Oct 29 2009

JQuery Part 2 – Basic Animation

Welcome to JQuery part 2, using basic animation techniques. You should already have a basic understanding of JQuery and it’s elements to complete this tutorial. If you don’t, please refer to my JQuery Introduction post found here. Now to get started…

Let’s start by creating a basic HTML page and call it index.html in the root of our web servers directory and add a basic page structure to that file. Let’s also make sure that we have the JQuery libraries imported and ready to use.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
	<head>
		<title>JQuery Animations</title>
 
		<script type="text/javascript" src="lib/jquery.js" />	
 
	</head>
	<body>
	</body>
</html>

Now, in order to complete animation we will need to display an element to animate. The easiest way to do this is to use some basic CSS. So for the purpose of this tutorial let’s create a style.css file and put it in the root of our directory. Let’s then link it to our index.html file so that we can use it.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
	<head>
		<title>JQuery Animations</title>
 
		<script type="text/javascript" src="lib/jquery.js" />
 
		<link rel="stylesheet" href="style.css" type="text/css" />
 
	</head>
	<body>
	</body>
</html>

Now that we have our CSS file linked to our HTML we’re going to need to add an element to animate. For this demonstration we’re just going to use a red box that’s 100px by 100px inside a div. Let’s add that to our CSS file.

#redBox
{
	width:100px;
	height:100px;
	background-color: red;
}

Now we’ll add the appropriate div tags to our HTML file so that our red box shows up. We’re also going to add an anchor tag directly below our red box to toggle the box between showing and disappearing.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
	<title>JQuery Animations</title>
 
	<script type="text/javascript" src="lib/jquery.js" />
 
	<link rel="stylesheet" href="style.css" type="text/css" />
 
</head>
	<body>
		<div id="redBox"></div>
		<a href="#">Show/Hide</a>
	</body>
</html>

Now we’re all ready to start coding our JQuery. If you run the HTML file right now you should see a red box sitting at the top left hand corner of the page. Right now the red box shouldn’t do anything as we haven’t coded the JQuery. So let’s start out by using the document ready function. and adding a function to all of our anchor tags.

<script>
	$(document).ready(function(){
		$('a').click(function({
 
		));
	});
</script>

Now we’re ready to be using some of the animation methods found in the JQuery library. First, since the box is by default showing up in the browser we’re going to make it hide by using the .hide() function. The .hide() function can be used without any parameters being passed or you can pass a speed and an optional callback(). The callback is a function to be executed when the animation has been completed. For the sake of this tutorial we’re only going to cover the speed parameter.

<script>
	$(document).ready(function(){
		$('a').click(function({
			$('#redBox').hide('slow');
		));
	});
</script>

Now, if you include the script section in the header of your index.html document and run it, when you click the anchor tag you should see the red box that we created disappear. However now the red box is gone and we can’t get it back. We’re going to need to change this so that we can get it back by clicking on the anchor tag again. In order to get this we’re going to need to add another function and pass it as a parameter to our .click() function for our anchor tags.

<script>
	$(document).ready(function(){
		$('a').click(function({
			$('#redBox').hide('slow');
		},function(){
			$('#redBox').show('slow');
		});
	});
	</script>

Since we’re adding the new function as another parameter to the click function, we need to terminate the current function before starting the new one. This is why we need to close the curly braces from the previous function before we start another. If we didn’t close the curly braces and just put it inside the first function then every time we clicked on the anchor tag, it would disappear and then show again without pressing the anchor tag. Now when we put that all together and run it, whenever we click the anchor tag the box should disappear and then re-appear when we click it again. Here is the complete code.

<html>
<head>
	<title>JQuery Animations</title>
 
	<script type="text/javascript" src="lib/jquery.js" />
 
	<link rel="stylesheet" href="style.css" type="text/css" />
 
	<script>
	$(document).ready(function(){
		$('a').click(function({
			$('#redBox').hide('slow');
		},function(){
			$('#redBox').show('slow');
		});
	});
	</script>
 
	</head>
	<body>
		<div id="redBox"></div>
		<a href="#">Show/Hide</a>
	</body>
</html>

In the tutorial I just used 2 of the more basic animation functions in the JQuery library. For a full reference to the JQuery animation API, please check out http://docs.jquery.com/Effects/. Stay tuned for JQuery part 3 :D .


Oct 28 2009

Introduction to JQuery: Part 1

JQuery is a javascript library that simplifies javascript’s interaction with HTML to speed up javascript coding.

Benefits of JQuery

- Lightweight Footprint
- CSS3 Compliant
- Cross-Browser compatibility

What you will need

- Javascript enabled browser
- JQuery Library
- An application to code in(Coda, Aptana, or even notepad)

Starting out

To start out coding with the JQuery library you will need to import the library. Usually I like to structure my site with a /lib folder at the root of the directory. This way I can include all of my javascript libraries in one central location so they don’t replicate down the road. So for this project i’ll setup my directory structure with my JQuery files inside the lib folder. Next we’ll create an index.html file inside the root directory. This will be our testing file for our JQuery code. Alright, let’s get started, let’s start by adding a basic page structure to your index.html file.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
	<head>
		<title>JQuery Test</title>
	</head>
	<body>
	</body>
</html>

Next we need to add in our JQuery script so that we can use it. Add in the following code inside your header tags. Use the src tag to point to your JQuery javascript file.

<script type="text/javascript" src="lib/jquery.js" />

Making Sure the document is ready

First off, any JQuery code that we want to include goes into script tags. This is because JQuery runs on top of javascript, so in order for the browser to understand what JQuery is doing, it needs to be included inside the script tags.

Now, the first thing that we need to do is make sure that the document is ready to be used. We do this to make sure that no changes occur before the user is ready to see it. So if the page isn’t loaded or the user is on a slow connection, the JQuery code will not start executing until the document is loaded and ready. To do this we use the document ready function in JQuery.

<script>
$(document).ready(function(){
});
</script>

Adding a click event to a link

Now that our document is ready for our JQuery code we can add some functionality to our site. The first thing we’ll deal with is adding a link to our index.html file. That way we have something to manipulate when we go to code our JQuery. Let’s add a link to our index.html file now.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
	<head>
		<title>JQuery Test</title>
 
		<script type="text/javascript" src="lib/jquery.js" />
 
	</head>
	<body>
 
		<a href="http://www.google.ca/">Link</a>
 
	</body>
</html>

Once we have our link added we can start to code the JQuery. What we’re going to do in this instance is instead of taking the user to google, we’re going to just display a simple javascript alert instead.

<script>
	$(document).ready(function(){
		$('a').click(function({
			alert("Obviously you're still here and not over at google");
			event.preventDefault();
		));
	});
</script>

Alright, so that probably looks a little confusing right off the bat, especially if you’re used to regular javascript coding. Let’s break it down into a little more detail. To start off, $(’a'). This means that we’re taking the element “a” from the html. If we wanted to use the id of say a form(id=”test”) then we could just do $(’#test’) instead. Then after we have a function. This will allow us to do something with the element that we retrieved from the HTML. In this case, we’re going to use the “.click()” function to allow us to process an event when any element with an attribute of “a” is clicked. Now because we want to do something with that event whenever it’s clicked, we can use a function inside of the click function. That’s where the .click(function(){}) section comes from. Now in order to actually accomplish something with the event that was created we need to put the rest of our code inside of the curly braces of the function. In this case we’re just creating a plain javascript alert box with a message in it. The next line, “event.preventDefault();” is just a function in JQuery that disables the default behavior of the element. In this case the default behavior is to send the user to google, so we’re going to make the user stay at our page and just simply display a javascript alert.

Since .click is a function we will need to close our the function using a “;”. That’s it, you just wrote your first function and created your first event. All together the code looks like this.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
	<head>
		<title>JQuery Test</title>
 
		<script type="text/javascript" src="lib/jquery.js" />			
 
		<script>
			$(document).ready(function(){
				$('a').click(function({
					alert("Obviously you're still here and not over at google");
					event.preventDefault();
				));
			});
		</script>
 
	</head>
	<body>
 
		<a href="http://www.google.ca/">Link</a>
 
	</body>
</html>

For more information on JQuery or more tutorials you can visit the jquery site at http://jquery.com/. If you have any questions or comments feel free to leave a comment and I’ll respond as quickly as possible.

Cheers


Mar 16 2009

Creating an Application Specific Console in QT Jambi

I am currently working on a project that required a console with a very specific purpose. It needed to communicate with a custom back-end protocol for use in a client/server environment. This sort of specific tutorial is not surprisingly unavailable online. The first step when setting up an application specific console is actually setting up the back-end. This is something that will be potentially done as a future tutorial. Anyways back to building the console window. The components included in the console window will be one QTextEdit, and one QLineEdit. This can be constructed in any way you like. The QTextEdit can be on the bottom and the QLineEdit on top or the other way around, that’s up to you.

Next, we will need to be adding a custom action listener to the QLineEdit so that when the enter key is pressed inside the QLineEdit the command will be sent to the server and then displayed in the QTextEdit window. As a future feature implementation, syntax highlighting could be implemented for an easier display inside the QTextEdit window. The custom action listener to add to the QLineEdit bar looks like this…

1
QLineEdit.returnPressed.connect(this, "NameOfActionListenerMethod()");

This will ensure that everytime the enter button is pressed, the string that the user entered will be able to be transfered to the server, or wherever else in the program you would like it to go. Now for the action listener method. The method should be declared as public with a return type of void.

1
2
3
4
5
public void terminalWindowEnterPressed()
    {
        terminalWindow.append(enterArea.text());
        enterArea.setText("Protocol Name > ");
    }

Then once you have the action listener built to just send the data to the window, you can do the same with sending it across a network.

All Together the code looks like this. All you have to do is copy/paste the code into your program and use it at will.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
/**
     *
     */
    public void buildTerminal()
    {
        terminalFrame = new QFrame();
        terminalFrame.setWindowTitle("Window Title");
 
        terminalWindow = new QTextEdit();
        terminalWindow.setReadOnly(true);
 
        enterArea = new QLineEdit();
        enterArea.setText("Protocol Name > ");
        enterLabel = new QLabel("Enter Command");
 
        terminalFrame.setMinimumSize(600, 400);
 
        enterArea.returnPressed.connect(this, "terminalWindowEnterPressed()");
 
        QGridLayout layout = new QGridLayout();
        layout.addWidget(terminalWindow,0,0,10,10);
        layout.addWidget(enterArea,11,1,1,9);
        layout.addWidget(enterLabel, 11,0,1,1);
 
        terminalFrame.setLayout(layout);
        terminalFrame.show();
    }
 
    /**
     *
     */
    public void terminalWindowEnterPressed()
    {
        terminalWindow.append(enterArea.text());
        enterArea.setText("Protocol Name > ");
    }

Cheers


Feb 26 2009

Adding Action Listeners in Qt Jambi

Adding an action listener to QT jambi is a little bit different then adding one in regular java. The first and major difference is the absence of an inner class which overrides the actionEvent method inside the action listener class, QT actually accepts string arguments of the method name to call an action listener. So in this case, technically any method can become an action listener. This allows for a greater amount of flexibility and customization when it comes to action listeners in QT.
There are a couple different terms that you need to know about as well when it comes to adding a QT action listener to your code.

Triggered:
When a QAction is created in QT, per say to go into a menu bar to perform something, is clicked… The QSignalEmitter sends off a triggered signal. This is the action listener call you want to keep in mind when taking care of QAction’s from menu bars and toolbars.

Clicked:
This one is pretty straight forward. The clicked keyword is used when a QButton is created. This is to determine if the button was clicked, when the button is clicked, the QSignalEmitter will send a clicked signal.

Connect:
Connect is a keyword used on top of either triggered or clicked. This is used to connect the QSignalEmmiter to the method that will be handling the event as an “action listener”.

The general syntax that is used for a QT Jambi Action Listener is as follows…

1
2
nameOfButton.clicked.connect(locationOfMethod, "methodName()");
nameOfQAction.triggered.connect(locationOfMethod, "methodName()");

The location of the method is this, if the method is in the current class. If it is not specify exactly where it is located so that it can find the method. Then the method name as a string. This will not respond with an error if you type the string in wrong so you will find out at run-time with an error if this has occurred. In this topic i only described both the triggered keyword as well as clickedt. However there are plenty more to choose from. Tutorials on those will come at a later point.

Cheers