Expression Blend For Developers

Transcription

1 Expression Blend For Developers Programming Silverlight just got a lot easier. A Note on This Tutorial. The history of the material for this tutorial is that Scott Guthrie wrote a terrific introduction to this material at the end of February, which he gave me permission to turn into a series of videos, currently (or soon to be) available on Silverlight.NET. This tutorial completes the circle by building on the videos and integrating the material into the Silverlight Tutorial series. The project we're setting out to build is very similar to the Silverlight chat service built by ScottGu, and is shown in Figure 5-1 Figure 5-1. Completed Application Getting Started The best way to get started is by opening Expression Blend. The first thing you'll see is the New Project window. Choose Silverlight 2 Application, set your language to Visual Basic and choose a location for your new project, which we'll name BlendForSilverlight, as shown in Figure 5-2

2 Figure 5-2. Creating the New Project The Solution Files Take a look in the upper right hand corner. The solution, project and other files created by Blend are identical to the files created by Visual Studio In fact; there is no exporting/importing between the two; you can open both development environments on the same files simultaneously and they will both work perfectly (see Figure 5-3) Figure 5-3. Blend Files A Very Quick Tour

3 The upper right hand corner not only contains the files, but also contains the properties window, the resources window and, below these, the data window. The central area has the "Art Board" (the design surface" and the Xaml (markup) which can be split as shown in Figure 5-4 Figure 5-4. Design Surface in Split Mode I've added highlighting in the upper right hand corner to point out the controls that allow you to switch among design, Xaml and split mode. The upper left hand corner contains the Interaction panel and the toolbar. Many of the tools in the tool bar have a small mark in the lower right hand corner indicating that they can be expanded to find related tools. For example, expanding the grid tool displays all the layout controls as shown in Figure 5-5

4 Figure 5-5. Expanding the Grid Tool The Chevron tool allows access to all the controls, including any user controls, custom controls or third party controls (be sure to click Show All) as shown in Figure 5-6 Figure 5-6. Chevron Expanded Note that from within the Asset Library exposed by expanding the Chevron you can also search for the control you want, and by clicking on the details radio button you can determine which library a control is in. Chat Application - First Steps

5 Begin by switching to design view, and then hold the control key and use the mouse wheel to zoom out so that you can see the entire grid. If your mouse doesn't have a wheel, you can zoom by picking a value (or filling in an arbitrary value) at the bottom of the design window or by using the menu choices View Zoom In and View Zoom Out You can move the surface by clicking on the hand and then using the mouse to click and drag or by using the scroll bars. Take a look at the upper right hand corner of your grid, as shown in Figure 5-7 Figure 5-7. Upper left corner of the grid Hovering over the upper left hand corner will tell you if you are in grid layout mode or Canvas layout mode. If you are in canvas layout, clicking will toggle you back to grid layout mode. You can create rows and columns just by sliding along the margins and clicking where you want the rows and margins placed, as shown in Figure 5-8 Figure 5-8. Creating a Row using The Mouse Immediately after I click, an open lock appears above and below my new row line. I'll add two lines, one for the top row and one for the bottom; thus implicitly creating a middle row, and thus three locks as shown in Figure 5-9.

6 Figure 5-9. Creating the bottom row Note that immediately after the row is created, not only are the locks shown but the cursor changes shape to indicate that you can easily move, and thus resize the rows. The open locks indicate that the rows will resize as the browser (inside of which your Silverlight application will run) is resized. We want the middle row to do so, but we want the top and bottom row to remain of fixed size, so click on the top and bottom lock, and then click on split view to examine the effects on the XAML, as shown in Figure 5-10.

7 Figure Middle Row has Star Sizing Note that (on line 10) the middle row definition has its Height property set to * (star) indicating that it will take up the remaining room after the other rows are allocated. Creating the Columns Let's create two columns, a smaller right column that has a fixed size and a larger floating size left column. Try this yourself without additional help. Creating the Background Color We'd like to give the entire application a light blue background, but to make it a bit more attractive, we'll use a linear gradient brush. To do this, please follow these numbered steps, reflected in Figure Click on the grid (Layout Root) in the Interaction Panel 2. Click on the properties panel and expose the Brushes subpanel. Click on the Background brush 3. Click on the Gradient Brush button 4. Add stops along the gradient by clicking and then 5. manipulating the color bar and 6. Moving the color dot for precise color choices Figure Adding a Linear Gradient By the Numbers Adding A Send Buton

8 The next step is to add a button to the lower right hand corner. Click on a button on the toolbar, drag it to approximate size in the area and then click in the properties window. Next, open the Layout subpanel and set the Width and Height to Auto and set a small value (e.g., 4) for the Margin, all around. This will fill the area, but with a reasonable margin from the edges of the column and row. The value you put in a property box does not take effect until you leave that box (e.g., using tab) There are a few things to notice about the Layout Panel (Figure 5-12) Figure Setting the Button Layout with the Layout Panel First, you can set the Width and/or Height to auto by pressing the button to the right of the field. Second, when you set a specific (non-default) value next to a property, a white dot appears (there are 5 white dots in Figure 5-12). Take a look at the Xaml once you have these values set, <Button HorizontalAlignment="Stretch" Margin="4,4,4,4" VerticalAlignment="Stretch" Grid.Column="1" Grid.Row="2" Content="Button"/> Blend has translated your choices into Xaml that will create the look you've chosen. We have, however, forgotten to change the "Content" property from Button to "Send". The easiest way to do so is to type Content into the property Search box, At "co" you will get back "Column", "Horizontal Content", "Data Content" and "Content" as shown in Figure 5-13

9 Figure Search with "co" Refine your search just a bit further, and you reduce the complexity a bit, as shown in 5-14, Figure Refined Search

10 In any case, remove the word Button from the Content field and put in the word Search. Your text task is to set the font size to 18 and the font family to Verdana. Oh, and set it to Bold. (No cheating! Do this in design, not in Xaml!) (You'll find the image on the next page) Some (few) controls have a text property and most have a content property. Those with a content property often fill that property with text, but they are free to fill it with almost anything else, including other controls. Figure Setting the Font Family and More

11 Creating The Rounded Rectangle Input Area Examining the finished application shown at the top of the tutorial reveals that the input area has a rounded rectangle as shown in Figure 5-16 Figure Input Area is a Rounded Rectangle This is slightly tricky to achieve since the TextBox does not have a setting for rounding its corners. It turns out, however, that the Border control does. Our tricky solution, therefore, is to put a TextBox within a border, and letting the Border handle the look and feel and the TextBox mange the text handling! Step one is to fill the grid square with a border. Click on the Grid pallet and expand it to click on a border, and then drag out the border into the appropriate grid location (we'll size it properly with the properties window). Once in the grid, set its Width and Height to Auto, and its Margin to 4 all around, as shown in Figure 5-17 Figure Sizing the Border in the Layout Panel

12 Let's set the background brush for the border, by setting the values in the Brushes property window by hand to 255, 255, 255 with an Alpha (opacity) of 45%.I highly recommend doing these one by one. AS you set the red value the background turns Red. When you set the Green background to 255 as well, the background turns bright yellow. Add 255 for Blue and the background turns bright white. Finally, knocking the Alpha down to 45% gives us the pale shade we're looking for, as shown in Figure 5-18 Figure Setting the Background Brush If you look carefully under the settings for RGBA you'll find the hex value #72FFFFFF which is the equivalent of setting the four values independently (with the alpha value first). Our Border control also needs its Border brush set (in 5-18 it is set to "No Brush"). The values we want (which it may well default to) are Alpha of 100% and full black (00,00,00). The Border brush won't appear unless we set its thickness (which defaults to zero); which we can do in the Appearance panel. Let's set it to 2. This is also where we get to set the rounded corners, which we'll set to 5 as shown in Figure Figure Setting the Border Thickness and Rounded Corners Placing the Text Box The border has the rounded corners, but as noted above, a border can't accept text input. For that we need a text box, but we don't want the text box to overwrite the background we just carefully placed in the border.

13 Zap! All we need to do is make the text box reside within the border, and set it to transparent! To place the text box within the border, double click on the border in the Interaction panel, signaling to Blend that it is now the container for the next control. That is, the next control we add will not be a sibling, but a child of the border. The yellow rectangle will jump from Layout Root to the Border as feedback that it is now the active container. When you drag the text box in, it will be placed inside the text box, as shown in Figure 5-20, both from a design view and a Xaml view. Figure Text Box Nested within Border Review of key points There are a few new concepts all put together in this one construct, so a quick review is in order: The border is set with a background color and the rounded corners The text box is nested fully within the border, and the text box's background opacity is set to 0 (making it transparent). That allows the text box to "pick up" the background color and rounded corners of the border In order to ensure that the text box will be nested within the border, double click on the border in the Interaction panel surrounding the border with a yellow box and thus indicating that it is now the container. Creating the Top Row We'll do the same thing on the top row, except that instead of using a TextBox we'll use a textblock, setting the text inside to a font family of Comic Sans MS, a font size of 48 and the text of your own name. To set the upper right hand corner, begin by double clicking on the LayoutRoot to make it the container, then click on an Image Control in the Chevron. Set the source property to point to any image file on your disk. Creating the Conversation Area

14 The final part of our IM application is the middle: the conversation area, which will in fact be a list box. We'll place that in a border that will stretch across both columns. You can place that manually, just by stretching a border across both columns using the mouse. You'll notice as you go to refine the placement in the Layout panel that the ColumnSpan has been set to 2, and all you need do is fix the Margins to make the border fit snugly (e.g., with a margin of 4 all around.) You'll want to set the background to a solid color ( FF03588D works nicely) and once again we'll set the corners to a radius of 5 all around, as well as setting the border to black and a thickness of 2. Once again, double click on the new border, and drag a list box (from the chevron) inside the new border, and set it to fill the border. Adding dummy data It is convenient to have dummy data to fill the list box, and the easiest way to do that is in Xaml. This is a good opportunity to switch to Visual Studio, so save all the files in Blend but leave blend open and switch over to the project in Visual Studio If your project was already open, you'll be notified that it has changed, say yes to accept the changes, and you should find that all the files are shown and your Page.xaml looks impressively similar to what you just saw in Blend.

15 Figure Examining the Project in Visual Studio You can now easily populate your list box with dummy list items, <ListBox Height="Auto" Width="Auto" x:name="conversation" > <ListBoxItem Content="Jesse: Is this working?" /> <ListBoxItem Content="Scott: Of course." /> <ListBoxItem Content="Jesse: I'm following the directions." /> <ListBoxItem Content="Scott: Then you should be fine." /> <ListBoxItem Content="Jesse: Great, thanks." /> </ListBox> Save your file and switch back to Blend (no need to close Visual Studio 2008). When you do, Blend lets you know the files were modified,

16 Figure Blend letting you know the files were modified Click yes, and your dummy data should be visible. You can press F5 to run the program as an interim check. You'll find that the image doesn't appear unless you place a copy of the image file in the bin/debug directory as well. That's not a big problem, however, as we'll be binding to the source for the image file. Building the Business Layer To support the exchange of instant messages, we will build (or, to be more honest, stub out) a service that will identify the remote user's name, image and that will manage the messaging. Because we are more interested in Silverlight than in building the service (at least for the purposes of this tutorial) we'll simplify this by creating a ChatSession class that will stand in for all the networking, sockets and other plumbing, and which will maintain instead a collection of Message objects. As you can guess, we'll also create, therefore, a Message class to represent each message "transmitted" by the service. Because Visual Studio 2008 is better suited to programming than is Blend, we'll do this work in Visual Studio 2008 but we'll get there by right clicking on the solution in Blend and choosing Edit In Visual Studio, as shown in Figure Figure Moving to Visual Studio from Blend

17 Once in Visual Studio 2008 right click on the project and choose Add Class. In the new items dialog select class and name your new class ChatMessage as shown in Figure 5-24 Figure Adding the Chat Message Class The Chat Message class is pretty straight forward, consisting only of two properties, Public Class ChatMessage Private privateusername As String Public Property UserName() As String Get Return privateusername End Get Set(ByVal value As String) privateusername = value End Set End Property Private privatetext As String Public Property Text() As String Get Return privatetext End Get Set(ByVal value As String) privatetext = value End Set End Property End Class The ChatSession is somewhat more complex, but we'll simplify greatly by stubbing out all the difficult parts. We begin by marking the class as implementing INotifyPropertyChanged, which as noted in the DataBinding Tutorial ensures that the UI fields will be updated as the data changes.

18 Public Class ChatSession Implements INotifyPropertyChanged This interface requires only that we provide a PropertyChangedEventHandler that implements the PropertyChanged event, Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged The class has two straight forward public properties: one for the user's name, and one for the URL of the user's Avitar (image), Private privateremoteusername As String Public Property RemoteUserName() As String Get Return privateremoteusername End Get Set(ByVal value As String) privateremoteusername = value End Set End Property Private privateremoteavatarurl As String Public Property RemoteAvatarUrl() As String Get Return privateremoteavatarurl End Get Friend Set(ByVal value As String) privateremoteavatarurl = value End Set End Property Next we want to create a collection of the ChatMessages. What we want, however, is to raise an event each time the collection changes (e.g., a message is added) and we want the list box to respond to that event. We could create all of that, but the framework makes it easy. Listbox already knows to respond to PropertyChanged events, and there is a special collection type ObservableCollection(of) that fires exactly that event every time the collection is changed. This makes life a walk in the park, Private privatemessagehistory As ObservableCollection(Of ChatMessage) Public Property MessageHistory() As ObservableCollection(Of ChatMessage) Get Return privatemessagehistory End Get Friend Set(ByVal value As ObservableCollection(Of ChatMessage)) privatemessagehistory = value End Set End Property Sending a message is now as simple as adding a new Chat message where the text is taken from the message box and the user name is taken from the current user's name (for now, hard coded to "Me")

19 Public Sub SendMessage(ByVal message As String) ' Todo: Send to remote chat server over sockets MessageHistory.Add(New ChatMessage With {.Text = message,.username = "Me"}) End Sub We leave it as an exercise for the reader to actually send the message across the network Before we can send messages, however, we must connect with the remote user, obtaining the remote user's name, avatar and initializing the observable collection of messages, Public Sub ConnectWithRemoteUser(ByVal remoteusername As String) ' Todo: 1) Wire-Up socket stack to receive notifications of received messages ' 2) Wire-Up to a remote avatar service instead of hard-coding my picture RemoteUserName = remoteusername RemoteAvatarUrl = "jesse.jpg" MessageHistory = New ObservableCollection(Of ChatMessage)() ' Notify any listeners of property changes RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("RemoteUserName")) RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("RemoteAvatarUrl")) RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("MessageHistory")) End Sub Finally, we'll add a method we can call that will simulate an exchange of IM's (but we'll only call this method when we're in design mode; not when the program is actually running) Private Sub PopulateWithDummyData() RemoteUserName = "BillG" RemoteAvatarUrl = "billg.jpg" MessageHistory = New ObservableCollection(Of ChatMessage)() MessageHistory.Add(New ChatMessage With {.UserName = "BillG",.Text = "How is your video going?"}) MessageHistory.Add(New ChatMessage With {.UserName = "BillG",.Text = "Hmmm...you there?"}) MessageHistory.Add(New ChatMessage With {.UserName = "BillG",.Text = "Hello???"}) MessageHistory.Add(New ChatMessage With {.UserName = "Jesse",.Text = "Sorry Bill - working on a video..."}) MessageHistory.Add(New ChatMessage With {.UserName = "BillG",.Text = "Oh - ok."}) End Sub To ensure that this dummy data is in place during design mode, we'll test in the constructor of ChatSession,

20 Public Sub New() If HtmlPage.IsEnabled = False Then PopulateWithDummyData() End If End Sub DataBinding With these classes in place (you did build to make sure all is well, yes?) we're ready to data bind. Let's do that in Blend (!) Make sure you've saved all your files in Visual Studio 2008 but don't close it, just switch over to Blend. Say yes to the "something has changed when I wasn't looking" dialog (your wording may vary). Under the project panel you should see a Data panel, within which is a tab marked CLR Object. Click on that and Hey! Presto! You will see Blend for Silverlight that will open up to show a dialog that lets you add any CLR object as a data source. Notice that ChatMessage and ChatSession are listed. Click on Chat session and click OK and Chat SessionDS appears in your Data list, as shown in Figure Figure Adding Chat Session as a Data Source Now, this is really scary how easy this is; click on RemoteUserName, and drag it onto the name field at the top of the design and let go, as shown in Figure 5-26

21 Figure Binding the RemoteUserName to the TextBlock by Drag and Drop When you let go, Blend recognizes that you are binding the data, and asks first which field you'd like to bind to (guessing you'd like to bind to Text) and then offers (if you expand the dialog) additional options, such as two-way binding (so that if the UI is updated, the changes will be written back to the data source), as shown in Figure 5-27 Figure Creating the Data Binding When you click OK the UI is immediately updated with the bound data.

22 Figure Bound Data Unfortunately, your list box does not know how to display a Chat Message (why would it?). We can fix that, of course, by using a Data template, <ListBox.ItemTemplate> <DataTemplate> <StackPanel Orientation="Horizontal" Margin="5"> <TextBlock FontFamily="Comic Sans MS" FontSize="16" Foreground="red" Text="{Binding UserName}"/> <TextBlock Text=": "/> <TextBlock FontFamily="Comic Sans MS" FontSize="16" Text="{Binding Text}"/> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> This teaches the ListBox how to display each of the list items, specifying that each will be dislayed with three TextBlocks, aligned horizontally by a stack panel, as shown in Figure 5-29

23 Figure Data Template at work Adding Templates The Listbox and especially the Start Button don't quite look the way we'd like. In the previous version of this tutorial we fixed them with hand-written templates, but Blend now offers a far better solution, which we will introduce in the next tutorial, so we're going to leave this as it is for now (not quite done, but a good way towards a solid introduction to using Blend and Visual Studio together for programming an application). Better not to finish, than to show you what amounts to an obsolete and inferior way of solving the problem. In the interim, both Tim Heurer and I and many others will be blogging about the new approach to Templates, and we'll have the full tutorial out within a few weeks.