DDevelopment & Design

How to change theme in Ext-Gwt (GXT) application

  • byRafal P
  • August 13, 2010
  • 2 minute read

Some time ago Sencha company included new theme in their GXT library. It’s called SLATE and can be viewed in GXT Explorer demo on this site: http://www.sencha.com/examples/explorer.html. I’ve been searching, but I coudn’t find any clear information in web, how to made my gwt app to change theme to new skin instead of standard BLUE or GREY themes. After short investigating I realized, that everything is easy, but only if You keep standard paths in Your app to css/images.

First of all You have to copy to Your’s project directory some directories from GXT example zip file (can be downloaded here: http://www.sencha.com/products/gwt/download.php). Those directories are: css (with BLUE/GREY theme’s csses), images (all gxt standard images) and themes (new SLATE theme). They can be found in resource directory in gxt-x.x.x zip file.

Now, after copying directories to own app in gwt html entry point file it has to be placed following line:   < link rel=”stylesheet” type=”text/css” href=”css/gxt-all.css” /&rt;   That’s all. Nothing more gxt’s csses have to be included (instead of what I’ve found on internet). Why ? Becouse we will switch theme in java code later. In apps entry point java file in onModuleLoad() method we need to insert some code. We want to tell GXT, that we will be using SLATE theme as default, but we would like to change it later. This is made by passing ‘false’ parameter in .setDefaultTheme(..) method. Code for this:   ThemeManager.register(Slate.SLATE); //register non standard theme // Theme.GRAY.set(“file”,”css/gxt-gray.css”); //set custom css’es path for grey theme // Theme.BLUE.set(“file”,”css/gxt-all.css”); //set custom css’es path for standard blue theme // Slate.SLATE.set(“file”,”gxt/themes/slate/css/xtheme-slate.css”); //set custom path for SLATE theme GXT.setDefaultTheme(Slate.SLATE, false); //set default theme to new SLATE skin

That’s not all. If we would like to rearange our paths (i.e. by moving themes/images/css directories in other places) we have to uncoment commented code and set proper paths.

Because we would like to allow user to switch theme by own. We have to add somewhere in our app’s panels ThemeSelector which will do all work. It’s very easy. Just add somewhere this code:

  [ourContainer].add(new ThemeSelector());

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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.