Category: javascript Page 1 of 2

I was trying to set up Cordova on my windows laptop this weekend. I followed all of the setup steps and ran

cordova requirements

but got this error:

Android target: not installed
avdmanager: Command failed with exit code 1 Error output: Exception in thread “main” java.lang.NoClassDefFoundError: javax/xml/bind/annotation/XmlSchema at com.android.repository.api.SchemaModule$SchemaModuleVersion.(SchemaModule.java:156) at com.android.repository.api.SchemaModule.(SchemaModule.java:75) at com.android.sdklib.repository.AndroidSdkHandler.(AndroidSdkHandler.java:81) at com.android.sdklib.tool.AvdManagerCli.run(AvdManagerCli.java:213) at com.android.sdklib.tool.AvdManagerCli.main(AvdManagerCli.java:200) Caused by: java.lang.ClassNotFoundException: javax.xml.bind.annotation.XmlSchema at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:582) at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:185) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:496)

A quick google search turned up lots of ideas for fixing the issue, including:

Downgrading to JDK 8 (Don’t do this – it’s outdated advice)
setting the environment and PATH variables (I did that already)
reinstall the JDK (I tried this – no luck)
create an AVD (This needs to be done, but still didn’t solve my issue)

Here’s a link to a helpful Stack Overflow thread that goes through some of these options.

I work on a Macbook for my job and I’m not too familiar with Windows dev tools setup. I spent hours trying to sort this out. Then I realized that Windows has TWO places to set environment variables: One for USER variables and one for SYSTEM variables:

So, I started going through the system variables. When I opened up the system Path variable, I saw my problem:

The JDK path was declared multiple times in the system variables. The image above is just an example – I actually had FOUR different JDK paths declared in my system path! Most of these paths pointed to non-existent JDKs. I removed all of the bad JDK paths, leaving only the path to the JDK I had just installed. Presto! My error went away!

Cordova requirements now threw a new error about not being able find ANDROID_SDK_ROOT, but that’s an easy fix. Just add a new User Environment variable called ANDROID_SDK_ROOT and give it the same value that you should already have for ANDROID_HOME.

As always, I hope that this saves you a little time and you won’t spend hours tracking down this issue like I did.

Pixi.js – HTML5 for Flash developers

By Andy

On March 24, 2013

In Actionscript/AS3, Flash, Game Development, HTML/CSS, javascript, Uncategorized

pixi js Pixi.js is another javascript framework that attempts to recreate some of the features of Flash. It even replicates a lot of Flash components: MovieClip, Sprite, Stage, DisplayObject. It’s an impressive javascript library. You can download the source and some examples from github. I spent a little time hacking around on the examples and picking through the source code. Here’s a video introduction if you prefer that, or you can skip down to the text below the video…

Here’s a quick primer on Pixi.js:

It’s really comfortable for Flash/Actionscript developers. The folks who created Pixi.js are clearly very familiar with Flash and used a lot of Flash terminology in Pixi.js. It also feels like they worked hard to make it very easy to dig in and start creating cool stuff with minimal boilerplate code. I really appreciate that.

There is no built-in way to set a target frame rate in Pixi.js. Technically, there is no way to force a specific frame rate in javascript and it will only do the best it can, but Flash worked that way too and you could still give it an FPS target. The Pixi.js examples seem to rely on requestAnimationFrame() to run at 60 FPS. This is not reliable, so if you use Pixi.js, be sure to write some code to handle the rendering frame rate.

Pixi.js has a really clever renderer: It detects if your browser is WebGL enabled. If not, it falls back to an HTML5 canvas renderer. Not only is it cool that it handles this for you, but browsers with WebGL (Chrome, Safari) are hardware accelerated. This means that they can unload the rendering from the CPU to the GPU, making everything run much faster. Firefox also supposedly has WebGL capability, but from what I’ve read, the performance is questionable. The WebGL thing is going to be a big deal as it becomes more widespread. As usual, IE10 doesn’t support it, but it does have hardware accelerated canvas.

As a side note, the hardware acceleration is all based on your browser and hardware configuration. So, if you have a relatively new device and an updated browser, it just kicks in automatically. iPhones and iPads all support hardware acceleration and many Android devices do too. Obviously, how you handle older browsers is the challenge. In most cases, a less full-featured backup may need to be served up. In a few cases, the user may need to have hardware acceleration to run your game or app at a reasonable frame rate. A smart way to handle this is to check the frame rate of the game and alert a user if it drops below a minimum threshold.

So grab the Pixi.js code and start building some HTML5 goodness.

Using jQuery on a non-DOM HTML String

By Andy

On January 24, 2013

In HTML/CSS, javascript

I had an interesting problem today at work – I needed to get the src attribute of an <img> tag that was not in the DOM. I had a string containing HTML that was not actually part of the page, but I needed to parse it for information. I was not able to change the data, but I had access to an object with a property called “innerHTML” which contained the following string:

<img src="img/myimage.png" width="1700" height="500" />
<p>this is some text</p>

The easy (but ugly) way to solve this problem is to simply write the string into a hidden <div> on your HTML page, then extract what you need with jQuery. I really didn’t want to do this because I was going to be writing several large images into the page, and it just seems like a really lame way to handle the problem.

With a bit of help from this Stack Overflow thread, I found a better way to handle it. Simply cast your string into a jQuery object and you can use regular jQuery methods on it. here’s an example of how it works:

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js">
</script>
<script type="text/javascript">
//create a sample object with a property containing HTML text:
var obj = {
    mystring: '<img src="img/myimage.png" width="1700" height="500"/>' +
        '<p>this is some text</p>'
}

$(document).ready(function() {
    //cast the string into jquery...
    //then use jquery's filter() function to isolate the image tag:
    var img_tag = $(obj.mystring).filter('img')[0];
    //to get the src attribute, we cast the above result into jquery again:
    var img_src = $(img_tag).attr('src');
    console.log(img_src); //ta da!!
});
</script>

This doesn’t come up very often, but it’s a good trick to have up your sleeve.

Why I Still Make Games in Flash/AS3 (for now)

By Andy

On January 14, 2013

In Actionscript/AS3, Flash, Game Development, HTML/CSS, javascript, Uncategorized

As I look ahead to this year, I have several posts planned around game development in ActionScript 3 (Flash). So, I thought I should post a brief explanation about why I’m STILL developing games in AS3. After all, isn’t Flash dead? Aren’t we all living in a brave, new HTML5 world? Here are a few of the reasons why I’m developing in AS3:

actionscript vs javascript As of this post, HTML5 <canvas> support is still inconsistent across major browsers. Admittedly, the main issue is Internet Explorer, but they still have a HUGE market share and can’t be completely ignored. For most of our <canvas> projects at work, we still end up building a Flash backup. If you’re targeting desktop devices for your games, publishing to Flash gives you a bigger market share than HTML5 <canvas>.

HTML5 <audio> support is pitiful. In some browsers (*cough* Mobile Safari *cough*), it barely works at all. Then there are issues with preloading sounds so they are actually available when you need them.

We see how you are

Category: javascript Page 1 of 2

Fix for Cordova error: Android target: not installed cmd: Command failed with exit code 1

Pixi.js – HTML5 for Flash developers

Using jQuery on a non-DOM HTML String

Why I Still Make Games in Flash/AS3 (for now)