jQuery Mobile Dynamicly Appending to Listview via AJAX issue

With jQuery Mobile you can create a Listview of list items but I wanted to populate that list dynamically via AJAX. The problem I was getting is it would work fine when I loaded it the first time but then I wanted to nuke (clear) the list and repopulate it with new content. If you’ve gone through half the trouble I went through to get this to work then I know this is going to help you out! So I won’t drag this out any longer… here’s the solution:

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//empty the list
$("#myList").empty();

//do some stuff to populate the content
myListContent += '<li><a>some content</a></li>';

//append the new content and create a new listview and refresh it
$("#myList").append(myListContent).listview().trigger("create");
$("#myList").listview('refresh');

timthumb and PHP thumbnails rotate with large images

I’ve been banging my head against the wall trying to figure out why large images were getting rotated when I made them into a thumbnail (either through timthumb or PHP’s imagejpeg). It turns out that with images that were in portrait the width and the height were swapped for very high resolution images (~3000 pixels wide and ~ 2000 pixels tall). So I wrote my own function that looks to see if the EXIF information says this is a portrait image (which is defined by the integer value 6). If it is then I check to see if the width is greater than the height. If so – it’s going to end up in landscape so I simply rotate the image 270 degrees (counter clockwise) and it works! So I’ve made the function to take two arguments; a path to the image, and the desired width of the thumbnail. So here it is:


header('Content-Type:image/jpeg');

//can be called like this:
//script.php?w=200&src=img/myPicture.jpg
echo thumb($_GET["src"],$_GET["w"]);

function thumb( $path, $thumbWidth )
{

 $info = pathinfo($path);
 // continue only if this is a JPEG image
 if ( strtolower($info['extension']) == 'jpg' )
 {

// load image and get image size
 $img = imagecreatefromjpeg( "{$path}" );
 $width = imagesx( $img );
 $height = imagesy( $img );

// calculate thumbnail size
 $new_width = $thumbWidth;
 $new_height = floor( $height * ( $thumbWidth / $width ) );

// create a new temporary image
 $tmp_img = imagecreatetruecolor( $new_width, $new_height );

// copy and resize old image into new image
 imagecopyresized( $tmp_img, $img, 0, 0, 0, 0, $new_width, $new_height, $width, $height );
 $exif = exif_read_data($_GET["src"]);
 $orientation = $exif["Orientation"]; //6 for portrait and 1 for landscape
 if($orientation == 6 && $width > $height) {
 $tmp_img = imagerotate($tmp_img, 270, 0);
 }
 return imagejpeg($tmp_img);

 }
}

AJAX made easy using jQuery

AJAX can seem daunting but it’s never been easier to implement with jQuery! So first, let me give my explanation of what AJAX is and can be used for. Imagine you have a piece of content you’d like to have updated every so often (e.g. an average number from a database), but you don’t want the user to have to reload the page to get the updated number. This is where AJAX comes into play – you can setup an AJAX call to GET the output of a script that queries the database and then use the results to update your page with jQuery. So let’s dive into this example:

index.html

<!DOCTYPE html>
<html>
  <head>  
  <script src="//code.jquery.com/jquery.js"></script>
  <script>
   updateNumber();
   var updateInterval=setInterval(function(){updateNumber()},3000);
			
   function updateNumber()
   {
	$.ajax({
	type: 'GET',
	url: 'ajaxScript.php'
	}).done(function( averageTime ) {
		$("div#num").html(averageTime);
	});
   }
  </script>
  </head>
  <div id="num"></div>
</html>

ajaxScript.php

<?php
  //get the average time from the last 10 minutes
  $stmt = $dbh->prepare("SELECT AVG(time) averageTime FROM `myTable` date >= DATE_SUB(NOW(),INTERVAL 10 MINUTE) LIMIT 1");
  $stmt->execute();
  $row = $stmt->fetch();
  echo $row["averageTime"];
?>

Velocity Cheat Sheet

Decided to make a velocity cheat sheet/quick start guide. Hopefully this is useful for anyone just starting out and also a good reference for experienced velocity developers. If I missed anything feel free to let me know.

## This line is a comment
## The next line is a variable assignment
#set($foo = "hello world")
## The next line uses the variable
<p>$foo</p>
## Velocity is good with dates
<p>Today is $_DateTool.getDate()</p>
## If your using velocity against XML data
## you can get a single node like so:
#set($singleNode = $_XPathTool.selectSingleNode('/path/to/node'))
## or you can select multiple nodes:
#set($multipleNodes = $_XPathTool.selectNodes('/path/to/nodes'))
## and iterate through the nodes like so:
#foreach ($node in $multipleNodes)
    ## You can use if statements like so:
    #if($node.getChild('elementName'))
        ## you can get the child nodes like so:
        $node.getChild('elementName').value
    #end
#end  

Also a useful reference chart provided by XNAT.org (https://wiki.xnat.org/display/XNAT/Velocity+Cheat+Sheet)

Description Usage Example
Variables #set() #set($foo = “hello”)
Comments (single line) ## ## Comment
Comments (multi lines) #* *#  #*
* Comments
* on multiple lines
*#
Arithmetic Operators +   –   *   /   % #set($age = $age + 1)
Comparison
(not just equivalency, can be used to compare objects)
== #if($gender == “female”)
Logic Operators &&   ||    ! #if($state == “Indiana” && $country == “USA”)
Range Operator
(used in loops)
[n..m]
Escape Character
Reference a variable $age <p>Jack is $age years old</p>
Reference a variable
(if value is null, print nothing)
$!age
Assign a value to a variable
(string literal)
#set ( $!foo = “Velocity” )
Refer to a hashtable key
or a get (Address) method
$customer.address
Conditional Statement #if ()
#elseif()
#else
#end
 #if ($foo)
<p>Velocity!</p>
#else
<p>XSLT</p>
#end
Loop #foreach ($criterion in $criteria) ## loop ArrayListCurrent Value: $!criterion#end