Posts Tagged ‘phonegap’

* Mobile Geolocation Implementations

Posted on August 19th, 2010 by Dave Johnson. Filed under Uncategorized, phonegap.

Today I found some time to take a look at the various mobile implementations of geolocation.

Below is a table showing the properties that the geolocation API uses on the various platforms. The W3C geolocation API for browsers specifies a PositionOptions interface that requires a maximum age, timeout and accuracy. Below that row is all of the mobile platforms that we are interested in for PhoneGap and the properties that they support in their native implementations. Some of them support a distance filter that will cause the device to only return geolocation positions if the location has changed by more than that distance while others also support an explicit interval for watching for location changes (note that on Android that interval is only a hint to let the device know how much power to use in getting a location - the position may be reported at an interval either shorter or longer than the specified interval).

I am probably going to be adding these two additional arguments to the PhoneGap PositionOptions and they can be used on platforms that support them.

Max age Timeout Accuracy Distance Interval
BlackBerry maxAge timeout - - interval
iPhone - - desiredAccuracy distanceFilter -
Android - - - minDistance minTime
webOS maximumAge responseTime accuracy - -
WRT updateMaxAge updateTimeout - - updateInterval
Winphone - - DesiredAccuracy MovementThreshold

Image from cloneofsnake

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* PhoneGap Native Bridge

Posted on August 13th, 2010 by Dave Johnson. Filed under JavaScript, mobile, phonegap.

The “native bridge” is the secret sauce of PhoneGap and is what allows JavaScript in an embedded browser talk to native code and vice-versa.

On every platform we do this differently depending on what features that native browser has. Here is the list of platforms and how we do it.

iPhone: To communicate from JavaScript to native we call window.location = “gap://Class.method/args” and then intercept the url in native code and parse our the parameters. The class / method is then dynamically loaded / called. To call JavaScript from native we use UIWebView.stringByEvaluatingJavaScriptFromString.

Android: Communication from JavaScript to native takes advantage of the native WebView.addJavascriptInterface to expose Java objects directly to JavaScript. To call JavaScript from native we currently use WebView.loadUrl(”javascript:…”) but that has some problems so we are soon moving over to polling a Java message queue calling a local HTTP server via a long-lived XHR connection.

BlackBerry 4.x: document.cookie is the only way to talk between JavaScript and native. JavaScript sets the cookie for native to read and JavaScript polls the cookie for messages from native. Fucking elegant!

BlackBerry Widgets: Astoundingly the new BlackBerry Widgets SDK is pretty damn nice. You can expose Java objects to JavaScript with ScriptEngine.addExtension and you can call JavaScript from native with ScriptEngine.executeScript. The context for the JavaScript execution can even be specified. Seriously great work there.

QT: This one is not quite ready but it will use the QWebFrame.addToJavaScriptWindowObject to expose native objects to JavaScript and will likely use polling of those exposed native objects to get data back into JavaScript - much like the Android approach

Windows Phone 7: There is something called window.external.Notify in the browser (mapped to a native object through the ScriptNotify event) on Windows Phone 7 that we use to send messages into native code. Going the other way there is WebBrowser.InvokeScript.

webOS, WRT: The platforms that are just JavaScript don’t have any native code. Well, we might look into the native side of webOS one day but no time soon.

In an attempt to clean up the PhoneGap JavaScript API a bit, I have isolated all the places that we communicate from JavaScript to native code and put it into a single PhoneGap class. I am now in the process of converting over all the JavaScript to use this new PhoneGap interface and then most of the PhoneGap JavaScript will be completely cross platform. Any call to native code now has to go through the PhoneGap.exec() JavaScript method. The new code is up on Github and with any luck all the platforms will be using it soon!

Image by hb2

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* PhoneGap Desktop

Posted on April 20th, 2010 by Dave Johnson. Filed under phonegap.

So if PhoneGap was running on the desktop, what would you call it? Well I have not come up with a good name yet but after a few nights of hacking we threw together a version of PhoneGap for Mac OS and a version for Windows

@shazron has implemented the sound API on the Mac version and I did Geolocation on the Windows version using a simple GeoIP lookup.

Check it out, write some code, and let us know what you think!

For the Windows version I have used the awesome WebKit .NET project written by Peter Nelson. If you use the Visual Studio 2008 solution file, you will have to download the source or binary versions of WebKit .NET and setup the references correctly. I have so far used the 0.3 release of WebKit .NET. It is pretty cool being able to write a native Windows app (or Mac OS) in Canvas using all free and open source code :)

One other caveat on the Windows side is that you might need to install some Visual Studio C++ redistributables for building it … check the WebKit .NET forum on SourceForge for all the details.

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* Work

Posted on January 11th, 2010 by Dave Johnson. Filed under phonegap.

Crap it has been busy at work the past few months!

More to come soon though since I am working on a few small JavaScript libraries and two services that I will be releasing soon!

There has of course also been a tonne of amazing work being done on PhoneGap (tests, Palm, Nokia, simulator) - though not by me so much :)

Check out the latest at GitHub

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* Long Live PhoneGap for BlackBerry

Posted on July 30th, 2009 by Dave Johnson. Filed under phonegap.

There have been some new developments in the PhoneGap on BlackBerry breathing new life into the project! It all boils down to the fact that in RIM OS >= 4.6 there is a browser rendering option that you can set to make the browser render using the modern rendering engine rather than the archaic one from OS 4.2.

It look something like this:

  RenderingOptions.CORE_OPTIONS_GUID, 17000, true);

After much trial and error it was found that the BrowserContentManager did not support this rendering option (and RIM says it is completely unsupported / experimental anyhow) yet the Field returned from BrowserContent.getDisplayableContent() does support it!

Long story short it looks like PhoneGap on RIM OS >= 4.6 is going to work really well.

Next up is looking at the new features in OS 5.0.

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* PhoneGap iPhone Approval

Posted on June 13th, 2009 by Dave Johnson. Filed under mobile, phonegap.

The guys over at Rhomobile posted about IPhone App Store rejection issues the other day - I can only assume due to the recent problems that some users of PhoneGap have been having. Rhomobile and PhoneGap are similar in that they are frameworks that enable developers to build native mobile apps in a language they are familiar with, Ruby and JavaScript respectively.

I think that they are pretty much spot on in terms of their interpretation of the App Store rule 3.2.2 that states:

An Application may not itself install or launch other executable code by any means, including without limitation through the use of a plug-in architecture, calling other frameworks, other APIs or otherwise. No interpreted code may be downloaded and used in an Application except for code that is interpreted and run by Apple’s Published APIs and built-in interpreter(s).

The two key points in this App Store rule are where it says an app “may not itself install or launch other executable code by any means” and this is exactly what users of PhoneGap are doing if their apps are downloading JavaScript over the network rather than including it in the application www folder. By downloading JavaScript over the network at runtime the application is downloading and running interpreted code that Apple has not control over during their app approval process.

So if any of you PhoneGap developers are worried about Apple rejecting your app just make sure that you don’t download any JavaScript at runtime and instead include it in the application. Having said that, also make sure that you apps don’t look like you just took a shit and emailed it to Apple :)

That is just my thoughts on the issue, whether or not that is the *real* reason that Apple is rejecting PhoneGap apps we may never know but that is certainly one reason that they would do it I think. It could just be because they feel like it…

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* Where 2.0 Slides

Posted on June 7th, 2009 by Dave Johnson. Filed under Conference, mobile.

Here are my slides from my workshop at the recent O’Reilly Where 2.0 conference down in San Jose.

Where 2.0
View more PDF documents from davejohnson.

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* Eclipse Plugin Q&A

Posted on March 25th, 2009 by Dave Johnson. Filed under Web, phonegap, programming.

If you are one of the unfortunate few that has decided to, for profit or insanity, write an Eclipse plugin here are a few of the questions that I had during my ordeal and the answer or closest thing to an answer that I can come up with.

Q: How should I get started with Eclipse plug-ins?

A: Read a book. I did not do this and really regret it now I think. There are few different ones available that I assume explain all the intricacies. The Google can only help so much. Having said that, the approach that I took was to look at the code of another Eclipse plug-in and borrow from that :) Some of the better links I put up on Delicious.

Q: How do I make my plugin show up in the new project list?

A: This one seems like it should be easy to find out how to do but it actually wasn’t that easy. So it is pretty easy to get started using one of the samples in Eclipse like the file editor sample that creates a “New file” wizard. While that wizard does not launch from the “New project” menu it can be augmented to be a project creation wizard pretty easily. The important bit is setting project=”true” on your wizard in the plugin.xml file for the Eclipse newWizards extension.

<extension point="org.eclipse.ui.newWizards">
    project="true" ... />

Q: Now that I have a new project wizard how do I know that a project was created using that wizard or is that type of project so that you can create debug or run configurations accordingly?

A: This is where project “Natures” come in. A project can have different natures associated with it to support different functionality in Eclipse. You need to create a class that implements the IProjectNature interface.

public class PhoneGapProjectNature implements IProjectNature

You can reference that project Nature from the plugin.xml through the org.eclipse.core.resources.natures extension point.

<extension id="com.phonegap.phonegapnature" name="PhoneGap Nature"
    <run class="com.phonegap.project.PhoneGapProjectNature"/>
  <builder id="com.phonegap.phonegapbuilder"></builder>

This enables one to connect certain builders to a nature - in the case of PhoneGap we don’t actually use a builder since it is just HTML and JavaScript but we do set and read the nature from the plug-in code.

To set the nature of the project when it is created in the new project wizard we can set the project nature(s) on the project description like this:

IWorkspace workspace = ResourcesPlugin.getWorkspace();
final IProjectDescription description =
description.setNatureIds(new String[] { PhoneGapPlugin.PHONEGAP_NATURE_ID });

In the case of PhoneGap, we use this project nature information in the properties of the Run and Debug configurations such that a developer can create configurations and choose the project that the configuration should launch when they click Run or Debug. In the configuration we iterate over the projects collection of the workspace and check if each project has the PhoneGap nature, if it does we add it to a combo box.

boolean bb = projects[i].hasNature(PhoneGapPlugin.PHONEGAP_NATURE_ID);
if (projects[i].hasNature(PhoneGapPlugin.PHONEGAP_NATURE_ID)) {

Q: How do I store preferences and configuration default values?

A: In your AddLaunch method of the LaunchAdder, which you call from the createProject method of your NewProjecWizard class like this:

  projectHandle.getName(), "");

you will need have some code like this:

ILaunchConfigurationWorkingCopy wc = DebugPlugin.getDefault()
.newInstance(null, DebugPlugin.getDefault()
wc.setAttribute("KEY", "value");
final ILaunchConfiguration config = wc.doSave();

Q: How do I access resources like files to populate a new project with?

A: Put any files that you will want to copy to a project into a namespace like com.phonegap.resources then you can access it like this:

String rootContent = StreamUtils.readContent(
this.getClass().getResourceAsStream("/com/phonegap/resources/root.html"), null

Where StreamUtils is just a wrapper for doing the stream reading.

Q: I am getting a “class not found” error when I debug what should I do?

A: Get Eclipse 3.4 if you don’t already have it.

Q: I want to support the debug / run menus but to do that I need org.eclipse.debug.ui/core references - where do I find those?

A: Add them to the dependcies list in the plugin.xml visual editor. First add core then the ui one will be available.

That’s about all I can muster for the moment but will try to put up some more tips later!

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* PhoneGap Project

Posted on March 24th, 2009 by Dave Johnson. Filed under phonegap, programming.

So I started putting together some wireframes for my first real PhoneGap project tonight. I have become sort of bored playing with BlackBerry and Android native development and figured it was about time to actually build something on top of the platform. The only problem I am having is that I can’t currently do offline apps on BlackBerry so am really looking forward to the next version of the RIM OS as I hear they may have fixed some of my gripes.

In the mean time I have been working on the PhoneGap simulator and Eclipse plugin as well that should be ready very soon - I actually have the simulator launching from my Eclipse PhoneGap project which is pretty cool.

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* PhoneGap Eclipse Plugin

Posted on February 18th, 2009 by Dave Johnson. Filed under Uncategorized, phonegap.

I have been putting this off for a while but finally got around to getting some Eclipse Plugin action going for PhoneGap.

More news on this very soon!

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