I had been wanting to have a play around with the native process classes that were added in AIR 2 for quite some time, but only recently managed to get around to doing so. Something that had always bugged me with AIR (and the Flash platform in general) was the lack of any way of getting the screen mouse position when the application wasn't being interacted with. So as a way of experimenting with the native process feature I wrote a little AIR application that interacts with a c++ process and outputs the mouse position at all times.
Starting and interacting with a native process from AIR is actually pretty straightforward. It is essentially a case of setting up a NativeProcessStartupInfo object, a NativeProcess object and adding event listeners to the NativeProcess. Here is this section in the example application:
This is in fact all the Actionscript code in the example. Application complete calls onAppComplete which checks if native process is supported. If so a NativeProcessStartupInfo is created and a reference to the process file set on it's executable property. This is then passed to a NativeProcess object, which is started and has several listeners added to it.
Of the listeners added the most important to this example is ProgressEvent.STANDARD_OUTPUT_DATA. This listens for updates to the process' standard output, and updates the output variable in the application.
The second part to this example is the c++ application. Before I go into this I'd like to note that I'm no c++ developer, so there are probably faster/cleaner/better ways to go about what I have done. Below is the code for the small application used:
This program takes the current mouse position, converts it to a string of the form 'x : y' and outputs it on the standard output. This is done on an infinite loop every 100 milliseconds. This output is picked up by the AIR application and displayed as described earlier.
This program is built and bundled with the AIR application, which is then built as a native installer for Windows. This is one of the limitations of using native processes. You have to build the application as a native application, which means having to do it for each individual platform you intend it to be deployed on. In this examples case, it will only work on Windows, because the underlying process will only work on Windows. Although it could be built to work on other platforms, doing so would add effort and potential problems.
The c++ element of this example was build using Microsoft Visual c++ 2010 Express as a Win32 console application.