1. Chapter 6: Creating Custom Forms

2. 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

3. Creating a Custom Form 1. Create the form 2. Create the form window and canvas manually 3. 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

4. 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

5. Program Units Self-contained programs Can be called from PL/SQL triggers Used to make triggers more modular, and reuse code within triggers

6. 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.

7. Referencing System Date and Time Values in Forms System VariableReturn 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

8. Form Triggers Categories Block processing Interface event Master-detail processing Message handling Navigational Query time Transactional Validation

9. 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

10. 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

11. 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.

12. 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

13. User Action Triggers Fired Result on User Screen Display User starts form PRE-FORM PRE-BLOCK Form appears, but with no data visible WHEN-NEW-FORM-INSTANCE WHEN-NEW-BLOCK-INSTANCE WHEN-NEW-RECORD-INSTANCE WHEN-NEW-ITEM-INSTANCE Form is available for use Triggers That Fire at Form Startup 1 2 3 4 5

14. 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 clicks the Next Record button Triggers That Fire as a Result Of External Navigation

15. User ActionTriggers Fired Result on User Screen Display User closes the Forms Runtime window Forms Runtime window closes POST-BLOCK POST-FORM Triggers That Fire When a Form Closes

16. Practice2 Create a department data block. Create an Update button. Create a Cancel button that uses a procedure.

17. Directing External Navigation Form tab order is based on item order in Object Navigator block list Form tab order

18. 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’)

19. 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

20. Suppressing Lower Level System Messages Set :SYSTEM.MESSAGE_LEVEL variable to a higher level in PRE-FORM trigger :SYSTEM.MESSAGE_LEVEL := 25;

21. 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

22. Messages Message Syntax: MESSAGE(‘message text’);

23. Alerts Form-level object Object properties define alert appearance Title Style icon Message Buttons

24. Code for Displaying an Alert DECLARE 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;

25. 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?)

26. 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.

27. 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

28. 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.

29. Structure of ON-ERROR Trigger BEGIN --trap FRM errors IF ERROR_CODE = FRM_error_code1 THEN error handler; ELSIF ERROR_CODE = FRM_error_code2 THEN error handler; … ELSE --trap ORA errors IF DBMS_ERROR_CODE = -ORA_error_code1 THEN error handler ELSIF DBMS_ERROR_CODE = -ORA_error_code2 THEN error handler … END IF END IF; END; Code to trap –FRM errors Code to trap –ORA errors

30. Form Validation Ensures that form data meets preset requirements so erroneous data is not sent to database Using validation properties or using validation triggers.

31. 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)

32. 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.

33. 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

34. Text Item Validation Properties Data Type Minimum Value Maximum Value Validate From List Insert Allowed Query Allowed Required …

35. Why do not we use validation properties instead of validation triggers? Question

36. We use validation triggers for more complex validations. (like what?) Answer

37. 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;

38. How To Disable Buttons SET_ITEM_PROPERTY E.g. : SET_ITEM_PROPERTY(‘Control.Delete’, ENABLED, PROPERTY_FALSE);

39. 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

40. Linking Data Blocks and Control Blocks 1. Create the control block as the master block 2. 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

41. 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;

42. Example 1. 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.

43. 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

44. 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

45. 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

46. Block Navigation Order Block order Canvas order doesn’t matter

47. 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.

48. 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.

49. Tab Canvases Multiple-page canvases that allow users to move among different canvas surfaces by clicking tabs

50. 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

51. 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

52. Important Tab Page Properties Name: how the page Is referenced in the form Label: Caption that appears on the associated tab

53. 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

54. Stacked Canvases Canvas that appears on an existing content canvas, and can be displayed or hidden as needed Allows user to configure canvas items

55. Stacked Canvas Example Stacked canvas Content canvas

56. 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

57. 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’);

58. 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)