Lập trình .net 4.0 và visual studio 2010 part 43 doc

CHAPTER 12  JQUERY 280 Adding Functions A common problem many designers and developers encounter is the separation of design from code. Many developers (in fact, I got you to do this in the very first example) if asked to call a JavaScript function when a button is clicked will write something such as this: <input id="cmdTest" type="button" value="Hello jQuery" onclick="javascript:hellojQuery();" /> However this is not the best way because it is very vulnerable to polo neck, snowboarding designer corruption and isn’t standards compliant. jQuery offers a neat solution with the .bind() method. The following code binds the hellojQuery() function to the click of the cmdTest button: $("#cmdTest").bind('click', hellojQuery());'' Animation/Effects Many people become aware of jQuery through seeing one of its many impressive graphical effects. Let’s check out the fadeOut effect using our original example. 1. Go back to default.htm and change the helloJQuery() function to contain the following: $("#div1").fadeOut(); 2. Press F5 to run your application, 3. Click the Hello jQuery button, 4. The div should then fade out of view. Effect Overloads Most of the effects in jQuery are overloaded, allowing fine-grained control (see Table 12-6). Table 12-6. Different overloads of fadeOut method Exa mple Me ani ng $("#div1").fadeOut(); Basic effect with default options $("#div1").fadeOut(10000); Effect time specified in milliseconds $("#div1").fadeOut('slow'); Specifies the time the effect will take to run: slow, normal, or fast CHAPTER 12  JQUERY 281 You can also specify a callback function to be executed when the effect has completed: function hellojQuery() { $("#div1").fadeOut('slow',funtionToCall); } Function functionToCall() { … } Core Library Effects Table 12-7 lists jQueries core effects. Table 12-7. Core libary effects Exa mple Me ani ng $("#div1").hide(); Hides element. $("#div1").show(); Shows element. $("#div1").fadeOut(); Fades out element. $("#div1").fadeIn(); Fades in element. $("#div1").toggle(); Toggles display of element. If it is hidden, it will become visible. If it is visible, it will be hidden. $("#div1").slideDown(); Animates element to become visible like a vertical blind sliding down. $("#div1").slideUp(); Animates element to become hidden like a vertical blind sliding up. $("#div1").animate({ Powerful function that animates an element to specified CSS property values over time span in milliseconds specified. width: "100%", fontSize: "100px" }, 1500 ); $("#div1").stop(); Stops any animation or effects in progress. CHAPTER 12  JQUERY 282 Additional Effects In addition to the previous effects, a number of additional effects can be downloaded: fold, pulsate, puff, bounce, and explode (my personal favorite). For more details on these effects please go to http://docs. jquery.com/UI/Effects. Glimmer If you don’t want to hand-code your jQuery effects, you can use a great tool called Glimmer produced by Microsoft that offers a wizard-based approach (see Figure 12-4). Refer to http://visitmix.com/lab/ glimmer. Figure 12-4. Glimmer allows you to easily construct jQuery effects Glimmer allows the construction of simple effects such as rotating images, drop-down menus, and animation. jQuery Tools jQueryPad ( (http://www.paulstovell.com/jquerypad) and http://jsbin.com/ can be very useful tools for prototyping and playing with jQuery. CHAPTER 12  JQUERY 283 Chaining Events The real power of jQuery comes from its capability to chain functions together. Imagine that we wanted to fade our div in and out a number of times. This procedure can be easily accomplished with the following code: $("#div1").fadeOut().fadeIn().fadeOut().fadeIn().fadeOut(); Customizing jQuery You can add your own functions to the jQuery library. For example, to create a simple function that will pop up an alert box, you can do so with the following code: //don't use $ alias in case user overrides it jQuery.fn.say = function (message) { alert("jQuery says " + message); return this; } You can then call the new function with the following code: $.fn.say("hello").say("good bye"); And there is, of course, no reason why you couldn’t write a new effects function and use it as part of a chain of effects. For more information, please refer to http://docs.jquery.com/Plugins/Authoring. AJAX Methods It is very common for performance optimization to need to retrieve data or code from an external source after a page is loaded. jQuery makes this very easy. Load and Run JavaScript File The following code loads an external JavaScript file called test.js and then executes it: $.ajax({ type: "GET", url: "test.js", dataType: "script" }); The test.js file consists of just the following line: alert('hello'); CHAPTER 12  JQUERY 284 Submitting Data You often need to submit data to another web page. This can easily be done with the following code: $.ajax({ type: "POST", url: "myForm.aspx", data: "firstname=Alex&lastname=Mackey", success: function() { alert("form submitted"); } }); You will use this functionality in the ASP.NET MVC example (see Chapter 13) to submit your form data: //Submit client side $.ajax({ type: "POST", dataType: "json", url: "Edit", data: { Description: InputDescription, Length: InputLength, DateShowing: InputDateShowing }, success: function(result) { alert(result.Message + " adding film at " + result.DateShowing); }, error: function(error) { alert('error '); } }); Getting the Latest Version of a Page We can retrieve the contents of a page in the same domain as the calling page with a few lines of code. This could be useful in AJAX scenarios in which you want to load content behind the scenes: $.ajax({ url: "default2.aspx", cache: false, success: function(returnHtml) { $("#div1").append(returnHtml); } }); CHAPTER 12  JQUERY 285 Retrieving a JSON Object JSON is a compact format for representing data. jQuery contains support for working with JSON objects. We will first create a page called default2.aspx that will return a JSON-formatted string (you will soon look at a better way of doing this). 1. Right-click your solution and add a new page called default2.aspx and select the place code in a seperate file option. 2. Remove all the code on default2.aspx except for the page declaration. 3. Add the following code to default2.aspx.cs: protected void Page_Load(object sender, EventArgs e) { Response.Buffer = true; Response.Clear(); Response.ContentType = "application/json"; Response.Write("{firstName: \"Alex\",lastName: \"Mackey\"}"); } 4. Open default.htm and alter the helloJQuery() function to the following (note that we pass a URL to which we send the query and then a function to be called when the query is completed): $.getJSON("default2.aspx", function (data) { alert(data.firstName); } ); 5. Press F5 to run the project. 6. Click the Hello jQuery button. You should see an alert box displaying “Alex” (the firstName property from the JSON object). A Better Way Visual Studio 2008 (and later) offers a better way: 1. Create a new page called default3.aspx and then open default3.aspx.cs. 2. Add the following using statement: using System.Web.Services; 3. Add the following class to represent our returned object: public class Person { public string firstName {get; set;} public string lastName { get; set; } } CHAPTER 12  JQUERY 286 4. Now add a new method to your page marked with the [WebMethod] attribute to expose it to the client script: [WebMethod] public static Person GetFirstname() { Person p = new Person(); p.firstName = "Alex"; p.lastName = "Mackey"; return p; } 5. Now amend the existing jQuery code to the following: $.ajax({ type: "POST", url: "Default3.aspx/GetFirstname", data: "{}", contentType: "application/json", dataType: "json", success: function (input) { alert(input.d.firstName); } }); Much easierand safer. Note that we had to access the d property in order to access the firstName property. This is to prevent the execution of the returned string as a script. For more information, please refer to: http://encosia.com/2009/02/10/a-breaking-change-between-versions-of-aspnet-ajax/. Utility Methods Browser detection is notoriouslly unreliable, but jQuery provides a number of methods to assist you with detecting the capabilities of your visitors’ browsers. For example, the following code will return true or false depending on whether the browser supports the box rendering model: alert($.support.boxModel); For the full list of functionality you can query, please see http://docs.jquery.com/Utilities/ jQuery.support. jQuery Additions In addition to the core jQuery functionality, a number of additional jQuery libraries and add-ons exist that you might find useful. Note some of these are not produced by the core jQuery team but are excellent nevertheless: • Drag and drop elements (http://docs.jquery.com/UI/Draggable) • Sorting (http://docs.jquery.com/UI/Sortable) • Selecting (http://docs.jquery.com/UI/Selectable) CHAPTER 12  JQUERY 287 • Resizing (http://docs.jquery.com/UI/Resizable) • jqgrid (http://www.trirand.com/blog/) jQuery also provides a number of UI elements (called widgets) that you might want to utilize: • Accordian • Data picker • Dialog • Progress bar • Slider • Tabs For more information, please refer to http://docs.jquery.com/Main_Page. Summary It is fantastic to see Microsoft not reinventing the wheel and choosing to integrate and provide support for jQuery. jQuery is a lightweight framework, and you would be crazy not to use it in your own projects. Further Reading • http://jquery.com/ • http://github.com/jquery/jquery • http://weblogs.asp.net/scottgu/archive/2009/09/15/announcing-the-microsoft-ajax- cdn.aspx • http://www.andy-gibson.co.uk/ • http://encosia.com/ For a more in-depth read on jQuery functions, I don’t think you can do much better than jQuery in Action by Bear Bibeault and Yehuda Katz, published by Manning. . property values over time span in milliseconds specified. width: " 100 %", fontSize: " 100 px" }, 1 500 ); $("#div1").stop(); Stops any animation or effects in progress a script. For more information, please refer to: http://encosia.com/ 200 9 /02 / 10/ a-breaking-change-between-versions-of-aspnet-ajax/. Utility Methods Browser detection is notoriouslly unreliable,. alert box displaying “Alex” (the firstName property from the JSON object). A Better Way Visual Studio 200 8 (and later) offers a better way: 1. Create a new page called default3.aspx and then