Using a user event
After you define a user event, you must write the script that
PowerBuilder will execute when that user event is triggered. If
it is an unmapped user event, you also write the code that will
trigger the user event.
User events display in alphabetical order in the Event List
view and the event list box in the Script view, along with the predefined
events. As with predefined events, the script tells PowerBuilder
what processing to perform when the user event occurs.
If the user event is not mapped to a Windows message (that
is, if there is no event ID associated with it), you must trigger
the event in a script. You can trigger the user event in an object
using the EVENT syntax. For information about
calling events, see the PowerScript Reference
.
Examples of user event scripts
This section includes two examples that use a mapped user
event and one example that uses an unmapped user event. For more
user event examples, see “Communicating between a
window and a user object “.
Example 1: mapped user event for a control
Situation You have several SingleLineEdit controls in a window and want the
Enter key to behave like the Tab key (if users press Enter, you
want them to tab to the next SingleLineEdit).
Solution Define a user event for each SingleLineEdit. Give the event
any name you want, such as ue_CheckKey.
Map the event to the event ID pbm_keydown.
Write a script for the user event that tests for the key that was pressed.
If Enter was pressed, set the focus to the SingleLineEdit that you
want the user to go to.
For example, in the script for the user event for sle_1,
you could code:
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// Script for user event ue_CheckKey<br>// which is mapped to pbm_keydown.<br>IF KeyDown(KeyEnter!) THEN // Go to sle_2 if<br> sle_2.SetFocus( ) // Enter pressed.<br>END IF |
Similarly, in the script for the user event for sle_2,
you could code:
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// Script for user event ue_CheckKey,<br>// which is mapped to pbm_keydown.<br> |
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IF KeyDown(KeyEnter!) THEN // Go to sle_3 if<br> sle_3.SetFocus( ) // Enter pressed. <br>END IF |
Example 2: mapped user event for an edit style
Situation You have a DataWindow control with a column that uses the RadioButton
edit style and you want to allow users to scroll through the RadioButtons
when they press Down Arrow or Up Arrow (normally, pressing Down
Arrow or Up Arrow scrolls to the next or preceding row).
Solution Declare a user event for the DataWindow control that maps
to the event ID pbm_dwnkey and write
a script like the following for it. dwn stands
for DataWindow notification.
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// Script is in a user event for a DataWindow control.<br>// It is mapped to pbm_dwnkey. If user is in column <br>// number 6, which uses the RadioButton edit style, and<br>// presses DownArrow, the cursor moves to the next item<br>// in the RadioButton list, instead of going to the next<br>// row in the DataWindow, which is the default behavior.<br>// Pressing UpArrow moves to preceding RadioButton.<br>//<br>// Note that the CHOOSE CASE below tests for data <br>// values, not display values, for the RadioButtons.<br> <br>int colnum = 6 // Column number<br>long rownum<br>rownum = dw_2.GetRow( ) // Current row<br> <br>IF KeyDown(KeydownArrow!) AND &<br> This.GetColumn( ) = colnum THEN <br> CHOOSE CASE dw_2.GetItemString(rownum, colnum) <br> case "P" // First value in RB<br> This.SetItem(rownum, colnum,"L") // Next <br> case "L" // Second value in RB<br> This.SetItem(rownum, colnum,"A") // Next <br> case "A" // Last value in RB<br> This.SetItem(rownum, colnum,"P") // First<br> END CHOOSE <br> This.SetActionCode(1) // Ignore key press<br>END IF |
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// The following code does same thing for UpArrow.<br>IF KeyDown(KeyupArrow!) AND &<br> This.GetColumn( ) = colnum THEN |
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CHOOSE CASE dw_2.GetItemString(rownum, colnum) <br> case "P" // First value in RB <br> This.SetItem(rownum, colnum,"A") // Last <br> case "L" // Another value in RB <br> This.SetItem(rownum, colnum,"P")<br> case "A" // Last value in RB <br> This.SetItem(rownum, colnum,"L") <br> END CHOOSE<br> This.SetActionCode(1)<br>END IF |
Example 3: unmapped user event for menu options
Situation Suppose you use the same menu in all your windows, but you
want to enable or disable some menu items, in this case database
update items, depending on which window the user is in.
Solution In the window that will be the ancestor of all the sheet windows
that do not have database update capability, define an unmapped
user event called ue_ct_menu_enable.
The event takes a boolean argument, ab_state,
to set or clear the enabled property on various menus. This is the
script for the ue_ct_menu_enable user
event in the ancestor window:
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// Enable / Disable Menu Options<br>im_CurrMenu.m_maint.m_add.enabled = Not ab_state<br>im_CurrMenu.m_maint.m_delete.enabled = Not ab_state<br>im_CurrMenu.m_maint.m_undelete.enabled = Not ab_state<br>im_CurrMenu.m_maint.m_update.enabled = Not ab_state<br>im_CurrMenu.m_maint.m_close.enabled = ab_state |
Then, in the script for the Activate event in the ancestor
window, call the user event and pass the value “true” for
the boolean variable ab_state.
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this.EVENT ue_ct_menu_enable ( TRUE ) |
Write a similar script for the Deactivate event with the value “false” for ab_state.
You can use this window as the ancestor of any sheet window
in your application that does not have database update capability.
When the window is active, the Add, Delete, Undelete, and Update
menu items are grayed out. When it is not active, the Close item
is grayed out.
For windows that have database update capability, you can
create a second ancestor window that inherits from the ancestor
window in which you defined ue_ct_menu_enable.
In the second ancestor window, you can override the ue_ct_menu_enable event
script so that the appropriate menu options are enabled.