1. Eyad Alshareef, Edited by: Mostafa Ali
Creating Custom Forms
Part B
Eyad Alshareef, Edited by: Mostafa Ali

2. Eyad Alshareef, Edited by: Mostafa Ali
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
Eyad Alshareef, Edited by: Mostafa Ali

3. 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
Eyad Alshareef, Edited by: Mostafa Ali

4. Oracle Error Message Severity Levels
5: informative message (one record saved)
10: informative message advising user of procedural error (cannot insert character )
20: condition that keeps trigger from working correctly
25 condition that keeps form from working correctly
>25: extreme severity (out of memeory)
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5. 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
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6. Suppressing Lower Level System Messages
Set :SYSTEM.MESSAGE_LEVEL variable to a higher level in PRE-FORM trigger
:SYSTEM.MESSAGE_LEVEL := 25;
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7. Eyad Alshareef, Edited by: Mostafa Ali
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
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Messages
Syntax:
MESSAGE(‘message text’);
Message
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9. Eyad Alshareef, Edited by: Mostafa Ali
Custom Messages
Short text string that displayed on form message line
Up to 200 characters
Syntax:
MESSAGE('message_string');
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Alerts
Form-level object
Object properties define alert appearance
Message
Title
Style
icon
Buttons
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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
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12. Eyad Alshareef, Edited by: Mostafa Ali
Alerts (continued)
Styles:
Note
Caution
Stop
Button Label property determines:
How many buttons appear on alert
Labels on buttons
Maximum 3 buttons
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13. Eyad Alshareef, Edited by: Mostafa Ali
Alerts (continued)
Create alert from Alert Navigation node
To declare/display alert:
DECLARE
alert_button NUMBER;
BEGIN
alert_button:=
SHOW_ALERT('alert_name');
END;
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14. Eyad Alshareef, Edited by: Mostafa Ali
Example Alert
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Syntax to Display an Alert and Execute Alternate Commands Depending on the Button the User Clicked
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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
Eyad Alshareef, Edited by: Mostafa Ali

17. 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
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18. Text Item Validation Properties
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19. 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
Eyad Alshareef, Edited by: Mostafa Ali

20. Disabling Form Command Buttons to Avoid User Errors
Enable or disable button while form running:
SET_ITEM_PROPERTY('item_name', property_name, property_value);
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21. Eyad Alshareef, Edited by: Mostafa Ali
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;
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How To Disable Buttons
SET_ITEM_PROPERTY
E.g. :
SET_ITEM_PROPERTY(‘Control.Delete’ , ENABLED, PROPERTY_FALSE);
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23. 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
Eyad Alshareef, Edited by: Mostafa Ali

24. 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
Eyad Alshareef, Edited by: Mostafa Ali

25. Forms Builder Built-in Procedures for Handling Errors
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26. Eyad Alshareef, Edited by: Mostafa Ali
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
Eyad Alshareef, Edited by: Mostafa Ali

27. Data Blocks vs. Control Blocks
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
Eyad Alshareef, Edited by: Mostafa Ali

28. 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
Eyad Alshareef, Edited by: Mostafa Ali

29. 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
Eyad Alshareef, Edited by: Mostafa Ali

30. 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
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31. Linking Data Blocks and Control Blocks
Create the control block as the master block
Create the data block as the detail block, but do not create a master-detail relationship
Create a master-detail relationship manually in the WHERE Clause property of the detail block:
data_block_field = :control_block.text_item
Eyad Alshareef, Edited by: Mostafa Ali

32. 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
Eyad Alshareef, Edited by: Mostafa Ali

33. 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
Eyad Alshareef, Edited by: Mostafa Ali

34. 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;
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35. 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
Eyad Alshareef, Edited by: Mostafa Ali

36. 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
Eyad Alshareef, Edited by: Mostafa Ali

37. 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
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38. 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
Eyad Alshareef, Edited by: Mostafa Ali

39. Block Navigation Order
Block order
Canvas order doesn’t matter
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40. 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
Eyad Alshareef, Edited by: Mostafa Ali

41. 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
Eyad Alshareef, Edited by: Mostafa Ali

42. 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
Eyad Alshareef, Edited by: Mostafa Ali

43. 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
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Tap Canvas
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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.
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Tab Canvases
Multiple-page canvases that allow users to move among different canvas surfaces by clicking tabs
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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
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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
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49. Important Tab Page Properties
Name: how the page
Is referenced in the form
Label: Caption that appears
on the associated tab
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50. 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
Eyad Alshareef, Edited by: Mostafa Ali

51. Creating and Configuring Tab Canvases in Forms
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
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Creating a Tab Canvas
Contains two or more tab pages
Tab page
Object representing surface
Displays form items
Has tab label identifier at top
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53. 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
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Stacked Canvas
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Stacked Canvases
Canvas that appears on an existing content canvas, and can be displayed or hidden as needed
Allows user to configure canvas items
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56. Stacked Canvas Example
Content
canvas
Stacked
canvas
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57. 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
Eyad Alshareef, Edited by: Mostafa Ali

58. 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’);
Eyad Alshareef, Edited by: Mostafa Ali

59. Eyad Alshareef, Edited by: Mostafa Ali
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
Eyad Alshareef, Edited by: Mostafa Ali