DDevelopment & Design

Running Qt4 Examples on Embedded Linux using ARM emulator

In this article I will show how to run Qt4-Embedded Examples on Angstrom Linux using QEMU. The procedure doesn’t require any compilation or cross compilation. It uses Angstrom Linux precompiled packages, online image builder, and works both on Windows and Linux. Qt4 Embedded allows to run Qt applications directly in Linux Framebuffer, bypassing X Windows completely. This is especially important during embedded development, because it allows to save a lot of memory and start up time. Qt4 has a rich set of examples directly embedded into Qt sources. Below is a few samples of how it looks like:

I will show how to run them. First, you need to install QEMU. For Windows, the easiest way is to download zipped executables, which I shared here:

Qemu-windows-0151. For Linux it’s usually apt-get install qemu-system. Then, we need to build Angstrom image. For those unpatient, I shared a prebuilt image here: angstrom-qt4-embedded. Angstrom has online image builder available here: Angstrom Image Builder. You need to pick console image and download it. The small trick is that you need to download kernel image yourself (from here: kernel-image-2.6.37.2_2.6.37-r4.6_qemuarm.ipk) and unpack it using ar -x kernel-image.ipk command. This is because online image builder doesn’t include kernel image for some reason. However this step is not required if you download the image I shared. Next, you need to start QEMU using kernel image and prebuilt angstrom image. The command looks like this: qemu-system-arm -M versatilepb -usb -usbdevice wacom-tablet -show-cursor -m 64 -kernel zImage-2.6.37.2 -hda disk.img -append “root=/dev/sda2 rw” For convenience, I prepared run script, which does that. Next, you need to login as root and install qt4-embedded using command: opkg install qt4-embedded. This can be again skipped if you use the image I prepared. In order to run demos, you need to use this command: qtdemoE -qws It looks like this:

You can run the other examples from Qt, in standalone mode from

/usr/bin/qtopia directory. You need to use similar command app -qws. The command is required to initialize Qt framebuffer. It is possible to run a few executables on the same display. In order to do this, you need to run the first one only with qws parameter. The other apps will connect to it. Have fun!

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DDevelopment & Design

Sonar Gerrit Plugin Release

I am happy to announce a first release of my Sonar Gerrit plugin. This plugin reports Sonar violations on your patchsets to your Gerrit server. Sonar analyses full project, but only files included in patchset are commented on Gerrit. Please forward to project page for installation instructions. This plugin is intended to use with Gerrit Trigger plugin for Jenkins CI server. Together they provide a great tool for automatic static code analysis.I am happy to announce a first release of my Sonar Gerrit plugin. This plugin reports Sonar violations on your patchsets to your Gerrit server. Sonar analyses full project, but only files included in patchset are commented on Gerrit. Please forward to project page for installation instructions. This plugin is intended to use with Gerrit Trigger plugin for Jenkins CI server. Together they provide a great tool for automatic static code analysis.
DDevelopment & Design

Phonegap / Cordova and cross domain ssl request problem on android.

In one app I have participated, there was a use case:
  • User fill up a form.
  • User submit the form.
  • System send data via https to server and show a response.
During development there wasn’t any problem, but when we were going to release production version then some unsuspected situation occurred. I prepare the production version accordingly with standard flow for Android environment:
  • ant release
  • align
  • signing
During conduct tests on that version, every time I try to submit the form, a connection error appear. In that situation, at the first you should check whitelist in cordova settings. Every URL you want to connect to, must be explicit type in: 
res/xml/cordova.xml
If whitelist looks fine, the error is most likely caused by inner implementation of Android System. The Android WebView does not allow by default self-signed SSL certs. When app is debug-signed the SSL error is ignored, but if app is release-signed connection to untrusted services is blocked.



Workaround


You have to remember that secure connection to service with self-signed certificate is risky and unrecommended. But if you know what you are doing there is some workaround of the security problem. Behavior of method 
CordovaWebViewClient.onReceivedSslError
must be changed.


Thus add new class extended CordovaWebViewClient and override ‘onReceivedSslError’. I strongly suggest to implement custom onReceiveSslError as secure as possible. I know that the problem occours when app try connect to example.domain.com and in spite of self signed certificate the domain is trusted, so only for that case the SslError is ignored. 

public class MyWebViewClient extends CordovaWebViewClient {

   private static final String TAG = MyWebViewClient.class.getName();
   private static final String AVAILABLE_SLL_CN 
                               = "example.domain.com";

   public MyWebViewClient(DroidGap ctx) {
       super(ctx);
   }

   @Override
   public void onReceivedSslError(WebView view, 
                                  SslErrorHandler handler, 
                                  android.net.http.SslError error) {

       String errorSourceCName = error.getCertificate().
                                  getIssuedTo().getCName();

       if( AVAILABLE_SLL_CN.equals(errorSourceCName) ) {
           Log.i(TAG, "Detect ssl connection error: " + 
                       error.toString() + 
                       „ so the error is ignored”);

           handler.proceed();
           return;
       }

       super.onReceivedSslError(view, handler, error);
   }
}
Next step is forcing yours app to  use custom implementation of WebViewClient. 

public class Start extends DroidGap
{
   private static final String TAG = Start.class.getName();

   @Override
   public void onCreate(Bundle savedInstanceState)
   {
       super.onCreate(savedInstanceState);
       super.setIntegerProperty("splashscreen", R.drawable.splash);
       super.init();

       MyWebViewClient myWebViewClient = new MyWebViewClient(this);
       myWebViewClient.setWebView(this.appView);

       this.appView.setWebViewClient(myWebViewClient);
       
       // yours code

   }
}
That is all ypu have to do if minSdk of yours app is greater or equals 8. In older version of Android there is no class 
android.net.http.SslError
So in class MyCordovaWebViewClient class there are errors because compliator doesn’t see SslError class. Fortunately Android is(was) open source, so it is easy to find source of the class. There is no inpediments to ‘upgrade’ app and just add the file to project. I suggest to keep original packages. Thus after all operations the source tree looks like:

Class SslError placed in source tree. 
 Now the app created in release mode can connect via https to services with self-signed SSl certificates.