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Data Block and Custom Forms Data block form
Based on data blocks that are associated with specific database tables
Reflect the structure of the database Custom form
Based on control blocks that process data from multiple tables
Reflect business processes rather than the database structure
Creating a Custom Form
1. Create the form2. Create the form window and canvas
manually3. Create a control block
Data block that is not associated with a specific table
Contains form items that you manually draw on the canvas
4. Create form triggers to process data
Form Triggers Code that is associated with a form
object and an event Can contain SQL INSERT, UPDATE,
DELETE, and SELECT commands Referencing form text item values
in triggers:
:block_name.item_name
Program Units Self-contained programs Can be called from PL/SQL triggers Used to make triggers more
modular, and reuse code within triggers
Practice1 Create a custom form that has:
Employee Name Employee Salary Department Name
Create a LOV to retrieve block records Use triggers to retrieve block records Create a button that calls a program
unit to clear the block.
Referencing System Date and Time Values in FormsSystem Variable Return Value
$$DATE$$ Current operating system date
$$TIME$$ Current operating system time
$$DATETIME$$ Current operating system date & time
$$DBDATE$$ Current DB server date
$$DBTIME$$ Current DB server time
$$DBDATETIME$$ Current DB server date & time
Form Triggers Categories
Block processing Interface event Master-detail processing Message handling Navigational Query time Transactional Validation
Trigger Timing PRE-
Fires just before associated event occurs POST-
Fires just after associated event occurs ON-, WHEN-, KEY-
Fires immediately, in response to specific user actions, such as key presses
Trigger Scope Defines where an event must occur to
make the trigger fire Trigger scope includes the object to
which the trigger is attached, as well as all objects within that object Form-level: fires when event occurs within
any block or item in the form Block-level: fires when event occurs within
any item in the form Item-level: fires only when event occurs
within that item
Trigger Execution Hierarchy If 2 related objects have the same
trigger, the lower-level object’s trigger fires instead of the higher-level one. Form & block, block’s trigger fires Block & item, item’s trigger fires
You can specify a custom execution order using the Execution Hierarchy property of the trigger.
Navigational Triggers External navigation: occurs when
user causes form focus to change Internal navigation: occurs as a
result of internal form triggers that fire in response to external navigation events
User Action Triggers FiredResult on User Screen Display
User starts formPRE-FORMPRE-BLOCK
Form appears, but with no data visible
WHEN-NEW-FORM-INSTANCEWHEN-NEW-BLOCK-INSTANCEWHEN-NEW-RECORD-INSTANCEWHEN-NEW-ITEM-INSTANCE
Form is
available for use
Triggers That Fire at Form Startup
12 3
4 5
User Action Triggers Fired Result on User Screen Display
User places the insertion point in a text item
WHEN-NEW-ITEM-INSTANCE Insertion point appears in item
WHEN-NEW-RECORD-INSTANCE WHEN-NEW-ITEM-INSTANCE
Next record appears
User clicksthe Next Recordbutton
Triggers That Fire as a Result Of External Navigation
User Action Triggers FiredResult on User Screen Display
User closes the Forms Runtime window
Forms Runtime window closes
POST-BLOCKPOST-FORM
Triggers That Fire When a Form Closes
Practice2 Create a department data block. Create an Update button. Create a Cancel button that uses a
procedure.
Directing External Navigation Form tab
order is based on item order in Object Navigator block list
Formtaborder
Moving to a Specific Form Item GO_ITEM(‘block_name.item_name’); Do not write colon(:) before the block name in this commnd.
E.g: GO_ITEM(‘emp.sal’);
Other navigational instructions: GO_BLOCK(‘block_name’) GO_FORM(‘form_name’)
Oracle Error Message Severity Levels 5: informative message 10: informative message advising
user of procedural error 20: condition that keeps trigger
from working correctly 25 condition that keeps form from
working correctly >25: extreme severity
Suppressing Lower Level System Messages Set :SYSTEM.MESSAGE_LEVEL
variable to a higher level in PRE-FORM trigger
:SYSTEM.MESSAGE_LEVEL := 25;
Providing User Feedback in Forms
Message Text in message line at bottom of form Informational only; user doesn't have to
respond
Alert Dialog box Allows user to choose different ways to
proceed
Code for Displaying an AlertDECLARE
alert_button NUMBER;
BEGIN
alert_button := SHOW_ALERT('alert_name');
IF alert_button = ALERT_BUTTON1 THEN
program statements for first button;
ELSE
program statements for second button;
END IF;
END;
Avoiding User Errors Make primary and foreign key
text items non-navigable (How?)
When user moves form focus to primary or foreign key text item, move focus to alternate form item (How?)
How to make nonnavigable item?
Set the text item property Keyboard Navigable to NO
Use When New Item Instance or
When Mouse Up triggers to make internal navigation from the nonnavigable item.
Trapping Runtime Errors Create an ON-ERROR event trigger
Form-level trigger Executes whenever an FRM- or ORA-
error occurs -FRM errors: generated by Forms
Runtime -ORA errors: generated by
database
Form Procedures That Return System Error Information DBMS_ERROR_CODE: The most
recent -ORA error number. (Negative Number)
DBMS_ERROR_TEXT: -ORA error message and number.
ERROR_CODE: The most recent FRM error number. (Positive Number)
ERROR_TEXT: FRM error message and number.
Structure of ON-ERROR Trigger
BEGIN --trap FRM errorsIF ERROR_CODE = FRM_error_code1 THEN
error handler;ELSIF ERROR_CODE = FRM_error_code2 THEN
error handler;…ELSE
--trap ORA errorsIF DBMS_ERROR_CODE = -ORA_error_code1 THEN
error handlerELSIF DBMS_ERROR_CODE = -ORA_error_code2 THEN
error handler…END IF
END IF;END;
Code totrap –FRM errors
Code totrap –ORA errors
Form Validation Ensures that form data meets
preset requirements so erroneous data is not sent to database
Using validation properties or using validation triggers.
Form Validation Categories Data
Specifies data types, lengths, and maximum and minimum values
Database Specifies which operations a user can
perform on a text item List of Values
Specifies whether a data value must be validated against the text item’s LOV (Validate From List text item property)
Validation Properties Validation unit form property:
specifies the largest data chunk that the user can enter before validation occurs Can be performed at the form, block,
record, or item level Specified in the Validation Unit property
on the form Property Palette By default, it is set to item level.
Cont. You should use the item level with
the custom forms, and the record or block level with the data block forms.
The validation properties that are checked always and before checking other properties and triggers are:
format mask, required, datatype, range, and validate from list
Text Item Validation Properties
Data Type Minimum Value Maximum Value Validate From List Insert Allowed Query Allowed Required …
Validation Triggers When Validate Item
It should be Item level trigger. Executes when the item validation occurs
depending on Validation Unit property. E.g. : IF NOT :student.s_class IN (‘FR’,’SO’) THEN Message(‘Legal Values are FR and SO);RAISE FORM_TRIGGER_FAILURE;END IF;
How To Disable Buttons SET_ITEM_PROPERTY E.g. :SET_ITEM_PROPERTY(‘Control.Delete
’ , ENABLED, PROPERTY_FALSE);
Data Blocks vs. Control Blocks Data block
Easy to create and use Is associated with a single table, and reflects
the table’s structure Control block
Requires a lot of custom programming Can contain items from many different tables
You can link data and control blocks to take advantages of the strengths of each
Linking Data Blocks and Control Blocks
1. Create the control block as the master block2. Create the data block as the detail block,
but do not create a master-detail relationship
3. Create a master-detail relationship manually in the WHERE Clause property of the detail block:
data_block_field = :control_block.text_item
Displaying and Refreshing the Data Block Values Create a trigger to:
Place the insertion point in the data block
GO_BLOCK(‘data_block_name’); Flush the data block to make its data
consistent with the master block and the database:
EXECUTE_QUERY;
Example1. Create a text field manually and name it
dept_no. Name the block containing this field ‘control’.
2. Create a data block depending on the table ‘dept’. Make it tabular with 5 rows.
3. Go to the dept block property: Where Clause
And write in it:
Deptno = :control.dept_no
4. Make a button and write in it the previous code
5. Run the form, enter an existing department number in the dept_no field, and press the button.
Converting a Data Block to a Control Block Create a data block and layout that
contains most of the required text items Convert the data block to a control
block by changing the following block property: Database Data Block = No
Then change the following text property: Required = No
Creating a Form with Multiple Canvases Users should be able to see all
canvas text items without scrolling For complex applications with
many text items, divide application into multiple canvases
Block Navigation Order First block in Object Navigator Data
Blocks list determines block items that first appear when form opens
Users can use the Tab key to navigate among different block items
Canvas that contains block items automatically appears
Controlling Block Navigation Block Navigation Style property
Same Record: navigation cycles through items on same record when you reach the end of the current record.
Change Record: navigation moves to the next record in the same data block when you reach the end of the current record.
Change Data Block: navigation moves to next data block in list when you reach the end of the current block.
Canvas It is the surface that has the form items
on it. It has many types:
Content (The default) Tab Stacked …
All canvases inside some window must have the property ‘Window’ has the name of the enclosing window.
Tab Canvases Multiple-page canvases that allow
users to move among different canvas surfaces by clicking tabs
Tab Canvas Components Tab canvas
Collection of related tab pages Tab pages
Surfaces that display form items Tab labels
Identifier at top of tab page A tab canvas lies on top of a
content canvas
Creating a Tab Canvas Use the Tab Canvas tool on
the Layout Editor tool palette to draw a tab canvas on an existing content canvas By default, a new tab canvas has 2
tab pages Create new tab pages as needed Adjust tab page properties
Important Tab Page Properties
Name: how the pageIs referenced in the form
Label: Caption that appears on the associated tab
Adjusting the Tab Page Order Tab page that appears first is tab
page whose block items appear first in the Object Navigator
Block order
Tab page order doesn’t matter
Stacked Canvases Canvas that appears on an
existing content canvas, and can be displayed or hidden as needed
Allows user to configure canvas items
Creating a Stacked Canvas Use the Stacked Canvas tool on
the Layout Editor tool palette to draw a stacked canvas on an existing content canvas
Create block items on the stacked canvas
Create buttons and triggers to display and hide the stacked canvas
Displaying and Hiding a Stacked Canvas Displaying a stacked canvas:GO_BLOCK(‘stacked_canvas_block’);
SHOW_VIEW(‘stacked_canvas’);
Hiding a stacked canvas:GO_BLOCK(‘content_canvas_block’);
HIDE_VIEW(‘stacked_canvas’);
Practice What are the smart triggers? What is the message displayed on saving
successfully? What is the message displayed when you click
SAVE without making any operation? What is the message displayed when the
insertion (or deletion) operation fails? What is the message displayed when you
enter an incorrect data type in the field? What is the type of the previous messages?
(FRM or ORA)