is it possible to use x:bind and design time data in uwp apps?
e.g if I had a textbox that used x:bind to bind to a property on viewmodel in the code behind, should that property's value appear in the textbox in the designer?
is there a way of achieving this?
cheers
Johnny
x:Bind doesn't support design-time data yet. Maybe it never will given it's designed for compile-time bindings to boost performance (I wish it would though).
For simple UI testing purposes, I would add a FallbackValue to the binding expression to force the designer to show me some dummy text. However, don't forget to remove it once you are done with the design.
<TextBlock Text="{x:Bind MyMoney, FallbackValue='$10,000,000'}" />
Update
Now it's easier with the new design-time data support.
<TextBlock Text="{x:Bind MyMoney}" d:Text="$10,000,000" />
Read more from here.
Related
I need help with a change of perspective.
I got stuck trying to approach UWP in a way I used to do in WPF regarding a MVVM pattern for managing UserControls dynamically.
I naturally tried to perform the same pattern in UWP but got stuck on various things like UWP not supporting 'x:Type' ...
Situation is; time to rethink this approach and look for a new direction. Seems I'm forced to abandon to use implicit binding in a similar fashion to the WPF pattern, using the Content property of a ContentPresenter and a VM property 'of type Object', which maintain a selected ViewModel. It was a simple and clean approach for matching up the correct View automagically with the VM set in ActiveViewModel.
the below was such a simple way of managing many views all over the place, odd MS not fixing this? But, back to the big Q: what now in UWP!?
<ContentPresenter Content="{Binding ActiveViewModel}">
<ContentPresenter.Resources>
<DataTemplate DataType="{x:Type local:OneViewModel}">
<local:OneView />
</DataTemplate>
<DataTemplate DataType="{x:Type local:TwoViewModel}">
<local:TwoView />
</DataTemplate>
</ContentPresenter.Resources>
</ContentPresenter>
What Shall I do instead of this!? Anyone found a new efficient way of doing it? I got stuck in my stubborn mind and need someone to kick my butt so I go forward. Getting to old to change, but due to this profession it seems I constantly have to. :)
Looking at the DataTemplate documentation, there's a paragraph explaining the situation which you are trying to figure out.
For advanced data binding scenarios, you might want to have properties
of the data determine which template should produce their UI
representations. For this scenario, you can use a DataTemplateSelector
and set properties such as ItemTemplateSelector to assign it to a data
view. A DataTemplateSelector is a logic class you write yourself,
which has a method that returns exactly one DataTemplate to the
binding engine based on your own logic interacting with your data. For
more info, see Data binding in depth.
Here, you have an example on how you can select distinct DataTemplate for items in a control such as a ListView based on defined conditions.
Your situation is a bit different from the one described above, but the solution should be within what is explained above.
Create a class which derives from DataTemplateSelector, and override the SelectTemplateCore methods exposed by it, where you define the logic of what DataTemplate should be selected for the specific presented object.
This Derived class should expose properties of type DataTemplate, which identify each single DataTemplate template object, you pretend to be able to choose from.
Just as in the example, you are probably better of by defining the DataTemplate resources on an higher level object, such as the Page itself.
Instantiate your DataTemplateSelector Derived class in XAML as a resource and set each of the properties exposed above of type DataTemplate to the analogous DataTemplate static resource.
Utilize the ContentTemplateSelector dependency property, by setting it your custom DataTemplateSelector.
With this logic, it should be possible to have your ContentPresenter decide correctly between which DataTemplate it should choose from, based on your required UI logic.
I want to display a textblock with latitude and longditude. In my model, the lat and lng are two variables, so I need to combine them, preferably with stringformat as this answer suggests. Unfortunately it doesn't seem like multi binding is supported in UWP applications.
That leaves me with a couple of options.
Create two text blocks that are bound to each variable and align them next to each other. I'm not sure if i need two extra textblocks to be able to display "lat" and "lng" in front of the values. And then an third label displaying "Position" in front of that again. This answer states that there is no stringformat property for Binding. A total of five textblocks is too much in my opinion.
<RelativePanel>
<TextBlock x:Name="EquipmentLatTextBox"
Text="{Binding Equipment.lat}"/>
<TextBlock x:Name="EquipmentLngTextBox"
Text="{Binding Equipment.lng}"
RelativePanel.RightOf="EquipmentLatTextBox"/>
</RelativePanel>
Create a value converter.
This also seems very unnecessary. I get the point of using converters to convert across data-types, but for concatinating strings there should be a buildt in property.
Create a property in the view model that returns a string of the values as it should be displayed. This seems like the best option as the method is not in the model, but i still think that i should be able to do this in the xaml markup.
Is there a better way to do this?
This can be solved by using runs. It's actually a lot easier to achieve this in UWP than with multi-binding in WPF. A TextBlock item can consist of several "runs" of text which can bind to different properties. The runs will behave like inline elements. Each run can have text directly between the tags, or as a text property. Each run-element can also have independent styling.
Documentation for the TextBlock class
For the example i provided in my question, i ended up formating it like this
<TextBlock x:Name="LocationTextBlock">
<Run FontWeight="Bold">Location: </Run>
<LineBreak />
<Run>Lat: </Run>
<Run Text="{x:Bind ViewModel.Equipment.Lat}"></Run>
<Run> Lng: </Run>
<Run Text="{x:Bind ViewModel.Equipment.Lng}"></Run>
</TextBlock>
The result looks like this
Location:
Lat: 00.000 Lng: 00.000
No, the Universal Windows Platform currently doesn't support multi binding. The best solution for you is indeed creating a dedicated property in the view model or alternatively using the two TextBox controls. As compared to WPF the binding syntax in UWP is more limited to ensure the best performance possible.
You could also consider using the x:Bind syntax to ensure strongly-typed and optimized bindings, which were introduced with UWP.
When using traditional {Binding} syntax you could specify element name to point to a specific control on the page, and be able to access its properties. For example if the page is named page you could do:
{Binding ElementName=Page, Path=Name}
With the {x:Bind} syntax it says
With x:Bind, you do not need to use ElementName=xxx as part of the
binding expression. With x:Bind, you can use the name of the element
as the first part of the path for the binding because named elements
become fields within the page or user control that represents the root
binding source.
So for the example above in {x:Bind} would be
{x:Bind page.Name}
Which works fine, until it is inside a data template (for example a ListView's ItemTemplate). In which case it no longer works as it is looking for Page on the data type specified which leads to the following error (assuming my data type is customer):
XamlCompiler error WMC1110: Invalid binding path 'Page.Name' :
Property 'Page' can't be found on type 'Customer'
What is the solution to use {x:Bind} syntax with datatemplates and access controls outside the data template?
Example code is available here (note specific commit)
As far as I know at this point in time there is no way to directly bind to a property of a control using the x:bind method as it does not support the element name inside of its binding definition.
That does not mean you cant bind to a control inside a dataTemplate you can still do something like this to access controls but you just aren't able to use the compiled binding x:Bind syntax.
<DataTemplate x:DataType="local:Customer">
<StackPanel Orientation="Vertical">
<Button Content="{Binding Name, ElementName=page}" />
<TextBlock Text="{x:Bind Title}" />
</StackPanel>
</DataTemplate>
The reason for the error you are getting is due to the way data templates parent their datasource. The x:Bind binding cannot reference a control object and your Customer type does Page.Name property or path. As shown above the only real way of accessing user control properties outside of your control only using XAML is to resort back to the standard binding mechanism.
I hope this answers your question.
I have started to develop for WP 8.1 using Windows Runtime recently, and I have faced a... "problem" that I don't seem to understand.
The application I am currently developing uses a Hub control, and I would like to tweak its header's appearance slightly. To do so, I changed the HeaderTemplateattribute of the Hub control. However, as I tried to localize the textual content of the header (note that this is WinRT, the localization process is slightly different from the process in WP8 and can be found here), I "accidentally" fixed the problem by making the template like this:
<Hub.HeaderTemplate>
<DataTemplate>
<TextBlock Text="{Binding}"
Foreground="Red"/>
</DataTemplate>
</Hub.HeaderTemplate>
I don't understand why it worked, though. When you do data binding like this (just using the expression {Binding}), doesn't the element get the same DataContext as its father? What's happening under the hood? Who's the parent element of the TextBlock, after all?
Thanks in advance.
EDIT
As igrali asked, here is a more complete view of the XAML:
<Page ...
DataContext="{Binding Data, RelativeSource={RelativeSource Self}}">
<Grid Background="#FFF6DB">
<Hub Name="MainPageHub"
x:Uid="MainPageHub"
Margin="0,27,0,0">
<Hub.HeaderTemplate>
<DataTemplate>
<TextBlock Text="{Binding}"
Foreground="White"/>
</DataTemplate>
</Hub.HeaderTemplate>
...
Then, in the /Strings/en-US/Resources.resx, I have a "MainPageHub.Header" property set to "foobar" (just an example), and what I get as a header is actually "foobar" (which is what I wanted, but even so it seems confusing!).
As Tim Heuer explains it here
Notice the x:Uid value here. This now maps back to the key in your
RESW file. Anything with that starting key will have properties
merged into it. So we can have a key in our RESW for “Text” using the
key name MyTextBlock.Text with a value of “Hello World” and the
runtime will do the replacement for you. This applies to properties
other than text (i.e. width) as well as attached properties.
All I can add is - notice the x:Uid. It's MainPageHub. In the localized resource file, you have a MainPageHub.Header. This means that the value of the resource string will be set to the Header of the control which has the x:Uid set to MainPageHub.
So, now that it's clear how the Header is set - there's still the binding part. Well, considering you have a different template for the Header, it needs to do the {Binding } part to actually get the value of the header which is set through the resources.
I am facing this issue regarding data binding and binding in a converter while developing a Windows Phone 8 app.
I am trying to send the button to a converter so I can access all of its properties using the following code
<Button Content="{Binding OwnBoard, Mode=OneWay}" Grid.Row="0" Background="{Binding RelativeSource={RelativeSource Mode=Self}, Converter={StaticResource BoardToBackConv}}" />
When I hit the break point in the converter I have the button as the binding object, but the Content property of the control is Null. I need to access the object stored in the Content property.
As far as I know, because of the order of the bindings, the Content property should already contain a value.
Any idea how to make this work?
I have managed to understand why what I want to do is not going to work.
Keeping it short, the converter is executed during the InitializeComponent() call, and at that time the other binding was not done, because there is not DataContext for the view yet.