MiamiCoder

Debugging Your BlackBerry Application’s Server Code with Visual Studio

Jorge — Mon, 01 Jun 2009 18:17:34 -0700

This is how you debug the .NET server code that handles your BlackBerry application’s requests. You can set breakpoints in the server page or module and have them hit when the BlackBerry simulator makes a request to the server. The steps below use my end-to-end BlackBerry application as an example.

Open the solution with Visual Studio and set the web application, KowledgeBase.Web.UI in this case, as the startup project.
Open the web project’s properties, Web tab. Set the handler (BBHandler.ashx) as the start page.
Set breakpoints in the handler’s code and start the debugger
Browse to the handler page. See how the breakpoint is hit. Press F5 to go past the breakpoints and allow the ProcessRequest function to return. Now the debugger is attached and you can move on to the BlackBerry project.
Start the BlackBerry MDS simulator.
Start debugging your BlackBerry project in your favorite IDE. Make sure the BlackBerry application is pointing to your server project's URL. You can grab this URL from your browser's address bar, since VS pointed the browser to it.
Now you can exercise the functionality that talks to the server. You should be able to step through the server code once you hit the first breakpoint in it.

Why Prices at the Supermarket Are Not Dropping. Four Reasons to Be Cynical

Jorge — Sun, 03 May 2009 01:29:23 -0700

A post on the Consumer Reports Money & Shopping Blog focuses on the fact that after the economic slowdown, while commodities costs sunk, prices at the supermarket and the pump did not drop as quickly, and prices of some goods actually kept rising.

According to different experts, there are at least four arguments companies use to justify their reluctance to drop prices:

Fear of a price war. Rather than production costs, prices are dictated by what the competition charges. Price wars ensue when competitors lower their prices. And the fear of tumbling profits because a price war makes stores keep their prices unchanged.

Manufacturers do not want to disappoint you. Since manufacturers think the bonanza will not last, it does not make sense to drop prices now and risk creating tension with the customers down the road, when prices will be hiked again.

You would not appreciate it. While people feel great pain from price increases, they tend to be less appreciative of price decreases. If companies are not sure that the decreases are going to last, it does not make sense for them to drop prices.

It is your turn to help. Companies not always burden the consumers with their extra costs. Keeping prices high is a way to recoup lost profits for companies whose price hikes were not enough to fully cover their own costs.

After reading these explanations, is there reason to shout conspiracy?

The Daily Stand-up Meetings Remind Me That…

Jorge — Sun, 26 Apr 2009 14:42:45 -0700

In no particular order:

There are plenty of reasons for a programmer to lose focus in a four-hour period.

Sometimes my boss goes directly to a developer and tries to reprioritize her tasks.

Learning the business domain by osmosis is not enough for most programmers.

Overanalysis and featuritis must be fought daily.

Overanalyzer and great coder are not synonyms.

It's hard for a programmer to explain what they are doing, even to another programmer.

Knowledge of, and love for the testing discipline, do not come spontaneously.

"Please create unit tests" does not do the trick.

"Please enter the bugs in the tracking system" does not work either.

If something can possibly be misunderstood, it will be misunderstood. If it can't possibly be misunderstood, guess what?

Ext JS With ASP.NET MVC Sample

Jorge — Sat, 21 Mar 2009 22:52:00 -0700

This is a simple example of how you can use Ext JS and ASP.NET MVC together. The scenario is the same I have used in my previous Ext JS with PHP articles: I am going to display a number of fictitious categories using an Ext JS combo box. In this case, the combo box items’ data – the categories – will be served by an ASP.NET MVC application.

The MVC application

When I create the ASP.NET MVC application, Visual Studio builds a default folder structure where the main components of the application are distributed like this:

The Controllers folder is where you put Controller classes that handle URL requests
The Models folder will contain classes that represent and manipulate data
Views is the folder where you put UI template files that are responsible for rendering output
Scripts is where you put JavaScript library files and scripts
Content is where you put CSS and image files, and other non-dynamic/non-JavaScript content
App_Data is where you store data files you want to read/write

Large applications will likely use multiple Visual Studio projects, but I will stick to this default structure in order to keep the example simple.

The View

In a model-view-controller scenario the View renders entities from the Model into a form suitable for interaction. The View in this example is the html page containing the Categories combo box.

I called this page combo.html, and the Ext JS components I use are a ComboBox and a JsonStore:

Ext.onReady(function() {

    var categoriesStore = new Ext.data.JsonStore({
        url: 'http://localhost/MvcApp/Categories',
        root: 'Categories',
        fields: ['Id', 'Name']
    });

    var combo = new Ext.form.ComboBox({
        store: categoriesStore,
        displayField: 'Name',
        valueField: 'Id',
        typeAhead: true,
        mode: 'remote',
        forceSelection: true,
        triggerAction: 'all',
        emptyText: 'Select a category...',
        selectOnFocus: true,
        applyTo: 'categories-combo'
    });
});

The Controller

To adhere to the default url routing rules in ASP.NET MVC, the Controller is named CategoriesController. This will permit that requests to the http://localhost/MvcApp/Categories url in the view (combo.html) get routed to my Controller.

CategoriesController will handle the View requests and will ask the Model to produce the needed data:

public JsonResult Index() {

    CategoriesContainer container = CategoriesDataContext.GetCategories();

    return  this.Json(container);

}

When a request is made to the http://localhost/MvcApp/Categories url, the Index() method will be executed. Note that the return value of Index() is of type JsonResult and not ActionResult. This indicates that the method returns JSON-encoded data. The encoding is acomplished with the call to Controller.Json() .

CategoriesContainer and CategoriesDataContext are part of the Model. Let’s now take a look at them.

Building the Model

The term “model” refers to the objects that represent the data of the application, as well as the corresponding domain logic with the business rules and validation. CategoriesContainer is a Class that exposes an array of Category objects:

public class CategoriesContainer
{
    public Category[] Categories { get; set; }
}

A key point here is that when serialized to JSON, an instance of CategoriesContainer will have the signature the View’s JsonStore is expecting.

CategoriesDataContext creates the categories data. In a real-world application this would likely be more involved than simply hard-coding the data. :-)

public class CategoriesDataContext
{
    public static CategoriesContainer GetCategories() {
        Category[] categoriesArray = new Category[10];
        for (int i = 0; i < 10; i++) {
            Category category = new Category { Id = i, Name = "Category " + i.ToString() };
            categoriesArray[i] = category;
        }
        CategoriesContainer container = new CategoriesContainer();
        container.Categories = categoriesArray;
        return container;
    }
}

And last, the definition of a category can be something as simple as this Category Class:

public class Category
{
    public int Id {get;set;}
    public string Name {get;set;}
}

Downloads

Download the full sample from my downloads page.

How to Add a Simulator to the BlackBerry JDE

Jorge — Wed, 25 Feb 2009 20:54:00 -0700

I am currently fixing a problem with one of our BlackBerry applications. The problem only shows on the 8330 devices and while trying to debug it, I realized that the 8330’s simulator was not showing in the JDE’s list of available simulators.

In this post I will explain what I did to add the 8330’s simulator to the list of available profiles.

After downloading the 8330 simulator pakage from the BlackBerry developers site and installing it, I opened the SimPackage-JDE.rc file located in the JDE installation folder (You can open it with a text editor). This file, which contains a couple of entries per simulator profile, is the settings file used by the JDE to run the different simulators. This is how the entries look:

## RIM Java Development Environment
# Settings file
SimulatorCommand7130-JDE=<install_dir>\fledge.exe /app=Jvm.dll /handheld=7130 /session=7130 /app-param=DisableRegistration /app-param=JvmAlxConfigFile:7130.xml /data-port=0x4d44 /data-port=0x4d4e /pin=0x2100000A
SimulatorDirectory7130-JDE=<install_dir>
SimulatorCommand7130e-JDE=<install_dir>\fledge.exe /app=Jvm.dll /handheld=7130e /session=7130e /app-param=DisableRegistration /app-param=JvmAlxConfigFile:7130e.xml /data-port=0x4d44 /data-port=0x4d4e /pin=0x2100000A
SimulatorDirectory7130e-JDE=<install_dir>
SimulatorCommand8100-JDE=<install_dir>\fledge.exe /app=Jvm.dll /handheld=8100 /session=8100 /app-param=DisableRegistration /app-param=JvmAlxConfigFile:8100.xml /data-port=0x4d44 /data-port=0x4d4e /pin=0x2100000A
SimulatorDirectory8100-JDE=<install_dir>

As you can see, each simulator’s settings consist of an entry that specifies the command used to run the simulator and an entry that specifies the folder where the simulator resides.

Knowing this, I created two more entries form my just-installed simulator. In this case, instead of using the <install_dir> placeholder, I used the actual path to the simulator. I also used the command line parameters for the 8330 simulator, which I grabbed from the 8330.bat file in C:\Program Files\Research In Motion\BlackBerry Smartphone Simulators 4.3.0\4.3.0.124 (8330):

SimulatorCommand8800-JDE="C:\Program Files\Research In Motion\BlackBerry Smartphone Simulators 4.3.0\4.3.0.124 (8330)\fledge.exe /app=Jvm.dll" /handheld=8330 /session=8330 /app-param=DisableRegistration /app-param=JvmAlxConfigFile:8330.xml /data-port=0x4d44 /data-port=0x4d4e /pin=0x2100000A
SimulatorDirectory8800-JDE="C:\Program Files\Research In Motion\BlackBerry Smartphone Simulators 4.3.0\4.3.0.124 (8330)"

After doing this, the 8330’s profile showed in the JDE’s simulators list:

Ext JS And PHP – Grid Panel Sample

Jorge — Wed, 11 Feb 2009 21:12:00 -0700

Continuing with the theme of my previous post, here is another ExtJS and PHP sample. This time my PHP page will be serving data to populate a grid panel.

Like the combo box in the previous post, the grid is going to display a list of categories sent from the webpage. This is the grid panel’s definition:

     var grid = new Ext.grid.GridPanel({

        store: categoriesStore,

        columns: [

            { id: 'id', header: "Id", width: 20, sortable: true, dataIndex: 'id' },

            { id:'name', header: "Category Name", width: 75, sortable: true, dataIndex: 'name' }

        ],

        stripeRows: true,

        autoExpandColumn: 'name',

        height: 350,

        width: 600,

        title: 'Categories'

    });

    grid.render('grid-example');

The JSON representation of the categories data will have the following form:

    {'categories':

            [{'id':'1', 'name':'Category 1'},

            {'id':'2', 'name':'Category 2'},

            {'id':'3', 'name':'Category 3'},

            {'id':'4', 'name':'Category 4'},

            {'id':'5', 'name':'Category 5'},

            {'id':'6', 'name':'Category 6'}]

    }

The categoriesStore data store points to the PHP page where I will retrieve the categories information from a MySQL database:

    var categoriesStore = new Ext.data.JsonStore({

        url: 'categories.php',

        root: 'categories',

        fields: ['id', 'name']

    });

And this is the PHP page:

    <?php

    function GetCategories() {

      $query = "SELECT * FROM `categories`";

      $categories = array("categories" => array());

      $conn = OpenDbConnection();

      $result = mysql_query($query);

      $num = mysql_numrows($result);

      $i = 0;

      while ($row = mysql_fetch_assoc($result)) {

        $categories["categories"][$i] = $row;

        $i++;

      }

      CloseDbConnection($conn);

      return json_encode($categories);

    }

    echo GetCategories();

    ?>

Where to find more information

Additional information about the topics covered by this post can be found in the ExtJS tutorials page and the PHP documentation.

Ext JS And PHP Sample

Jorge — Thu, 05 Feb 2009 21:48:00 -0700

In this post I will demonstrate how you can use PHP to back your Ext JS-based user interface.

One of the advantages of Ext JS and other javascript frameworks is the degree of compartmentalization you can achieve between the user interface and other pieces of your website or application. The most visible of the different factors that promote this compartmentalization, is the physical separation among the deployed application modules -- while the majority of business logic and data handling modules usually reside on the server, in general, the user interface lives within the confines of the browser.

It’s all about generating JSON

Reliable and efficient communications between the client-side and server-side elements of the system becomes a critical need in this scenario. Like most javascript frameworks, Ext JS uses JSON as its primary data interchange format. Regardless of the back-end technology you choose (PHP, .NET, Java, etc.), if you produce http responses containing JSON-encoded data, you will be able to relay information to Ext JS.

Let’s examine a couple of ways to create JSON-encoded data with PHP. For my examples, I will assume that I need to send to the browser the data needed to populate a combo box that will display a list of categories.

This is the definition of my Ext JS combo box:

    var combo = new Ext.form.ComboBox({

        store: categoriesStore,

        displayField: 'name',

        valueField:'id',

        typeAhead: true,

        mode: 'remote',

        forceSelection: true,

        triggerAction: 'all',

        emptyText: 'Select a category...',

        selectOnFocus: true,

        applyTo: 'categories-combo'

    });

The categoriesStore data store is a JsonStore that points to a PHP page where I will create the categories data:

    var categoriesStore = new Ext.data.JsonStore({

        url: 'categories.php',

        root: 'categories',

        fields: ['id', 'name']

    });

As defined in the store, the data will need to have a form similar to this:

    {'categories':

            [{'id':'1', 'name':'Category 1'},

            {'id':'2', 'name':'Category 2'},

            {'id':'3', 'name':'Category 3'},

            {'id':'4', 'name':'Category 4'},

            {'id':'5', 'name':'Category 5'},

            {'id':'6', 'name':'Category 6'}]

    }

The above is just a JSON representation of an object containing a categories array. Each array element is an object that represents a category, which in turn has two properties: id, and name. Our categories.php page will need to produce this data and send it to the browser.

Hand-crafting a JSON representation of an object

The first approach I will show you consists of hand-crafting the JSON representation of the categories object. Although PHP has facilities for creating JSON-encoded data, I recommend you try this approach as a way to get familiar with the JSON structures. This is how the PHP page would look like:

    <?php

    function GetCategories() {

        $categories = "{'categories':[";

        $categories .= "{'id':'1', 'name':'Category 1'},";

        $categories .= "{'id':'2', 'name':'Category 2'},";

        $categories .= "{'id':'3', 'name':'Category 3'},";

        $categories .= "{'id':'4', 'name':'Category 4'},";

        $categories .= "{'id':'5', 'name':'Category 5'},";

        $categories .= "{'id':'6', 'name':'Category 6'}";

        $categories .= "]}";

        return $categories;

    }

    echo GetCategories();

    ?>

In a more realistic scenario the categories information could have been obtained through a database call. Let’s assume I will use MySQL as the database and change the page like so:

    <?php

    function GetCategories() {

      $categories = "{}";

      $conn = OpenDbConnection();

      $query ="SELECT * FROM `categories`";

      $result=mysql_query($query);

      $num=mysql_numrows($result);

      if (0 != $num) {

        $i=0;

        $categories = "{'categories':[";

        while ($i < $num) {

          $id = mysql_result($result,$i,"category_id");

          $name = mysql_result($result,$i,"category_name");

          $categories .= "{'id':'" . $id . "','name':'" . $name . "'}";

          $i++;

          if ($i < $num) {

            $categories .= ",";

          }

        }

        $categories .= "]}";

      }

      CloseDbConnection($conn);

      return $categories;

    }

    echo GetCategories();

    ?>

Here I just transformed the query results into a JSON-encoded string in the form that my Ext JS ComboBox needs.

The second approach I want to show you uses a PHP facility for JSON-encoding strings.

Using PHP’s JSON manipulation functions

Json_encode($value) is a function that returns a string containing the JSON representation of a value. In the code below I create and populate a two-dimensional array that contains the categories information, which I then pass to the json_encode function.

    <?php

    function GetCategories() {

      $query = "SELECT * FROM `categories`";

      $categories = array("categories" => array());

      $conn = OpenDbConnection();

      $result = mysql_query($query);

      $num = mysql_numrows($result);

      $i = 0;

      while ($row = mysql_fetch_assoc($result)) {

        $categories["categories"][$i] = $row;

        $i++;

      }

      CloseDbConnection($conn);

      return json_encode($categories);

    }

    echo GetCategories();

    ?>

As you might have expected, using json_encode considerably simplifies creating JSON data. I encourage you to read its documentation to gain full understanding of its capabilities and limitations.

These examples are a good foundation for you to build upon when working with PHP and Ext JS. I hope you find them useful. And don’t forget that these approaches also apply when working with other javascript frameworks.

Where to find more information

You can find additional information on the subject of this post by visiting the Ext JS tutorials page and the PHP documentation.

How to Set a Rollover Icon for Your BlackBerry Application

Jorge — Sat, 24 Jan 2009 12:03:00 -0700

In this post I will explain the different methods you can use to set the rollover icon that your BlackBerry application will display on the device’s Home Screen.

Accompanying sample code is available here.

First, get the right icon size and resolution for your device and theme

You have probably observed that the size of the application’s icon is not the same across device models and themes. This is a consequence of the different screen sizes and evolving graphic capabilities of the smartphones.

The following table lists the different device models and common icon sizes (An up-to-date version of this information can be obtained from the BlackBerry developers Developers Knowledge Base).

Model	Icon Dimensions
BlackBerry® 6200 Series and BlackBerry® 6500 Series	28 x 28
BlackBerry® 7100 Series and BlackBerry® Pearl™ 8100 Series	Icon theme: 60 x 55
BlackBerry® 7100 Series and BlackBerry® Pearl™ 8100 Series	Today and Zen theme: 48 x 36
BlackBerry® 7200 Series and BlackBerry® 7700 Series	32 x 32
BlackBerry® 7290 smartphone	36 x 36
BlackBerry® Curve™ 8300 Series, BlackBerry® 8700 Series, and BlackBerry® 8800 Series	Icon theme: 53 x 48
	Zen theme: 48 X 36
BlackBerry® Bold™ 9000 smartphone	Precision theme: 80 X 80

If you intend to use the same icon on multiple BlackBerry smartphone models, you need to understand how this icon will be displayed. These are the scenarios you will encounter.

On smartphones running BlackBerry Device Software prior to version 4.2, icon images that are larger than the maximum dimensions are cropped.
On smartphones running BlackBerry Device Software version 4.2 to 4.5, if you use an icon with dimensions larger than those displayed on the smartphone, the icon will be scaled down to the device’s maximum icon size. If scaling occurs on an image that is not square and the result is an image that is square (or vice versa), the image may appear distorted.
On smartphones running BlackBerry Device Software version 4.5 or earlier, if you use an icon of the smallest dimensions, it will not be scaled up on the smartphone with a higher resolution. The actual image size will be the same and the remainder of the icon area will be transparent, so the icon will appear smaller than the standard icons.
On devices with Device Software 4.6, icons are scaled in the application grid menu to match the icons of the current theme. If your icon is larger than the current theme icon, the icon is scaled down to match. If it is just marginally smaller, it will be left un-scaled. If it is 25% (or more) smaller, it will be scaled up to match the current theme icon.

Specifying rollover icons in versions of the BlackBerry JDE prior to 4.7

The ability to add a rollover icon to an application was introduced in the BlackBerry API 4.1 set through the function HomeScreen.setRolloverIcon(…). This function sets the icon to use when the application icon is in focus.

Since you need the icon in place before the device user scrolls to your application, the function must be called at startup time. You can achieve this by defining an alternate entry point to the application. This entry point will run on startup and will produce the call to HomeScreen.setRolloverIcon(…).

In order to allow the application to identify when it was launched by the user from the ribbon and when it was started from the alternate entry point, you will configure the alternate entry to pass in an argument to the main() method. If main() encounters this argument, it will proceed to set the rollover icon and exit the application afterwards. In the absence of the argument, the assumption is that the user launched the application from the ribbon and the application should start normally.

The main() method would look like this

     public static void main(String[] args)

    {

       if ( args != null && args.length > 0 && args[0].equals("alternate") ){

          //  Alternate entry point 

          Bitmap icon = Bitmap.getBitmapResource("rollover_icon.png");

          HomeScreen.setRolloverIcon(icon);

       } else {

          //  Main entry point 

          Test theApp = new Test();

          theApp.enterEventDispatcher(); 

       }

    }

Now, there’s an issue in BlackBerry Device Software 4.1 where the HomeScreen.setRolloverIcon(…) method can throw an IllegalArgumentException. This issue has been resolved in BlackBerry Device Software 4.2. You can work around this issue by allowing the application to finish its startup before setting the rollover icon. In code, it would look like this

    public class RolloverIconApp extends UiApplication

    {

        public RolloverIconApp(boolean autoStart)

        {

            if (autoStart)

            {

            // If the application started using the auto start 

            // entry point, we setup the our icons.

            final Bitmap regularIcon = Bitmap.getBitmapResource("unfocused_icon.png");

            final Bitmap rolloverIcon = Bitmap.getBitmapResource("rollover_icon.png");

            invokeLater(new Runnable() 

            {

                public void run() 

                {

                    ApplicationManager myApp =

                      ApplicationManager.getApplicationManager();

                    boolean inStartup = true;

                    while (inStartup)

                    {

                        if (myApp.inStartup())

                        {

                            // Wait for the device to finish the startup process.

                            try

                            {

                                Thread.sleep(1000);

                            }

                            catch (Exception ex)

                            {

                              // TODO: handle exception.

                            }

                        }

                        else

                        {

                            HomeScreen.updateIcon(regularIcon, 0);

                            HomeScreen.setRolloverIcon(rolloverIcon, 0);

                            inStartup = false;

                        }

                     }

                     // We're done setting up the icons. Exit the app.

                     System.exit(0);

                }

            });

        }

        else

        {

             // The application was started by the user, display the UI.

             MainScreen ms = new MainScreen();

             ms.setTitle("Did you see the rollover icon?");

             pushScreen(ms);

        }

      }

        public static void main(String[] args)

        {

            RolloverIconApp theApp;

            //Check for the argument defined in the project properties.

            if (args != null && args.length > 0 && args[0].equals("autostart"))

            {

                theApp = new RolloverIconApp(true);

            } 

             else 

            { 

                theApp = new RolloverIconApp(false);

            }

            theApp.enterEventDispatcher();

        }

    }

Specifying rollover icons in the BlackBerry JDE 4.7

As opposed to previous versions, the BlackBerry JDE 4.7 allows you to specify a rollover icon via the project’s properties. These are the steps you need to follow.

In BlackBerry JDE, right-click the project.
Select Properties.
Select the Resources tab.
Add the non rollover/unfocused application icon in the Icon Files field and add the rollover/focused icon in the Focus Icon Files field.

Setting rollover icons in the BlackBerry JDE Plug-in for Eclipse™

While this option is always present in the BlackBerry® JDE Plug-in for Eclipse™ it will only take effect when the application is built using the BlackBerry JDE Component Package 4.7.0 or later.

In the Eclipse™ Package Explorer, right-click the project.
Select Properties.
Select BlackBerry Project Properties.
Select the Resources tab.
Add the non-rollover/unfocused application icon in the Icon Files field and add the rollover/focused icon in the Focus Icon Files field.

Conclusion

This pretty much covers the information available on the rollover icons topic as of the date of this post. Remember to check the sample project available from the downloads page.

Ease of Use Is Difficult To Achieve

Jorge — Thu, 15 Jan 2009 22:01:00 -0700

A reminder of how fallible we software developers are came last night in the form of a call from my Dad. He was asking for help with his blog. He told me that he went in to “replace one word” in one of his posts and when he was done he noticed that all the images in the post had disappeared. And he didn't know how to bring them back.

Although I was not able to find out how he did it, it is evident that my Dad modified the html of the post in such a way that the image tags were accidentally removed from it.

My Dad is no html connoisseur. He does not need to be one. I am sure the very popular blogging software he prefers was designed with the expectancy that its users do not know html.

The users of my systems are like my Dad. Are the users of your software like him, too?

Most times, users just want to “replace one word”. I think we still have a long road ahead when it comes to making this easy for them.

How to “Spy” On a Windows Program: Tracking Main Window Activation

Jorge — Mon, 24 Nov 2008 12:04:00 -0700

In this article I will walk you through the creation of a sample program that, each time I use any application on my pc, will record the application name, window title and time. While I do this, I will touch on techniques that, used for evil in spyware, are also applied with noble goals in areas like time tracking, application monitoring and computer-aided learning.

Practical information about this subject is hard to find. So, if you have ever been curious about how spyware programs work, how you can keep tabs on what a user does on a computer or how applications behave, read along.

To understand how you can “spy” on a running Windows program, you first need to be familiar with the concept of event-driven applications.

Windows Architecture

Unlike applications that make function calls to obtain user input, Windows-based applications are event-driven. This simply means that they wait for the system to pass input to them.

The system passes all input for an application - for example, when the user types, moves the mouse, or clicks a control such as a scroll bar - to the various windows in the application. This input is passed in the form of messages. Besides the system, other applications can also generate windows messages.

If we could somehow inspect this message traffic, then we would have a way to know what it is that the system or other applications are asking any application to do. This is where you can put Windows Hooks to good use.

Windows Hooks

The MSDN documentation defines a hook as a point in the system message-handling mechanism where an application can install a subroutine to monitor the message traffic in the system and process certain types of messages before they reach the target window procedure.

There are different types of hooks, each providing access to different aspects of the system’s message handling mechanism. For example, keyboard hooks allow you to monitor keyboard messages (keyloggers make use this type of hook), mouse hooks allow you to monitor mouse messages and WindProc hooks allow you to monitor all messages processed by the Window Procedure, the message handling function in any window.

Armed with this knowledge, let’s go back to my sample program.

Tracking Window Activation

We know that when an application window becomes active, it is because the system sent it a message asking it to do so. Then, a way to track application usage is to install a system-wide hook that will inspect the messages the system sends to any application asking it to activate its main window.

To write my sample program I used C#, and to save time used an excellent Windows Hooks library written by Chris Wilson. In my sample program this is what I do:

Install a global Shell hook. This type of hook allows me to intercept the messages sent by the system when a top-level window is activated.
Upon intercepting a message indicating a top-level window activation, I record the time, the name of the application the window belongs to and the text displayed in the window’s title bar.

Sounds good? Let’s look at each step in detail.

The sample program is a Windows Form application with just one form.

Thanks to the excellent hooks library I am using (you can read more about it here), all I need to do to be able to intercept top-level windows activation messages is subscribe to the WindowActivated event and install my shell hook. I subscribe to the event right inside the constructor for my only form.

     public Form1()

    {

        InitializeComponent();

        // Instantiate our GlobalHooks object

        hooks = new GlobalHooks(this.Handle);

        hooks.Shell.WindowActivated += 

            new GlobalHooks.WindowEventHandler(hooks_ShellWindowActivated);

    }

The hook is installed and uninstalled by pushing the “Start Monitoring” and “Stop Monitoring” buttons.

    private void button1_Click(object sender, EventArgs e)

    {

        hooks.Shell.Start();

    }

    private void button2_Click(object sender, EventArgs e)

    {

        hooks.Shell.Stop();

    }

Once the hook is installed, the message handling function of my form will start receiving not only messages directed to it, but also the messages intercepted by the shell hook.

Shell hooks intercept a variety of messages. Since I am just interested in top-level windows activations, I forward the messages to a utility function in the hooks library, which filters them and fires the WindowActivated event when the intercepted event indicates a top-level window activation.

    protected override void WndProc(ref Message m)

    {

        // Send the messages to the library for filtering.

        if (hooks != null)

        hooks.ProcessWindowMessage(ref m);

        base.WndProc(ref m);

    }

Within the WindowActivated event handler, I use the window handle contained in the event arguments to lookup the application name and the window caption. Then I just display them in a listbox, together with the time the window was activated.

    private void hooks_ShellWindowActivated(IntPtr Handle)

    {

        // Insert information at the top of the list.

        listBox1.Items.Insert(0,"");

        listBox1.Items.Insert(0, "Window caption: " + GetWindowCaption(Handle));

        listBox1.Items.Insert(0,"Application: " + GetModuleName(Handle));

        listBox1.Items.Insert(0,string.Format("Time: {0}", DateTime.Now.ToLongTimeString()));

        listBox1.Items.Insert(0, "Window activation!");                

    }

You might have noticed how once you know when a top-level window was activated it becomes really easy to compute the time any application was actively used. I will leave the exercise to you.

Grabbing the window’s caption is accomplished with a call to the GetWindowText API function.

    [DllImport("user32.dll")]

    private static extern int GetWindowText(IntPtr hWnd, StringBuilder title, int size);

    private string GetWindowCaption(IntPtr Hwnd)

    {

        // This function gets the name of a window from its handle

        StringBuilder caption = new StringBuilder(256);

        GetWindowText(Hwnd, caption, 256);

        return caption.ToString().Trim();

    }

Obtaining the application’s executable name is a a little more involved, yet easy.

    [DllImport("user32.dll", SetLastError = true)]

    public static extern uint GetWindowThreadProcessId(IntPtr hWnd, 

      out uint lpdwProcessId);

    [DllImport("kernel32.dll")]

    public static extern IntPtr OpenProcess(ProcessAccessFlags dwDesiredAccess, 

        [MarshalAs(UnmanagedType.Bool)] bool bInheritHandle, uint dwProcessId);

    [DllImport("psapi.dll")]

    public static extern uint GetModuleFileNameEx(IntPtr hProcess, 

      IntPtr hModule, [Out] StringBuilder lpBaseName, 

      [In] [MarshalAs(UnmanagedType.U4)] int nSize);

    [DllImport("kernel32.dll", SetLastError = true)]

    public static extern bool CloseHandle(IntPtr hHandle);

    private string GetModuleName(IntPtr Hwnd)

    {

        uint processId = 0;

        GetWindowThreadProcessId(Hwnd, out processId);

        IntPtr hProcess = OpenProcess(ProcessAccessFlags.QueryInformation | 

          ProcessAccessFlags.VMRead, true, processId);

        StringBuilder FileName = new StringBuilder(256);

        GetModuleFileNameEx(hProcess, IntPtr.Zero, FileName, 256);

        CloseHandle(hProcess);

        return FileName.ToString().Trim();

    }

And that is it. I hope you found the topic interesting and the sample useful. You can download the source for the sample from the downloads page.

Mobile Application Development Tips: Preventing Unbounded Result Sets

Jorge — Sat, 01 Nov 2008 17:34:00 -0700

An issue that too many times goes overlooked is the possibility that database queries return more data (rows) than what your application can handle.

It is typical for applications to send a query to the database and process each row of the result set. Often times, this processing is accompanied by the creation of a data structure (list, collection, etc.) that holds a one or more business objects derived from the query results.

Unbounded result sets are a threat to your mobile application

Do you know what would happen if your mobile application sent a query to the database and received a million rows instead of a hundred? Or if it made a request to a web service and received a collection with ten thousand objects? A cause of countless problems on application servers, unbounded result sets are also a threat to your mobile applications. Given the memory and processing constraints in mobile devices, paying attention to this issue is of particular importance.

Result sets without bounds are more likely to occur when your application makes a request without specifying what type of response it can accept and how much of it can process. You are also asking for trouble when your application blindly trusts the systems it calls, database server included.

An ounce of prevention…

So, what are some of the measures you can take to prevent the occurrence of unbounded result sets?

Limit the number of retrieved rows. If you have control over the data access code, limit the number of rows you retrieve in your queries. Remember Murphy's_Law. Even when you know that a table will never have more than fifty rows, write your SQL code so it retrieves no more than fifty rows.

     -- MySQL

    select client_id, client_name from clients

    limit 50

Limit the number of elements in retrieved collections. Design your web services routines so they accept a parameter indicating the maximum number of elements you are prepared to process.

     
    int maxNumberOfClients = 50;

    List<Client> clients = service.GetClients(maxNumberOfClients);

Break out of loops. When looping over elements of a result set or a collection, break out when you reach the maximum number of elements you can process. Although this measure does not avoid the retrieval of all the results, it stops the pernicious effects from propagating to other areas of your application.

    int clientsCount = 0;

    int maxClients = 50;

    foreach (DataRow clientRow in clientsTable.Rows) {

        Client client = Client.FromDataRow(clientRow);

        clientsList.Add(client);

        clientsCount ++;

        if (maxClients == clientsCount ) break;

    }

Conclusion

I hope you find this helpful. As usual, let me know your thoughts!

Ext JS Sample: Dynamically Adding Components to a Container

Jorge — Thu, 09 Oct 2008 18:13:00 -0700

How do you go about creating Ext JS components on the fly?

I have been working on a reports viewer web application that uses Ext JS. Its main goal is to allow users to type in or select values for the parameters of any report available, run the report and view the results.

For this application, the available reports are not known beforehand, and one of the challenges I am facing is the fact that the user interface elements that will allow users to enter values for the report parameters need to be created and added to their containers on the fly, upon reading a report definition file for the report selected by the user.

Here is a simplified version of the approach I am taking. Even though I am not an Ext JS expert, I am presenting it hoping that it will help some of you.

First, I created a few helper functions that build the different UI elements I am going to need, combo boxes, radio groups, checkbox groups, etc.

     function CreateComboBox() {

        var combo = new Ext.form.ComboBox({

            store: CreateSimpleStore(),

            displayField: 'name',

            typeAhead: true,

            mode: 'local',

            forceSelection: true,

            triggerAction: 'all',

            emptyText: 'Select item...',

            selectOnFocus: true,

            fieldLabel: 'ComboBox'

        });

        return combo;

    }

    function CreateCheckBoxGroup() {

        var grp = new Ext.form.CheckboxGroup({

            fieldLabel: 'CheckboxGroup',

            columns: 1,

            items: [{boxLabel: 'Box 1', checked: true}, {boxLabel: 'Box 2', checked: false}]

        });

        return grp;

    }

    function CreateRadioButtonGroup() {

        var grp = new Ext.form.RadioGroup({

            fieldLabel: 'RadioGroup',

            columns: 1,

            items: [{ boxLabel: 'Radio 1', checked: true }, { boxLabel: 'Radio 2', checked: false}]

        });

        return grp;

    }

And then I wrote a function that, called once a report definition has been retrieved from the server, will dynamically compose the required user interface elements and add them to their container.

    function AddControlsHandler(button, evt) {

        switch (button.text) {

            case 'Add ComboBox':

               mainPanel.add(CreateComboBox());

               mainPanel.doLayout();

               break;

           case 'Add CheckboxGroup':

               mainPanel.add(CreateCheckBoxGroup());

               mainPanel.doLayout();

               break;

           case 'Add RadioGroup':

               mainPanel.add(CreateRadioButtonGroup());

               mainPanel.doLayout();

               break;

        }

    }

I hope this is useful. Please let me know about the approaches you use. I am sure that, like with any other software topic, there are many ways to tackle the challenge presented here.

Downloads

Download the full sample from my downloads page.

How to Embed Images in the Body of an Email Message

Jorge — Sat, 04 Oct 2008 00:05:00 -0700

Another very simple C# sample based on a mail merge application I have been working on. This time I would like to show you how to use the System.Net.Mail facilities to programmatically embed images in the html body of an email.

     public static void SendMessage(string server, 

        string from, string to, string cc, string bcc,

        string subject, string body, List<string> attachments,

        string[] embeddedFiles)

    {

        MailMessage message = new MailMessage(from, to);

        message.Subject = subject;

        string[] ccArray = cc.Split(';');

        if (ccArray.Length > 0)

        {

            foreach (string address in ccArray)

            {

                if (address.Length > 0)

                {

                    message.CC.Add(new MailAddress(address));

                }

            }

        }

        string[] bccArray = bcc.Split(';');                

        if (bccArray.Length > 0)

        {

            foreach (string address in bccArray)

            {

                if (address.Length > 0)

                {

                    message.Bcc.Add(new MailAddress(address));

                }

            }

        }

        message.IsBodyHtml = true;

        if (null != embeddedFiles && embeddedFiles.Length > 0)

        {

            foreach (string filePath in embeddedFiles)

            {

                string fileName = Path.GetFileName(filePath);

                body = body.Replace(fileName, "cid:" + fileName);

            }

            AlternateView view = AlternateView.CreateAlternateViewFromString(body,

                null,MediaTypeNames.Text.Html);

            foreach (string filePath in embeddedFiles) {

                LinkedResource res = new LinkedResource(filePath);

                res.ContentId = Path.GetFileName(filePath);

                view.LinkedResources.Add(res);

            }

            message.AlternateViews.Add(view);

        } else {

            message.Body = body;

        }

        foreach (string file in attachments) {

            Attachment data = new Attachment(file);

            message.Attachments.Add(data);

        }

        SmtpClient client = new SmtpClient(server);

        client.Credentials = CredentialCache.DefaultNetworkCredentials;

        client.Send(message);

    }

The trick here consists in creating an AlternateView instance for the body of the email and adding the images to this view via LinkedResource instances. Also, note how the paths to the original images inside de html body are replaced with unique identifiers that map to their embedded siblings.

More details on this approach can be found here.

Programmatically Accessing Mail Merge Fields in MS Word Documents

Jorge — Fri, 03 Oct 2008 21:33:00 -0700

I have been working on a mail merge application that will allow for sending messages from a desktop computer by connecting directly to an SMTP server and not using the installed email client.

Based on this application’s code, this simple C# example shows how to programmatically replace a mail merge field in a Microsoft Word document with a desired value.

     using Word = Microsoft.Office.Interop.Word;

    ...

    public static void ReplaceMailMergeField(string msWordFileName, 

        string mailMergeFieldName, string mailMergeFieldDesiredValue)

    {          

        object docName = msWordFileName;

        object missing = Missing.Value;

        Word.MailMerge mailMerge;

        Word._Document doc;

        Word.Application app = new Word.Application();

        // Hide MS Word's window.

        app.Visible = false;

        doc = app.Documents.Open(ref docName,

            ref missing, ref missing, ref missing, ref missing, 

            ref missing, ref missing, ref missing, ref missing,

            ref missing, ref missing, ref missing, ref missing, 

            ref missing, ref missing, ref missing);

        mailMerge = doc.MailMerge;

        // Try to find the field name.

        foreach (Word.MailMergeField f in mailMerge.Fields)

        {

            // Assuming the field code is: MERGEFIELD  "mailMergeFieldName"

            if (f.Code.Text.IndexOf("MERGEFIELD  \"" + mailMergeFieldName +"\"") > -1)

            {

                f.Select();

               // Replace selected field with supplied value.

                app.Selection.TypeText(mailMergeFieldDesiredValue);

            }

        }

        // Save changes and close MS Word.

        object saveChanges = Word.WdSaveOptions.wdSaveChanges;

        doc.Close(ref saveChanges, ref missing, ref missing);

        app.Quit(ref missing, ref missing, ref missing);

    }

I hope you find this sample helpful.

Optimized HTTP Handling for Your BlackBerry Java Application

Jorge — Sun, 28 Sep 2008 10:00:00 -0700

In this post I’m going to explore some examples of the approaches to reading HTTP responses in your BlackBerry Java application and how they can impact the application’s performance.

I realize that the performance of your HTTP-handling routines might not impose critical limitations to your application. But if you are considering ways to optimize these routines, I encourage you not only to take a look at these approaches, but also measure their performance characteristics in the context of your application.

The first approach, which I have successfully used in a commercial application, consists of reading the contents of the HTTP response one character at a time. Although slow, this approach is attractive because it is simple and does not require any HTTP-specific behavior from your code:

     StreamConnection c = null;

    InputStream s = null;

    try {

        c = (StreamConnection)Connector.open(url);

        s = c.openInputStream();

        int ch;

        StringBuffer response = new StringBuffer();

        while ((ch = s.read()) != -1) {

            response.append((char)i);

        }

    } finally {

        if (s != null)

            s.close();

        if (c != null)

            c.close();

    }

Reading the response data in bulk is a way to gain efficiency. However, this code relies on the underlying connection being able to provide the length of the response:

    ContentConnection c = null;

    DataInputStream dis = null;

    try {

        c = (ContentConnection)Connector.open(url);

        int len = (int)c.getLength();

        dis = c.openDataInputStream();

        if (len > 0) {

            byte[] data = new byte[len];

            dis.readFully(data);

        } else {

            int ch;

            while ((ch = dis.read()) != -1) {

                ...

            }

        }

    } finally {

        if (dis != null)

            dis.close();

        if (c != null)

            c.close();

    }

A version of the previous approach that I use in my KnowledgeBase application is this:

    HttpConnection c = null;

    InputStream in = null;

    String response = null;

    try {    

        c = (HttpConnection)Connector.open(url)

        in = c.openInputStream();                         

        int len = (int)c.getLength();

        if (len > 0) {

          int actual = 0;

          int bytesread = 0 ;

          byte[] data = new byte[len];

          while ((bytesread != len) && (actual != -1)) {

            actual = in.read(data, bytesread, len - bytesread);

            bytesread += actual;

          }

          response = new String(data);

        } 

    }

While the methods above produce a byte array and thus require a parsing or conversion step – omitted from the sample code – in order to deserialize the data, if your application has intimate knowledge of the response’s contents, you can use specialized methods of the DataInputStream class to read and deserialize the different values in the response in one step:

    HttpConnection c = null;

    DataInputStream is = null;

    int rc;

    try {

        c = (HttpConnection)Connector.open(url);

        rc = c.getResponseCode();

        if (rc != HttpConnection.HTTP_OK) {

            throw new IOException("HTTP response code: " + rc);

        }

        is = (DataInputStream)c.openInputStream();

        String lastName = i.readUTF();

        String firstName = i.readUTF();

        int numberOfOrders = i.readInt();

        boolean isActive= i.readBoolean();

    } catch (ClassCastException e) {

        throw new IllegalArgumentException("Not an HTTP URL");

    } finally {

        if (is != null)

            is.close();

        if (c != null)

            c.close();

    }

As you can see, the performance gains have a cost in the amount of complexity of your code and the knowledge of the response contents that your application should have. You will find that this is true for the approaches above as well as other approaches that exist. When deciding on one, consider the tradeoffs and always measure your gains before making a decision.