Welcome!

Silverlight Authors: Automic Blog, Michael Kopp, Jyoti Bansal, Kaazing Blog, Steven Mandel

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
SYS-CON Events announced today that DXWorldExpo has been named “Global Sponsor” of SYS-CON's 21st International Cloud Expo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Digital Transformation is the key issue driving the global enterprise IT business. Digital Transformation is most prominent among Global 2000 enterprises and government institutions.
21st International Cloud Expo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Me...
SYS-CON Events announced today that Massive Networks will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Massive Networks mission is simple. To help your business operate seamlessly with fast, reliable, and secure internet and network solutions. Improve your customer's experience with outstanding connections to your cloud.
When shopping for a new data processing platform for IoT solutions, many development teams want to be able to test-drive options before making a choice. Yet when evaluating an IoT solution, it’s simply not feasible to do so at scale with physical devices. Building a sensor simulator is the next best choice; however, generating a realistic simulation at very high TPS with ease of configurability is a formidable challenge. When dealing with multiple application or transport protocols, you would be...
SYS-CON Events announced today that Akvelon will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Akvelon is a business and technology consulting firm that specializes in applying cutting-edge technology to problems in fields as diverse as mobile technology, sports technology, finance, and healthcare.
SYS-CON Events announced today that Secure Channels, a cybersecurity firm, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Secure Channels, Inc. offers several products and solutions to its many clients, helping them protect critical data from being compromised and access to computer networks from the unauthorized. The company develops comprehensive data encryption security strategie...
SYS-CON Events announced today that WineSOFT will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Based in Seoul and Irvine, WineSOFT is an innovative software house focusing on internet infrastructure solutions. The venture started as a bootstrap start-up in 2010 by focusing on making the internet faster and more powerful. WineSOFT’s knowledge is based on the expertise of TCP/IP, VPN, SS...
WebRTC is the future of browser-to-browser communications, and continues to make inroads into the traditional, difficult, plug-in web communications world. The 6th WebRTC Summit continues our tradition of delivering the latest and greatest presentations within the world of WebRTC. Topics include voice calling, video chat, P2P file sharing, and use cases that have already leveraged the power and convenience of WebRTC.
SYS-CON Events announced today that App2Cloud will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct. 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. App2Cloud is an online Platform, specializing in migrating legacy applications to any Cloud Providers (AWS, Azure, Google Cloud).
When shopping for a new data processing platform for IoT solutions, many development teams want to be able to test-drive options before making a choice. Yet when evaluating an IoT solution, it’s simply not feasible to do so at scale with physical devices. Building a sensor simulator is the next best choice; however, generating a realistic simulation at very high TPS with ease of configurability is a formidable challenge. When dealing with multiple application or transport protocols, you would be...
An increasing number of companies are creating products that combine data with analytical capabilities. Running interactive queries on Big Data requires complex architectures to store and query data effectively, typically involving data streams, an choosing efficient file format/database and multiple independent systems that are tied together through custom-engineered pipelines. In his session at @BigDataExpo at @ThingsExpo, Tomer Levi, a senior software engineer at Intel’s Advanced Analytics ...
Internet-of-Things discussions can end up either going down the consumer gadget rabbit hole or focused on the sort of data logging that industrial manufacturers have been doing forever. However, in fact, companies today are already using IoT data both to optimize their operational technology and to improve the experience of customer interactions in novel ways. In his session at @ThingsExpo, Gordon Haff, Red Hat Technology Evangelist, shared examples from a wide range of industries – including en...
Detecting internal user threats in the Big Data eco-system is challenging and cumbersome. Many organizations monitor internal usage of the Big Data eco-system using a set of alerts. This is not a scalable process given the increase in the number of alerts with the accelerating growth in data volume and user base. Organizations are increasingly leveraging machine learning to monitor only those data elements that are sensitive and critical, autonomously establish monitoring policies, and to detect...
"We're a cybersecurity firm that specializes in engineering security solutions both at the software and hardware level. Security cannot be an after-the-fact afterthought, which is what it's become," stated Richard Blech, Chief Executive Officer at Secure Channels, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. Jack Norris reviews best practices to show how companies develop, deploy, and dynamically update these applications and how this data-first...
Intelligent Automation is now one of the key business imperatives for CIOs and CISOs impacting all areas of business today. In his session at 21st Cloud Expo, Brian Boeggeman, VP Alliances & Partnerships at Ayehu, will talk about how business value is created and delivered through intelligent automation to today’s enterprises. The open ecosystem platform approach toward Intelligent Automation that Ayehu delivers to the market is core to enabling the creation of the self-driving enterprise.
The question before companies today is not whether to become intelligent, it’s a question of how and how fast. The key is to adopt and deploy an intelligent application strategy while simultaneously preparing to scale that intelligence. In her session at 21st Cloud Expo, Sangeeta Chakraborty, Chief Customer Officer at Ayasdi, will provide a tactical framework to become a truly intelligent enterprise, including how to identify the right applications for AI, how to build a Center of Excellence to ...
SYS-CON Events announced today that Massive Networks will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Massive Networks mission is simple. To help your business operate seamlessly with fast, reliable, and secure internet and network solutions. Improve your customer's experience with outstanding connections to your cloud.
Everything run by electricity will eventually be connected to the Internet. Get ahead of the Internet of Things revolution and join Akvelon expert and IoT industry leader, Sergey Grebnov, in his session at @ThingsExpo, for an educational dive into the world of managing your home, workplace and all the devices they contain with the power of machine-based AI and intelligent Bot services for a completely streamlined experience.
Because IoT devices are deployed in mission-critical environments more than ever before, it’s increasingly imperative they be truly smart. IoT sensors simply stockpiling data isn’t useful. IoT must be artificially and naturally intelligent in order to provide more value In his session at @ThingsExpo, John Crupi, Vice President and Engineering System Architect at Greenwave Systems, will discuss how IoT artificial intelligence (AI) can be carried out via edge analytics and machine learning techn...