xaml ninja » Silverlight

PathListBox Adventures – radial layout

rich — Mon, 29 Mar 2010 11:13:45 +0000

The PathListBox ROCKS, if you have not heard of this control before then checkout Christians blog for more details and also his session at mix 10. The PathListBox solves some of the tricky issues related to creating custom panels for a ListBox or ItemsControl. Previously when we need custom layout of visual elements inside of these controls we would typically create a custom Panel and crank C# code and some positioning logic to layout the elements as we needed. However, with the introduction of the PathListBox we nolonger have to resort to building a panel and thus lowers the barrier to entry for designers who want to create custom layouts without having to be reliant on a developer to build the panel.

To get going with the PathListBox I wanted to create an simple Silverlight app which pulled back some results from digg, this is something which I have done in the past to illustrate the basics of MVVM in my session from PDC. While on the topic of MVVM its great to see that we now have an MVVM template inside of Blend that we can use. In this post I am not going to talk about the MVVM templates as I have only started out with them and so to give a comparison would not be justifiable at this stage, but I will posting an article when I have it straighten out in my head.

So for this first adventure I created a new MVVM Silverlight application and added a Model and a Service folder. As we already have the code for the digg service and the model created I copied these classes and moved them into their respective folders in the project. Open up the VM that has been added into the project and we can see that it implements INPC. The other thing to notice is that the constructor in parameter less, which is unlike my VM’s where I would normally inject an interface. So for the purposes of this example i am going to new up the interface inside of the constructor.

Ok so there are 3 steps that we need to perform in order to recreate the radial panel visual layout that is illustrated above. First we need to create our path on the design surface and then add the PathListBox to the design surface and associate the path with the PathListBox. As with a regular ItemsControl or ListBox we need to bind it to a list of items which in this case is our collection of FeedItems. Blend 4 Beta does quite alot of work for free, you will notice it has created the DataTemplate, ItemContainerStyle and ItemPanelTemplate which is rather nice. So here we start our 3 Steps and each step is associated with the templates and style.

First select the DataTemplate of the PathListBox either from the crumb bar or from right clicking in the objects panel. What we need to do here is add a ChangePropertyAction which fires when we LeftMouseButtonDown on to the DataTemplate so that we can set a flag on the data bound object so that it gets removed from the current list and added to second list. Once we have added this we need to change the RotateTransform on the StackPanel to 90.

Navigate back to the PathListBox and this time we want to edit the orientation on the items on the path so that they are OrientToPath and check the Wrap Items checkbox.

The second step is to move into our ItemContainerStyle for the PathListBox and change the VSM states so that we have a nice transition for the items when they are loaded and unloaded. With the release of Blend 4 Beta a new set of states have been added to the ListBoxItem. PathListBoxItem subclasses ListBoxItem and so we have the ability to modify the transitions for the BeforeLoaded and AfterLoaded states. For these I

simply changed the Opacity on the root element so that we can have a simple fade in type transition. Next we need to change the length of the transition in this case to 0.3 seconds, and change the easing function to your desired choice. The other changes I made here was to enable the Fluid Layout and turned on the design time layout transitions so that you can see your transitions during design time. Navigate back to the PathListBox.

The final piece to the puzzle is to change the ItemPanelTemplate. Edit the template either via the assets panel or the crumb bar. Here we are looking to add the FluidMoveBehavior on to our PathPanel which will be responsible for providing the animation effect for moving items between the two PathListBox’s.

The important things to note here include; we have selected the Children option from the AppliesTo dropdown as we want this particular FluidMoveBehavior to effect all the items in the ListBox; I changed the duration and also the easing functions that I wanted to use; I also selected the DataContext option from the Tag dropdown as I want to capture the data object associated with the item that is being animated. Navigate back to the PathListBox……

And we are done.

3 simple steps for you to add a radial panel layout into your project.

Change the data template so that it can handle a user interaction
Change the ItemContainerStyle BeforeLoaded and AfterLoaded States
Change the ItemPanelTemplate by adding in the FluidMoveBehavior

We also used ChangePropertyAction to manipulate the data in our collections exposed by the VM, and we used the FluidMoveBehavior to animate selected items from one PathListBox to another. The ability to do this without having to write any C# is a great step forwards, it does have some consequences but the advantages from my prospective outweigh the disadvantages.

The next thing that I want to do is animate each individual PathListBoxItem depending on where they are on the Path associated with the PathListBox.

All the code for this example you can find on my SkyDrive Folder.

Resource Dictionaries

rich — Tue, 23 Feb 2010 11:46:08 +0000

In this post I thought that it would be interesting to share some of my thoughts that I have been having recently around Resource Dictionaries (RD) and how they are structured. It is very easy to just put everything into your generic.Xaml or even into your app.Xaml files and let the designer run away with implementing their designs, but this is not too say that its the best way to roll.

From a developer prospective these files can become large very quickly and the result is a complete management headache when it comes to maintaining the styles, control and data templates. Its is also rather easy to allow this to happen as its in the Xaml and its what the designer produces, in effect its someone else’s responsibility. What is rather interesting and confusing at the same time is that Blend actually works very well when it comes to dealing with resources that are all in one file and it provides the designer with an easy way manage styles and templates. The other interesting thing about RD is that its actually at the heart of the Designer and Developer collaboration, its one of the areas where these two worlds collide. Therefore one of the ways in which we can help improve the workflow is to have a better understanding of RD and create some guidelines on how to best go about structuring them.

Unfortunately, even though RD are one of the core parts that make up the presentation layer there is very little information on best practices on how we should be doing this and why its important to get it right in order from which to have a good platform to move off from. Structuring RD in the wrong way can have rather serious performance problems.

There is a great article on the WPF Disciples pages providing very good advice on how to structure your RD and naming conventions, but I want to attempt to take it a little further. There are a number of different scenarios that I have come across and I am sure that there will be more along the way. These include; a POC application where this is built quickly and iteratively and requires a compelling UI but there is a high potential the application will not make it into production; themeable applications where a number of different themes can be applied to change the look and feel; and also applications that leverage 3rd party controls which have their own and sometimes rather interesting ways of how they are styled and templated. Each scenario is different but can be solved in the same way by using well structured RD to produce a clean, performant and easy to maintain application.

Ok, so how can we achieve a better structuring of the RD, help improve collaboration and provide a basic pattern and best practices in order to satisfy the different scenarios outlined above ?

Putting your RD in a separate project is the first thing to do, there are a number of advantages in doing this; but primarily this is about separation of concerns to help with workflow; and it helps to provide a blue print of a theme that can be reused over time.

In addition to the guidelines put forwards from the WPF list I am also going to add some more into the mix.

Suggested WPF Disciples Resources :-

BrushResources – solid brushes, linear gradient brushes and drawing brushes

ConverterResources – allows us to reference any of the converters by merging our resource dictionary with this file, rather than re-declaring our converters every time.

ImageResources – as above, allows us to declare an ImageSource once and reference it from anywhere.

TextResources -styles applied to textual elements (Hyperlinks, TextBlocks, etc.)

Additional Resources:-

Colours – for simple colours used as a swash for branding of clients colour palette.

DataTemplates – holds all the Data Templates used in the application.

Storyboards – holds all the Storyboard animations.

VectorGraphics – holds all the vectors graphics

CustomControls – holds styles and templates for those custom lookless controls

CommonControls- holds styles and templates for those common controls

Now the above list is not an exhaustive one and there is a high potential that this may change in the future but for now these provide a good platform from which to start. There are a number of ways in which you can slice and dice the RD used in your application some of which I will talk about shortly, but in general its best to think about the RD as a whole. The reason for this is that its best to see the Xaml assets as what constitutes your design and interaction of the UI that you are projecting onto the view for the user to experience. Therefore a change in the template or style means a complete new design. By thinking about them in a more holistic view as a the sum of all parts.

Therefore by splitting up the styles, templates etc into different high level RD categories provides the capabilities for the designers to work in an independent way and not have the constraints of working in the same project as the developers. The majority of times you will want to split out the RD into a separate project, and provide an area where they can create and design controls and elements. It also means that as they are working in a separate project they are completely separated from the developers but they are both working in the same solution.

What are those other views of RD that I mentioned earlier. Another potential way of looking at splitting up the RD is to break out the control templates and styles and place those into separate files. This will provide the ability to change the colours, font types etc and leave the control templates alone, which is great for those situations where you want to restyle the application and want to retain the layout of the controls. However, there are some problems with this approach; making significant changes to the style of controls will almost certainly mean that you will have to change the layout of the control, or building a custom control to handle the different styles; support in Blend for this type of structure is sub optimal in that it becomes more difficult to navigate and manage the styles and templates.

So why is it important to structure the RD in this way ? Why can they live all in the same Generic.Xaml file ? Is it the developer or the designer who owns the files ? How does this make my application more themeable ?

So those are a few of the questions which I have been asked about recently from both designers and developers, and they are all good questions and ones which i have also been thinking about hence my solution attempts to tackle these questions and provide a simpler implementation of how to use RD in your app.

One of the main problems with coming up with a good structure is the lack of guidance that is actually out there, plenty of high level information around some structure and naming conventions but no real information on the details. Rather frustratingly although we have gone head first into solving and building frameworks that address MVVM and come up with some notable solutions. It does feels like we have neglected an important area of the presentation layer.

What is rather interesting is how differently developers and designers perceive RD and this comes out in how they implement them in the app.

Developer : As a developer it is a natural and in the interest of best practices to split out each individual control so that each control is sat in its own RD.

Designer: As a designer its natural to think of all the controls at a higher level so that at set of individual controls contribute to the overall design of the app.

So as you can see neither side is right or wrong its their interpretation of RD which differs and this is natural as the different roles have different views and priorities on what is required to build the User Experience. What is interesting as well is that these opinions are skewed by the tools that they use and how they interpret and solve problems. The developer is very much focused on detail and implementation, mean while the designer is more interested in the higher level and the total experience of their design.

Therefore a combination of both these views seems to feel right where we split up the RD into a higher level categorisation with good naming conventions. This approach meets both parties needs and is Blendable allowing the designer to work in an environment which has a reduced reliance on the developer world and vice versa.

So I am hoping this that has made you think a little more about RD. In the next post I am going to talk more about how to implement the RD in your application and drill into the performance issues related to implementing RD and some sample code to help with guidance.

PDC09 – Meet the Griffs Code drop

rich — Thu, 19 Nov 2009 18:58:35 +0000

Ian and myself really enjoyed presenting our pre conference session “Getting the most out of Silverlight” and we both hope that you enjoyed the sessions. The slide decks will be posted at some point by the event team and I will update the post when this happens so that you can get copies of the decks.

As promised I have stashed all the final code examples up on my skydrive folder so that you can download and play with the samples. As we ran out of time in the last session what I will do in the next week or so is to record a Camtasia session and capture what I unfortunately did not get time to go over during the session.

I have named the zip files as intuitively as possible so these line up with the title of the session.

What I also wanted to briefly mention is that in the MEF and Ninject demos you will see that I am using Commands from the Silverlight Extensions project on CodePlex. The command pattern that is used here is a standard command pattern common to WPF. In the current release there is no support for Commands so what you will see included in the projects are the Command classes that I need in order to harness the power of Commands.

In a previous life I wrote a post on WPF commands that you may want to take a look at if you are not familiar to the Command pattern used in WPF and how it helps to separate out UI logic into you View Model and helps increase the testability of your code that responds to the behaviours in your application. The refactor that I did here was to remove the click event handler on the button and replace this with a command. There are 3 steps for refactoring out the event handler.

First we need to create a commands.cs file and create a Commands class which will hold all our commands associated with our view model. In essence we are going to be providing a list of possible actions that the View Model can perform in relation to the view. Once we have created the class we need to define our commands that we want which in our demo is called RefreshFeedItems then we need to add in public mechanism so that we can invoke the command from the view so that it can be wired up to a button.


using StandardViewModel.SLExtensions.Input;

public class Commands
{
      private static readonly Command refreshFeeds = new Command(RefreshFeedItems);

      public static Command RefreshFeedItems

      { get { return refreshFeeds; } } }

Now that we have defined the command that we want to fire we need to do the second part which is to wire up the command in the Xaml of the view.

     Input:CommandService.Command=RefreshFeedItems

We can now remove the click handler code behind of the view.

The finally part is to implement the CanExecute and Executed code in the ViewModel, so move into the Constructor of the ViewModel and here wire up the commands.

       Commands.RefreshFeedItems.CanExecute += (sender, args) args.CanExecute = true;
       Commands.RefreshFeedItems.Executed += delegate(object sender, ExecutedEventArgs args)
         {
                        Refresh();
         };

And we are done. Enjoy. One thing to note is that there are other types of commands, RelayCommand and DelegateCommand which are also very cool black belt ninja moves for dealing with separation when building your MVVM apps

MVVM, design time data, and Blendability

rich — Fri, 02 Oct 2009 08:44:15 +0000

With the introduction of design time data support in Blend I thought that I would try and take advantage of using design time data and MVVM. For a while now I have been using Ninject, with a Service Locator Pattern to provide the ability to build WPF and Silverlight apps in an MVVM pattern where I prefer to use a View first mechanism. There are a number of benefits from using this approach, one of the ones that we are good to drill to in this post is around Blendability of the controls that developers create. Prior to me using Ninject I would have a heavy reliance on the DesignerProperties IsInDesignMode call to check to see if the control was being render in Blend, as i would normally have to do something to stop the control from crashing and allow myself and the designer to use Blend in order for us to Style and Template the controls we created.

What we are going to cover here is the journey which i went on when adding support for design time data to my project, I really like it as the refactoring from the standard inbuilt mechanism in Blend to the final output is a nice series of steps that feel good.

The screen shot on the right shows the simple looking UI displaying contextual data in Blend allowing the designer to see how the control will look. I think providing the ability for your application to look exactly the same at design time as at run time is going to mean that you can produce better looking applications quicker as the designer is design the screens in the context of the data.

When first adding the design time data to your project Blend takes over control and this means that you need to use Blend to shape your design time data classes to match your data types used in the system. So if we were building a throw away prototype then I would agree this is the best way forwards, but when you are moving from prototype to production this does not really work. On of the reasons behind the research for this post is around the transition from prototype to production and even from sketch to prototype, once we have sign off from the client on a number of ideas and we want to start to build these out then there is a high potential one will become production quality and because of this its good to have the right architecture in place, so reshaping to MVVM early on will almost certainly cost your client less.

The Xaml below is what i put together to represent the shape of data that was in the mock classes. Blend then hooks this data up to the design time data context for you.

Xaml data for shopping cart

When the design time data shape matches your real data shape you can then go ahead and use the new d:DataContext Dependency Property and bind your design time data to this property.

Xaml Source code for the control

Nothing too tricky there, the new design time data context is the key to making all this happen, it also means that you can bind any sort of data you want to the design time data context to provide contextual data in Blend during design time. It was at this point that i started to think about how we can really bend the design time data features. My initial refactor was not a great result in that I ended up with 2 sets of mock data; one set of data would be used by the designers in Blend; and the second set of data would be used by the unit test, Not nice, management nightmare to ensure that both data sets are keep in sync.

So the goal was to provide design time data which was the same data used by the unit tests, meaning that we only have one data set to maintain and manage, allowing us to leverage the powerful features of design time data in Blend and also keeping our unit tests looking sweet, pleasing both the designers and the developers on the team.

In order to do this I needed to restructure the existing shape of my data classes that I use in my mock service layer classes, first I needed to change the OnCompleted method to be a virtual implementation and also the method which retrieves the data. This simple change means that we can now provide two mock services that can be injected in.

Refactored mock service class with new virtual methods

    using System;
    using System.Collections.ObjectModel;

    public class MockShoppingCartService : IShoppingCartService
    {
        public event GetShoppingCartCompletedHandler GetShoppingCartCompleted;

        public bool LoginToShoppingCart(string username, string password)
        {
            throw new System.NotImplementedException();
        }

        public virtual void RetrieveShoppingCart()
        {
            this.OnGetShoppingCartCompleted(null, MockShoppingCartData.CreateShoppingCartRuntime());
        }

        protected virtual void OnGetShoppingCartCompleted(Exception error, ShoppingCart result)
        {
            if (this.GetShoppingCartCompleted != null)
            {
                this.GetShoppingCartCompleted(new GetShoppingCartCompletedEventArgs(error, result));
            }
        }
    }

The new mock service class which is used specifically for working with Blend

namespace DesignDataSample.Mocks
{
    public class MockShoppingCartServiceDesignData : MockShoppingCartService
    {
        public override void RetrieveShoppingCart()
        {
            this.OnGetShoppingCartCompleted(null, MockShoppingCartData.CreateShoppingCartDesigntime());
        }
    }
}

How we can use ninject to inject the service we want to use, design time data, mock or real.

this.Bind().To().OnlyIf(c => isBrowser);
this.Bind().To().OnlyIf(c => isBlend);
this.Bind().To().OnlyIf(c => isBrowser);
this.Bind().ToSelf();

Xaml code for how we leverage the data context and the new design time data context for providing contextual data.

So I hope that this article has opened your eyes to how useful design time data can be to enhance the Blendability of the controls which you produce both lookless and user. In the majority of cases designers that you are working with really like that they can view the control at deign time how it will appear when running in your application and populated with data. When implementing the MVVM pattern in you application incorporating support for design time data is also possible and provides you with the ultimate Xaml Ninja experience.

You can download the source from my Skydrive.