Silver Light 2 Unleashed [q6zp11vy88zp]

Silver Light 2 Unleashed

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2. Open the file Default.html in a web browser: The video starts, and you see the background color change according to the saved markers. This simple example shows how a video file can communicate with its host by sending script commands.

NOTE We saw earlier (in Chapter 5) how to handle the event MediaEnded on the MediaElement control in C#. You can do the same with MarkerReached. This allows you to react to embedded script commands in your Silverlight 2 application with .NET. In JavaScript, the event is named markerReached while in C# (and in XAML) it is named MarkerReached (with a capital “M”). The difference in naming is due to historical reasons and naming guidelines. Don’t mix them up.

Modifying the Player Template in Blend One great feature of Silverlight, especially when you use it to play videos, is the ability to go full screen. All the video players support this feature, but sometimes it is not very well documented: In the Expression video player, you must double-click the video screen to make it go full screen. In this section, we add a Full Screen button to this template in Expression Blend.

Adding a Full Screen Button Since the player is made of XAML, you can edit it in Blend. Here we will add a button to the player with the following steps. Silverlight 1 (which is what Expression Encoder creates) doesn’t have controls; the button is simulated using a Canvas to stay in line with the rest of the player’s controls.

Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

Prepared for Andre John Cruz, Safari ID: [email protected] Licensed by Andre John Cruz Print Publication Date: 2008/10/15 User number: 1076800 © 2009 Safari Books Online, LLC. This PDF is made available for personal use only during the relevant subscription term, subject to the Safari Terms of Service. Any other use requires prior written consent from the copyright owner. Unauthorized use, reproduction and/or distribution are strictly prohibited and violate applicable laws. All rights reserved.

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Modifying the Player Template in Blend

257

1. Prepare a video for encoding; then in Expression Encoder, in the Output panel, select the Expression template. 2. Using the small white square located on the right of the Template combo box (refer to Figure 13.2), open the context menu and select Edit Copy in Expression Blend. 3. Give a name to the copy of the template you want to edit—for example, ExpressionFullScreen. Click OK. Expression Blend starts and opens the file player.xaml.

5. In the top-right corner, add a new FIGURE 13.6 button. To do this, add a small Canvas and set its Width to 18 and Height to 15.

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4. Expand the top Canvas, and make sure that the Canvas directly underneath is selected with a yellow border as shown in Figure 13.6 (double-click on that Canvas until this occurs). Canvas selected

6. Line the new button up with the existing ChapterToggleButton (Top = 27.5743) and set its Left property to 598. 7. Name this Canvas FullScreenToggleButton. 8. Set its Cursor property to Hand. 9. Select FullScreenToggleButton until it gets a yellow border, and then add a rectangle with the following: . The same width and height as the button’s canvas (18¥15) . Fill = #FF555355 . Stroke = #FFAAAAAA . StrokeThickness = 1.33 . RadiusX = RadiusY = 1 10. In the same Canvas, on top of the background rectangle, add two small rectangles, as shown in Figure 13.7. 11. Right-click on the Canvas FullScreenToggleButton and select FIGURE 13.7 Full Screen button in Blend View XAML. This command is visible only in Design mode. If you set Blend in Split mode, the XAML editor automatically displays the XAML markup corresponding to your selection.

Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

Prepared for Andre John Cruz, Safari ID: [email protected] Licensed by Andre John Cruz Print Publication Date: 2008/10/15 User number: 1076800 © 2009 Safari Books Online, LLC. This PDF is made available for personal use only during the relevant subscription term, subject to the Safari Terms of Service. Any other use requires prior written consent from the copyright owner. Unauthorized use, reproduction and/or distribution are strictly prohibited and violate applicable laws. All rights reserved.

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CHAPTER 13

Progressing with Videos

12. In the Canvas’s XAML markup, add the following event handler: MouseLeftButtonDown=”ToggleFullScreenButton_MouseLeftButtonDown”

Handling the Event in Script We need to make a few changes to the JavaScript code to toggle the full screen mode. In fact, Microsoft planned that you would want to modify the existing templates, and provides a player.js file where you can add your own code with the following steps: 1. Back in Expression Encoder, click on the small white square next to the Template. Select Open Template Location. 2. Open the file player.js in a text editor. 3. Modify the constructor ExtendedPlayer.Player. We need to save a reference to the instantiated player for further use, as in Listing 13.7:

LISTING 13.7

Modified Constructor ExtendedPlayer.Player

ExtendedPlayer.Player = function(domElement) { ExtendedPlayer.Player.initializeBase(this, [domElement]); ExtendedPlayer.Player.instance = this; }

4. Finally, implement the event handler declared in the XAML markup for the FullScreenToggleButton. This event handler uses the instance of Player that we just saved and calls its method _onToggleFullScreen.

LISTING 13.8

Event Handler ToggleFullScreenButton_MouseLeftButtonDown

function ToggleFullScreenButton_MouseLeftButtonDown(sender, args) { if (ExtendedPlayer.Player.instance != null) { ExtendedPlayer.Player.instance._onToggleFullScreen(); } }

To keep it simple, we didn’t create a different look for the “mouse over” state or the “pressed” state. The point of this section is to show that a Silverlight video player is in no way different from any other Silverlight application, and that the XAML file can be edited in Blend just like any other XAML-based content. You can learn a lot about the Silverlight 1 video players created by Expression Encoder by opening the XAML and JS files of the other templates. Even though the code looks a bit

Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

Prepared for Andre John Cruz, Safari ID: [email protected] Licensed by Andre John Cruz Print Publication Date: 2008/10/15 User number: 1076800 © 2009 Safari Books Online, LLC. This PDF is made available for personal use only during the relevant subscription term, subject to the Safari Terms of Service. Any other use requires prior written consent from the copyright owner. Unauthorized use, reproduction and/or distribution are strictly prohibited and violate applicable laws. All rights reserved.

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Summary

259

“messed up” sometimes, using other templates as examples will help you creating your own video players for Expression Encoder!

Testing the Result To test the result, save everything, and then encode a video using the newly created template ExpressionFullScreen. Any change you just made to the XAML and JavaScript will be applied when you use this template. Once the player is displayed, click on the new button to show the video in full screen.

13

Summary In this chapter, we learned how to take advantage of Expression Encoder 2 to create customized videos and to enhance the viewing experience. Expression Encoder has other advanced features that we didn’t study here—for example, the capability to stream live events directly to Silverlight players. One attractive thing about Expression Encoder is that it is really easy to get a result, fast. Once this is done, you can spend hours refining the result (especially if you are as obsessed with details as this author).

Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

Prepared for Andre John Cruz, Safari ID: [email protected] Licensed by Andre John Cruz Print Publication Date: 2008/10/15 User number: 1076800 © 2009 Safari Books Online, LLC. This PDF is made available for personal use only during the relevant subscription term, subject to the Safari Terms of Service. Any other use requires prior written consent from the copyright owner. Unauthorized use, reproduction and/or distribution are strictly prohibited and violate applicable laws. All rights reserved.

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Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

Prepared for Andre John Cruz, Safari ID: [email protected] Licensed by Andre John Cruz Print Publication Date: 2008/10/15 User number: 1076800 © 2009 Safari Books Online, LLC. This PDF is made available for personal use only during the relevant subscription term, subject to the Safari Terms of Service. Any other use requires prior written consent from the copyright owner. Unauthorized use, reproduction and/or distribution are strictly prohibited and violate applicable laws. All rights reserved.

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CHAPTER

14

Letting .NET and JavaScript Talk

IN THIS CHAPTER . Making .NET Available to JavaScript. . Handling .NET Events in JavaScript. . Calling JavaScript Methods from .NET.

Interoperability is a vast and complex subject in the history of software development. Many technologies are available and “letting them talk” is crucial and sometimes difficult.

. Calling .NET Methods from JavaScript. . Adding a “Login” Dialog to the Thumbnails Application.

Over time, JavaScript has grown to be a key component of the web client. It is present in all the major web browsers, it is mostly enabled, and it is mostly standardized. Silverlight 1 relies heavily on JavaScript to create and interact with all the Silverlight controls in the web page. In Silverlight 2, JavaScript is less crucial to the operation, but communication between Silverlight and JavaScript opens a world of possibilities.

Making .NET Available to JavaScript Interoperability in Silverlight goes in both directions, as we will see in the course of this chapter. Let’s start by considering how JavaScript can directly interact with the .NET environment in Silverlight.

Using the ScriptableMember Attribute Attributes in .NET are used to decorate classes, methods, or other elements to add information without modifying their body or their signature. For example, we need to signal the Silverlight framework that some of the methods, properties, and events in our .NET objects are “scriptable”—that is, that they can be used from JavaScript.

Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

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CHAPTER 14

Letting .NET and JavaScript Talk

To make a public .NET member scriptable, simply add [ScriptableMember] before the member’s declaration as in Listing 14.1:

LISTING 14.1

ScriptableMember

public class AnyObject { [ScriptableMember] public int Index { get; set; } }

Licensed by Andre John Cruz

WARNING

The attribute ScriptableMember belongs to the namespace System.Windows.Browser. To make this namespace available to your .NET object, you must add it explicitly to the using section as we saw in previous chapters! You will also have to add other using directives later in this chapter. The attribute can either be referenced as ScriptableMember or ScriptableMemberAttribute. By convention, you can always omit the Attribute suffix when you reference an attribute.

Similarly, any method, event, or property that you want to make available to JavaScript must also be marked with the ScriptableMember attribute.

Registering the Object

WARNING The RegisterScriptableObject method must be used only if at least one ScriptableMember method, property, or event is defined in the class. If that’s not the case, an error will occur!

In addition to using the ScriptableMember attribute, you must register the .NET object with the Silverlight application as in Listing 14.2.

LISTING 14.2

Call to RegisterScriptableObject

public Page() { InitializeComponent(); AnyObject myObject = new AnyObject(); HtmlPage.RegisterScriptableObject(“MyObject”, myObject); }

Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

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Handling .NET Events in JavaScript

263

The first parameter of the RegisterScriptableObject method is a name that can be used in JavaScript to address the object. We see an example in the next section.

Handling .NET Events in JavaScript We saw in Chapter 10, “Progressing with .NET,” how to create and raise events, and how a .NET object can subscribe to events raised by another .NET object. Now we will see how we can raise events in .NET and catch them in JavaScript! This enables an elegant oneway communication (a bit later we see how to communicate back from JavaScript to .NET).

Preparing the scriptable Class 14

Let’s create a new Silverlight class that will be used to communicate with JavaScript with the following steps: 1. Start by creating a new Silverlight 2 application in Visual Studio. Name it JavaScriptDotNet. 2. In the Add Silverlight Application dialog (refer to Figure 9.2), select the Add a New Web to the Solution option, and select Web Site as the Project Type. 3. Open the file Page.xaml.cs. Under the Page class, create a new class deriving from EventArgs. We use this class to pass additional information about the event. Because we want to access the CounterValue from JavaScript, we need to decorate this property with the ScriptableMember attribute. This class (see Listing 14.3) must be placed inside the namespace JavaScriptDotNet.

LISTING 14.3

Class CounterTickedEventArgs

public class CounterTickedEventArgs : EventArgs { [ScriptableMember] public int CounterValue { get; internal set; } }

4. Under the CounterTickedEventArgs class, create a delegate specifying the signature of the CounterTicked event handler: public delegate void CounterTickedHandler(object sender, CounterTickedEventArgs e);

Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

Prepared for Andre John Cruz, Safari ID: [email protected] Licensed by Andre John Cruz Print Publication Date: 2008/10/15 User number: 1076800 © 2009 Safari Books Online, LLC. This PDF is made available for personal use only during the relevant subscription term, subject to the Safari Terms of Service. Any other use requires prior written consent from the copyright owner. Unauthorized use, reproduction and/or distribution are strictly prohibited and violate applicable laws. All rights reserved.

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CHAPTER 14

Letting .NET and JavaScript Talk

Let’s take care of the Page class itself now (see the code in Listing 14.4): 1. Declare the CounterTicked event and mark it as a ScriptableMember. 2. Implement the OnCounterTicked method. 3. In the Page constructor, register the Page object with the Silverlight application. We simply use the name Page as an identifier for JavaScript. 4. After you enter the code, build your application to check if everything is fine.

LISTING 14.4

JavaScriptDotNet Application, Page Class

public partial class Page : UserControl { [ScriptableMember] public event CounterTickedHandler CounterTicked; public void OnCounterTicked(CounterTickedEventArgs e) { if (CounterTicked != null) { CounterTicked(this, e); } } public Page() { InitializeComponent(); HtmlPage.RegisterScriptableObject(“Page”, this); } }

Raising the Event We will raise the CounterTicked event every time the user clicks five times on a button. Implement this with the following steps: 1. First, let’s add the button (Listing 14.5) in Page.xaml, inside the LayoutRoot:

LISTING 14.5

New Button

<Button x:Name=”CounterButton” Width=”80” Height=”40” Content=”Count” Click=”CounterButton_Click” HorizontalAlignment=”Left” Margin=”100,20,0,0” />

Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

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Handling .NET Events in JavaScript

265

2. In the Page class in Page.xaml.cs, declare a private attribute for the counter value. This attribute will be incremented every time the button is clicked (see Listing 14.6). 3. In addition to incrementing the counter, the event handler CounterButton_Click will check the value. If it is a multiple of 5, the CounterTicked event will be raised. This uses the modulo operator % that we introduced in Chapter 9, “Understanding .NET.” You can build the application again.

LISTING 14.6

Event Handler CounterButton_Click

private int _counter = 0; private void CounterButton_Click(object sender, RoutedEventArgs e) { _counter++;

14

if ((_counter % 5) == 0) { // true every time the counter is a multiple of 5 CounterTickedEventArgs args = new CounterTickedEventArgs(); args.CounterValue = _counter; OnCounterTicked(args); } }

Subscribing to the Event on the JavaScript Side Now comes the time of interoperability. We will implement a JavaScript class that will call subscribe to the Silverlight event we created with the following steps. 1. Open the test page JavaScriptDotNetTestPage.html. 2. Enter the code shown in Listing 14.7 in the script section, right under the function onSilverlightError.

LISTING 14.7 1 2 3 4 5 6 7 8 9 10 11

JavaScriptDotNet Application, JavaScript Code

JavaScriptDotNet = function(page) { page.CounterTicked = JavaScriptDotNet.createDelegate(this, this.handleCounterTicked); } JavaScriptDotNet.createDelegate = function(instance, method) { return function() {

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CHAPTER 14

LISTING 14.7 12

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Letting .NET and JavaScript Talk

Continued

return method.apply(instance, arguments);

13 14

}

15 16

JavaScriptDotNet.prototype =

17 18

}

{ handleCounterTicked : function(sender, e)

19 20 21 22 23 24 25 26 27 28 29

{ alert(“Counter ticked: “ + e.CounterValue); } } var jsDotNetInstance; function onSilverlightLoaded(sender, args) { jsDotNetInstance = new JavaScriptDotNet(sender.getHost().Content.Page); }

. On lines 1 to 6, we define a constructor for our new JavaScript object. Note that it takes a parameter called page. This parameter is the “gateway” to the Page object that we registered on the .NET side when we called the method HtmlPage.RegisterScriptableObject. . On lines 3 to 5, we register a JavaScript method for the .NET event CounterTicked. That’s right, we can cross the language boundaries this easily! WARNING . Lines 8 to 14 define the method createDelegate that we studied earlier (in Chapter 8, “Programming Silverlight with JavaScript”). It is defined as a “static” method.

There is another way to register multiple event handlers for one event, using the JavaScript method addEventListener. We see examples in Chapter 21, “Taking Silverlight 2 Even Further.”

. Lines 16 to 22 define the object’s prototype. It has only one method, called handleCounterTicked. This method creates a JavaScript alert every time it is called. . Notice how the parameter e is a JavaScript representation of the CounterTickedEventArgs instance that we created on the .NET side: You can access the property CounterValue, because we marked it as a ScriptableMember. . Lines 24 to 29 define a global function named onSilverlightLoaded. Due to the Silverlight event model, this method has to be global. It is as simple as possible: It creates a new instance of the class JavaScriptDotNet, saves it in a global variable, and lets it do the rest of the work.

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Calling JavaScript Methods from .NET

267

. Notice the complicated syntax to get the Page control that we registered earlier: . sender.getHost() returns the instance of the Silverlight control. This is in fact a reference to the object tag in the HTML page. . This “host” has a property named Content that is the entry point on the XAML page and all the objects registered for JavaScript, as we see in the next section. Finally, we need to “hook” the global function onSilverlightLoaded to the onload event of the Silverlight object. Simply add the following parameter in the HTML page, in the object tag, under the other event handler named onerror: <param name=”onload” value=”onSilverlightLoaded” />

14

Testing the Code And now comes the exciting part, testing what we just implemented. Follow the steps: 1. Right-click on the website JavaScriptDotNetWeb and select Set As StartUp Project. 2. Right-click on the file JavaScriptDotNetTestPage.html and select Set As Start Page. 3. Press Ctrl+F5 to run it. 4. Click five times on the button. This raises the .NET event and triggers the alert. If you click OK and then click on the button five more times, the alert will be triggered again (see Figure 14.1).

FIGURE 14.1

.NET event handled in

JavaScript

Calling JavaScript Methods from .NET In addition to raising events from .NET to JavaScript, you can also simply call JavaScript methods from the .NET code with the following steps: 1. Modify the JavaScriptDotNet object prototype as follows. We now only declare a second method with Listing 14.8.

LISTING 14.8

Method saySomething

JavaScriptDotNet.prototype = { handleCounterTicked : function(sender, e) { alert(“Counter ticked: “ + e.CounterValue); }, saySomething : function(message1, message2, message3)

Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

Prepared for Andre John Cruz, Safari ID: [email protected] Licensed by Andre John Cruz Print Publication Date: 2008/10/15 User number: 1076800 © 2009 Safari Books Online, LLC. This PDF is made available for personal use only during the relevant subscription term, subject to the Safari Terms of Service. Any other use requires prior written consent from the copyright owner. Unauthorized use, reproduction and/or distribution are strictly prohibited and violate applicable laws. All rights reserved.

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CHAPTER 14

LISTING 14.8

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Letting .NET and JavaScript Talk

Continued

{ alert(message1 + “/” + message2 + “/” + message3); } }

2. In Page.xaml, add a new button under the one we added before (see Listing 14.9):

LISTING 14.9

Another Button

<Button x:Name=”SaySomethingButton” Width=”80” Height=”40” Content=”Say” Click=”SaySomethingButton_Click” HorizontalAlignment=”Right” Margin=”0,20,100,0” />

3. and in Page.xaml.cs (Listing 14.10):

LISTING 14.10

Event Handler SaySomethingButton_Click

private void SaySomethingButton_Click(object sender, RoutedEventArgs e) { ScriptObject instance = HtmlPage.Window.GetProperty(“jsDotNetInstance”) as ScriptObject; instance.Invoke(“saySomething”, new object[] { “Hello”, “World”, DateTime.Now }); }

. The class HtmlPage is a useful entry point from .NET to the HTML and JavaScript realm. With its two static properties Window and Document, you can access most of the JavaScript and HTML elements of the page hosting the Silverlight application. . Remember how we saw (in Chapter 8) that a global variable is actually a property of the global object? And that the global object is the Window? Well, here is a practical use for this knowledge: We access the global variable jsDotNetInstance by using the method GetProperty on the Window! . Finally, calling the Invoke method on any ScriptObject will try to call the corresponding JavaScript method. In our case, we call Invoke on the instance we just fetched. If you have a global method, you can Invoke it on the HtmlPage.Window!

Silverlight 2 Unleashed Silverlight 2 Unleashed By Laurent Bugnion ISBN: 9780768686845 Publisher: Sams

Prepared for Andre John Cruz, Safari ID: [email protected] Licensed by Andre John Cruz Print Publication Date: 2008/10/15 User number: 1076800 © 2009 Safari Books Online, LLC. This PDF is made available for personal use only during the relevant subscription term, subject to the Safari Terms of Service. Any other use requires prior written consent from the copyright owner. Unauthorized use, reproduction and/or distribution are strictly prohibited and violate applicable laws. All rights reserved.

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Calling .NET Methods from JavaScript

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. Even though our JavaScript NOTE method expects strings, we can pass it a DateTime object. The HtmlPage.Window has three handy shortcuts: Alert, Confirm, and Prompt. They call method ToString will automatithe corresponding functions in JavaScript cally be called on this object. Since and can be really helpful when you’re debug.NET types and JavaScript types are ging your code! not equivalent, a conversion must take place. In Chapter 21, we talk more about type conversions and the ScriptObject type. After you made these changes, run the application and test it by clicking on the new button.

14

Calling .NET Methods from JavaScript Now that we saw how to handle .NET events in JavaScript and to call JavaScript methods from .NET, the opposite way is straightforward: To call .NET methods from JavaScript code, simply use the following syntax: [control].Content.[objectname].[methodname]([parameters]);

. [control] is the Silverlight control added in the HTML markup. You can get a reference to that using the sender.getHost() in the JavaScript function handling the onload event (as we did before). . Another way to get a reference to the Silverlight control is to set an ID in the object tag:

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