Chapter 6 Creating Custom Forms Guide to Oracle

Chapter 6: Creating Custom Forms Guide to Oracle 10 g

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 10 g 2

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 10 g 3

Identifying the Business Processes and Database Operations • Identify processes that form supports • Identify associated database tables • Describe process Guide to Oracle 10 g 4

Designing the Interface • Visualize how form will look Guide to Oracle 10 g 5

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 10 g 6

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 10 g 7

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 10 g 8

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 10 g 9

Creating the LOVs • LOV – Retrieve data from database table • Use LOV Wizard • Run form – To test LOV Guide to Oracle 10 g 10

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 10 g 11

Forms Builder Date and Time System Variables Guide to Oracle 10 g 12

Creating Command Buttons • Create and configure buttons • Create form triggers associated with buttons Guide to Oracle 10 g 13

Creating and Configuring Command Buttons • Draw button on canvas using Button tool – Button 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 10 g 14

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 10 g 15

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 10 g 16

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 10 g 17

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 10 g 18

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 10 g 19

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 10 g 20

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 10 g 21

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 10 g 22

Forms Debug Console Guide to Oracle 10 g 23

Debug Console Windows Guide to Oracle 10 g 24

Form Trigger Properties • Trigger activated – In response to event such as clicking button • Trigger name defines event that activates it Guide to Oracle 10 g 25

Trigger Categories Guide to Oracle 10 g 26

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 10 g 27

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 10 g 28

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 10 g 29

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 10 g 30

Setting the Form Tab Order • Set tab order – Place items in correct order under Items node • In Object Navigator window Guide to Oracle 10 g 31

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 10 g 32

Built-in Subprograms to Control External Navigation Guide to Oracle 10 g 33

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 10 g 34

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 10 g 35

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 10 g 36

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 10 g 37

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 10 g 38

Custom Messages • Short text string that displayed on form message line – Up to 200 characters • Syntax: – MESSAGE('message_string'); Guide to Oracle 10 g 39

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 10 g 40

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 10 g 41

Alerts (continued) • To declare/display alert: DECLARE alert_button NUMBER; BEGIN alert_button: = SHOW_ALERT('alert_name'); END; Guide to Oracle 10 g 42

Example Alert Guide to Oracle 10 g 43

Syntax to Display an Alert and Execute Alternate Commands Depending on the Button the User Clicked Guide to Oracle 10 g 44

Avoiding User Errors • Help users avoid errors – Configure forms that validate input values – Programmatically disable form command buttons – Disable navigation form text items containing values that users should not change Guide to Oracle 10 g 45

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 10 g 46

Text Item Validation Properties Guide to Oracle 10 g 47

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 10 g 48

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 10 g 49

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 10 g 50

Generating Runtime Errors • Deliberately generate errors while updating and deleting records – View error messages Guide to Oracle 10 g 51

Trapping Form Runtime Errors • ON-ERROR event occurs – Whenever ORA- or FRM- error occurs while form running • Create form-level trigger that corresponds to ONERROR event – Use decision control structure to handle different errors Guide to Oracle 10 g 52

Forms Builder Built-in Procedures for Handling Errors Guide to Oracle 10 g 53

General Syntax for an ON-ERROR Trigger Guide to Oracle 10 g 54

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 10 g 55

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 10 g 56

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 10 g 57

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 10 g 58

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 10 g 59

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 10 g 60

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 10 g 61

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 10 g 62

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 10 g 63

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 10 g 64

The Northwoods University Student Services Process • Identify sequence of actions that user will employ to interact with canvases Guide to Oracle 10 g 65

Interface Design • • • Student Log On canvas Menu canvas Student Information canvas Course Grades canvas Enrollment canvas Guide to Oracle 10 g 66

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 10 g 67

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 10 g 68

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 10 g 69

Object Navigator Guide to Oracle 10 g 70

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 10 g 71

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 10 g 72

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 10 g 73

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 10 g 74

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 10 g 75

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 10 g 76

Summary • • • Custom form Runtime errors Forms Debugger Form triggers Create custom messages and alerts Validate user inputs Guide to Oracle 10 g 77

Summary (continued) • Convert a data block to a control block • Create relationship between control block and data block • Display information on multiple canvases • Tab canvas Guide to Oracle 10 g 78