Welcome!

Silverlight Authors: Yeshim Deniz, Greg O'Connor, Trevor Parsons, Sandi Mappic, Liz McMillan

Blog Feed Post

PB Event Order

PowerBuilder - Events and Precedence


     The order in which events happen within a PowerBuilder Classic application is in most cases, a very predictable model. The PB developer should be aware of this aspect when developing GUI based applications. For instance, when focus is shifted from one object to another object, the first object will experience the Modified and LoseFocus events before the second object experiences a get focus event.

To understand this further, consider the following scenarios and the resulting events.
 

An Application starts and window "A" is opened

APPLICATION OPEN
WINDOW "A" OPEN
WINDOW "A" ACTIVATE
CHILD OBJECT GET FOCUS (First object in tab order)
 

Window "B" is opened (Window "A" stays open)

WINDOW "A" CURRENT OBJECT LOSE FOCUS
WINDOW "A" DEACTIVATE
WINDOW "B" OPEN
WINDOW "B" ACTIVATE
WINDOW "B" CHILD OBJECT GET FOCUS (First object in tab order)

Window "B" closed, return to Window "A".

WINDOW "B" CLOSEQUERY
WINDOW "B" CURRENT OBJECT LOSE FOCUS
WINDOW "B" CLOSE
WINDOW "B" DEACTIVATE
WINDOW "A" ACTIVATE
OBJECT GET FOCUS (Last object that had focus)
 

"Click" on new object within Same Window

OBJECT 1 MODIFIED (if changed)
OBJECT 1 LOSE FOCUS
OBJECT 2 GET FOCUS
OBJECT 2 CLICKED
 

"Tab" to new object within Same Window

OBJECT 1 MODIFIED (if changed)
OBJECT 1 LOSE FOCUS
OBJECT 2 GET FOCUS (next object in tab order)

Interestingly enough, events can and will occur even when no actions are performed by the user. If you are
using a screen saver, such as the one in Windows, the following will happen.

Flip to screen saver (After period of inactivity)
   WINDOW DEACTIVATE
   OBJECT LOSE FOCUS
Return from screen saver
   WINDOW ACTIVATE
   OBJECT GET FOCUS


DataWindows and Events

A DataWindow is a single object within a window. As such, events happen to the DataWindow as a single object (DW COntrol) and not to the individual items that are within the DataWindow object itself. In order to make up for this, there are a number of special events that exist only for DataWindows. These events are not quite the same as those of other Window objects and therefore must be considered on their own.

Consider the following scenario:

The User Clicks on a field in a data window, keys something, clicks on another field within the data window, keys something and then clicks on a Command Button (outside of the DataWindow). The sequence of DataWindow events is as follows:

DW GET FOCUS
DW CLICKED
DW EDIT CHANGED (once for each keystroke)
DW CLICKED
DW ITEMCHANGED
DW ITEM FOCUS CHANGED
DW EDIT CHANGED (once for each keystroke)
DW LOSE FOCUS

COMMAND BUTTON GET FOCUS
COMMAND BUTTON CLICKED

A number of significant aspects are happening at this time! For example: there was only one get focus and one lose focus event. Only one item changed event occurred (even though two items were changed). A clicked event occurred two times. One edit changed event occurred for every keystroke made within the DataWindow.

If DataWindow edits were behind the two modified fields, only the first field would have been edited. For all intents and purposes, the second field has nothing in it!

Now let us insert the ACCEPTTEXT() function into the command button Clicked script. Now the sequence of events flows as follows:

DW GET FOCUS
DW CLICKED
DW EDIT CHANGED (once for each keystroke)
DW CLICKED
DW ITEMCHANGED
DW ITEM FOCUS CHANGED
DW EDIT CHANGED (once for each keystroke)
DW LOSE FOCUS

COMMAND BUTTON GET FOCUS
COMMAND BUTTON CLICKED

DW ITEMCHANGED

The last item changed event was triggered by the AcceptText ( ) functionality. You might be tempted to put this function in the DataWindow Control's losefocus event script, but this makes it very difficult for a user to cancel a transaction when they can not get past the edit rule!
 

Events Precedence Table

The following is a table that shows the order of events for each object type:

Objects Events Order Notes

Window
Open 1
Activate 2 Also after closing of
another Window
Key 3 Each Keystroke (not all objects)
CloseQuery 4
Close 5
Deactivate 6

Single Line Edit, Multi Line Edit
Get Focus 1
Modified 2
LoseFocus 3

List Box, Drop Down List Box
GetFocus 1
SelectionChanged 2 When choice made from list
Modified 3
DoubleClicked 4 Only possible when "always show
list box" is active
LoseFocus 5

Static Text, Picture, Picture Button
GetFocus 1
Clicked 2
DoubleClicked 3 Always issues a Clicked event first
LoseFocus 4

Check Box, Command Button, Radio Button
GetFocus 1
Clicked 2
LoseFocus 3

DataWindow
GetFocus 1
Clicked 2
DoubleClicked 3 Always issues a Clicked event first
EditChanged 4 Once for each keystroke
ItemError 5 When item doesn't pass validation
ItemChanged 6 When object loses focus within dw
RowFocusChanged 7
ItemFocusChanged 8
LoseFocus 9
 

Events Notes

Triggerevent Function

At any time in an application, an event can occur through use of the TRIGGEREVENT() function. This can be a very handy thing to know and use. It can also cause problems if the application is counting on certain events to occur in a certain sequence.

DataWindow Clicked Event

Often, the clicked event in a data window is used to trigger a choice made by the user. In the script for this event it is always a good policy to check that the clicked row value is greater than zero. If the click is made on the borders or white space of a data window, the GETCLICKEDROW function will return a zero.

Although the ItemError! event listed after EditChanged! event under dw events order is a bit confusing, I am
sure it is correct as per the 4 phases of validation:

. edit-changed check
. data-type check (ItemError! fires here...)
. item-changed check
. validation-rule check

***********************************************************
Note: You can not safely predict the event model in PB.Net applications as the object drawing and interaction is outside the application's control in the WPF layer of the O/S. WPF controls all aspects of event handling and even imposes restrictions for the PB.Net application! 
***********************************************************

Regards ... Chris

Read the original blog entry...

More Stories By Chris Pollach

Chris Pollach is a Senior Consultant with over 30 years experience in Systems and Software Analysis, Development, Maintenance and Technical Support, mainly in the areas of GUI Design, MS-Windows Programming, Java / .NET Programming, Wireless, Application / Web Server Design & Programming, Object Oriented Development Tools and Methodologies, Data Base, Data Communications and Network application development. He has participated in numerous technical, planning and management roles, as well as consulted and educated in these fields for a diverse clientele. He is also the owner of “Software Tool & Die Inc.” a company dedicated to provide custom software and education solutions on Object Oriented business systems.

As an educator, Chris is certified to teach PowerBuilder (first in Canada), MS-SQLServer, Sybase’s Enterprise Application Studio and EAServer integrated application/web development environment. He is former Certified SilverStream developer (CSSD) and current Certified PowerBuilder Developer – Associate / Professional (CPD-P) as well as a Certified Sybase Tools Instructor (CSI).

Chris has written numerous articles in various popular personal computer magazines, newsletters and is the author of the PowerGuide and PowerExpert products as well as the STD Foundation Classes. Currently, Chris has developed a Foundation Class library for Sybase's PocketBuilder, SAP's PowerBulder and EAServer products and now Appeon Web & mobile products that integrates JSP or ASP web development, Section 508 / CLF web standards and mobile applications. A new Web Service framework has also been released for IIs to support PowerBuilder based web service NVUO's!

Chris recently became a 2nd Degree Black in the TaeKwonDo martial art and has developed a Martial Art multimedia study guide using the Component-One “Doc2Help” and Sybase PowerBuilder products. Since the fall of 2004 he became a TaeKwonDo instructor for the City of Ottawa’s Goulbourn program. He has also been certified with the World TaeKwonDo Federation (February 2005 - 1st Dan and October 2008 - 2nd Dan).

Chris was awarded the Sybase “Innovation and Achievement” award for 2005 as voted for by the International Sybase User Group (ISUG). This award was presented for innovations to the PocketBuilder mobile development product, contributions to the PowerBuilder News groups and support of the Ottawa Sybase User Group.

To round his management and leadership skills, Chris is the former president of the Kiwanis Club of Goulbourn and still volunteers his time with the service clubs in his area. He is also the coordinator of the Ottawa Sybase User group and a certified NAUI scuba instructor. For the last three years, Chris has been voted onto the ISUG Board of Directors and holds the position of "Director - North American User Groups".

@ThingsExpo Stories
Scott Jenson leads a project called The Physical Web within the Chrome team at Google. Project members are working to take the scalability and openness of the web and use it to talk to the exponentially exploding range of smart devices. Nearly every company today working on the IoT comes up with the same basic solution: use my server and you'll be fine. But if we really believe there will be trillions of these devices, that just can't scale. We need a system that is open a scalable and by using the URL as a basic building block, we open this up and get the same resilience that the web enjoys.
The Internet of Things is tied together with a thin strand that is known as time. Coincidentally, at the core of nearly all data analytics is a timestamp. When working with time series data there are a few core principles that everyone should consider, especially across datasets where time is the common boundary. In his session at Internet of @ThingsExpo, Jim Scott, Director of Enterprise Strategy & Architecture at MapR Technologies, discussed single-value, geo-spatial, and log time series data. By focusing on enterprise applications and the data center, he will use OpenTSDB as an example t...
P2P RTC will impact the landscape of communications, shifting from traditional telephony style communications models to OTT (Over-The-Top) cloud assisted & PaaS (Platform as a Service) communication services. The P2P shift will impact many areas of our lives, from mobile communication, human interactive web services, RTC and telephony infrastructure, user federation, security and privacy implications, business costs, and scalability. In his session at @ThingsExpo, Robin Raymond, Chief Architect at Hookflash, will walk through the shifting landscape of traditional telephone and voice services ...
The Domain Name Service (DNS) is one of the most important components in networking infrastructure, enabling users and services to access applications by translating URLs (names) into IP addresses (numbers). Because every icon and URL and all embedded content on a website requires a DNS lookup loading complex sites necessitates hundreds of DNS queries. In addition, as more internet-enabled ‘Things' get connected, people will rely on DNS to name and find their fridges, toasters and toilets. According to a recent IDG Research Services Survey this rate of traffic will only grow. What's driving t...
Enthusiasm for the Internet of Things has reached an all-time high. In 2013 alone, venture capitalists spent more than $1 billion dollars investing in the IoT space. With "smart" appliances and devices, IoT covers wearable smart devices, cloud services to hardware companies. Nest, a Google company, detects temperatures inside homes and automatically adjusts it by tracking its user's habit. These technologies are quickly developing and with it come challenges such as bridging infrastructure gaps, abiding by privacy concerns and making the concept a reality. These challenges can't be addressed w...
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at Internet of @ThingsExpo, James Kirkland, Chief Architect for the Internet of Things and Intelligent Systems at Red Hat, described how to revolutioniz...
Bit6 today issued a challenge to the technology community implementing Web Real Time Communication (WebRTC). To leap beyond WebRTC’s significant limitations and fully leverage its underlying value to accelerate innovation, application developers need to consider the entire communications ecosystem.
The definition of IoT is not new, in fact it’s been around for over a decade. What has changed is the public's awareness that the technology we use on a daily basis has caught up on the vision of an always on, always connected world. If you look into the details of what comprises the IoT, you’ll see that it includes everything from cloud computing, Big Data analytics, “Things,” Web communication, applications, network, storage, etc. It is essentially including everything connected online from hardware to software, or as we like to say, it’s an Internet of many different things. The difference ...
Cloud Expo 2014 TV commercials will feature @ThingsExpo, which was launched in June, 2014 at New York City's Javits Center as the largest 'Internet of Things' event in the world.
SYS-CON Events announced today that Windstream, a leading provider of advanced network and cloud communications, has been named “Silver Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. Windstream (Nasdaq: WIN), a FORTUNE 500 and S&P 500 company, is a leading provider of advanced network communications, including cloud computing and managed services, to businesses nationwide. The company also offers broadband, phone and digital TV services to consumers primarily in rural areas.
"There is a natural synchronization between the business models, the IoT is there to support ,” explained Brendan O'Brien, Co-founder and Chief Architect of Aria Systems, in this SYS-CON.tv interview at the 15th International Cloud Expo®, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
The major cloud platforms defy a simple, side-by-side analysis. Each of the major IaaS public-cloud platforms offers their own unique strengths and functionality. Options for on-site private cloud are diverse as well, and must be designed and deployed while taking existing legacy architecture and infrastructure into account. Then the reality is that most enterprises are embarking on a hybrid cloud strategy and programs. In this Power Panel at 15th Cloud Expo (http://www.CloudComputingExpo.com), moderated by Ashar Baig, Research Director, Cloud, at Gigaom Research, Nate Gordon, Director of T...

ARMONK, N.Y., Nov. 20, 2014 /PRNewswire/ --  IBM (NYSE: IBM) today announced that it is bringing a greater level of control, security and flexibility to cloud-based application development and delivery with a single-tenant version of Bluemix, IBM's platform-as-a-service. The new platform enables developers to build ap...

An entirely new security model is needed for the Internet of Things, or is it? Can we save some old and tested controls for this new and different environment? In his session at @ThingsExpo, New York's at the Javits Center, Davi Ottenheimer, EMC Senior Director of Trust, reviewed hands-on lessons with IoT devices and reveal a new risk balance you might not expect. Davi Ottenheimer, EMC Senior Director of Trust, has more than nineteen years' experience managing global security operations and assessments, including a decade of leading incident response and digital forensics. He is co-author of t...
Technology is enabling a new approach to collecting and using data. This approach, commonly referred to as the "Internet of Things" (IoT), enables businesses to use real-time data from all sorts of things including machines, devices and sensors to make better decisions, improve customer service, and lower the risk in the creation of new revenue opportunities. In his General Session at Internet of @ThingsExpo, Dave Wagstaff, Vice President and Chief Architect at BSQUARE Corporation, discuss the real benefits to focus on, how to understand the requirements of a successful solution, the flow of ...
The security devil is always in the details of the attack: the ones you've endured, the ones you prepare yourself to fend off, and the ones that, you fear, will catch you completely unaware and defenseless. The Internet of Things (IoT) is nothing if not an endless proliferation of details. It's the vision of a world in which continuous Internet connectivity and addressability is embedded into a growing range of human artifacts, into the natural world, and even into our smartphones, appliances, and physical persons. In the IoT vision, every new "thing" - sensor, actuator, data source, data con...
"BSQUARE is in the business of selling software solutions for smart connected devices. It's obvious that IoT has moved from being a technology to being a fundamental part of business, and in the last 18 months people have said let's figure out how to do it and let's put some focus on it, " explained Dave Wagstaff, VP & Chief Architect, at BSQUARE Corporation, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Focused on this fast-growing market’s needs, Vitesse Semiconductor Corporation (Nasdaq: VTSS), a leading provider of IC solutions to advance "Ethernet Everywhere" in Carrier, Enterprise and Internet of Things (IoT) networks, introduced its IStaX™ software (VSC6815SDK), a robust protocol stack to simplify deployment and management of Industrial-IoT network applications such as Industrial Ethernet switching, surveillance, video distribution, LCD signage, intelligent sensors, and metering equipment. Leveraging technologies proven in the Carrier and Enterprise markets, IStaX is designed to work ac...
C-Labs LLC, a leading provider of remote and mobile access for the Internet of Things (IoT), announced the appointment of John Traynor to the position of chief operating officer. Previously a strategic advisor to the firm, Mr. Traynor will now oversee sales, marketing, finance, and operations. Mr. Traynor is based out of the C-Labs office in Redmond, Washington. He reports to Chris Muench, Chief Executive Officer. Mr. Traynor brings valuable business leadership and technology industry expertise to C-Labs. With over 30 years' experience in the high-tech sector, John Traynor has held numerous...
The 3rd International @ThingsExpo, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that it is now accepting Keynote Proposals. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - computers, smartphones, tablets, and sensors - connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades.