or Collapsed as possible values. Try returning Visibility from your converter instead of bool. That should work. For example in your converter:
if (value == null) return Visibility.Collapses;
var val = (value as bool);
if (val)
return Visibility.Visible;
else
return Visibility.Collapsed;
I got the following code:
namespace SomeApp
{
public partial class MyClass : PhoneApplicationPage, IValueConverter
{
SOME METHODS...
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return true;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return true;
}
}
}
I would like to bind this class to a ValueConverter of a RadioButton. Is there any way to reference to the current class I'm working with? For example:
<phone:PhoneApplicationPage
x:Class="SomeApp.MyClass"
xmlns:local="clr-namespace:SomeApp">
<phone:PhoneApplicationPage.Resources>
<local:MyClass x:Key="myClass"/>
</phone:PhoneApplicationPage.Resources>
<RadioButton IsChecked="{Binding Converter={StaticResource myClass}}"/>
Thanks in advance =)
First using your page as a converter don't seem like a good idea, it's better practice to separate the converter fonctionality in a separate class. Particularly it would be a very bad idea to create a StaticResources of a converter created that way as it will use a lot of unessessary memory to create the whole page.
The only thing a converter can be binded in xaml is a StaticResource so you will not be able to do it in xaml but if you really want to do it you could do it by creating the binding from code behind (for example in the constructor of the page):
Binding binding=new Binding();
binding.Converter = this;
myRadioButton.SetBinding(CheckBox.IsCheckedProperty, binding);
I have a piece of code for a Text Box in a XAML File. The text box takes as input Numeric Value.Below is the piece of code:-
<TextBox Text="{Binding Path=Revenue, StringFormat=c0, Mode=TwoWay, Converter={StaticResource NullableConverter}, NotifyOnValidationError=True, ValidatesOnDataErrors=True, ValidatesOnExceptions=True}" Grid.Column="3" Grid.Row="2"/>
However if I input 5 and tab out the input does not become 5 $. However, on saving the data in the page and loading the page the formatting is intact. Any thoughts on this ??
please remove the converter and try it, you should get it. should be something wrong with converter.
this is what I tried for Nullable Converter it worked.
public class NullableConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value == null)
return 0;
else
return value;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return value;
}
}
If you are using SL5 I think this is a bug, the StringFormat is not triggered when the binding is updated. For more details here is the MS connect issue. You can check the workaround it might help you solving the problem.