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Chapter 6: Creating Custom Forms
Guide to Oracle 10g
Guide to Oracle 10g 2
Lesson A Objectives
After completing this lesson, you should be able to:• Create and use custom forms• Create command buttons that use form triggers to
manipulate data• Use the Forms Debugger to find form logic and
runtime errors• Work with form triggers• Create form navigation triggers
Guide to Oracle 10g 3
Introduction to Custom Forms
• Custom form – Displays data fields from variety of database tables– Contains programs that support organizational
processes– Use lists of values (LOVs) to retrieve data values– Manipulate data using form triggers
Guide to Oracle 10g 4
Identifying the Business Processes and Database Operations
• Identify processes that form supports• Identify associated database tables• Describe process
Guide to Oracle 10g 6
Creating a Custom Form
• Manually create form canvas in Object Navigator• Create form items by “painting” items on canvas
– Using tools on Layout Editor tool palette• Write code that controls form functions
Guide to Oracle 10g 7
Creating the Form Canvas
• Manually create form canvas in Object Navigator• Start Forms Builder
– Create and rename form canvas– Rename form module and form window– Change Title property of form window
• Perform in Visual View in Object Navigator
Guide to Oracle 10g 8
Creating a Control Block
• Control data block– Also called control block– Data block not associated with particular database
table• Create new data block in Object Navigator
– Specify data block created manually– Use Ownership View
Guide to Oracle 10g 9
Creating the Form Items
• Create – Boilerplate logo image and text– Form text items – Command button items
• Display form in Layout Editor– Draw items on form canvas using tools in tool
palette
Guide to Oracle 10g 10
Creating the LOVs
• LOV– Retrieve data from database table
• Use LOV Wizard• Run form
– To test LOV
Guide to Oracle 10g 11
Displaying System Date and Time Values in Form Text Items
• System variable – Variable representing value always available to any
form• Display value in text item automatically
– Set text item’s Initial Value property
Guide to Oracle 10g 12
Forms Builder Date and Time System Variables
Guide to Oracle 10g 13
Creating Command Buttons
• Create and configure buttons• Create form triggers associated with buttons
Guide to Oracle 10g 14
Creating and Configuring Command Buttons
• Draw button on canvas using Button tool – Button tool on tool palette
• Button group– Buttons should all be same size
• Wide enough to accommodate longest button’s label– Draw button with longest label first
Guide to Oracle 10g 15
Creating the Button Triggers
• Select Triggers node under button in Object Navigator– Click Create button to create trigger– Select trigger event– Specify trigger code
• WHEN-BUTTON-PRESSED button event– Trigger code executes when user clicks button
Guide to Oracle 10g 16
Creating the Button Triggers (continued)
• Reference form items:– :block_name.item_name
• Clear form text items in form trigger: – Use CLEAR_FORM built-in procedure– Create program unit to set value of text items to blank
text string• Procedure
– Code block that executes commands to change one or more values
Guide to Oracle 10g 17
Creating the Button Triggers (continued)
• Function– Code block – Returns single value
• Create program unit:– Open Object Navigator – Select Program Units node– Click Create button
• Program unit does not use DECLARE keyword
Guide to Oracle 10g 18
Using the Forms Debugger to Find Runtime Errors
• Runtime error – Error that does not keep program from compiling– Generates error while program running– Often result of user error
• Retrieve error messages associated with errors• Forms Debugger
– Step through triggers and other PL/SQL programs one line at a time
– Examine variable values during program execution
Guide to Oracle 10g 19
Retrieving FRM- Error Messages
• Investigate nature of error by looking up error code explanation– Oracle Technology Network (OTN) Web site
• FRM- prefix – Forms Builder error codes
• ORA- prefix – Generated by the DBMS
Guide to Oracle 10g 20
Using the Forms Debugger
• Click Run Form Debug button• Set breakpoint
– Pauses execution on specific program command– Examine current values of all program variables– Step through program commands to observe
execution path– Examine variable values to see how values change
Guide to Oracle 10g 21
Using the Forms Debugger (continued)
• Breakpoint – Pauses execution on specific command– Set on:
• Program lines that contain executable program commands
• SQL queries– To set:
• Double-click mouse pointer in gray shaded area on left side of PL/SQL Editor window
Guide to Oracle 10g 22
Using the Forms Debug Console
• Control form execution and examine form values• Buttons:
– Go– Step Into– Step Over– Step Out
• Execution arrow – Shows program line to execute next
Guide to Oracle 10g 25
Form Trigger Properties
• Trigger activated– In response to event such as clicking button
• Trigger name defines event that activates it
Guide to Oracle 10g 27
Trigger Timing
• Specifies when trigger fires• PRE-
– Fire just before event successfully completes• POST-
– Fire just after event successfully completes• ON-,WHEN-, and KEY-
– Fire in response to actions
Guide to Oracle 10g 28
Trigger Scope
• Defines where event must occur in order for associated trigger to fire
• Includes object to which trigger attached– And objects within trigger object
Guide to Oracle 10g 29
Trigger Execution Hierarchy
• Defines which trigger fires – When object within form object contains same
trigger that form object contains• By default trigger in higher-level object overrides
trigger in lower-level object• Can specify custom execution hierarchy
Guide to Oracle 10g 30
Directing Form External Navigation
• External navigation – User causes form focus to change by making
different form item active• Form focus
– Item currently selected on form• Internal navigation
– Result of internal form code that responds to external navigation operations or trigger commands
Guide to Oracle 10g 31
Setting the Form Tab Order
• Set tab order – Place items in correct order under Items node
• In Object Navigator window
Guide to Oracle 10g 32
Directing External Navigation Using Built-in Subprograms
• Built-in subprograms– Called built-ins – Use to direct external form navigation
• Cannot use in navigational triggers
Guide to Oracle 10g 33
Built-in Subprograms to Control External Navigation
Guide to Oracle 10g 34
Lesson A Summary
• Custom form – Displays data fields from variety of database tables – Processes data using triggers that contain SQL
commands• Runtime errors
– Errors that occur while form running• Forms Debugger
– Create breakpoints that pause execution
Guide to Oracle 10g 35
Lesson A Summary• Form triggers support:
– Block processing– Interface events– Master-detail processing– Message handling– Navigational events– Query processing– Transaction processing– Validation
Guide to Oracle 10g 36
Lesson B Objectives
After completing this lesson, you should be able to:• Suppress default system messages• Create alerts and messages to provide system
feedback to users• Create applications that avoid user errors• Trap common runtime errors
Guide to Oracle 10g 37
Controlling System Messages
• Forms Services message line– Displays FRM- and ORA- messages– Classified according to
• Severity• Whether or not they require user intervention
• Suppress default system messages – Replace with custom messages– Set :SYSTEM.MESSAGE_LEVEL variable
• In PRE-FORM trigger
Guide to Oracle 10g 38
Providing System Feedback
• Important application design principle – Provide users with feedback about what is
happening in application• Make applications forgiving
– Allow users to undo unintended operations
Guide to Oracle 10g 39
Custom Messages
• Short text string that displayed on form message line– Up to 200 characters
• Syntax:– MESSAGE('message_string');
Guide to Oracle 10g 40
Alerts
• Dialog box – Display text message longer than 200 characters– Displays one or more buttons
• Allow user to select between alternatives that execute associated program statements
• Top-level form object
Guide to Oracle 10g 41
Alerts (continued)
• Styles:– Note– Caution– Stop
• Button Label property determines:– How many buttons appear on alert – Labels on buttons– Maximum 3 buttons
Guide to Oracle 10g 42
Alerts (continued)
• To declare/display alert:DECLAREalert_button NUMBER;
BEGINalert_button:=
SHOW_ALERT('alert_name');END;
Guide to Oracle 10g 44
Syntax to Display an Alert and Execute Alternate Commands
Depending on the Button the User Clicked
Guide to Oracle 10g 45
Avoiding User Errors
• Help users avoid errors– Configure forms that validate input values – Programmatically disable form command buttons– Disable navigation for form text items containing
values that users should not change
Guide to Oracle 10g 46
Validating Form Input Values
• Validate input values– Ensure that values meet specific preset
requirements– Use
• Text item validation properties • Form validation triggers
• Validation unit– Represents largest chunk of data that user can enter
before form validates all input values
Guide to Oracle 10g 47
Text Item Validation Properties
Guide to Oracle 10g 48
Validating Form Input Values (continued)
• Item validation trigger – Item-level trigger – Associate with item’s WHEN-VALIDATE-ITEM
event– Fires when item validated
• As determined by form validation unit– If not valid
• Raises built-in exception named FORM_TRIGGER_FAILURE
Guide to Oracle 10g 49
Disabling Form Command Buttons to Avoid User Errors
• Enable or disable button while form running:– SET_ITEM_PROPERTY('item_name', property_name, property_value);
Guide to Oracle 10g 50
Disabling Text Item Navigation
• Nonnavigable– User cannot press Tab key to place insertion point
in text item– Set item’s Keyboard Navigable property to No– User can still click mouse pointer in text item to
enter value• Create trigger that moves insertion point to another
form item• WHEN-MOUSE-UP event
Guide to Oracle 10g 51
Generating Runtime Errors
• Deliberately generate errors while updating and deleting records – View error messages
Guide to Oracle 10g 52
Trapping Form Runtime Errors
• ON-ERROR event occurs– Whenever ORA- or FRM- error occurs while form
running• Create form-level trigger that corresponds to ON-
ERROR event– Use decision control structure to handle different
errors
Guide to Oracle 10g 53
Forms Builder Built-in Procedures for Handling Errors
Guide to Oracle 10g 54
General Syntax for an ON-ERROR Trigger
Guide to Oracle 10g 55
Lesson B Summary
• Create custom messages and alerts – Provide feedback to users
• Validate user inputs using – Text item validation properties– Form validation trigger
Guide to Oracle 10g 56
Lesson C Objectives
After completing this lesson, you should be able to:• Convert data blocks to control blocks• Link data blocks to control blocks• Create a form that has multiple canvases• Create tab canvases• Create stacked canvases
Guide to Oracle 10g 57
Converting a Data Block to a Control Block
• Use Data Block and Layout Wizards to create data block form and form layout– Convert data block to control block– Add command buttons to control form processing– Simplify creation of control blocks
Guide to Oracle 10g 58
Converting a Data Block to a Control Block (continued)
• To convert data block to control block:– Change data block’s Database Data Block property
value to No– Change Required property value of text item that
represents data block table’s primary key to No
Guide to Oracle 10g 59
Linking a Data Block to a Control Block
• Create forms that link data blocks and control blocks to work together– Usually represent master-detail relationship
Guide to Oracle 10g 60
Creating the Data Block
• Use Data Block Wizard and Layout Wizards – To create and configure data block – Must contain field that links it to control block– Create data block without master-detail
relationship • Link two blocks later
Guide to Oracle 10g 61
Linking the Control Block and the Data Block
• Open detail data block’s Property Palette– Modify data block’s WHERE Clause property
• General syntax:– fieldname := control_block.text_item_name
Guide to Oracle 10g 62
Refreshing the Data Block Values
• Add commands to: – Initially populate data block display– Periodically refresh data block records
• Use the GO_BLOCK built-in:– To move form focus to data block
• Then execute EXECUTE_QUERY built-in– Flushes block– Makes information consistent with corresponding
database data
Guide to Oracle 10g 63
Creating Forms with Multiple Canvases
• Good practice not to show too much information on user’s screen display
• Single-form approach – Create one form with multiple canvases– Enables form to share data among different
canvases– Impossible for multiple programmers to work
simultaneously on different canvases of same application
Guide to Oracle 10g 64
Creating Forms with Multiple Canvases (continued)
• Multiple-form approach – Create multiple forms with different .fmb file for
each application canvas– Works well when multiple programmers
collaborate to create complex application– Enables programmers to use form in many
different applications– More difficult for related forms to share data
Guide to Oracle 10g 65
The Northwoods University Student Services Process
• Identify sequence of actions that user will employ to interact with canvases
Guide to Oracle 10g 66
Interface Design
• Student Log On canvas• Menu canvas• Student Information canvas• Course Grades canvas• Enrollment canvas
Guide to Oracle 10g 67
Working with Multiple Canvases and Data Blocks
• Create form that contains multiple canvases– Create individual canvases– Specify to display specific block items on specific
canvas• Create new data block
– Select canvas name on which block items appear • On Layout Wizard Canvas page
Guide to Oracle 10g 68
Working with Multiple Canvases and Data Blocks (continued)
• Often forms that have multiple canvases also have multiple data blocks– Group items that appear on same canvas in single
data block • To keep blocks small and manageable
– Cannot create two items that have same name in same data block
• Ensure that Forms Builder places new items in correct block
Guide to Oracle 10g 69
Specifying the Block Navigation Order
• Specify which canvas initially appears when user runs form– Canvas whose block items appear first under Data
Blocks node in Object Navigator window– Order of canvases in Object Navigator Canvases
list does not matter• Only order of data blocks
Guide to Oracle 10g 70
Object Navigator
Guide to Oracle 10g 71
Referencing Different Canvases, Form Blocks, and Block Items
• All form items have Canvas property – Specifies name of canvas on which item appears
• Form always displays canvas on which item with focus appears
• Execute GO_ITEM built-in– Move form focus to item on target canvas– Good practice to include block name
Guide to Oracle 10g 72
Creating and Configuring Tab Canvases in Forms
• Tab canvases– Multiple-page canvases – Allow users to move between multiple canvas
surfaces • By selecting tabs at top of canvas
– Display large number of related items in modular way
– Direct user through sequence of steps for performing task
Guide to Oracle 10g 73
Creating a Tab Canvas
• Contains two or more tab pages• Tab page
– Object representing surface – Displays form items– Has tab label identifier at top
Guide to Oracle 10g 74
Creating a Tab Canvas (continued)
• Create form that contains tab canvas– Create form– Create new content canvas in form– Create tab canvas on content canvas– Configure tab pages
Guide to Oracle 10g 75
Creating Form Items on a Tab Canvas
• Use tab pages as any content canvas• Create items on tab pages
– Using Data Block Wizard– By creating control block and drawing text items
directly on tab canvases• Must be sure to specify placement of items on tab
canvas
Guide to Oracle 10g 76
Lesson C Summary
• Convert data block to control block• Create relationship between control block and data
block• Display information on multiple canvases:
– Single-form approach– Multiple-form approach
• Tab canvas – Multiple-page canvas
Guide to Oracle 10g 77
Summary
• Custom form • Runtime errors • Forms Debugger • Form triggers• Create custom messages and alerts • Validate user inputs